NOTES 1359

(MMC-47) to J. R. Geraci at the New England1.triurn.

,HOLD, P. W., AND D. E. GASKIN. 1975. Lungworms(Metastrongyloidea: Pseudaliidac) of harbor porpoisePhocoena phocoena (L. 1758). Can. J. Zool. 53: 713-735.

En, J. G. 1932. Contribution a l'etude des Cestodes deCetaces. Rev. Suisse Zool. 39: 195-228.

1954. Revision taxonomique et etude biologiquedes Cestodes de in famille des Tetrabothriidae para-sites dDiseaux de haute mer et de Mammiferes marins.Mein. Universite neuchiltel, serie In-quarto No. 1,121 p.

"VERLEY-BURTON, M., AND J. H. C. P IPPY. 1977. Morpho-metric variations among larval A nisakis simplex(Nematoda: Ascaridoidea) from fishes of the NorthAtlantic and their use as biolog ical indicators of hoststocks. Env. Biol. of Fishes 2: 309-314.

1978. Distribution, prevalence and mean numbersof larval A nisakis simplex (Nematoda: Ascaridoidea)in Atlantic salmon, Salmo solar L. and their use asbiological indicators of host stocks. Env. Biol. ofFishes 3: 211-222.

1LEY, M. D., AND R. L. BROWNELL. 1972. A checklist ofmarine mammal parasites, p. 528-589. In S. H. Ridg-way [ed.] Mammals of the Sea. Biology and medicine.Charles G. Thomas, Springfield, Ill.

WES, B. 1946. The Trematoda. Cambridge UniversityPress, New York, N.Y.

Irit.YANtuRE, S. L. 1955. Helminthofauna of marine mam-mals (Ecology and Phylogeny). Academy of ScienceUSSR, Moscow. Jerusalem, Israel Program for Scien-tific Translations, 1968.

GERACI, J. R., NI. D. DsILEY, AND D. J. ST. AUBIN. 1978.Parasitic mastitis in the Atlantic white-sided dolphin,Lagenorhyncluts actin's as a probable factor in herdproductivity. J. Fish. Res. Board Can. 35: 1350-1355.

GERACI, J. R., S. A. TESTAVERDE, D. J. ST. AUBIN, ANDT. H. Loot, . 1975. A mass stranding of the Atlanticwhite-sided dolphin, Lagenorhynchus actutts: A studyinto pathobiology and life history. Rep. #NINIC-47. NewEngland Aquarium, Boston, Mass.

GIBSON, D. I. 1972. Flounder parasites as biological tags.J. Fish. Biol. 4: 1-9.

KABATA, Z. 1963. Parasites as biological tats. Int. Comm.Northwest Atl. Fish. Spec. Publ. 4: 31-37.

MARGOLIS, L. 1963. Parasites as indicators of the geo-graphical origin of sockeye salmon, Oncorhynch usnerka (Walbaum), occurring in the North PacificOcean and adjacent seas. Int. North Pac. Fish. Comm.Bull. 11: 101-156.

PIPPY, J. H. C. 1969. Pomphorhyncluts laevis (Zoega)Muller, 1776 (Acanthocephala) in Atlantic salmon(Salmo solar) and its use as a biological tag. J. Fish.Res. Board Can. 26: 909-919.

SERGEANT, D. E. 1959. Age determination in odontocetewhales from dentinal growth layers. NorwegianWhaling Gazette. 6: 273-288.

SKRJABIN, K. I. 1948. Trematodes of Animals and Man. 2.Moscow-Lenin grad, Izdatee'stvo Akad. Nauk SSSR.

YAMAGUTI, S. 1942. Studies on the Helminth Fauna ofJapan. Part 40. Three new species of trematodes fromthe bile ducts of marine mammals. Trans. Biologr.Soc. Japan 3: 399-407.

1971. Synopsis of Digenetic Trematodes of Verte-brates. Vol. 1 and 2. Keigaku Publishing Co., Ltd.

Stomach Flushing: Effectiveness and Influence on Survival andCondition of Juvenile Salmonids

WILLIAM R. MEEHAN AND RICHARD A. MILLER

USDA Forest Service, Pacific Northwest Forest and Range Experiment Station,Forestry Sciences Laboratory, Corvallis, Oreg. 97331, USA

MEEHAN, W. R., AND R. A. MILLER. 1978. Stomach flushing: effectiveness and influenceon survival and condition of juvenile salmonids. J. Fish. Res. Board Can. 35:1359-1363.

Hydraulic stomach flushing was an effective method to analyze relative food con-sumption and feeding habits of young salmonids. Coho salmon (Oncorhynchus kisatch)stomachs were most effectively flushed - 99% of invertebrate or ganisms (96% of weightof stomach contents); 92% of organisms (83% of weight) were flushed from cutthroattrout (Salmo clarki) stomachs, 90% of organisms (77% of wei ght) were flushed fromrainbow trout (S. gairdneri) stomachs. Stomach flushing did not affect survival of juvenilecoho salmon. A significant difference in change in mean condition factor between wildand hatchery fish was found after 30 d (greater change in wild fish), and a significantchange was observed between the mean condition factors of control and treated hatcheryfish. No difference was found between control and treated wild fish.

Key words: stomach flushing, juvenile salmonids, survival, condition, food habits

1360 J. FISH. RES. BOARD CAN., VOL. 35, 1978

MEEHAN, W. R., AND R. A. MILLER. 1978. Stomach flushing: effectiveness and influenceon survival and condition of juvenile salmonids. J. Fish. Res. Board Can. 35:1359-1363.

Le curage hydraulique de l'estomac est une methode efficace de determination de]'importance relative des divers item consommes et des habitudes alimentaires des jeunessalmonides. Les estomacs de saumons coho (Oncorhynchus kisutch) sont ceux qui sont leplus efficacement cures — 99% des invertebres (96% du poids des contenus stomacaux);92% des organismes (83% du poids) sont evacues des estomacs de truites fardees (Satin°clarki), 90% des organismes (77% du poids) sont evacues des estomacs de truites arc-en-ciel (S. gairdneri). Le curage stomacal n'affecte pas la survie des jeunes saumons coho.Nous observons une difference si gnificative dans le changement de l'indice d'embonpointde poissons sauvages et de poissons d'elevage apres 30 jours (chan gement plus marquechez les poissons sauvages), ainsi qu'un changement significatif de l'indice d'embonpointde poissons temoins et de poissons d'elevage traites. Nous n'observons aucune differenceentre les poissons temoins et les poissons sauvages traites.

Received January 4, 1978 Recu le 4 janvier 1978Accepted June 15, 1978 Accepte le 15 juin 1978

STUDIES of the food and feeding habits of fish are im-portant in the study of aquatic ecosystems. Heretofore,food habit studies have required that many fish be killedfor stomach removal and examination. In small streamswith low fish populations, the removal of a few fish canseriously deplete the population. Thus, several methodshave been developed to remove stomach contents with-out injuring the fish. These include (1) pressing on thestomach after a rigid tube has been inserted (White1930), (2) injecting emetics (Markus 1932). (3) gas-troscope viewing (Dubets 1954), (4) tube flushing(Seaburg 1957). (5) inserting forceps (Wales 1962),(6) back flushing intestines and stomach by placementof a pressure tube into the vent (Baker and Fraser1976), and (7) syringe flushing (Aho 1976).

In this study a syringe flushing technique (Aho 1976)was used for examination of stomach contents of threesalmonids: coho salmon, Oncorhynchus kisutch; cut-throat trout. Salmo clarki; and rainbow (steelhead)trout, S. gairdneri. We used this technique during thepast 3 yr and found it to be reasonably harmless to fish,This paper addresses the following questions: (1) Howare contents flushed from the fish stomachs correlatedwith total contents? (2) Are certain food items morelikely to be flushed? (3) Is there a difference in foodrecovery between sizes, species, or stocks of fish? (4)How does handling affect survival and condition?

Methods — Effectiveness of stomach flushing — With aportable, battery-powered electroshocker, 51 juvenile rain-bow trout, 51 cutthroat trout, and 53 young coho salmonwere collected. The rainbow were collected from CanyonCreek, central Oregon, on July 29, 1975; cutthroat and cohowere taken from Green River, a coastal stream in theSiuslaw National Forest, on August 1, 1975. Fish of a givenspecies were collected in less than 2 h. They were thenanesthetized with MS-2228, measured (fork length in milli-metres), and the stomach contents were flushed into 56.7-g(2-ounce) collecting jars.

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Flushing was done by inserting a blunt 5.1-cm No. 18hollow needle mounted on a 20-mL syringe filled with waterthrough the mouth and esophagus into the cardiac stomach.When the water was forced into the stomach, the stomachcontents were flushed back through the esophagus andmouth and via a funnel into the collecting jar. Usually one20-mL injection was sufficient to flush out all the availablecontents, although larger fish sometimes required an addi-tional injection. Care was taken to remove food items caughtin the mouth. Before sealing collection jars, a 10% formalinsolution and labels were added. Each fish was killed afterstomach flushing and the stomach was removed and pre-served in a second labeled collecting jar.

In the laboratory, food items flushed from the stomachswere identified (family or genus) and counted, and eachtotal stomach sample was freeze-dried and weighed to thenearest 0.1 mg. Certain fragments such as head capsulesrepresented one organism for numerical purposes; all frag-ments were included in sample weight. Food remaining inthe preserved stomachs was handled identically. Regressionanalyses were run to establish relationships between (1) fishsize and species and (2) amonnt of material flushed fromstomachs. Covariance analysis was used to compare slopesand intercepts.

Effects on survival and condition — Wild and hatcherycoho salmon juveniles were used in this phase of the studs.Wild fish were collected from Green River in westernOregon; hatchery fish were obtained from the Oregon De-partment of Fish and Wildlife Hatchery on Fall Creek.Green River and Fall Creek are in the Alsea River drainage.All fish were collected by electroshocking, including thosefrom the hatchery pond.

The fish were brought to the laboratory and held inseparate large holding tanks for 3 d. During this time andthroughout the experiment, they were fed 1.6-mm OregonPellets. Treatments at the beginning of the experiment con-sisted of electroshocking, measuring (fork length in milli-metres), weighing (nearest 0.1 g), and finclipping all fish(treatment 1). Additional treatments were anesthetizing(treatment 2), and anesthetizing and stomach flushim:(treatment 3). Control fish (treatment 1) were not addi-tionally treated.

Three wild fish of each treatment (nine total) were placedinto each of 10 glass jars (18-L). Each jar was individuall:-aerated and supplied with fresh water. Hatchery fish wer.:similarly arrayed in an adjacent unit of 10 jars.

85 125 165 205 245FORK LENGTH (mm)

100

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80

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NOTES 1361

TABLE 1. Number of invertebrates and weight of contents in stomachs of three species of salmonids.

Stomach contents

Flushed Remaining Percent flushedbFork length (mm)

No. Wt No. No.Species No. Mean Range organisms (g)a. organisms Wt organisms Wt

Coho 53 65 52-92 596 639 6 24 99 96Cutthroat 51 113 65-225 792 2336 70 446 92 83Rainbow 51 139 93-232 845 2896 89 2259 90 77Total 155 105 52-232 2233 5871 165 2729 93 85

aFreeze-dried weight.bPercentage of stomach contents flushed was derived by calculating the percentage flushed from each fish and then finding

the mean of these percentages.

The conditions in all jars were identical. Individual fishwithin each jar were identified by utilizing combinations ofadipose, dorsal, upper, and lower caudal finclips. A total of90 hatchery and 90 wild fish were used; mean lengths were67.3 and 68.3 mm, respectively. Fish that died during thisstudy were removed as soon as possible from the jars. After30 d the surviving fish were again measured and weighed.Differences in survival and condition were tested by analysisof variance. Condition factor (K), a measure of relativerobustness, was calculated as

Kw

L3 x 10'

where K is the condition factor, W is wet weight of fish ingrams, and L is fork length of fish in millimetres.

Results and discussion E/Jectiveness of stomachflushing — Flushing the 155 salmonid stomachs yieldeda total of 2233 invertebrate organisms or 93% of thetotal number of prey (flushed and remaining) in thestomachs (Table 1). The total weight of stomach con-tents flushed from the three fish species was 5871 g or

Flo. I. Fish length vs. percent of material by weightflushed from stomachs of rainbow trout.

85% of the total weight of contents (flushed and re-maining).

Examination of several specimens revealed that thepyloris of rainbow trout was longer and the diameter ofthe esophagus smaller in relationship to stomach sizethan in the other two species. These differences couldinhibit the force of hydraulic current in the posteriorstomach and decrease passage of contents out throughthe esophagus. Coho salmon were the smallest .fishstudied, cutthroat trout were intermediate, and rainbowtrout were the largest. Food items found in the rainbowtrout stomachs included more larger prey, such as smallcrayfish (Astacus sp.). sculpins (Coccus sp.), large stone-flies (e.g. Acroneuria sp), and large cased caddisfliessuch as Dicosmoecus sp. These larger, more rigid formswere much more difficult to flush from the stomachs; asa result, the percentage of material flushed from stom-achs of the larger rainbows was smaller than that flushedfrom cutthroat and coho stomachs. Conversely, fooditems found in coho stomachs were much smaller andmore pliable (e.g. Diptcra larvae and Ephemeropteranymphs) and were not as likely to become lodged inthe stomach or esophagus.

Despite removal of caddisfly (Trichoptera) cases,snail shells, stones, and large wood pieces prior toweighing, much of the freeze-dried and weighed materialin the stomachs of the three fish species was non-digestable matter. Small sand and wood particles, skele-tons of hard-bodied insects, and densely packed scleritesfrom fully digested arthropods made up the bulk ofthe stomach contents. These fragments and partiallydigested material are densely compacted in the pylorisin preparation for passage through the intestine. As fishbecome larger and the muscle mass of the stomachincreases, dislodgement of the contents from the pyloricstomach becomes more difficult.

A regression analysis of fish length vs. percent byweight of stomach contents flushed from rainbow trout(Fig. 1) established a negative linear correlation(r2 .32). This relationship did not exist for cohosalmon (r2 = .05), or cutthroat trout (r= == .02). This

1362

280

260

CO240

zu.1

220

200O

160

1602O 140

120F-a: 100 -

80

aZ 60

40

20

-n=38 N. XX

REMAINING

FLUSHED

n = 7

n=15

*9542

n = 4 9n=17

n=29

TOTAL

0 and ^ June 2• and 19 July 1mean 95% confidence limits

(n) (27) (25) (26) (78) (25) (23) (28) (76) -

J. FISH. RES. BOARD CAN., VOL. 35, 1978

30-59 60-89 90-119 120-149 150-179 >179

FISH SIZE CLASS (FORK LENGTH-mm)

*PERCENT RECOVERY (wr FLUSHED / TOTAL WT X100)

FIG. 2. Relationship between fish size and effectiveness ofstomach flushing. Data are combined for coho salmon, cut-throat trout, and rainbow trout.

may be due to a higher percentage of fish havin g stom-achs totally flushed (74 and 43%, respectively, com-pared to 25% for rainbow trout) and a preponderanceof smaller fish (mean fork length 65 and 113 mm, re-spectively, compared to 139 nun for rainbow trout).These data are generally consistent with those obtainedby Aho (1976) for cutthroat trout.

When data for the three fish species are combined,it appears that as fish size increases, the percent of ma-terial that is flushed from the stomach decreases (Fig.2). This may be somewhat influenced, as mentionedearlier, by slight anatomical differences in the stomachand esophagus among the three species or by differ-ences in the consistency of food items taken by eachspecies.

Effects on survival and condition — Seventy-six(84%) of the hatchery fish and 7S (87% ) of the wildfish survived the experiment. There was no significantdifference in survival in either group between treatedand control fish after 30 d (Table 2). Aho (1976) ob-tained similar results with cutthroat trout. Electroshock-in g. which causes severe trauma (Edwards and Higgins1973), was probably the major cause of mortality,although measurin g . wei g hing. and finclipping probablycaused additional stress.

A significant difference in change in condition factor< .01) during the study was found between hatchery

and wild fish when all treatments were considered to-

TABL E 2. Survival of wild and hatchery coho salmon after30 d (June 2 through July 1, 1975). Treatment 1 (control) -electroshocked; treatment 2 - electroshocked and anesthetized;treatment 3 - electroshocked, anesthetized, and stomachflushed. In addition, all fish were measured, weighed, andfinclipped. For each treatment there were 30 fish in each group.

Wild fish Hatchery fish

Treatments No. 0 No.

I (control) 27 90.0 25 83.32 25 83.3 23 76.73 26 86.7 28 93.3Total 78 86.7 76 84.4

140

:1.30

cc0

120

017- 1.10

6-z0

1.00

WILD HATCHERY

1 2 3 (combined) I 2 3 (combined)TREATMENTS

FIG. 3. Change in mean condition factor and 95% confi-dence limits of wild and hatchery coho salmon after 30 d(June 2 through July I, 1975). Treatment 1 —electro-shocked; treatment 2 — electroshocked and anesthetized;treatment 3 -- electroshocked, anesthetized, and stomach-flushed.

gether. The mean body condition of hatchery fish waspoorer initially, but was less affected by treatment thanthat of wild fish. There was a significant difference(P < .05) in change in body condition between controland treated hatchery fish (Fig. 3). Mean condition fac-tor was reduced to 96% (treatment 2) and 97% (treat-ment 3) of mean condition at the beginning of the ex-periment in the two treated groups; condition factor ofcontrol fish (treatment 1) was 103% of the originalcondition. No difference was found in change in bodycondition between control and treated wild fish. Con-sidering the drastic change from their natural diet, i.e.from live invertebrates to Oregon Pellets, it is not sur-prising that they would do poorly. Any treatment differ-ences that might have occurred would probably havebeen masked by effects of diet change.

Alto, R. S. 1976. A population study of the cutthroat troutin an unshaded and shaded section of stream. M.S.Thesis. Oregon State Univ., Corvallis, Oreg. 87 p.

NOTES 1363

BAKER, A. M., AND D. F. FRASER. 1976. A method for se-curing the gut contents of small, live fish. Trans. Am.Fish. Soc. 105: 520-522.

DUBETS, H. 1954. Feeding habits of the largemouth bass asrevealed by a gastroscope. Prog. Fish-Cult. 16: 134-136.

EDWARDS, J. L., AND J. D. HIGGINS. 1973. The effects ofelectric currents on fish. Final Tech. Rep., Projects B-397, B-400, and E-200-301, Georgia Institute of Tech.,Eng. Exp. Stn., Atlanta, Ga. 73 p.

MARI:us, H. C. 1932. The extent to which temperature

changes influence food consumption in largemouthbass (II uro floriclana). Trans. Am. Fish Soc. 62: 202-210.

SE:thURG. K. G. 1957. A stomach sampler for live fish. Prog.Fish-Cult. 19: 137-139.

WALES. J. H. 1962. Forceps for removal of trout stomachcontent. Frog. Fish-Cult. 24: 171.

WHITE. H. C. 1930. Some observations on the eastern brooktrout ( Sal • elinus fontinalis) of Prince Edward Island.Trans. Am. Fish. Soc. 60: 101-108.

Use of Aniline Blue for Distinguishing Between Live and DeadFreshwater Zooplankton

B. SEEPERSAD AND R. W. CRIPPEN

Beak Consultants Limited, 6870 Goreway Drive, Mississauga, Ont. L4V 1L9

SEEPERSAD, B., AND R. W. CRIPPEN. 1978. Use of aniline blue for distinguishing betweenlive and dead freshwater zooplankton. J. Fish. Res. Board Can. 35: 1363-1366.

It is possible to distinguish between live and dead freshwater zooplankton after 15-min immersion in an aqueous solution of aniline blue. Organisms physiologically dead atthe time of staining are dyed blue, whereas living organisms remain unstained. This mortalstaining technique has been repeatedly used in evaluating the survival of individuals be-longing to all major groups of freshwater zooplankton. It has special application wherethe survival of large numbers of plankters must be determined either within a short interval,for successive intervals, or where conditions do not permit such evaluations immediatelyfollowing collection or treatment. Stained samples preserved in formalin showed noevidence of leaching when stored at 4-15°C for several months. This technique has beenused successfully for entrainment studies for power plants with once-through coolingsystems.

Key words: freshwater plankton, zooplankton, phytoplankton, ichthyoplankton, dead—livedeterminations, mortal staining, power plant (s) entrainment, industrial monitoring

SEEPERSAD, B., AND R. W. CRIPPEN. 1978. Use of aniline blue for distinguishing betweenlive and dead freshwater zooplankton. J. Fish. Res. Board Can. 35: 1363-1366.

Une immersion de 15 min clans une solution aqueuse de bleu d'aniline permet de dis-tinguer entre le zooplancton d'eau douce vivants et le zooplancton molt Les organismesphysiologiquement morts au moment de l'immersion se colorent en bleu, alors que lesorganismes vivant ne prennent pas le colorant. On a utilise cette technique a plusieursreprises pour evaluer la survie d'individus appartenent a tons les principaux groupes dezooplanctontes d'eau douce. Elle est particulierement utile lorsqu'il s'agit de determiner lasurvie d'un grand nombre de planctontes, soit durant un court intervalle de temps pourplusieurs intervalles successifs, soit dans les cas ou les conditions rendent impossibles detelles determinations immediatement apres la collecte ou le traitement. Les echantillonscolores conserves dans de la formaline durant plusieurs moil a des temperatures de 4 a15°C ne montrent aucun signe de decoloration. Cette technique a etc' utilisee avec succesdans des etudes d'entrainement dans les centrales eleztriques avec systemes refroidisseursmonocycliques.

Received February 14,1978

Regu le 14 fevrier 1978Accepted June 22,1978

Accepte le 22 juin 1978

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