651

Sea Lamprey Control: Past, Present, and FutureMichael J. Siefkes, Todd B. Steeves, W. Paul Sullivan,

Michael B. Twohey, and Weiming Li

Introduction

Th e establishment of non-native species, whether intentional or accidental, combined with anthropogenic

exploitation of fishes and their habitats have significantly and irreversibly altered the ecosystems of the

Laurentian Great Lakes (Smith 1968; Loftus and Regier 1972; Eshenroder and Burnham-Curtis 1999;

Leach et al. 1999). One invasive species that has had a marked impact upon Great Lakes fish populations

is the Sea Lamprey (Petromyzon marinus). Th e history of Sea Lamprey invasion and control has been

well-documented (Applegate 1950a, 1950b; Lawrie 1970; Smith et al. 1974), and the proceedings of two

international symposia were published as supplementary issues of scientific journals (Canadian Journal

of Fisheries and Aquatic Sciences 1980 37[11]; Journal of Great Lakes Research 2003 29[Supplement 1];

SLIS I and SLIS II). Th e Sea Lamprey Control Program in the Great Lakes is a case study in coordinated

and integrated binational fishery management and is the only reported successful control program for

a non-native, vertebrate pest species, as evidenced by the 90 percent reduction from peak levels of Sea

Lamprey abundance and the resultant rehabilitation of fisheries across the Great Lakes basin.

Sea Lamprey Invasion and Fisheries Collapse

Th e earliest record of Sea Lamprey in the Great Lakes occurred in 1835 in Lake Ontario (Lark 1973), where

a naturalist described what is accepted to be a mature, spawning-phase Sea Lamprey in Duffins Creek,

Ontario. Th e timing of this observation is consistent with colonization after the opening of the Erie Canal

during 1819 (Smith 1995). To the contrary, colonization of Lake Ontario via the Erie Canal is skeptically

viewed (Daniels 2001), and genetic evidence supports the concept that Sea Lampreys from Lake Ontario

are distinct from presumed Atlantic origins and are native (Waldman et al. 2004; Bryan et al. 2005).

Nevertheless, the debate regarding the origin of Sea Lampreys in Lake Ontario continues (see Eshenroder

2009; Waldman et al. 2009).

Th e invasion of the remainder of the Great Lakes has been well-documented (Dymond 1922; Applegate

1950b; Lawrie 1970; Smith 1971; Pearce et al. 1980; Smith and Tibbles 1980), with first observations of Sea

Michael J. Siefkes et al.652

Lampreys in Lake Erie in 1921, Lake Huron in 1937, Lake Michigan in 1936, and Lake Superior in 1938.

Examination of Sea Lamprey length data and location of the observation of these first sightings indicate

Sea Lampreys were likely present in the lakes above Niagara Falls for several years, without being observed

either as parasites on fish or in tributaries during their spawning phase (Smith 1971; Smith and Tibbles

1980; Eshenroder and Amatangelo 2005).

Th ere is widespread agreement among fishery biologists that changes in lake ecosystems during the

period of Sea Lamprey invasion are due to a combination of overfishing, Sea Lamprey predation, and

habitat alteration (Hile et al. 1951; Smith and Tibbles 1980; Coble et al. 1990; Eshenroder and Burnham-

Curtis 1999; Hansen 1999; fig. 1). Debate remains about the proportional impacts of each of these factors in

the decline of fish species, particularly commercial species, such as the Lake Trout (Salvelinus namaycush),

Lake Whitefish (Coregonus clupeaformis), and deepwater Ciscoes (C. spp.; Hansen 1999; Coble et al. 1990;

Eshenroder and Amatangelo 2005). Regardless of the cause of fishery decline, rehabilitation of the Lake

Trout populations became the measure of fishery restoration for each lake. Stocking of hatchery-reared

Lake Trout, improvement to Lake Trout habitat, and fishery regulation are part of the eff ort to restore Lake

Trout to abundances observed during the early 1900s. It was evident by the 1950s that a program to control

the Sea Lamprey would also be a vital part of Lake Trout restoration.

Chapter Goal and Outline

Th is chapter’s goal is to describe the past, present, and future of Sea Lamprey control in the Great Lakes. Th e

remainder of this chapter begins with a history of Sea Lamprey control. Th e development, implementation,

and future of each component in Sea Lamprey control are then summarized. Given this background, the

present status of Sea Lamprey control in each of the Great Lakes is examined. Th e chapter concludes with

a brief look into new developments in Sea Lamprey control, including two promising areas in which recent

research has shown encouraging results for their use in Sea Lamprey control: pheromones and genomics.

Early Development of the Sea Lamprey Control Program

Th e Sea Lamprey invasion in the Great Lakes was the primary catalyst for the governments of Canada

and the United States to establish a binational entity to develop coordinated approaches to protect and

rehabilitate shared fish stocks (Fetterolf 1980; Gaden et al.2012). Previously, fishery management was not

widely coordinated among the states and province bordering the Great Lakes (Dochoda and Koonce 1994).

During 1946, the Great Lakes Sea Lamprey Committee was formed to develop coordinated, cooperative,

and binational management focused on the life history and biological eff ects of the Sea Lamprey in the

Great Lakes (Smith et al. 1974). Th en, on September 10, 1954, the Convention on Great Lakes Fisheries

(the Convention) was signed by Canada and the United States, establishing the Great Lakes Fishery

Commission (GLFC; GLFC 1955). Th e Convention mandated the GLFC “to formulate and implement a

comprehensive program for the purpose of eradicating or minimizing Sea Lamprey populations” in the

Great Lakes and to create and manage a fishery research program focusing on important fish stocks (GLFC

1955). Th e GLFC contracted with the Fisheries Research Board of Canada and the U.S. Fish and Wildlife

Service (USFWS) to implement Sea Lamprey control in Canada and the United States, as recommended

in Article VI of the Convention (Christie and Goddard 2003). During 1966, the Canadian Department

FIG. 1. Commercial Lake

Trout (Salvelinus namaycush)

harvest for each Great

Lake. Vertical dashed lines

indicate first observation of

Sea Lamprey (Petromyzon

marinus) in the lake (Lake

Ontario is 1835) and the

vertical black lines indicate

the year of first lampricide

application.

Data from Baldwin et al. (2002).

Michael J. Siefkes et al.654

of Fisheries and Oceans (DFO) assumed the responsibility for Sea Lamprey control in Canada (Christie

and Goddard 2003). Agency personnel contracted by the GLFC to implement the Sea Lamprey Control

Program are termed control agents.

Early Sea Lamprey control was guided by an advisory committee, consisting of members of the GLFC,

control agents, and research biologists, that met annually to discuss recommendations for program funding

and direction (Christie and Goddard 2003). A series of reviews during the 1980s led the GLFC to expand

the advisory committee to include fishery management agencies to better link fish community objectives

with Sea Lamprey control (Koonce et al. 1982; Spangler and Jacobson 1985). Experts in integrated pest

management were also invited to the newly structured advisory committee (Christie and Goddard 2003),

which was named the Sea Lamprey Integration Committee (SLIC). Technical task forces were established

under the SLIC to provide details and recommendations about control activities. Th ese task forces included

control agents, fishery managers, research biologists, and other relevant experts. Th e SLIC and its task

forces continue to support the GLFC’s decision-making process with input from a diverse group of experts

as Sea Lamprey control continues to evolve.

Another important guide for the Sea Lamprey Control Program was the development of the GLFC

Vision (GLFC 1992, 2001). First established during 1992 and then revised during 2001, the GLFC Vision

provided milestones for the Sea Lamprey Control Program and the restoration of the fishery for each

Great Lake. Specifically, targets for Sea Lamprey abundance in each lake were established and were to

be achieved through the optimal implementation of control strategies, including appropriate assessment

of Sea Lamprey recruitment, an integrated mix of lampricide and alternative controls, and control of Sea

Lampreys in the St. Marys River. Overall, the GLFC Vision called for the successful control of Sea Lamprey

populations to allow the rehabilitation of native and desirable fish stocks in each lake. Th e GLFC Vision

continues to guide the Sea Lamprey Control Program.

Two elements were crucial to the early Sea Lamprey control in the Great Lakes, before the establish-

ment of the GLFC: the determination of the Sea Lamprey life cycle (fig. 2) and the cataloguing of the

tributaries used for spawning (Applegate 1950a, 1950b). In the Laurentian Great Lakes, the Sea Lamprey

has a potamodramous (migrating within fresh water only) life history comprehensively described in other

publications (Applegate 1950a, 1950b; Scott and Crossman 1973). Sea Lampreys begin life in Great Lakes

tributaries as non-parasitic larvae, where they filter-feed on microorganisms for three to six years. Larval

Sea Lampreys then begin a dramatic metamorphosis, developing eyes, oral disks, and tongues covered

with teeth and begin migrating downstream to the lakes; downstream-migrating Sea Lampreys are called

transformers. Once larval Sea Lampreys have completely transformed and migrated to the lakes, they

enter the parasitic-phase, feed on fish, and grow for twelve to eighteen months. During the late winter or

early spring, parasitic-phase Sea Lampreys stop feeding, enter the spawning-phase of their lifecycle, and

begin to search for suitable spawning tributaries. On finding and entering a tributary, spawning-phase

Sea Lampreys begin the final stages of sexual maturation, reproduce during the spring and early summer,

and die shortly after spawning.

Review of the Sea Lamprey life history by early fishery managers indicated that impacts to populations

would best be made during the stages spent in tributaries; larvae, transformers, and spawning-phase

adults. Initial eff orts to control the Sea Lamprey began in the 1940s and focused on preventing migrating

Sea Lampreys from reaching spawning areas through the use of mechanical and electrical weirs and

low-head barriers (Lavis et al. 2003a). As problems with weirs and barriers were encountered, fishery

SEA LAMPREY CONTROL 655

managers quickly realized that finding a pesticide (lampricide) that could be applied to tributaries to target

larvae, limit the recruitment of Sea Lampreys to the Great Lakes prior to their parasitic-phase, and aff ect

as many as five generations of larvae in the same tributary would likely be the most eff ective method of

reducing Sea Lamprey populations.

Principal Techniques of Sea Lamprey Control—Lampricides

Development of Lampricides

Investigations to find a lampricide that could selectively kill larval Sea Lampreys, while having little or

no eff ect on non-target organisms, were undertaken at Hammond Bay Biological Station in Millersburg,

Michigan, during 1950. It was envisioned that the lampricide could be applied to tributaries throughout the

Great Lakes, killing multiple generations of larval Sea Lampreys in the tributary prior to metamorphosis

and the start of the parasitic phase. Ideally, a lampricide would kill larvae at a low concentration, work

FIG. 2. Th e Sea Lamprey (Petromyzon marinus) life cycle.

Great Lakes Fishery Commission.

Michael J. Siefkes et al.656

eff ectively over a short period, be metered into flowing water at precise rates, be soluble and mix thoroughly

throughout the tributary, have no deleterious residual compounds once larvae were killed, and be inexpen-

sive to produce. More than six thousand predominantly organic chemicals were examined for diff erential

toxicity to larvae and twelve other fish species in static bioassay and simulated stream experiments. A group

of mono-nitrophenols containing bromine, chlorine, or fluorine was found to possess all of the desirable

traits of an eff ective lampricide. Of these, the sodium salt form of 3-trifluoromethyl-4-nitrophenol (TFM)

was found the most suitable compound for use as a liquid lampricide.

The evaluation of compounds also led to the discovery of a second lampricide, 2,'5-dichloro-4'-

nitrosalicylanilide, during 1963 (Howell et al. 1964). Initially registered as Bayer 73 and now registered as

Bayluscide, 2,'5-dichloro-4'-nitrosalicylanilide is a water-soluble powder not as selectively toxic to Sea Lam-

preys as TFM; one of Bayluscide’s additional uses is as a molluscicide, to control outbreaks of swimmer’s

itch by reducing the population of snails that serve as vectors for the parasite that causes the disease. To

date, three formulations of Bayluscide have been developed for application in the field: a wettable powder

and an emulsifiable liquid are used as a synergistic additive during TFM treatments to reduce the amount

of TFM required, resulting in a significant cost savings during the treatment of high-discharge tributaries;

and a granular form, consisting of a grain of sand that is coated with Bayluscide and encapsulated within a

water soluble coating containing a surfactant that enables application of the Bayluscide to waters greater

than 1 m in tributaries and in lentic areas adjacent to tributary mouths. Bayluscide granules are used as

an assessment tool to determine larval Sea Lamprey presence and abundance or as a method of control

where the application of TFM is not practical.

Experimental applications of TFM to tributaries was completed in Lake Huron during 1957; the success

of these treatments resulted in the scheduling of treatments for twelve tributaries to Lake Superior during

1958 and an additional sixty from 1959 to 1960 (Smith and Tibbles 1980; Heinrich et al. 2003). Th ese initial

treatments had dramatic eff ects on the resident larval Sea Lampreys, subsequently reducing the lake-wide

spawning-phase Sea Lamprey abundance estimate in Lake Superior from 1.35 million during 1960 to

approximately 200,000 during 1962. Similar dramatic decreases in Sea Lamprey abundance estimates have

been observed in each Great Lake, following the implementation of lampricide treatments.

Environmental Fate of Lampricides and Effects on Non-Target Organisms

Hubert (2003) and Dawson (2003) provide a comprehensive review of the fates of TFM and Bayluscide in

the aquatic environment. Th e persistence of TFM and Bayluscide after treatment application is relatively

short, with the active ingredients in TFM and Bayluscide aff ected by both abiotic and biotic processes

in the stream environment. Th e primary abiotic processes aff ecting lampricides are sediment binding,

particularly to sediments with high organic content, and photodecomposition, especially for Bayluscide.

Th e rate of removal by these processes is inversely aff ected by pH. Hydrolysis and volatilization were not

significant contributors to the breakdown of lampricides in the environment. Biotic processes appear less

important to TFM, where water and sediment concentrations are below detectable limits before microbial

breakdown can reduce TFM to non-detectable levels in the stream environment. Microbial activity,

however, is important in the transformation of Bayluscide.

Th e non-target eff ects of TFM, as used in the Sea Lamprey Control Program, are limited to the aquatic

environment. Birds and mammals that may drink from, swim in, or consume larval Sea Lampreys killed

SEA LAMPREY CONTROL 657

by TFM treatment, are not aff ected (Hubert 2003). In general, hard-bodied macroinvertebrates are less

susceptible to TFM than soft-bodied macroinvertebrates, with aquatic annelids having the potential to be

eliminated from a tributary after TFM treatment (Gilderhus et al. 1975). Th e eff ects of TFM in concentra-

tions sufficient to kill larval Sea Lampreys was estimated for stream invertebrates by Maki et al. (1975),

based on the results of toxicity assays. Maki et al. (1975) found populations of annelids and black fly

larvae would be reduced by 50 percent, three genera of mayflies would “suff er high mortalities” and the

caddis fly Chimarra obscura would be virtually eliminated. Field observations support laboratory results,

indicating significant mortality on the mayfly genus Hexagenia (Gilderhus and Johnson 1980). Torblaa

(1968) and Maki (1980, cited in ACSCEQ 1985), however, found that abundance within pool and riffle

stream assemblages before and after lampricide treatment were not significantly diff erent, despite the

fact that the number of macroinvertebrates was reduced between 64 percent and 80 percent one day after

treatment. One of the most notable eff ects was a ten-fold increase in the number of macroinvertebrates

drifting downstream (drift rate) immediately after the start of TFM application, with a decline to a stable

drift rate of twice the initial rate within three hours. Both authors noted a rapid recovery of macroinver-

tebrates within six weeks. Sampling one year post-treatment indicated a full recovery of the diversity and

abundance of major taxonomic groups.

As with macroinvertebrates, teleosts exhibit a range of sensitivity to TFM. Th e eff ect of TFM on fish

varies with life stage, physiological condition, and species. In general, smaller fish of any species are more

susceptible than larger specimens of the same species, with the exception that eggs and sac fry are robust

to the eff ects of TFM (Boogaard et al. 2003). Fish weakened from the rigors of spawning or through disease

are also more susceptible to TFM.

A number of studies have examined the eff ects of TFM on teleosts. Dahl and McDonald (1980) exam-

ined field records from 1,300 lampricide treatments and found suckers (Catastomous spp.) were the most

widely aff ected by TFM, but the Stonecat (Noturus flavus) was the most dramatically aff ected, significantly

reducing Stonecat abundance in five of the nine tributaries in which it occurs in the western end of Lake

Superior. Despite the toll that lampricide application has on Stonecats, in-stream refugia are found in

some smaller tributaries not treated and their populations have not been completely extirpated. A similar

situation exists for the Stonecat populations in northwestern Lake Ontario (Dahl and McDonald 1980).

Other species that commonly experience some mortality during lampricide application include the

Brown Bullhead (Ictalurus nebulosus), Brown (Salmo trutta) and Rainbow (Oncorhynchus mykiss) Trout,

Northern Pike (Esox lucius), and Walleye (Sander vitreus), with smaller fish, such as Logperch (Percina

caprodes) and Trout Perch (Percopsis omiscomaycus), also suff ering higher rates of mortality during

TFM treatment (Dahl and McDonald 1980; ACSCEQ 1985). Of particular concern is the Lake Sturgeon

(Acipenser fulvescens), in which laboratory studies have shown that young-of-year Lake Sturgeon less

than 100 mm total length are as susceptible to TFM as larval Sea Lampreys, although survival was

improved by using a TFM/1 percent Bayluscide mixture (Boogaard et al. 2003). Th ese observations on

Lake Sturgeon resulted in changes to lampricide application protocols in the United States, by using

lower lampricide concentrations applied later during the year to reduce the impacts on young-of-year

Lake Sturgeon (Adair and Young 2004), although, during recent years, Michigan and Wisconsin have

removed restrictions on concentration in response to concerns that lampricide treatment efficacy was

being compromised. Canada has not adopted restrictions to concentration or timing of lampricide

treatments, because field observations of non-target impacts since the 1960s have not demonstrated

Michael J. Siefkes et al.658

that lampricides are inflicting undue mortality on Lake Sturgeon, which is consistent with observations

made during lampricide treatments in the United States over the same period. Recently, an in situ

study has shown that survival of young-of-year Lake Sturgeon exposed to lampricides during treatment

was identical to that in a control group (94 percent; Tom Pratt, personal communication). In addition,

research has shown that Sea Lamprey mortality on Lake Sturgeon adults and sub-adults is significant

(Patrick et al. 2009) and that protecting adults from mortality provides the most benefit to population

maintenance and rehabilitation (Sutton 2004). Th ese studies have led to a reevaluation of the benefits

of using less lampricide and delaying treatment to later in the year, when more variable environmental

conditions can hamper the delivery of eff ective lampricide treatments.

Teleosts are not the only aquatic vertebrates aff ected by TFM. Th e Mudpuppy (Necturus maculosus), a

native amphibian of the Great Lakes region, also experiences some mortality during lampricide application

(Gilderhus and Johnson 1980). Lampricide toxicity tests, however, indicate that adult Mudpuppy popula-

tions would not be significantly aff ected by lampricide treatments (Boogaard et al. 2003). Additional tests

are needed to determine the toxicity of lampricides to juvenile Mudpuppies.

By far, the greatest non-target eff ect of TFM has been on the native lamprey species: the non-parasitic

American Brook (Lampetra appendix) and Northern Brook (Ichthyomyzon fossor) Lampreys, and the

parasitic Silver (Ichthyomyzon unicuspis) and Chestnut (Ichthyomyzon castaneus) Lampreys. As all

lamprey species in the Great Lakes have similar spawning requirements and virtually identical larval

habitat requirements, the overlap among species in some tributaries is inevitable. Although laboratory

studies have demonstrated that the Sea Lamprey is slightly more susceptible to TFM than the native

lamprey species (Davis 1970), the diff erence is negligible and insufficient to enable the selective removal

of larval Sea Lampreys from tributaries inhabited by native lamprey species (Dawson et al. 1975). Th e

biology of the Silver Lamprey is most like the Sea Lamprey, and the Silver Lamprey has been the most

aff ected by TFM treatments. Schuldt and Goold (1980) reported a capture of 4,278 Silver Lampreys in

Lake Superior electrical weirs during 1959, but only 91 were captured during the five year span from 1973

to 1977, including the catch from the St. Marys River. Th e decline in Silver Lampreys can be attributed

to the eff ects of lampricide application to mutually shared natal tributaries and, to a lesser extent, the

eff ects of the Sea Lamprey barrier program limiting the access of spawning-phase Silver Lampreys to

suitable spawning habitats. Non-parasitic native lamprey species are less impacted by Sea Lamprey

control activities. Th e lack of a parasitic phase in the Brook Lampreys means they do not leave their natal

tributary in search of a blood meal, and their presence in the head waters of tributaries above barriers

provides a refuge from Sea Lamprey control activities and a source of Brook Lampreys to repopulate the

tributary after TFM treatment.

Th e various forms of Bayluscide are less species-specific than TFM and, as such, can have wider

eff ects on non-target species. Powdered bayluscide is used in conjunction with TFM in a 98:2 or 99:1,

TFM:Bayluscide ratio to reduce the amount of TFM required to treat high discharge tributaries. Th ese

mixtures follow the same toxicity patterns to fish and invertebrates that a TFM-only treatment exhibits,

but the LC50 for many species is lower in the TFM:Bayluscide powder mixture (ACSCEQ 1985; Boogaard

et al. 2003).

Th e most acute non-target eff ect is observed when using Bayluscide granules. As Bayluscide granules

are designed to sink to the substrate before the active ingredient is released, bottom-dwelling species

are most often aff ected, with species more commonly found in the water column able to swim out of the

SEA LAMPREY CONTROL 659

application area. As expected, mollusks are particularly susceptible to Bayluscide, with both snails and

clams experiencing significant, sometimes complete, mortality within the treated area (ACSCEQ 1985).

Invertebrates, such as oligochaetes, turbellarians, and leeches also experience high rates of mortality

(Dawson 2003).

Bayluscide is more toxic to teleosts than TFM. As with TFM, free-swimming, exogenously feeding life

stages are most susceptible, whereas eggs and sac fry are relatively resistant to Bayluscide (Dawson 2003).

Because the granular formulation of Bayluscide is less selective than TFM for controlling Sea Lampreys,

Bayluscide is not used as a lampricide for stream-wide application. Granular Bayluscide use is limited to

evaluating and controlling populations in areas in which TFM is typically not eff ective, such as lentic or

estuarine areas of tributaries.

As the application of lampricides are generally limited to once every three to five years, and the duration

is no longer than sixteen hours in any single application, the long-term eff ects of lampricide control on

most non-target species, with the exception of the native lamprey, are minimal.

Scheduling Lampricide Applications

Although there are approximately 5,400 tributaries to the Great Lakes, only 450 have produced Sea

Lampreys (fig. 3; table 1). Funding is not sufficient to allow treatment of all tributaries that may produce Sea

Lampreys within a year; consequently, a method of selecting tributaries for treatment is required. Th e long

history of Sea Lamprey Control Program enables the control agents to forecast when a tributary is expected

to produce parasitic-phase Sea Lampreys. Consequently, approximately one-half of the tributaries cur-

rently selected for lampricide treatment during a given year are selected using this knowledge. Th e other

half are selected from a rank list of tributaries using cost per larval Sea Lamprey killed. Th e scheduling of

tributaries for treatment begins as much as eighteen months before the lampricide is actually applied.

Larval Sea Lamprey population assessment is a critical component of Sea Lamprey control. Th e pres-

ence, abundance, and size structure of larval Sea Lamprey populations in approximately two hundred

tributaries and lentic areas throughout the Great Lakes basin are evaluated each year, one year prior to

the expected recruitment of parasitic-phase Sea Lampreys to the lake (Christie et al. 2003). Larval Sea

Lamprey populations are sampled using one of two methodologies: backpack electrofishing in waters

TABLE 1. Numbers of Tributaries to Each Great Lake, Including Historically Infested, Treated, and That Are Regularly Treated Due to Consistent Sea Lamprey (Petromyzon marinus) Recruitment and Growth

NUMBER OF TRIBUTARIES

LAKE TOTAL TRIBUTARIES INFESTED BY SEA LAMPREYS TREATED AT LEAST ONCE REGULARLY TREATED

Superior 1,566 148 84 53

Huron 1,761 117 71 45

Michigan 511 121 72 34

Erie 842 22 9 5

Ontario 659 65 39 29

FIG. 3. Historic distribution of Sea Lamprey

(Petromyzon marinus)-producing tributaries

to the Great Lakes.

Great Lakes Fishery Commission.

Michael J. Siefkes et al.662

that are less than 0.8 m deep (Slade et al. 2003) and with granular Bayluscide in waters too deep or turbid

to allow eff ective sampling using electrofishing gear (Weise and Rugen 1987).

Initial methods to evaluate whether a tributary required lampricide treatment were based primarily on

the subjective interpretation of sampling data by control agent biologists (Weise and Rugen 1987; Christie

et al. 2003). Th e basin-wide allocation of treatment resources among tributaries on both sides of the border

necessitated the development of standardized sampling techniques to enable a more objective evaluation

of the need to treat tributaries (Slade et al. 2003). Initial protocols focused on the development of index

stations within each Sea Lamprey-producing tributary, accompanied by mark-recapture estimates of larval

Sea Lamprey abundance at the time of treatment to determine the relative accuracy of abundance at the

index stations, both within and among tributaries (Weise and Rugen 1987).

More rigorous methods to estimate the abundance of larval Sea Lampreys, as well as the potential

production of newly metamorphosed Sea Lampreys, began in 1995 (Slade et al. 2003). Standardized

protocols were developed to estimate the density and size structure of the larval Sea Lamprey population,

as well as evaluate the quantity and quality of larval habitat in Great Lakes tributaries (Christie et al. 2003).

Th ese measures of larval Sea Lamprey density and available larval habitat are inputs into the Empiric

Stream Ranking Model (ESTR; Christie et al. 2003), in which they are combined with estimates of sampling

efficiency, growth, and metamorphosis to derive tributary-specific estimates of the abundance of large

Sea Lamprey larvae during the fall of the year of sampling and forecast the production of parasitic-phase

Sea Lampreys the following year (Christie et al. 2003). Methods used to rank tributaries for lampricide

application were reviewed, and several recommendations to improve the ability to estimate larval Sea

Lamprey abundance within a tributary were made, including increased sampling of less-preferred larval

habitats, reducing uncertainties associated with larval growth and metamorphosis parameters, and a better

understanding of the factors that contribute to variation in larval density (Hansen et al. 2003). During the

previous decade, several parameters of the ESTR model were refined, including electrofisher sampling

efficiency (Steeves et al. 2003), metamorphosis (Treble et al. 2008), and larval Sea Lamprey habitat use

(Sullivan 2003), and the uncertainty in model parameters has been quantified (Steeves 2002).

To rank tributaries for treatment, the abundance of large larvae in each tributary is divided by the

tributary-specific cost of lampricide application to calculate a per-dollar cost to kill each transformer, and

all tributaries sampled each year are ranked based on the cost per kill value (Christie et al. 2003; Slade et

al. 2003). Th e amount of control eff ort that can be expended annually is known, and as many tributaries

as possible are treated with this control eff ort, starting with the lowest cost per kill tributary. Ranking of

tributaries for lampricide treatment is done across the Great Lakes basin, regardless of lake.

During 2008, the control agents changed the sampling protocol for wadable waters and the criteria

used to rank tributaries for lampricide treatments (Hansen and Jones 2008). Th e methods used between

1995 and 2008 were labor-intensive, such that a significant portion of the Sea Lamprey control budget was

spent assessing tributaries for treatment, rather than actually applying lampricides. Th e new methods

build on the information collected since 1995, and the control agents now sample only the best quality

habitat in each tributary. Th e new method reduces the amount of time spent collecting data by 40 percent,

and the time saved can be applied to lampricide treatments. Th e ranking criterion in the ESTR model was

also changed from the forecast of parasitic-phase production the year after assessment to the abundance

of larvae greater than100 mm in the year of assessment. Th e ranking criteria change reduces the overall

uncertainty, by removing the uncertainty associated with the model of metamorphosis within ESTR

SEA LAMPREY CONTROL 663

(Steeves 2002) and the tributary-specific eff ects not captured in the ESTR program (Treble et al. 2008).

Although the new method results in less precise estimates of larval Sea Lamprey abundance overall, the

added uncertainty is compensated for by increased lampricide treatments and, thus, Sea Lamprey control

each year (Hansen and Jones 2008).

Methods of assessing larval Sea Lamprey populations in deep and turbid tributaries and lentic areas

diff er from the usual methods required, as backpack electrofishing is not eff ective in these areas. As-

sessment begins with an evaluation of the location and amount of suitable larval habitats. Prior to 2007,

assessment was done using a labor-intensive method of collecting dredge samples of substrate along

transects placed throughout the suspected infested area. Although the use of dredge sampling continues for

evaluation of estuarine habitat in small and medium-sized streams, the control agents have adapted geo-

referenced RoxAnn sonar technology to enable a more rapid and comprehensive collection of substrate

data to evaluate suitability to harbor larval Sea Lampreys in large estuaries and adjacent lentic areas. Th e

data collected using RoxAnn sonar and the resulting habitat areas are sampled using a dredge to verify

substrate composition. Larval Sea Lamprey abundance, size structure, and distribution are determined

by spreading granular Bayluscide over a number of plots throughout the surveyed area. A target treatment

area is identified and the same cost per kill criterion is calculated for larvae greater than 100 mm to rank

these deep and turbid tributaries and lentic areas along with tributaries for lampricide treatment.

One exception to the application of assessment methods just described is the St. Marys River. Th e

St. Marys River was discounted as a major contributor of Sea Lampreys to Lakes Huron and Michigan

during the 1970s and 1980s (Schleen et al. 2003), but the eff ects of remediation led to an estimated larval

Sea Lamprey population of 6.2 million during 1987 (Eshenroder et al. 1987). Flow modeling (Shen et al.

2003) indicated that a traditional TFM treatment would not be eff ective on the St. Marys River (Schleen

et al. 2003). Th ere was an obvious need to identify areas of high larval Sea Lamprey abundance to enable

large-scale granular Bayluscide applications to control Sea Lampreys in the St. Marys River. As a solution,

a backpack electrofisher was modified to enable samples to be taken from deep water areas, coupled with

a GPS system and mounted on a pontoon boat, to allow specific densities of larval Sea Lampreys to be

mapped. Between 1993 and 1996 a total of 11,809 points were sampled over 71 km2 of river (Fodale et al.

2003) and the areas of highest density demarcated.

Applying Lampricides

During the initial years of the lampricide control, static bioassays conducted prior to lampricide treatments

were used to determine a safe, yet eff ective, concentration of TFM (Johnson and Stephens 2003). Th e ap-

plication of a fixed volume of TFM, however, did not always result in eff ective treatments. Initial measures

of stream discharge could be inaccurate, resulting in too high or low a concentration of TFM in the river

and either unacceptable non-target mortality or insufficient toxicity to kill larval Sea Lampreys. In addition,

application of lampricides for no more than the requisite nine hours of minimum lethal concentration

could result in the lengthening of the lampricide block through areas of higher water velocity, whereas

backwater areas, often containing the highest density of larval Sea Lampreys, took longer for TFM to

accumulate to the proper concentration, and resulted in ineff ective treatments.

Th e need to adapt TFM concentrations to changing stream conditions necessitated the ability to

measure concentrations of TFM on the order of milligrams per liter (parts per million, ppm), while being

Michael J. Siefkes et al.664

applied to the tributary (Johnson 1961). During 1960, Smith et al. (1960) developed a colorimetric method

to quantify TFM concentrations in the tributary, and application rates could be changed to compensate

for changes in discharge. At the same time that the colorimetric method of measuring TFM concentration

was being developed, initial testing of TFM demonstrated that the toxicity of the compound was aff ected

by chemical and physical parameters of the water (Howell et al. 1964). Lower temperatures have been

shown to decrease toxicity of TFM to non-target species, but toxicity to larval Sea Lampreys is not similarly

reduced. Alkalinity and pH have the largest eff ect on TFM toxicity, with an increase in these parameters

requiring a higher concentration of TFM to kill larval Sea Lampreys (Kanayama 1963; Johnson and

Stephens 2003). Tributaries that flow over the Canadian Shield have lower pH and alkalinities and require

less TFM to achieve the same level of toxicity than do tributaries of Lakes Ontario, Erie, or Michigan. Th e

U.S. Geological Survey in La Crosse, Wisconsin, developed standardized charts to enable control agents to

forecast the required concentration to kill larval Sea Lampreys through standard measurement of chemical

and physical properties immediately prior to TFM application (Bills et al. 2003).

Once the list of tributaries to be treated is finalized, during the winter of a given year, the control

agents begin extensive consultation and application for permits with provincial, state, and tribal fisheries

and environmental management agencies. Th e presence of threatened or endangered species within the

proposed treatment area is taken into consideration, and treatment plans are adapted as needed.

Th e present protocol for the application of TFM combines elements of the current stream-specific

conditions with experience from previous treatments of the same or similar tributaries (Smith and Tibbles

1980). Discharge, pH, alkalinity, dissolved oxygen, and temperature are measured precisely over the

course of the treatment, beginning one or two days prior to TFM application. Some treatments also require

verification of the required TFM concentrations forecasted by the standardized charts through stream-side

bioassays using larval Sea Lampreys collected from the target tributary (Johnson and Stephens 2003).

Once the target lampricide concentration is determined, application points are mapped based on the

distribution of larval Sea Lampreys and the requirement to augment lampricide concentration at specific

access points to accommodate additional water inputs, such as tributaries or groundwater infiltration.

Sample points to determine lampricide concentration are also identified based on the flow timing of the

lampricide moving through the system. In newly infested tributaries, or in tributaries in which current

discharge is outside of previous treatment experience, a dye study may be conducted prior to lampricide

treatment to gather information on flow timing and dilution and to identify problem areas.

Although the majority of larval Sea Lampreys are found within the flowing portion of Great Lakes

tributaries, some populations exist in lentic areas, including sheltered bays closely associated with Sea

Lamprey-producing tributaries, as well as within the deep sections of channels and rivers that connect the

Great Lakes, such as the St. Marys, St. Clair, and Niagara rivers. Contributions to Sea Lamprey populations

from lentic areas were originally thought to be negligible, as these areas were presumably harsher condi-

tions for larval Sea Lampreys, with fewer nutrients and degree days to accumulate the length required

for metamorphosis (Smith and Tibbles 1980). Th e use of aging techniques on Sea Lamprey statoliths

(Beamish and Medland 1988), a structure analogous to otoliths in teleosts, for both larval and recently

metamorphosed Sea Lampreys, demonstrated that larval Sea Lampreys in the St. Marys River transformed

in four to seven years (Schleen et al. 2003) and that significant recruitment of Sea Lampreys to lakes Huron

and Michigan from the St. Marys River was occurring. Investigation into the recruitment of Sea Lampreys

from lentic areas is currently being conducted (B. Swink, Hammond Bay Biological Station, Millersburg,

SEA LAMPREY CONTROL 665

Michigan, personal communication), but the observation of large larvae and transformers, during lentic

surveys and treatments, indicates Sea Lampreys can complete the larval life stage in lentic environments.

Th e use of TFM is not an acceptable control method for lentic areas because of rapid dilution in lentic areas

and the immense costs incurred by treatment of connecting channels by virtue of their large discharge

and complexity (Schleen et al. 2003). Bayluscide granules are used to treat these areas and are applied

from boats, using broadcast type spreaders, which can produce Bayluscide dust, requiring the use of

safety equipment by control agents. Recently, a new type of spray boat that applies a dust-free Bayluscide

granule/water slurry has been developed for faster, safer lentic area treatments

The Future of Lampricide Control

Lampricide application has been the cornerstone of the Sea Lamprey Control Program since 1958. Cur-

rent strategies to target and apply lampricides, however, have resulted in an annual average of 430,000

spawning-phase Sea Lampreys in the Great Lakes basin. Innovative strategies to apply lampricides

within and among tributaries are required to further reduce Sea Lamprey abundance. One such strategy

involves the treatment of all nine Sea Lamprey-producing tributaries on Lake Erie, during two consecutive

years, taking advantage of the significant and immediate reduction in Sea Lamprey abundance observed

following the initial treatments during 1986. Although treating all Sea Lamprey-producing tributaries in

consecutive years is applicable to Lake Erie, given the low number of Sea Lamprey-producing tributaries,

other approaches are required for the remaining lakes. For example, models of Sea Lamprey control have

consistently indicated that repeated treatment of large populations reduces larval Sea Lamprey abundance

over time (Treble 2006; Jones et al. 2008). An application strategy that ensures these populations are

successfully treated would increase the probability of success.

Th e mode of toxic action of TFM and Bayluscide to larval Sea Lampreys is not fully understood (Dawson

2003; Hubert 2003; McDonald and Kolar 2007) but is associated with the inability to detoxify TFM in the

liver (Lech and Statham 1975). Recent research indicates TFM interferes with oxidative ATP production,

which causes death through starvation (Wilkie et al. 2007). Research into the modes of uptake, location of

toxic action, and the physiological detoxification of lampricides in larval Sea Lampreys and teleosts is also

currently in progress. Research results may enable the development of diff erent formulations of lampricides

that retain selective toxicity to larval Sea Lampreys, while reducing eff ects on non-target species.

Alternative Sea Lamprey Control Techniques

In addition to the application of selective lampricides, alternative control techniques have become

increasingly important, as part of an integrated pest management (IPM) approach to Sea Lamprey control.

Th e GLFC originally endorsed an IPM approach during the 1970s (Policy Statement of the GLFC adopted

December 1, 1975, and Guidelines for Barrier Dam Program for Sea Lamprey Control, June 16, 1977; for

details see U.S. Department of the Interior 1978) and further embraced the concept of IPM, based on

recommendations from the proceedings of SLIS I (see Sawyer 1980). During the 1980s, the GLFC commit-

ted to the concept of IPM through development of policy on the integrated management of Sea Lampreys

(IMSL; Sawyer 1980; Davis et al. 1982; Christie and Goddard 2003). Th e IMSL policy allowed development

of alternative controls (both old ideas and new ideas) for use in Sea Lamprey control. To date, three

Michael J. Siefkes et al.666

alternative control techniques have been used, including blocking spawning-phase Sea Lampreys from

reaching spawning grounds using barriers, trapping and removing spawning-phase Sea Lampreys from

the spawning population; and using sterilized spawning-phase male Sea Lampreys to reduce reproductive

potential in isolated spawning populations.

Sea Lamprey Barriers

Th e development and use of Sea Lamprey barriers to reduce recruitment, by limiting the number of tribu-

taries and amount of spawning and larval habitat used by Sea Lampreys, is well documented in the SLIS

I and SLIS II special issues (Hunn and Youngs 1980; Lavis et al. 2003a). During early Sea Lamprey control

eff orts, mechanical and electrical barriers to spawning-phase Sea Lamprey migration and reproduction in

Great Lakes tributaries were the main focus. After the development of lampricides and the recognition that

barriers reduced species richness of native or desirable migratory fishes and their habitats (McLaughlin

et al. 2006), the role of barriers in Sea Lamprey control was diminished. Th e use of barriers, however, is an

eff ective tool to control Sea Lampreys in certain situations, providing an alternative to lampricide control

on tributaries in which physical, chemical, or other constraints made lampricide treatments difficult,

expensive, or ineff ective. Barriers also reduce the number of tributaries needing regular lampricide treat-

ments, saving time, eff ort, lampricide, and money. Because of these benefits, Sea Lamprey barriers will

continue to be part of the Sea Lamprey Control Program.

Mechanical Weirs

Th e first attempts at Sea Lamprey control in the Great Lakes were made by installing mechanical weirs in

tributaries, to block spawning-phase Sea Lampreys from reaching spawning areas. Early designs included

permanent weirs with associated traps to block and capture Sea Lampreys in larger tributaries; screen weirs

and associated traps that were portable to block and capture Sea Lampreys in small and medium-sized

tributaries; barrier dams to block Sea Lampreys; and dams with inclined screen traps to block Sea Lampreys,

but also capture downstream migrating Sea Lampreys that have transformed (Applegate 1950a; Applegate

and Smith 1951a, 1951b; Applegate and Brynildson 1952; Applegate et al. 1952; Hunn and Youngs 1980).

Th e first mechanical weir was constructed during 1944 on the Ocqueoc River, a Lake Huron tributary;

however, the weir was not successful in blocking spawning-phase Sea Lampreys (Shetter 1949). Th e first

successful weir was constructed during 1947 on the Black Mallard River, another tributary to Lake Huron.

Th e Black Mallard River weir was constructed out of steel grating and blocked nearly 100 percent of the

Sea Lamprey run from 1947 to 1949 (Applegate 1950a). During 1948, a weir similar to the Black Mallard

River weir was constructed on the Ocqueoc River and was operational well into the 1950s. In general,

permanent or portable weirs constructed with steel grating and associated traps, such as the Black Mallard

and Ocqueoc weirs, were the best design at the time, achieving some measure of Sea Lamprey control

(Hunn and Youngs 1980), and were constructed in many tributaries to lakes Huron, Michigan, and Superior

during 1950 (Applegate and Smith 1951a).

Although steel-grating mechanical weirs did provide some Sea Lamprey control, they also presented

problems. For instance, the relatively small mesh clogged easily with debris, especially during ice-out,

floods, and other periods with high debris loads causing these weirs to frequently fail (Applegate 1950a).

SEA LAMPREY CONTROL 667

To help prevent the weirs from failing, frequent checks were made to clear the mesh of debris and inspect

the integrity of the weir (Applegate 1950a); however, these frequent checks made the weirs expensive to

operate and maintain. Steel grating weirs also proved to be expensive to build (Hunn and Youngs 1980).

Th ese shortcomings inspired the search for better barrier designs and, eventually, steel-grating weirs

were phased out. Today, very few steel-grating weirs are in operation and are not expected to block 100

percent of the Sea Lamprey run but are used, instead, to direct spawning-phase Sea Lampreys into traps.

Electromechanical Barriers

Experiments began in 1951 to develop barriers that could overcome the deficiencies of the early mechanical

weirs (Hunn and Youngs 1980). Several types of alternating current (AC) electrical barriers have been

described (Applegate et al. 1952; Erkkila et al. 1956; Hunn and Youngs 1980) and were placed in tributaries

to Lake Superior during 1953, to test their usefulness in blocking spawning-phase Sea Lampreys (McLain

et al. 1965). Traps were often installed along with the electrical barriers, but the traps often interrupted the

electrical field, allowing Sea Lampreys to pass through the barrier (Hunn and Youngs 1980). Subsequently,

the fields of electrical barriers that contained traps were modified, and traps were moved downstream to

establish uninterrupted electrical fields from bank to bank that would successfully block all Sea Lampreys.

Th e AC electrical barriers developed proved more cost-eff ective and efficient at blocking Sea Lampreys,

when compared to mechanical weirs, and, by 1960, 162 electrical barriers had been installed in the United

States and Canada (Smith and Tibbles 1980).

Excessive mortality of non-target fishes was a continuous problem associated with early AC electrical

barriers, and, therefore, the electrical fields were modified (Erkkila et al. 1956; see McLain 1957 for a review

of non-target mortality associated with early electrical barriers). Pulsed direct current (DC) was used to

direct fish away from the AC barriers (McLain and Nielsen 1953; McLain 1957; McLain et al. 1965) and was

successful at reducing mortality, but mortality was not eliminated. Eventually, fueled by the development

of selective lampricides (Smith and Tibbles 1980) and the non-target mortality and frequent breakdown

issues associated with the AC electrical barriers, AC electrical barriers were phased-out of the Sea Lamprey

Control Program (Lavis et al. 2003a).

Although the early AC electrical barriers had the potential to block entire runs of Sea Lampreys (McLain

et al. 1965), they probably did not have a significant impact on Sea Lamprey control (Smith and Tibbles

1980). Th e eff ects of the electrical barriers on Sea Lamprey populations were impossible to measure

(McLain et al. 1965), because most were operated for only a short period of time and a complete system

of electrical barriers was never realized within a lake (Hunn and Youngs 1980).

Today, electrical barriers have been all but eliminated from the Sea Lamprey Control Program.

Electrical barriers evolved to use pulsed DC generators and bottom-mounted electrodes to produce an

electrical field perpendicular to the stream flow (Lavis et al. 2003a), and have only been constructed on the

Jordan (Lake Michigan), Pere Marquette (Lake Michigan) and Ocqueoc (Lake Huron) rivers. Th e Jordan

River electrical barrier, built during 1988, only operated for eight years. Failure to block spawning-phase

Sea Lampreys and eliminate the need for lampricide treatments made the Jordan River electrical barrier

no longer cost-eff ective to operate. Th e Pere Marquette River electrical barrier, built during 1988 and

refurbished with a fish passage device during 1999, is still in operation but will likely suff er the same fate

as the Jordan River electrical barrier. Th e Ocqueoc River electrical barrier is actually a hybrid low-head,

Michael J. Siefkes et al.668

fixed-crest, and electrical barrier (built during 1999). Th e hybrid design allows for constructing a smaller-

crested barrier, reducing environmental and economic costs, on systems prone to spring flooding. Th e

Ocqueoc River barrier has been successful at blocking Sea Lampreys, and the design is a model for

tributaries with similar qualities that limit construction of conventional barriers.

Barrier Dams

Much like mechanical weirs and electrical barriers, the use of dams to block spawning-phase Sea Lampreys

was investigated during the infancy of the Sea Lamprey Control Program. During 1951, a wooden low-head

barrier with a steel overhanging “lip” was constructed in the Black River (Lake Michigan), to test its design

in blocking Sea Lampreys; it was operated until 1957 (Applegate and Smith 1951b; Stauff er 1964; Hunn

and Youngs 1980). During 1957, the first low-head barrier to specifically block Sea Lampreys was built in

the Harris River (Lake Huron). Other low-head barrier projects were conducted on Cayuga Lake (Wigley

1959; Webster and Otis 1973). Th ese early low-head barrier studies helped provide valuable information

on the design of low-head barriers for use in Sea Lamprey control, such as minimum crest height during

Sea Lamprey migration and the addition of an overhanging “lip” to the top of the dam (Hunn and Youngs

1980). Almost all purpose-built Sea Lamprey barriers constructed since the 1950s have been of the low-

head, fixed-crest, with an overhanging “lip” design (Lavis et al. 2003a).

Other Sea Lamprey barrier designs have emerged over the years largely to deal with fluctuating water

levels and in response to concerns about the impacts of barriers on non-target fish; however, they are not

often used. Th ese designs include low-head, adjustable-crest barriers, velocity barriers, and hybrid low-

head/electrical barriers (Lavis et al. 2003a). Adjustable-crest barriers have been designed to be manually

or automatically adjusted and to allow crest height to be lowered or the barrier to be removed entirely

when Sea Lampreys are not migrating in the tributary, allowing the passage of non-target fish. Adjustable

designs, however, also increase the chance of spawning-phase Sea Lampreys escaping upstream, which

would negate the benefits of the barrier and not reduce the need for lampricide treatment. A velocity barrier

was constructed on the MacIntyre River (Lake Superior) and was subsequently removed because of its

failure to block Sea Lampreys. Th e water velocity needed to overcome the burst speed of a Sea Lamprey is

likely impractical to achieve (Hunn and Youngs 1980). Low-head, electrical barriers like the one operating

on the Ocqueoc River have shown promise.

Other barriers not constructed primarily to block spawning-phase Sea Lampreys are also important

to Sea Lamprey control. Th ese barriers include the modification of natural waterfalls into permanent

structures that block Sea Lampreys and, more importantly, existing dams originally built for other

purposes (Smith and Tibbles 1980). Th ese dams have been termed de facto Sea Lamprey barriers during

recent years and have presented a unique set of issues for the Sea Lamprey Control Program. Th ere are

literally thousands of existing dams within the Great Lakes basin, and many of these add some value to Sea

Lamprey control. Th ere has not been a thorough inventory of these dams, so identifying and tracking the

condition of those that are critical to Sea Lamprey control has been difficult. A database that will identify

all dams important to Sea Lamprey control within the Great Lakes basin is currently under construction.

As important dams age and begin to fail and support for dam removals to create free-flowing lotic systems

and promote access for fish to upstream habitats grow (McLaughlin et al. 2007), the barrier database will

be critical in identifying situations that would jeopardize Sea Lamprey control.

SEA LAMPREY CONTROL 669

Th e eff ects of Sea Lamprey barriers on stream habitats and non-target fish species has always been an

issue for the Sea Lamprey Control Program. Although few studies have been published on the impacts of

low-head Sea Lamprey barriers to the biological integrity of river systems (Lavis et al. 2003a), the impacts

are typically less than their larger counterparts, because crest heights are rarely high enough to significantly

impound water behind them. Impacts can, however, be significant for non-jumping fish species (Dodd

1999; Porto et al. 1999; Noakes et al. 2000). Th e Sea Lamprey Control Program has adopted barrier designs to

minimize the eff ects to non-target species. For example, the crest heights used in low-head barrier designs

easily allow the passage of jumping fish. Jumping pools are also often constructed with these structures to

assist in jumping fish passage. In addition, adjustable crest designs can be removed when spawning-phase

Sea Lampreys are not migrating, allowing the passage of all fish. Furthermore, experiments with other

means of fish passage, such as fish ladders and vertical slot, trap-and-sort fishways, are being conducted.

Barrier Policy

Th e use of barriers in Sea Lamprey control pre-dates the formation of the GLFC and was the main focus

of the Sea Lamprey Control Program until selective lampricides were developed for wide-scale use. Even

with the shift to lampricides, the GLFC endorsed the continued use of barriers in the Sea Lamprey Control

Program as an alternative control method. Th e GLFC, however, did not formalize a barrier program until

the late 1970s. Prior to the formation of the GLFC barrier program, federal, state and provincial entities

were largely responsible for the construction of Sea Lamprey barriers (Lavis et al. 2003a).

During 1971, the GLFC recommended the formation of barrier task forces in the United States and

Canada that would plan construction and integrate barriers into the Sea Lamprey Control Program (GLFC

1973). Th ese task forces produced a rank list of Sea Lamprey-producing tributaries for the installation of

barriers based on several criteria, including larval Sea Lamprey population size, lampricide treatment

cost and eff ectiveness, and eff ects of lampricide application on non-target species (Lavis et al. 2003a). By

1975, the GLFC fully recognized the usefulness of barriers and adopted a policy statement that officially

established the GLFC barrier program and encouraged federal, state, and provincial governments and the

GLFC to cooperate in the installation of barriers (Lavis et al. 2003a). Funds were first allocated specifically

for the Sea Lamprey barrier program beginning in 1978, and three barriers were constructed by 1979.

During the next three decades, the importance of the barrier program cycled. Th e Sea Lamprey bar-

rier program gained momentum during SLIS I, with the continued emphasis on an IPM approach to Sea

Lamprey control (Sawyer 1980) and the indication that barrier construction costs could be decreased,

because the crest height needed to block spawning-phase Sea Lampreys was shown to be lower than

expected (Hunn and Youngs 1980). Th e momentum gained during SLIS fueled the construction of thirty-

one Sea Lamprey barriers between 1980 and 1989 (Lavis et al. 2003a). Barrier construction waned during

the early 1990s, mostly because the escalating costs of lampricides required much of the Sea Lamprey

control budget and only two Sea Lamprey barriers were built, both in Canadian tributaries, from 1990 to

1993 (Lavis et al. 2003a). Th e barrier program experienced a renaissance during 1993, with the publication

of the GLFC vision, which stated barriers would be used to help reduce lampricide use by 50 percent of

1980 levels by the year 2000 (GLFC 1992). Th e new vision allowed the United States and Canada to hire

full-time barrier coordinators to formulate a unified, basin-wide barrier program (Lavis et al. 2003a). From

1994 to 1998, the GLFC investment in the barrier program increased more than three-fold, the U.S. Army

Michael J. Siefkes et al.670

Corp of Engineers became a valuable partner in the construction of Sea Lamprey barriers, and sixteen

barriers were constructed (eight in the United States and eight in Canada; Lavis et al. 2003a). Th e revival

of the barrier program continued during the late 1990s and early 2000s, with the development of standard

operating procedures and recommendations on ways to expand and accelerate the barrier program (Millar

et al. 2000) and with the GLFC’s intent to use alternatives to lampricide treatments for at least 50 percent

of Sea Lamprey suppression by 2010 (Christie and Goddard 2003); however, barrier construction never

returned to levels achieved during the 1980s and 1990s (from 1998 to 2008, only ten new or replacement

barriers were constructed). Presently, the barrier program has still not regained momentum because of

increasing concerns regarding the environmental impact of barriers and difficulties in gaining landowner

cooperation and acquiring real estate for barrier projects. Instead, the focus of the barrier program has

shifted to the inventory, maintenance, and replacement of the many de facto Sea Lamprey barriers

important to the Sea Lamprey Control Program.

The Future of Sea Lamprey Barriers

Th e GLFC is still focused on delivering an integrated Sea Lamprey Control Program, and barriers are still

the only eff ective alternative to lampricide control (Lavis et al. 2003a; see fig. 4 for the location of Sea

Lamprey barriers). Future policy on barriers needs to continue educating the public about the value of Sea

Lamprey barriers and encourage landowner participation in barrier projects. Also, new or replacement

barrier projects will likely only be constructed on lands owned by corporations or governments or on

private lands that have full landowner cooperation. In addition, barriers will not be constructed where

the biological integrity of a tributary would be damaged beyond the benefits provided by the barrier.

Furthermore, the barrier program will continue to focus on inventory, maintenance, and replacement

of de facto Sea Lamprey barriers and fish passage research, both of which will be particularly important

in the cases of aging dams on rivers with huge Sea Lamprey production capability, such as rivers like the

Black Sturgeon (Lake Superior), Manistique (Lake Michigan), and Saugeen (Lake Huron).

Fish passage and human safety are issues for the future use of barriers in the Sea Lamprey Control

Program. Research is ongoing to develop the most eff ective Sea Lamprey barrier, while mitigating safety and

fish passage issues (McLaughlin et al. 2003). Current Sea Lamprey barriers employing trap-and-sort fishways

have been shown to have an attraction rate of 80 percent for tagged fish but a highly variable passage rate of

the attracted fish (Pratt et al. 2009). Fish passage success has been correlated with consistency of attractant

flow from the trap, fish retention once in the trap, timing of operation of the fishway, and crest height of

the barrier (Lavis et al. 2003a; Klingler et al. 2003; McLaughlin et al. 2007; Pratt et al. 2009). McLaughlin

et al. (2007) identified thirteen topics by which additional information could improve the eff ectiveness of

barriers, while reducing the non-target eff ects and safety issues surrounding barriers, including placement

of barriers and traps within tributaries, retention of all fish species once trapped, and alternate designs for

barriers, traps, and fishways that can selectively remove migrating spawning-phase Sea Lampreys.

Sea Lamprey Traps

During the early years of the Sea Lamprey Control Program, several methods were used to capture

spawning-phase Sea Lampreys in tributaries as they migrated upstream to spawn. Dip nets (Applegate

SEA LAMPREY CONTROL 671

and Smith 1951b), gill and trap nets (Smith and Elliot 1953), wooden-framed traps and barrier nets (Wigley

1959), and traps associated with mechanical weirs and electrical barriers (McLain et al. 1965) were all

used to capture Sea Lampreys, by exploiting their strong innate migratory drive. In all cases, capturing Sea

Lampreys worked best when the trapping device was associated with a barrier; barriers concentrate Sea

Lampreys in a relatively small area and increase the chance they will repeatedly interact with the trapping

device, thus, increasing the probability of capture.

Th e incorporation of two technological advances helped make spawning-phase Sea Lamprey trapping

more cost-eff ective. Th e first was the incorporation of an easy to operate and maintain portable trap placed

below natural Sea Lamprey barriers or dams (Schuldt and Heinrich 1982). Th e second was to strategi-

cally integrate a permanent trap or traps into existing barriers or to design new barriers with permanent

barrier-integrated traps. Barrier-integrated traps consist of a concrete vault with a trap insert that can be

lifted for easy servicing. Th ese two designs require less maintenance and can be operated by smaller crews.

Trapping for Sea Lamprey Population Assessment

Although significant numbers of spawning-phase Sea Lampreys could be captured using traps, control

agents quickly learned trapping methods were expensive to operate (Schuldt and Heinrich 1982),

inefficient, and could not remove enough Sea Lampreys from the spawning population to reduce reproduc-

tive potential and, therefore, were not likely to become a viable control method using existing technologies.

Trapping Sea Lampreys did, however, provide a means of assessing populations through calculations of

relative abundance and, thus, success of the Sea Lamprey Control Program.

Since the late 1970s and early 1980s, spawning-phase Sea Lamprey populations have been assessed

using traps in all of the Great Lakes (Mullett et al. 2003 and reference therein; fig. 5). Population estimates

on some tributaries with barriers are determined through mark-recapture methods, using a modified

Schaefer (1951) estimate. Mark-recapture studies cannot be conducted in all trapped tributaries because

of funding constraints. Th erefore, in trapped tributaries, but without mark and recapture data, trap catch

can be an indicator of Sea Lamprey abundance, if trapping operations are held constant from year to year.

In untrapped tributaries, a model was developed to generate Sea Lamprey abundance estimates. Th e

model uses five independent variables: drainage area, geographic region, larval Sea Lamprey production

potential, number of years since last lampricide treatment, and spawning year. For each lake, abundance

estimates for each Sea Lamprey-producing tributary are summed to generate a lake-wide spawning-phase

Sea Lamprey abundance estimate, which is used as the primary metric to assess Sea Lamprey Control

Program success.

Trapping for Sea Lamprey Control

Trapping spawning-phase Sea Lampreys is currently only considered a control strategy in the St. Marys

River. Th e St. Marys River, which connects lakes Superior and Huron, has unique characteristics that

make it impractical to treat with TFM (Schleen et al. 2003). As an alternative to TFM treatments, an IPM

approach consisting of trapping sterile-male releases and selective Bayluscide treatments was developed.

Trapping Sea Lampreys from Great Lakes tributaries provides male Sea Lampreys for sterilization and

release into the St. Marys River. Trapping Sea Lampreys from the St. Marys River removes viable individuals

FIG. 4. Location of tributaries with Sea

Lamprey (Petromyzon marinus) barriers.

Great Lakes Fishery Commission.

FIG. 5. Location of tributaries with Sea

Lamprey (Petromyzon marinus) traps.

Great Lakes Fishery Commission.

Michael J. Siefkes et al.676

from the population and provides more male Sea Lampreys to be sterilized and released back to the river.

Th e combination of trapping sterile-male releases and selective Bayluscide treatment has reduced the

reproductive potential of the river about 90 percent. Finally, trapping Sea Lampreys also provides research

and educational specimens to individuals and institutions across Canada and the United States.

The Future of Sea Lamprey Trapping

McLaughlin et al. (2007) details further development of spawning-phase Sea Lamprey trapping. Current

research relevant to trapping has focused on better understanding Sea Lamprey behavior, both in the

context of the physical environments of tributaries and of reproductive pheromones, and will provide

exploitable information to enhance trapping by taking advantage of Sea Lamprey behavior. In addition,

alternative trapping methods are also being developed to capture Sea Lampreys in larger tributaries, where

conventional trapping methods are difficult to conduct, as well as methods that function independent of

Sea Lamprey barriers and capture transforming Sea Lampreys as they migrated downstream to the lakes.

Current research will provide better population assessment, turn trapping into a viable control strategy

in tributaries outside of the St. Marys River, and better integrate trapping with other control techniques.

Trapping spawning-phase Sea Lampreys to generate abundance estimates in tributaries, and, ulti-

mately, lake-wide abundance estimates, evaluate the entire Sea Lamprey Control Program. Th e trapping

program was reviewed by an expert panel during 1998, and several recommendations for improving the

accuracy, precision, and value were made. One recommendation was to improve trapping on large rivers.

Trapping is easier on smaller tributaries, and, therefore, the Sea Lamprey abundance model (Mullett et al.

2003) is largely based on information from these small systems. Th e model would be improved, if more data

from larger tributaries and other data sources, such as parasitic-phase abundance, could be incorporated

into the model (Jones 2007).

Th e precision of mark-recapture estimates could be improved, if trapping efficiency were increased.

Progress on the current behavior and alternative trapping research should provide means to increase

trapping efficiency. Not only will trapping research increase the precision of spawning-phase Sea Lamprey

abundance estimates, and, ultimately, measures of program success, it should also improve the eff ective-

ness of using trapping as a control strategy through physical removal of a greater number of Sea Lampreys

from trapped tributaries. Recent technologies, such as radio and acoustic telemetry and passive integrated

transponder systems, provide unique tools for current and future research.

Sterile-Male-Release Technique

Th e sterile-male-release technique, as proposed during 1937 by Knipling (1968), is a method of reproduc-

tive suppression to control pest species. Sterilized males are released to “over-flood” the wild population

of males and to cause the wild population of females to waste their reproductive potential. Reproduction

of the pest is reduced in proportion to the prevalence of sterile to untreated males in the population.

Sterilized males must exhibit sufficient sexual vigor to compete for mates and engage in normal mating

behaviors. Th e technique was first used to eradicate the Screwworm Fly (Cochliomyia hominivorax) from

the West Indies island of Curacao during 1954 (Baumhover 1966). Since then, the technique has been used

worldwide to manage or eradicate many pest insect species (Klassen and Curtis 2005).

SEA LAMPREY CONTROL 677

Investigations to find an eff ective means of sterilizing spawning-phase Sea Lampreys began during the

early 1970s at the Hammond Bay Biological Station, Millersburg, Michigan. Laboratory tests showed that P,

P-bis (1-aziridinyl)-N-methylphosphinothioic amide (Bisazir; Chang et al. 1970) was the most promising

of fourteen potential chemosterilants to test on Sea Lamprey in the field (Hanson and Manion 1978).

Field tests were conducted in the Big Garlic River near Marquette, Michigan (Hanson and Manion 1978,

1980; Hanson 1981). Sterile and untreated male Sea Lampreys were introduced in various combinations

in barrier-divided sections of the river, and mating and egg survival were observed. Th e tests confirmed

that Bisazir-treated male Sea Lampreys were sterile and behaved normally; they made nests, competed for

mates, and mated with female Sea Lampreys in a normal manner. Larval production in the study tributary

was reduced to near the expected rate. Th e investigations also suggested that Bisazir was an eff ective steril-

ant for female Sea Lampreys, but the result was not conclusive and sterilization of female Sea Lampreys

was not pursued at that time. Other methods of sterilization were also investigated, in part, because of the

human health concerns working with chemosterilants like Bisazir (Borkovec 1972; Rudrama and Reddy

1985; Hanson 1990), but few methods showed promise and none were as eff ective as Bisazir (Hanson 1990).

A specialized facility for sterilizing spawning-phase male Sea Lampreys was constructed at the Ham-

mond Bay Biological Station during 1990 (Twohey et al. 2003a) because of the station’s proximity to major

sources of male Sea Lampreys, a good source of water, waste treatment facilities, electrical power needs,

and technical and analytical support. Th e new facility was designed to sterilize approximately 1,400 male

Sea Lampreys per day and contain the toxic and mutagenic hazards of Bisazir. Th e facility was designed

to hold Sea Lampreys for forty-eight hours after treatment, after which Bisazir does not persist in tissues

(Allen and Dawson 1987). Inside the facility, a unique computer controlled robotics device designed to

administer Bisazir to male Sea Lampreys was installed (Twohey et al. 2003a). Th e device minimized the

risk of Bisazir exposure to personnel and assured accurate dosage administration. Th e device calculated

the proper amount of Bisazir based on weight (100 mg/kg), determined the injection position based on

length (40 percent of body length from head), and administered the Bisazir by inter-peritoneal injection

in an enclosed chamber to protect personnel.

Sources of Male Sea Lampreys

Spawning-phase male Sea Lampreys were captured for sterilization from a network of traps operated in

spawning tributaries in the United States and Canada (Mullett et al. 2003; Twohey et al. 2003a). From 1991

to 1996, an average of twenty-six thousand (range nineteen thousand to thirty-six thousand) male Sea

Lampreys were collected for sterilization from seven tributaries that had ongoing assessment trapping

operations in northern lakes Huron and Michigan. Th e network of traps supplying male Sea Lampreys for

sterilization has expanded to include twenty-four tributaries across four Great Lakes (i.e., lakes Superior,

Michigan, Huron, and Ontario). Male Sea Lampreys were transported to the sterilization facility from as far

as 750 km (Duffins Creek, Ontario). Augmenting the supply of male Sea Lampreys for the technique using

Lake Champlain, Finger Lakes, or Atlantic origin Sea Lampreys was considered, but concerns regarding

Th e discovery, during 2000, of heterosporis, a microsporidian parasite, in Lake Ontario prompted a recom-

mendation by the Great Lakes Fish Health Committee to screen all spawning-phase Sea Lamprey transfers

destined for the Upper Great Lakes. Transfers and screening began in 2003 and followed the American

Fisheries Society blue book protocols (AFS-FHS 2004) and included all restricted pathogens, including viral

Michael J. Siefkes et al.678

hemorrhagic septicemia virus (VHSv). Neither heterosporis nor VHSv, nor any other pathogen that would

preclude transfer from Lake Ontario has been found. Sea Lampreys can harbor a number of pathogens,

including bacterial kidney disease, furunculosis, and enteric redmouth, but these pathogens found in

Sea Lampreys from Lake Ontario have been of strains common in other fishes in the upper Great Lakes.

Sea Lampreys were not screened prior to transfer among the upper three lakes, because these are open

systems among which Sea Lampreys move freely.

Lake Superior Releases

Lake Superior was selected as an experimental site to implement the sterile-male-release technique from

1991 to 1996, because it met the basic criteria set forth by the sterile-male-release technique task force: low

numbers of spawning-phase Sea Lampreys, isolation from other Sea Lamprey populations, and potential

for evaluation of the eff ects of the technique on Sea Lamprey and fish populations. An in-stream release

strategy was implemented during 1991 (Kaye et al. 2003; Twohey et al. 2003a). From 1991 to 1996, an

average of 16,100 sterilized male Sea Lampreys were release into thirty-three Lake Superior tributaries

(Twohey et al. 2003a), achieving an average ratio of 1.5:1 sterile to untreated male Sea Lampreys. Th e

logistics of capturing, sterilizing, and releasing Sea Lampreys was a success. Behavioral observations

indicated sterilized male Sea Lampreys appeared on nests at near the expected ratios, mated normally, and

reduced production of larvae from nests (Bergstedt et al. 2003b). Other indices were not as encouraging.

Th e mean relative abundance of Sea Lampreys in the lake increased from the previous ten years (Heinrich

et al. 2003). Changes in Sea Lamprey wounding rate estimates on Lake Trout did not decline as expected

during 1998 or 1999. In retrospect, the number of sterilized male Sea Lampreys available for release in

Lake Superior was not adequate for sufficient change to be observed against the backdrop of independent

population variation and other management actions in the system (Twohey et al. 2003a).

St. Marys River Releases

Th e St. Marys River was initially selected for the sterile-male release technique, because a growing larval

population in the river defied lampricide control tactics, using TFM (Schleen et al. 2003), and the technique

off ered a possible solution. Also, male spawning-phase Sea Lampreys collected from the extremely late

run in the St. Marys River could not be used for sterile-male releases elsewhere. Sterile-male releases into

the St. Marys River from 1991 to 1996 primarily relied on male Sea Lampreys captured from only the St.

Marys River. An average of 4,600 sterile-males were released into the St Mary’s River, achieving an average

ratio of 0.6:1 sterile to untreated male spawning-phase Sea Lampreys (Twohey et al. 2003a). Th e eff ective

number of spawning pairs in the river was reduced from an annual average of 11,100 to 5,000.

Sterile-male releases into the St. Marys River were enhanced during 1997, as part of a two-pronged

strategy to reduce Sea Lamprey recruitment from the river. Traps and sterile-males were used to reduce

reproduction, and Bayluscide was used to spot treat high density concentrations of larvae (Schleen et

al. 2003). From 1997 to 2009, traps removed an average of 40 percent of the spawning population in the

river. Th e average number of sterile-males released annually was 27,000. An average ratio of 3.7:1 sterile

to untreated male spawning-phase Sea Lampreys was achieved. Th e eff ective number of spawning pairs

in the river was further reduced to 1,100. Key indices showed the integrated control strategy for the St.

SEA LAMPREY CONTROL 679

Marys River was working, as measures of larval populations, transformers, spawning-phase populations,

and Sea Lamprey wounding and mortality on Lake Trout were consistently lower since inception of the

strategy (Bergstedt and Twohey 2007).

The Future of the Sterile-Male-Release Technique

Bergstedt and Twohey (2007) details further development of the sterile-male-release technique. Greater

use of the sterile-male-release technique in Sea Lamprey control is limited by the supply of male

spawning-phase Sea Lampreys. Th e harvest of male Sea Lampreys is inherently limited, because the Sea

Lamprey Control Program is actively treating the population from which male Sea Lampreys are obtained.

Male Sea Lampreys captured outside the basin could supplement male Sea Lampreys from the Great

Lakes and could increase the eff ectiveness of the sterile-male-release technique, particularly when Sea

Lamprey population levels in the Great Lakes are greatly reduced. In addition, modest improvements

in trapping would increase eff ectiveness of sterile-male release. Removal of more female Sea Lampreys

from the treated population would further reduce reproductive potential, and removal of more male Sea

Lampreys would further reduce male competitors and provide more male Sea Lampreys for sterilization.

Better understanding of Sea Lamprey behavior and new trapping technologies are being pursued. Also,

advances in pheromone technology (Twohey et al. 2003b; Li et al. 2007) may provide a boost to trapping

eff ectiveness. Pheromones integrated with eff ective traps would be a powerful advancement of the

sterile-male-release technique.

Bisazir is a hazard to human health, during the injection and holding period prior to release of

the sterilized male spawning-phase Sea Lampreys. Further development of the handling and release

portion of the program depends on the development of a safer sterilant, and is particularly important

if the ability to trap, inject, and release a greater number of male Sea Lampreys can be realized. Th e

release of additional sterilized male Sea Lampreys into the St. Marys River, however, carries another

set of questions about the response of the Sea Lamprey population to an excess of male Sea Lampreys

(Bergstedt and Twohey 2007). Would mate selection become more sensitive toward non-sterilized male

Sea Lampreys? Could sterilized male Sea Lampreys be made more competitive or attractive, providing

greater reduction in reproduction per sterilized male Sea Lamprey released? Answers to these questions

will help determine the cost-eff ectiveness of increasing the number of sterilized male Sea Lampreys

released into the St. Marys River.

Research that may expand the use of Bisazir-sterilization in the Sea Lamprey Control Program is

underway. Studies are being conducted to determine if female spawning-phase Sea Lampreys can be

sterilized and eff ectively compete for mates and if their release will result in reduced larval recruitment.

An abundance of female Sea Lampreys are available for sterilization, if that technique proves useful.

Finally, recent work by Jones et al. (2003) indicates that density independent variation can mask benefits

of reproductive suppression, except when spawning stocks are very low. Better understanding of Sea

Lamprey population dynamics will allow the prediction of eff ects of techniques to reduce reproduction

and to set suppression targets with greater confidence.

Th e sterile-male-release technique is an integral part of the control strategy for the St. Marys River,

along with trapping and the treatment of larval populations with granular Bayluscide. Th e eff ect of any

individual component of the control program on the reduction of spawning-phase Sea Lampreys from the

Michael J. Siefkes et al.680

river cannot be determined from the available data, although modeling analysis indicates all three tactics

play a role (Haeseker et al. 2003). A direct method of evaluating the eff ectiveness of the sterile-male-release

technique is required.

Status of Sea Lamprey Control in Each Lake

Each of the Great Lakes diff ers in the number and size of Sea Lamprey-infested areas, as well as Sea

Lamprey production and growth. Each infested area also varies in how eff ectively it can be treated with

lampricides or alternative Sea Lamprey control techniques. Th ese variables create unique situations in

each lake and can sometimes aff ect adjoining lakes.

Sea Lamprey Control Program success is primarily measured by comparing annual estimates of

lake-wide spawning-phase Sea Lamprey abundance with lake-specific targets. For each of the Great

Lakes, spawning-phase Sea Lamprey targets are prescribed in fish community objectives or in Lake Trout

rehabilitation plans developed by each lake committee. Sea Lamprey targets, approved by the fishery

management agencies, vary by lake and equal the mean abundance during a five-year period when Sea

Lamprey wounding rates on Lake Trout were lowest in all the lakes, except Huron. In Lake Huron, the

target is one-quarter of the mean abundance from 1992 to 1996 (the highest five-year mean abundance

of the time series). Progress toward Sea Lamprey targets is measured against the estimates of lake-wide

abundance (Mullett et al. 2003). Sea Lamprey targets have been met on each of the Great Lakes; unfortu-

nately, never on all the lakes at the same time. Measures of Sea Lamprey abundance are highly variable,

so that a reduction (or increase) observed in a given lake during a given one- or two-year span may be

fleeting (e.g. Lake Huron 1987 and 2003). Low Sea Lamprey abundance observed over a longer duration,

such as a five-year span, would indicate successful Sea Lamprey control.

A second metric of Sea Lamprey Control Program success is an annual measure of fresh Sea Lamprey

wounds (King 1980; fig.6) per one hundred Lake Trout longer than 533 mm (age 5 Lake Trout in Lake

Erie and Lake Trout longer than 433 mm in Lake Ontario) captured by the fishery management agencies

during standardized gill-net surveys. Wounding rate estimates are reflective of the number of Sea Lam-

preys that escape Sea Lamprey control activities each year and are an indicator of Sea Lamprey-induced

mortality on Lake Trout. Nevertheless, although there is a positive relationship between wounding rate

and spawning-phase Sea Lamprey abundance among years, the relationship is quite variable, indicating

there are other factors that influence these measures of program success. In addition, the Sea Lamprey

is not a species-specific parasite, and, although it prefers large-bodied, cold water species, such as Lake

Trout, it is opportunistic in its feeding habits (Farmer and Beamish 1973; Harvey et al. 2008), preying on

warm water species and lower trophic level species in areas, such as Lake Superior’s Black Bay, where Lake

Trout abundance is very low. Nevertheless, a target of five wounds per one hundred Lake Trout, which was

selected to ensure that sufficient numbers of mature fish survive to enable natural reproduction, is applied

in all the lakes, except Ontario, where a target of two Sea Lamprey wounds per one hundred Lake Trout

was selected. Th e diff erent wounding rate target used in Lake Ontario is thought to be a better estimate for

that system (Schneider et al. 1996). Rutter and Bence (2003) have identified limitations with this approach,

specifically the failure to recognize spatial and temporal patterns in wounding and the predictability

between the number of wounds and host length. Interpretation of wounding rates may also be subject to

bias resulting from seasonal diff erences in the timing of the gill-net surveys (Spangler et al.1980), which are

SEA LAMPREY CONTROL 681

conducted on lakes Superior and Michigan during spring, on lakes Huron and Ontario during fall, and on

Lake Erie during late summer. Regardless of the method, wounding rate is only relevant when considered

in the context of Lake Trout abundance, as one would expect an inverse relationship between Sea Lamprey

wounding rate on Lake Trout and Lake Trout abundance, if the Sea Lamprey population is held static.

Finally, program success can also be measured at the individual tributary level, through the post-

treatment assessment of the relative abundance of Sea Lamprey larvae that survive lampricide treatment.

Lampricide application is estimated to kill 95–99 percent of the Sea Lamprey larvae within a tributary

(Heinrich et al. 2003). Treatment eff ectiveness can, however, vary both among tributaries and within

tributaries over successive years of lampricide treatment because of fluctuations in water chemistry, influx

of water from ground water exchange or from a rain event, or from reduced flows aff ecting distribution of

lampricide within the tributary. Although post-treatment assessment cannot detect minor diff erences in

treatment eff ectiveness because of the uncertainty in larval relative abundance estimates, a large reduction

in treatment eff ectiveness will likely be detected.

Lake Superior

Sea Lamprey production has been recorded in 148 of 1,566 tributaries to Lake Superior (Heinrich et al.

2003; Young and Adair 2008). Of these, 84 have been treated with lampricides at least once since 1998, and

53 require treatment on a regular cycle. Lampricide control in Lake Superior also includes the application

FIG. 6. A Sea Lamprey (Petromyzon marinus) wound on a Lake Trout (Salvelinus namaycush).

W. P. Sullivan.

Michael J. Siefkes et al.682

of the Bayluscide granules to lentic areas associated with Sea Lamprey-producing tributaries. Although

not unique to Lake Superior, this lake has the majority of these lentic Sea Lamprey populations, and

only the St. Marys River has a higher abundance of Sea Lampreys treated with Bayluscide granules. In

addition, Sea Lamprey barriers on 15 tributaries (Young and Adair 2008) complement the lampricide

control program in Lake Superior. Spawning-phase Sea Lamprey are also trapped in 22 tributaries

for population assessment purposes and to provide male Sea Lampreys for the sterile-male-release

technique in the St. Marys River.

Lake-wide spawning-phase Sea Lamprey abundance has remained at a level less than 10 percent of

peak abundance (Heinrich et al. 2003; fig. 7a). Sea Lamprey abundance was near the target during the late

1980s and mid-1990s and reached the lowest recorded level during 1994. Sea Lamprey abundance trended

upward between 1994 and 2001, but has been trending downward since then and was below the target

during the most recent years (2008 and 2009). Th e 2009 Sea Lamprey abundance estimate is twenty-seven

thousand, which is under the target of thirty-six thousand, but only continued suppression for at least a

five-year period will indicate successful Sea Lamprey control.

Sea Lamprey wounds per one hundred Lake Trout longer than 533 mm have not shown the same

pattern of decrease, but recent wounding rate estimates have declined (fig. 7b). Th e lake-wide wounding

rate estimate, most recently at nine, is above the target of five wounds per one hundred Lake Trout and has

been increasing since 1994. Lake Trout abundance had been holding steady but appears to be increasing

during recent years (fig. 7c), which could account for the recent decline in the wounding rate estimates.

Th e wounding rate estimate seems highest in the western portion of the lake but has recently declined in

Minnesota waters. Th e wounding rate estimate in Michigan waters indicates Sea Lamprey-induced mortal-

ity on Lake Trout exceeds fishery-induced mortality, but fishery induced-mortality is low in Michigan

waters. Overall, fishery objectives for Lake Trout continue to be met, but Lake Trout populations are still

threatened by high Sea Lamprey-induced mortality.

In response to lake-wide spawning-phase Sea Lamprey abundance and wounding rate estimates above

targets, increased lampricide control eff orts were initiated during 2001 and then further increased during

2006. Th e recent decline of Sea Lamprey abundance to below the target is likely the result of the most

recent increases in lampricide control eff ort initiated during 2006. Sea Lamprey abundance is expected to

remain near the target during future years, and the upward trend in wounding rate estimates is expected

to reverse as increased lampricide control eff orts are maintained.

Lake Michigan

Sea Lamprey production has been recorded in 121 of 511 tributaries to Lake Michigan (Young and Adair

2008). Of these, 72 have been treated with lampricides at least once since 1998 and 34 require treatment

on a regular three- to five-year cycle. Lampricide control in Lake Michigan also includes the application of

Bayluscide granules to lentic areas associated with Sea Lamprey-producing tributaries. Lentic Sea Lamprey

populations in Lake Michigan, however, are not as problematic as in Lakes Superior and Huron. In addition,

Sea Lamprey barriers on 11 tributaries complement the lampricide control program. Spawning-phase Sea

Lampreys are also trapped in 16 tributaries for population assessment purposes and to provide male Sea

Lampreys for the sterile-male-release technique. Sea Lamprey control eff orts in Lake Huron also influence

Lake Michigan, as Sea Lampreys are known to move between lakes Michigan and Huron (Moore et al.

FIG. 7. Status of Sea Lamprey

(Petromyzon marinus) control

in Lake Superior: (A) lake-wide

spawning-phase Sea Lamprey

abundance estimates (line with

diamonds) compared to the

target (black horizontal line);

(B) lake-wide Sea Lamprey

wounding rate per one

hundred Lake Trout (Salvelinus

namaycush; line with circles)

longer than 533 mm compared

to the five-wound target (black

horizontal line); and (C)

lake-wide Lake Trout relative

abundance (CPE = fish/km/net

night of lean Lake Trout longer

than 533 mm; line with cubes).

Great Lakes Fishery Commission

Spaw

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Michael J. Siefkes et al.684

1974; Bergstedt et al. 2003a), and Sea Lampreys produced from northern Lake Huron, particularly from

the St. Marys River, significantly contribute to the Lake Michigan population.

Lake-wide spawning-phase Sea Lamprey abundance is at about 10 percent of peak levels, but has

been trending upward since 1980 (Lavis et al. 2003b) and has fluctuated greatly since 2003, with sharp

increases observed during 2004, 2006, and 2007 and sharp decreases during 2005, 2008, and 2009 (fig.

8a). Sea Lamprey abundance (sixty-thousand) was below the target (sixty-two thousand) during the

most recent year (2009), but only continued suppression to target levels for at least a five-year period will

indicate successful Sea Lamprey control.

Sea Lamprey wounds per one hundred Lake Trout longer than 533 mm has also shown an upward

trend (fig. 8b), and the most recent wounding rate estimate (thirteen) is above the lake-wide target of

five wounds per one hundred Lake Trout. Lake Trout abundance appears to be holding steady (fig.

8c), but declining abundance of larger Lake Trout may be contributing to increasing wounding rate

estimates. Increased Sea Lamprey-induced mortality on Lake Trout in the northern waters has set Lake

Trout restoration eff orts back at least a decade. Furthermore, increased Sea Lamprey-induced mortal-

ity is aff ecting the quota for the commercial fishery to the extent that components of the Lake Trout

management regimen in the consent decree between the tribes, the state, and the federal government

are currently suspended. Achievement of Lake Trout rehabilitation will continue to be hampered, if Sea

Lamprey-induced mortality remains high.

Increases in the spawning-phase Sea Lamprey abundance and wounding rate estimates during the

1990s can be partially attributed to Sea Lamprey production from the St. Marys River. In response, an

integrated control strategy was initiated in the St. Marys River (Schleen et al. 2003). Th e continued upward

trend in Sea Lamprey abundance and wounding rate estimates during the late 1990s and early 2000s

indicated there were other significant sources of Sea Lampreys. Increased lampricide control eff orts were

initiated during 2001 and included the treatment of newly discovered larval Sea Lamprey populations in

lentic areas and the Manistique River, a large system in which the deterioration of a dam near the river

mouth allowed Sea Lampreys access to more than 400 km of river. Lampricide control eff orts were further

increased during 2006. Th e recent decline of Sea Lamprey abundance to the target is likely a result of

increased lampricide control eff orts and lampricide treatments in the Manistique River during 2003, 2004,

2007, and 2009. Sea Lamprey abundance is expected to remain near the target during future years, and

the upward trend in the wounding rate estimates is expected to reverse as increased lampricide control

eff orts are maintained and the barrier on the Manistique River is replaced.

Lake Huron

Sea Lamprey production has been recorded in 117 of 1,761 tributaries to Lake Huron (Young and Adair

2008). Of these, 71 have been treated with lampricide at least once since 1998 and 45 require treatment

on at a regular four- to six-year cycle. Lampricide control in Lake Huron also includes the application of

Bayluscide granules to lentic areas associated with Sea Lamprey-producing tributaries and the St. Marys

River, which has the highest abundance of larval Sea Lampreys treated with Bayluscide granules. In

addition, Sea Lamprey barriers on 19 tributaries complement the lampricide control program, and the

sterile-male-release technique is a component of the integrated Sea Lamprey control strategy in the St.

Marys River. Spawning-phase Sea Lampreys are also trapped in 21 tributaries for population assessment

FIG. 8. Status of Sea Lamprey

(Petromyzon marinus) control

in Lake Michigan: (A) lake-wide

spawning-phase Sea Lamprey

abundance estimates (line with

diamonds) compared to the

target (black horizontal line);

(B) lake-wide Sea Lamprey

wounding rate per one

hundred Lake Trout (Salvelinus

namaycush; line with circles)

longer than 533 mm compared

to the five-wound target (black

horizontal line); and (C)

lake-wide Lake Trout relative

abundance (CPE = fish/km/net

night of lean Lake Trout longer

than 533 mm; line with cubes).

Great Lakes Fishery Commission

Spaw

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(tho

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Sea

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Abu

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Michael J. Siefkes et al.686

purposes and to provide male Sea Lampreys for the sterile-male-release technique, and trapping in the

St. Marys River is a component of the integrated control strategy. Sea Lamprey control eff orts in Lake

Michigan also influence Lake Huron, as Sea Lampreys from northern Lake Michigan tributaries, such as

the Manistique River, contribute to the Lake Huron population.

Lake-wide spawning-phase Sea Lamprey abundance has remained at a level less than 10 percent of

peak abundance (Morse et al. 2003; fig. 9a). During the early 1980s, Sea Lamprey abundance increased

from the target, particularly in the northern portion of the lake, and peaked during 1993. Sea Lamprey

abundance has not declined to target in Lake Huron for more than twenty-five years. Th e 2009 Sea Lamprey

abundance estimate is 122,000, which is above the target of 73,000.

Sea Lamprey wounds also have not decreased to the lake-wide target of five wounds per one hundred

Lake Trout longer than 533 mm, but significant declines occurred during the mid-1990s and wounding

rate estimates have been at a relatively low level since 2002 (fig. 9b). Th e wounding rate estimate was most

recently estimated to be eight wounds per one hundred lake trout. Lake Trout abundance appears to be

increasing (fig. 9c), which could account for the decline in wounding rate estimates. Th rough the 1990s,

there were more Sea Lampreys in Lake Huron than in all other lakes combined, and fishery objectives were

not being achieved. Sea Lamprey-induced mortality was so severe that, during 1995, Lake Trout restora-

tion eff orts were suspended in the northern portion of the lake. After significant decreases in wounding

rate estimates, Lake Trout restoration eff orts were restored, and, although wounding rate estimates are

still above the target, Lake Trout populations are increasing and showing signs of natural reproduction.

Further reduction in Sea Lamprey-induced mortality on Lake Trout, however, is needed to further advance

rehabilitation of the Lake Trout population.

Above target lake-wide spawning-phase Sea Lamprey abundance and Lake Trout wounding rate

estimates can be primarily attributed to Sea Lamprey production from the St. Marys River. In response, an

integrated control strategy was initiated in the St. Marys River (Schleen et al. 2003), starting with an initial

880-hectare treatment of Sea Lamprey-infested areas of the river with Bayluscide granules (made possible

by a $3 million grant from the state of Michigan), followed by the use of the sterile-male-release technique,

trapping, and Bayluside granule spot treatments to maintain population suppression in subsequent years.

Measures of success of the St. Marys River control strategy indicated Sea Lamprey recruitment had been

dramatically reduced (Adams et al. 2003). As expected, Sea Lamprey abundance and Lake Trout wounding

rate estimates in Lake Huron significantly declined following the implementation of the strategy. Ad-

ditional lampricide control eff orts in the St. Marys River and other tributaries were initiated during 2001

and further enhanced during 2006. Nevertheless, Sea Lamprey abundance and Lake Trout wounding rate

estimates have not continued to decline and are still above target, and larval Sea Lamprey populations in

the St. Marys River are increasing. Sea Lamprey abundance and Lake Trout wounding rate estimates are

expected to decrease during future years, as lampricide control eff orts are further enhanced, including

another large-scale treatment of the St. Marys River.

Lake Erie

Sea Lamprey production has been recorded in 22 of 842 tributaries to Lake Erie (Young and Adair 2008). Of

these, 10 have been treated with lampricides at least once since 1999 and 7 require treatment on a regular

cycle. Lampricide control in Lake Erie using Bayluscide granules is minimal. In addition, Sea Lamprey

FIG. 9. Status of Sea Lamprey

(Petromyzon marinus) control

in Lake Huron: (A) lake-wide

spawning-phase Sea Lamprey

abundance estimates (line with

diamonds) compared to the

target (black horizontal line);

(B) lake-wide Sea Lamprey

wounding rate per one

hundred Lake Trout (Salvelinus

namaycush; line with circles)

longer than 533 mm compared

to the five-wound target (black

horizontal line); and (C)

lake-wide Lake Trout relative

abundance (CPE = fish/km/net

night of lean Lake Trout longer

than 533 mm; line with cubes).

Great Lakes Fishery Commission

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Michael J. Siefkes et al.688

barriers on 7 tributaries complement the lampricide control program. Spawning-phase Sea Lampreys are

also trapped in 4 tributaries for population assessment purposes.

Lake-wide spawning-phase Sea Lamprey abundance has been widely variable in Lake Erie (Sullivan

et al. 2003; fig. 10a), with periods of time within which abundance estimates were at pre-Sea Lamprey

control levels (i.e., 1980–1987, 1998–2000, and 2005–2007) and periods of time within which abundance

estimates were below or near the target (i.e., 1988–1997, 2001–2004, and 2008). Sea Lamprey abundance

(thirty-six thousand) was nearly twice the pre-Sea Lamprey control abundance level and almost an order

of magnitude above the target (four thousand) during the most recent year (2009).

Sea Lamprey wounds per one hundred Lake Trout longer than 533 mm have also been widely variable

in Lake Erie (fig. 10b). Except during 1989–1994, the achievement of the lake-wide wounding rate target

of five wounds per one hundred Lake Trout has been elusive. Wounding rate estimates have declined

during recent years and fell to 6.7 wounds per one hundred fish during 2008, providing optimism that the

target would be achieved in the near future. Th e wounding rate estimate for 2009, however, is projected

to be over three times the target (J. Markham, personal communication). Lake Trout abundance has been

variable but has also been increasing during recent years (fig. 10c), which could account for the recent

decline in wounding rate estimates. Lake Trout survival increased to a sufficient level to meet rehabilitation

objectives in the eastern basin of the lake during the late 1980s to mid-1990s. Above target wounding rate

estimates since the mid-1990s, however, have set Lake Trout restoration eff orts back. Further reduction

in Sea Lamprey-induced mortality on Lake Trout is needed to further advance rehabilitation of the Lake

Trout population.

Th e initial lampricide treatments in Lake Erie, conducted during 1986 and 1987, reduced spawning-

phase Sea Lamprey abundance and wounding rate estimates to the targets, which were maintained

through treatment of reinfested tributaries in the late 1980s and early 1990s. Th e high variation in the

Sea Lamprey abundance estimates since then is likely due to an oscillating pattern of control: a period of

high Sea Lamprey abundance, followed by intensive lampricide control eff ort and suppression, leading

to relaxation of eff ort and a rebound in the population (Sullivan et al. 2003). Water quality and stream

habitat improvements and changes in the fish community in the eastern basin of Lake Erie have likely

enhanced Sea Lamprey survival. A limitation in the Sea Lamprey abundance estimate due to the relatively

few Sea Lamprey-producing tributaries also adds to the variation. A recent large-scale treatment strategy,

conducted during 2008 and 2009, in which all Sea Lamprey-producing tributaries in Lake Erie were treated

in back-to-back years is expected to break this oscillating pattern and reduce Sea Lamprey abundance

to the target, possibly for an extended period of time delaying the need for further lampricide control.

Lake Ontario

Sea Lamprey production has been recorded in 65 of 659 tributaries to Lake Ontario (Young and Adair

2008). Of these, 39 have been treated with lampricide at least once since 1999 and 29 require treatment

on a regular cycle. Lampricide control in Lake Ontario using Bayluscide granules is limited to a few

lentic areas associated with Sea Lamprey-producing tributaries. In addition, Sea Lamprey barriers on

15 tributaries complement the lampricide control program. Spawning-phase Sea Lampreys are also

trapped in 12 tributaries for population assessment purposes and to provide male Sea Lampreys for the

sterile-male-release technique.

FIG. 10. Status of Sea Lamprey

(Petromyzon marinus) control

in Lake Erie: (A) lake-wide

spawning-phase Sea Lamprey

abundance estimates (line with

diamonds) compared to the

target (black horizontal line);

(B) lake-wide Sea Lamprey

wounding rate per one

hundred Lake Trout (Salvelinus

namaycush; line with circles)

longer than 533 mm compared

to the five-wound target (black

horizontal line); and (C)

lake-wide Lake Trout relative

abundance (CPE = relative

abundance of age 5+ Lake

Trout sampled from the eastern

basin; line with cubes).

Great Lakes Fishery Commission

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Michael J. Siefkes et al.690

Lake-wide spawning-phase Sea Lamprey abundance estimates significantly declined during the 1980s

(Larson et al. 2003), have been below or near the target since the late 1980s, and remain at a level less

than 10 percent of peak abundance (fig. 11a). Th e 2009 Sea Lamprey abundance estimate is thirty-eight

thousand, which is slightly above the target of thirty-one thousand. Continued suppression of Sea Lamprey

populations for nearly twenty-five years indicates the successful control of Sea Lampreys in Lake Ontario.

Sea Lamprey wounds per one hundred Lake Trout longer than 433 mm also significantly declined

during the 1980s and have been near the lake-wide target of two wounds per one hundred Lake Trout since

the mid-1980s (fig. 11b). Th e most recent wounding rate estimate of 1.5 is below the target, but wounding

rates off the mouth of the Niagara River have been high. Lake Trout abundance has steadily declined since

the mid-1990s (fig. 11c), which may be aff ecting wounding rate estimates. Achievement of Lake Trout

rehabilitation objectives will continue to be hampered, if Lake Trout abundance further declines and Sea

Lamprey-induced mortality increases.

Th e application of lampricides to important Sea Lamprey-producing tributaries during the 1980s,

including the Black and Oswego systems, precipitated a significant decline in spawning-phase Sea Lamprey

abundance and wounding rate estimates to below or near the targets. Subsequent lampricide control

eff orts have maintained Sea Lamprey abundance and wounding rate estimates below or near the targets.

Lampricide control eff orts will continue at the same level and Sea Lamprey abundance, and wounding

rate estimates are expected to remain close to targets in the future.

Enhancing Measures of Program Success

Improving measures to determine program success is a priority of the Sea Lamprey Control Program.

Confidence intervals around wounding rate estimates are currently being developed, and plans to mea-

sure spatial and temporal patterns in wounding rates have been made. Estimates of Lake Trout relative

abundance are also currently being developed, and error estimation and analysis of spatial and temporal

patterns are planned. Furthermore, plans to estimate wounding rates on other fish species and how fish

abundance, size, habitat, etc. interact with wounding rate estimates are underway. Th ese data will better

link Sea Lamprey control to the fish community as a whole, not just Lake Trout, and will allow a more

thorough assessment of the impacts of the Sea Lamprey Control Program.

In the ESTR model, the production of Sea Lampreys is valued equally among all tributaries to the

Great Lakes, as evidenced in the cost per kill criteria used to rank tributaries for lampricide treatment.

Th e damage a Sea Lamprey causes, however, is not necessarily valued equally among lakes (Stewart et al.

2003). Th e way Sea Lamprey production and damage are valued needs to be reconciled to better measure

program success. Additionally, the survival of recently metamorphosed Sea Lamprey as they emerge from

the tributary has been linked with the abundance of initial host species (Young et al. 1996; Harvey et al.

2008). Th erefore, consideration of the entire fish community should be part of the method to allocate Sea

Lamprey control resources and, subsequently, be a measure of overall program success.

To determine the holistic measure of program success, it is most appropriate to combine the evaluation

of stream-specific treatment eff ectiveness; the likelihood surviving larvae will find an initial host as newly

metamorphosed parasitic-phase Sea Lampreys; the abundance of initial, intermediate, and terminal hosts;

and the assessment of spawning-phase Sea Lamprey abundance. Many of these parameters are already

quantified; the next step is to combine predator-prey dynamics, bioenergetics, compensatory mechanisms,

FIG. 11. Status of Sea Lamprey

(Petromyzon marinus) control

in Lake Ontario: (A) lake-wide

spawning-phase Sea Lamprey

abundance estimates (line with

diamonds) compared to the

target (black horizontal line);

(B) lake-wide Sea Lamprey

wounding rate per one

hundred Lake Trout (Salvelinus

namaycush; line with circles)

longer than 433 mm compared

to the two-wound target (black

horizontal line); and (C)

lake-wide Lake Trout relative

abundance (CPE = fish/km/net

night of lean Lake Trout longer

than 433 mm; line with cubes).

Great Lakes Fishery Commission

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Michael J. Siefkes et al.692

and stock-recruitment relationships in a complex ecological model, to evaluate the places in the current

program where changes in Sea Lamprey control practices can reduce Sea Lamprey abundance in the

Great Lakes even further.

New Developments in Sea Lamprey Control

Th e current Sea Lamprey Control Program takes an integrated approach to evaluating tributaries and lentic

areas for Sea Lamprey production (i.e., larval assessment), evaluating and implementing options for control

of Sea Lamprey (i.e., lampricide and alternative controls), and evaluating the eff ects of control activities

(i.e., spawning-phase Sea Lamprey abundance and Lake Trout wounding rate estimates). Although the

techniques used in the Sea Lamprey Control Program have been evolving for more than fifty years, method

refinement and implementation of new technologies continue to change the application of Sea Lamprey

control within the Great Lakes. What the future holds for each of the specific techniques within the Sea

Lamprey Control Program is outlined in the previous sections of this chapter. Five research theme papers

that capture the state of knowledge and outline additional research needs for barriers and trapping,

lampricide control, Sea Lamprey population dynamics, sterile-male release, and the implementation of

pheromones in the Sea Lamprey Control Program are also available (McLaughlin et al. 2007; McDonald

and Kolar 2007; Jones 2007; Bergstedt and Twohey 2007; Li et al. 2007). Above and beyond the principle

Sea Lamprey Control Program elements, the future seems bright for two emerging areas: pheromones

and genomics.

Pheromones

For decades, Sea Lamprey pheromones have been thought to hold potential for development of alternative

Sea Lamprey control strategies (Teeter 1980). Pheromones are “substances that are excreted to the outside

by an individual and received by a second individual of the same species in which they release a specific

reaction, for example a definite behavior or developmental process” (Karlson and Luscher 1959). Initial

laboratory studies indicated that spawning-phase Sea Lampreys detect and respond to odorants released

by stream-dwelling larvae and by sexually mature individuals of the opposite sex (Teeter 1980). In principle,

responses to pheromones are often innate, specific, and robust, rendering target animals vulnerable to

manipulation with minute amounts of pheromones (Li et al. 2003). Recognizing that pheromones may

very well be developed into environmentally benign and eff ective alternative control strategies, the Sea

Lamprey research community and control agents in the Great Lakes basin have collaborated in search of

pheromonal chemicals. Th is extensive research eff ort has come to fruition (Li et al. 2007).

A series of studies has identified a mating pheromone that could potentially be developed for

incorporation into the Sea Lamprey Control Program. Spawning-phase male Sea Lampreys have long

been suspected of releasing a pheromone that attracts female Sea Lampreys (Teeter 1980). Behavioral

studies have demonstrated that ovulating female Sea Lampreys show search behavior, when exposed to

water conditioned with spermiating male Sea Lampreys, also called washings (Li et al. 2002; Siefkes et al.

2005). In a spawning tributary, traps baited with spermiating male Sea Lampreys (Johnson et al. 2005) or

washings from spermiating male Sea Lampreys (Johnson et al. 2006) capture a substantial proportion of

ovulating female Sea Lampreys. Mature male Sea Lampreys rely on specialized cells in their gills to release

SEA LAMPREY CONTROL 693

this pheromone (Siefkes et al. 2003), of which the main component is 3kPZS (3-keto Petromyzonol sulfate;

7α, 12α, 24-trihydroxy-5α-cholan-3-one 24 sulfate; Li et al. 2002). 3kPZS, and its synthesized copy, have

been extensively studied in the Ocqueoc River, Michigan, for its potential use in Sea Lamprey control. Th e

synthesized copy of 3kPZS was highly eff ective in attracting ovulating female Sea Lampreys to artificial

nests upstream (Siefkes et al. 2005). When applied to the river, reaching concentrations between 10–14 and

10–10 molar (M), synthesized and natural 3kPZS were equally potent in inducing highly robust upstream

movement in ovulating female Sea Lampreys and, eventually, luring them into baited traps (Johnson et al.

2008). Clearly, these findings demonstrate the possible use of 3kPZS in the Sea Lamprey Control Program.

Studies of chemicals released by larval Sea Lampreys have also resulted in identification of previously

unknown compounds believed to function as migratory pheromones. Unlike salmon, migratory spawning-

phase Sea Lampreys do not select their natal tributaries for reproduction (Bergstedt and Seelye 1995);

rather, Sea Lampreys seem to prefer tributaries that contain a higher abundance of conspecific larvae

(Moore and Schleen 1980) and are attracted to the odor of larvae (Teeter 1980; Bjerselius et al. 2000; Vrieze

and Sorensen 2001; Wagner et al. 2006). Larval Sea Lamprey compounds, petromyzonol sulfate (PZS),

petromyzonamine disulfate (PADS), and petromyzosterol disulfate (PSDS), have been found to modify

behaviors of migrating Sea Lampreys placed in laboratory mazes (Haslewood and Tokes 1969; Bjerselius

et al. 2000; Sorensen et al. 2005). Based on these chemical and behavioral studies, Sorensen et al. (2005)

further postulated that PADS is the major component of the migratory pheromone and that PS and PSDS

are minor components. Th is hypothesis, when further confirmed by empirical examination under natural

conditions, may very well lead to the development of eff ective strategies for Sea Lamprey control.

Application of pheromones in pest management has been studied more extensively for insects in

which female pheromones are often deployed to trap males or disrupt reproductive behaviors (Beroza and

Knipling 1972; Gaston et al. 1977). Field deployment of a vertebrate pheromone for control of vertebrate

pests, however, has not been reported. Nevertheless, the most intensively studied Sea Lamprey pheromone

compound, 3kPZS, appears to have several advantages for future deployment as an important strategy

for the integrated control of the Sea Lamprey. Johnson et al. (2008) summarized an important feature of

3kPZS for potential use in Sea Lamprey control: 3kPZS alone modifies behaviors of ovulating female Sea

Lampreys across a long distance. When 3kPZS is used to remove ovulating female Sea Lampreys from a

spawning ground, it will result in a proportional reduction in viable eggs and, thus, is likely more eff ective

than removal of male Sea Lampreys. An additional advantage of 3kPZS is that a single compound is less

expensive to develop and register than multiple compounds. In addition to trapping, pheromones could

potentially be used in other ways to control the Sea Lamprey, such as the development of antagonists to

Sea Lamprey pheromones to disrupt mating or directing Sea Lampreys away from tributaries difficult or

expensive to treat with lampricides to tributaries easy or cheap to treat with lampricides (Li et al. 2007).

Genomics

Th e advent and development of genomics have had a seismic eff ect on biological research. Th e genome

sequence endows a global view of the genetic landscape, potentially enabling identification of all the

molecular components in cells and understanding of how these cells interact and function in various life

stages. Wherever a genome is sequenced, the assembled sequence and other genomic resources have

become a major impetus for discovery in that species. Fortunately, the Sea Lamprey genome has been

Michael J. Siefkes et al.694

sequenced by the National Institute of Health. Th is genome is the blueprint that makes the Sea Lamprey

a unique life form that has thrived in the Atlantic Ocean for more than five hundred million years (Kumar

and Hedges 1998; Shu et al. 1999) and that has recently become the most successful predator in the Great

Lakes (Smith and Tibble 1980). Does this seemingly invincible species, however, have vulnerable parts?

Th e answer may be hidden in the same genome that makes the Sea Lamprey so successful. Eventually,

knowing the Sea Lamprey genome may enable the identification of the Sea Lamprey’s Achilles’ heel.

A direct benefit of sequencing the Sea Lamprey genome is new insights into biochemical, genetic,

metabolic, and physiological pathways that could be exploited for Sea Lamprey control, with few eff ects

on other organisms. It is known that many aspects of Sea Lamprey physiology are substantially diff erent

from teleost fish. Th is is expected, because molecular studies of clusters of genes (Force et al. 2002; Irvine

et al. 2002) and phylogenetic analysis of gene families (Escriva et al. 2002; Fried et al. 2003) indicate at

least one of the two rounds of Sea Lamprey genome duplication happened after divergence between

agnathans and gnathostomes. Th is independence in genome duplication may be a key evolutionary event

that resulted in the agnathan pedigree. Th e Sea Lamprey genome sequence will provide a panoramic view

of the Sea Lamprey genetic landscape, which, when compared to global views of gnathostome genomes,

may unravel the molecular events that could be targeted for Sea Lamprey control.

Th e Sea Lamprey genome sequence will also facilitate and accelerate research of genetic control of

the Sea Lamprey. Rapid development of biotechnology during recent years has generated new strategies

for control and eradication of invasive species and pests (Gould 2008). Although autocidal technology has

not been field tested on species outside the insect taxa, this technology has been developed for invasive

fish species under laboratory conditions (Th resher 2008). Similar approaches, based on the recombinant

genetic technology, should be applicable for Sea Lamprey control. A major obstacle is that the ability to

genetically engineer Sea Lampreys is not yet been fully developed. Th is problem can be ameliorated, when

the ever-increasing array of molecular genetic methods are tested in the Sea Lamprey. When this happens,

genomic resources will implicate ample targets for development of a genetic control for the Sea Lamprey.

Summary

The Sea Lamprey Control Program in the Great Lakes is a case study in coordinated and integrated

binational fishery management and is the only reported successful control program for a non-indigenous,

vertebrate pest species. Since its inception in the mid-1900s, the program has evolved as knowledge and

environmental momentum have shifted. Currently, lampricides serve as the backbone of the control

program, but various alternative controls, such as barriers, trapping, and sterile-male releases, have also

been implemented and are quite successful. Although Sea Lamprey populations in each lake are at about

10 percent of their peak levels prior to the Sea Lamprey Control Program, measures of program success

indicate there is much work to be done, as spawning-phase Sea Lamprey abundance and Lake Trout

wounding rate estimates are still above targets in most of the lakes. Enhancement of current Sea Lamprey

control strategies and development of new strategies are needed to further improve Sea Lamprey control

and bring their populations and the damage they inflict to target levels. Exciting new prospects wait on

the horizon, as more knowledge is gained about pheromone communication in Sea Lamprey and the

benefits of having the Sea Lamprey genome sequenced are realized. Successful Sea Lamprey control is

the cornerstone of fish community restoration in the Great Lakes.

SEA LAMPREY CONTROL 695

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