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Osprey 44.1 MarineInvasion

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THEOSPREYNature Journal of Newfoundland andLabrador

Winter 2013 Volume 44 Issue 1

NatureNewfoundland and LabradorISSN 0710-4847

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8 The Osprey

The Marine Aquatic Invasion Continues

By Kyle MathesonFisheries and Oceans Canada

Aquatic invasive species (or AIS, commonly also

referred to as nuisance species, aliens,

unwanted visitors, or non-indigenous) are species

that are not native to coastal Newfoundland (NL)

waters. The transport of these species from foreign

locations to our shores is often attributed to human

traffic including, but not limited to exchange of

ballast water from ships, attachment to boat hulls and

fishing/aquaculture equipment, movement of docks

and barges, and transportation of live seafood and

bait. The prospect of climate change and warming

waters may also allow a species to expand its range

into new territory where conditions may have limited

previous spread (such as colder waters in NL). These

species generally share numerous traits that make

them successful invaders. They often dominate

native species in competition for food or living space

due to aggressiveness, fast growth, or rapid

reproduction and population growth. They tolerate a

wide range of environmental conditions, and easily

adapt to different food sources. Once they become

established in a new area they reproduce and spread,

threatening local biodiversity, functions of coastal

marine ecosystems, and human economic activities.

Aquatic invasive species have been an increasing

concern for coastal NL ecosystems during the last 10

years. Collaboration in research and monitoring

programs between scientists at Fisheries and Oceans

(DFO), Memorial University (MUN), and other non-

government stakeholders has provided information

on the abundance and spread as well as the ecology

of several high interest species. In NL to date, the

European green crab, three tunicate (or sea squirts)

species (Violet, Golden Star, and Vase), the Lacy

Crust Bryozoan, and a large green algae know as

Oyster Thief have been documented as invasive

species. Vase tunicate and Oyster Thief were

discovered in NL for the first time in 2012. While

these species are a relatively new ecological threat to

NL, the fishery and aquaculture industries in the

northeastern United States and Maritime Provinces

have battled against and suffered the ecological and

economic consequences of such invasions. For

example, the voracious appetite of green crab led to

substantial declines in the economically important

soft-shell clam in New England, while the clubbed

and vase tunicates have been the most problematic

invasive species for mussel aquaculture operations in

the Maritime Provinces. Species may respond

Green crab (Photo by Kyle Matheson).

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Winter 2013 9

uniquely to the different marine environments in NL

compared to elsewhere, but previous knowledge and

experience enhances our ability to prepare for and

manage threats ofAIS in NL.

High amounts of shipping traffic to and within NL

generate vectors that may transport species into the

province from around the globe and once introduced

spread within NL. A National Risk Assessment

identified locations that receive high amounts of

vessel traffic and ballast exchange,

such as Placentia Bay, which has

been an invasive species hotspot in

NL. Although attention has centred

on the risk of ballast exchange,

movement by recreational and small

crafts can act as secondary vectors

that assist and accelerate the spread

of invasive species. Fisheries and

Oceans have been surveying

recreational boaters to understand common routes

and high activity areas within NL (readers are

encouraged to contact AIS DFO, see website below,

if interested in participating in the boating survey).

Such surveys provide critical information to fine-tune

monitoring and research efforts. It is largely

acknowledged that the complete eradication of an

aquatic invasive species is not realistic, especially

once the species has become established. Prevention

and early detection of introduction and spread may

be the most effective management tools. Currently,

regulations are being developed between Provincial

Governments and DFO to manage and control the

introduction and spread of species.

The European green crab has invaded coastlines of

North America for over a century, including more

recent invasions along both the Pacific and Atlantic

coasts of Canada, but was first discovered in North

Harbour, Placentia Bay in 2007. The range and

populations of green crab in Placentia Bay have

exploded and have expanded to the west coast of the

island, particularly in shallow, protected coastal

locations (such as eelgrass beds).

In locations where few green crab

were captured, it has not been

uncommon to capture several

hundred crab the next year. In fact,

numbers have been so large that

research has been unable to

effectively estimate population size

because not enough crab have been

recaptured during tagging

experiments. The high abundances of green crab in

NL (several times that captured in Atlantic Canada or

British Columbia) have surprised many. The

presence of more native coastal crab species larger

than green crab in British Columbia (5 compared to

only one in NL, the rock crab) may act as predators

and limit the population of green crab. Currently,

green crab is the most prominent and destructive

invasive species in NL, and is one of the most

unwanted species globally.

Green crabs are voracious generalist predators and

aggressive competitors. They prefer shellfish such as

"In locationswhere few greencrab were

captured, it has notbeen uncommon tocapture severalhundred crab thenext year. "

(Left) Green crab (Photo by Kyle Matheson). (Right) Oyster Thief(Photo by Terri Wells) .

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1 0 The Osprey

mussels and clams and large green crab populations

are having dramatic impacts on local abundances of

these species, practically leaving areas barren. Recent

research by DFO has provided evidence that green

crab feed on juvenile scallops, particularly when

preferred foods become limited. Green crab can also

alter underwater habitats. Crabs dig to find food and

bury themselves, which destroys roots of eelgrass, an

ecologically significant species in Canada and crucial

habitat for many juvenile fish, including Atlantic cod.

Anecdotal evidence suggests that this important sea

grass has declined throughout Atlantic Canada in

areas with increasing green crab

populations. Research by DFO in

2012 throughout Placentia Bay

has shown dramatic declines in

eelgrass coverage in areas with

the largest and longest

established green crab


As with other locations in

North America, an established green crab population

is nearly impossible to exterminate. For example,

volunteer harvesters captured approximately 350 000

crab in North Harbour (considered the hotspot for

green crab in NL) in under 3 weeks, but it provided

only a temporary reduction in the

invasive crab. Efforts now

include population control with

the objective that decreasing the

number or prominent size of

green crab increases their

vulnerability to natural predators.

The use of green crab as compost

and fertilizer is another option

being considered to control


Tunicates are aquatic animals

with sac-like bodies protected by

a coat (or tunic) that can live in

large colonies and feed by

filtering out food from water.

While the violet tunicate (first

discovered in Belleoram in 2007)

has not spread outside of

Belleoram harbour, the golden-

star tunicate (first identified in Placentia Bay in

2006) has spread throughout Placentia Bay and has

recently been confirmed in Conception Bay.

Tunicates are referred to as opportunistic animals.

Tunicate larvae settle on new, clean surfaces (such as

wharves or clean boat hauls) with little competition

from existing animals. Once the larvae settle,

invasive tunicates grow rapidly and cover other

plants and animals and deprive them of resources

such as food or light. These characteristics make

tunicates potentially very disruptive to shellfish

harvesters and aquaculture operations. Fortunately,

no invasive tunicates are present

in NL aquaculture operations.

Tunicates are most commonly

transferred between locations by

hitching a ride on boat hauls,

barges, or fishing equipment.

Boat hulls should be inspected

visually, cleaned, and dried on

land for 24 h as fragmentation of

colonies in water only

perpetuates further spread of the species. Anti-

fouling treatments on boats can also effectively

prevent the transfer of invasive tunicates.

Attempts to eradicate populations of these invasive

"Once the larvaesettle, invasive

tunicates grow rapidlyand cover other plantsand animals anddeprive them of

resources such as foodor light. "

Vase Tunicate (Photo by Bob O'Donnell) .

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Winter 2013 11

tunicates have not been

successful despite early

detection, further emphasizing

that the prevention of spread is

crucial. Boats and wharf

structures in Belleoream have

been wrapped with plastic and

filled with freshwater to

suffocate and remove violet

tunicate, but the tunicate

persisted. In 2011 , the detection

of golden star tunicate only on

floating docks in Foxtrap

marine (Conception Bay)

provided a rare opportunity to

attempt to locally eradicate this

tunicate. The floating docks

were removed and although

early indications showed no evidence of the species

return, it was discovered again the subsequent fall on

the main wharf structures.

Although violet and golden star tunicates are not

the most economically devastating of the invasive

tunicates, the vase tunicate has had a high economic

impact in some regions. This species was found in

Marystown and Burin regions (highest abundances in

Little Bay) on wharf structures, boat hauls, and

eelgrass during regular surveys by DFO in 2012. In

the Maritime Provinces, vase tunicate has infested

mussel farming operations, which has decreased

growth of mussels and in some cases caused loss of

the crop and some closure of mussel operations.

Removal of vase tunicates from mussel sleeves is

very labour intensive and costly. Due to its potential

for large economic and ecological impacts further

options for mitigating vase tunicate population

growth and spread are being investigated.

Finding lower impact tunicates first increased our

awareness and monitoring programs for the potential

introduction of vase tunicate and other dangerous

invasive tunicates (such as clubbed tunicate and

Didemnum sp., which are currently in the Maritime

Provinces and NE United States, but not NL). For

example, researchers have developed genetic tools

that can detect a single tunicate larva in the water

column. Such tools and awareness lead to further

progress in proactive introduction and transfer

protocols to lessen the risk of invasive species.

Moving forward, public education and awareness

are considered vital components in the struggle to

Recognize! Report! and Remove! invasive species.

The more awareness the public has on the issues, the

more that can be done to reduce future risks of

introduction and spread. We encourage the public to

visit the AIS DFO website (http://www.nfl.dfo-

mpo.gc.ca/ais-eae) to learn how to identify each

species and where they are most commonly found

(especially for those who often travel by boat). The

public are encouraged to take pictures and report any

new finding of an invasive species or a species that

cannot be identified.

Lacy Crust Bryozoan (Photo by Terri Wells) .

"Nature always tends to act in the simplest way. "

- Johann Bernoulli