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Notes on the Ecology of Cutthroat ( clarki) t>in Great Central to, · bVancouver Island •· ~

by David W. Narver

FISHERIES AND MARINE SERVICE SERVICE DES PECHES ET DES SCIENCES DE LA MER TECHNICAL REPORT No. 567 RAPPORT TECHNIQUE N"

1975 Environment Environnement 1+ Canada Canada Fisheries SeNice des peches and Marine et des sciences Service de la mer Technical Reports

Technical Reports are research documents that are of sufficient importance to be preserved, but which for some reason are not appropriate for primary scientific publication. Inquiries concerning any particular Report should be directed to the issuing establishment.

Rapports Techniques

Les rapports techniques sont des documents de recherche qui revetent une assez grande importance pour etre conserves mais qui, pour une raison ou pour une autre, ne conviennent pas a une publication scientifique prioritaire. Pour toute demande de renseignements concernant un rapport particulier, il faut s'adresser au service responsable. Department of the Environment Ministere de l'Environnement

Fisheries and Marine Service Service des peches et des Sciences de la mer

Research and bevelopment Directorate Direction du Recherche et Developpement

TECHNICAL REPORT NO. 567 RAPPORT TECHNIQUE NO. 567

, (Numbers 1-456 in this series were (Les numeros 1-456 dans cette furent

issued as Technical Reports of the utilises comme Rapports Techniques de

Fisheries Research Board of Canada. I' office des recherches sur les pecheries

The series name was changed with du Canada. Le nom de la serie fut change

report number 457.) avec Ie rapport numero 457.)

NOTES ON THE ECOLOGY OF CUTTHROAT TROUT (SALMO CLARKI) IN

GREAT CENTRAL LAKE, VANCOUVER ISLAND, BRITISH COLUMBIA

by

David W. Narver

th em This is the 246 Ceci est Ie 246

Technical Report from the Rapport Technique de la Direction du

Research and Development Directorate Recherche et Developpement

Pacific Biological Station La Station de Biologie du Pacifique

Nanaimo, British Columbia Nanaimo, Colombie-Britannique

1975 - i i-

ACKNa.JLEDGEMENTS

The assistance of Mrs. D. Ostrander in sampling the landings at the Ark Resort and of Bruce Andersen and Ron Ptolomey in helping to prepare and interpret the scales is acknowledged. I appreciate comments and criticisms by associates Robin LeBrasseur and Jim Manzer. - iii-

ABSTRACT

Narver, D.W. 1975. Notes on the ecology of cutthroat trout (Salmo clarki) in Great Central Lake, Vancouver Island, British Columbia. Fish. Mar. Ser~ Res. Dev. Tech. Rep. 567: 20 p.

Trout catches in the sport fishery of Great Central Lake we~e sampled in the fall of 1969 and spring-summer of 1970, The main objective was to determine age and growth of trout before experimental lake fertiliz­ ation. Of the 349 fish sampled, 324 were cutthroat, 23 rainbow and 2 Dolly Varden. The sex composition of 60 cutthroat trout sampled for stomach contents in 1970 was 41.710 d and 58.3%~. Cutthroat ranged in age from 1+ to VII+ and in length from 197 to 598 mm (x = 366) , The most common age groups were III, IV and V which comprised 86/0 of the total sample with age IV fish being the most common at 34%. Cutthroat scales had a characteristic pattern of slow growth in the first 2 or occasionally 3 years, followed immediately by 1 or 2 years of rapid growth and then years of successively slower growth. This probably represents stream and subsequent lake growth. The mean length of fish at time of each annulus formation was estimated as 45 mm for age I, 94 for age II, 206 for age III, 319 for age IV, 405 for age V and 465 for age VI.

The major food items in percent occurrence were total fish (including unidentified) (35%), juvenile sockeye (10%), threespine stickleback (8%), carpenter (60%) and cicada (28%). Nonfish, aquatic food items occurred in 15% of the cutthroat and empty stomachs occurred in 10%.

RESUME

Narver, D.W. 1975. Notes on the ecology of cutthroat trout (Salmo clarki) in Great Central Lake, Vancouver Island, British Columbia. Fish. Mar, Ser~ Res. Dev. Tech. Rep. 567: 20 p.

Pendant l'automne de 1969 et Ie printemps et l'ete de 1970, on a echantillonne des truites provenant de la peche sportive dans Ie Grand lac Central, afin de determiner l'age et la croissance des poissons avant l'en­ semencement experimental du lac. Les 349 truites echantillonnees se repartissaient comme suit: 324 fardees, 23 arc-en-Giel et 2 Dolly Varden. Le sex-ratio des 60 truites fardees echantillonnees en 1970 pour le contenu stomacal etait: 41.7% d et 58.3%~. L'age des truites fardees variait de I+a VII+ et leur longueur de 197a 598 mm ex = 366). Les groupes d'age les plus nombreux , etaient III, IV et V soit 86% de la totalite des echantillons , le groupe IV etant le plus abondant, 34%. Les ecailles des truites fardees avaient des caracteristiques de croissance lente pour les deux premieres annees (parfois la troisieme aussi) suivies immediatemertt p~r une ou deux annees de croissance rapide et se terminant par des annees ou lacroissance -iv-

etait de moins en moins rapide. Ce qui represente probablement la croissance en ruisseau suivie de la croissance en lac. La longueur moyenne des poissons au moment de la formation de chaque anneau a ete estimee a 45 rnm pour Ie groupe I, a 94 rnm pour Ie groupe II, a 206 rnm pour Ie groupe III, a 319 mm pour Ie groupe IV, a 405 rnm pour Ie groupe V et a 465 mm pour Ie groupe VI .

Les frequences, en pourcentage, des principaux aliments ingeres ont ete: total des poissons (incluant les poissons non identifies) 35%; saumons rouges juveniles, 10%; epinoches a trois epines, 8%; fourmis gate-bois, 60%; et cigales, 28%. On a retrouve des aliments aquatiques autres que d~s poissons dans 15% des truites f ardees et 10% des estomacs etaient vides. -1-

INTRODUCTIOO

In the fall of 1969 and late spring of 1970 trout captured in the sport fishety on Great Central Lake were sampled for species, size, age and stomach contents. Great Central Lake is the site of an experimental lake enrichment program that started in 1970 and was aimed primarily at improving the growth and survival of juvenile sockeye salmon ( nerka) (Barraclough and Robinson 1972). The trout program reported here was ancillary to the fertilization program and had as its b as ic objective the establishment of a pre-enrichment baseline for age and growth of trout in the lake. It was anticipated that a successful enrichment program might result in a marked increase in juvenile sockeye and thus substantially increase the food base for trout.

In addition to the lake fertilization orientation of the cutthroat program, almost nothing is known about the trout populations of the large of Vancouver Island aside from the fact that they attract SOme rather intense fisheries for relatively large fish. Sport fisheries in large lakes cannot be as easily or economically supplemented by artificial propagation as can small lakes and thus large lakes are heavily dependent on native stocks. Thus the information on Great Central will provide biologists with a firmer base for a management program.

Great Central Lake is a deep, clear lake about 21 miles (34 km) long and averages 1 mile (1.8 km) wide. Public access by boat is mainly at the lake outlet, although limited launching of cartop boats occurs at the B.C. Hydro powerhouse about 5 miles up the lake. The sport fishery is centred primarily in the vicinity of the powerhouse and at the upper end of the lake where the major , Drinkwater and McBride creeks, enter the lake.

METHODS

Sampling of sport fishery catches took place at the Ark Resort (east end of the lake) where the only concrete boat ramp on the lake is located. The resort operators were employed to collect scales, fork lengths, round weights and stomachs (the latter only in 1970) from trout brought to their ramp. Not all fish landed were examined .

The sampler was instructed to collect scale "scrapes" near the lateral line between the posterior edge of the dorsal and anterior edge of the anal fin. The scales were placed in an envelope on which was recorded length and weight of the fish, date, location caught, and lure. Stomachs were removed and placed in 10% formalin along with corresponding information on individual fish.

In the laboratory scales from each fish were cleaned in a detergent solution, several of the best scales were placed on gummed cards, and pressed in acetate (Koo 1962; Clutter and Whitesel 1956). The "best" scales were those (a) that had the least amount of regeneration (resulting from loss of scale at an earlier age), and (b) were the largest and most uniform in shape. -2-

Scales were interpreted by projecting them on graph paper at 100x (1970) or 133x (1969). For each scale the focus was outlined and each annulus and the scale margin along the anterior radius was marked. Two biologists experienced with trout interpreted the scales independently and the approximately 20% disagreement was settled by concurrent re-examination. From the tabulated data grouped by age the mean growth zone (scale radius in magnified units) at each annulus was calculated.

A regression line of the magnified scale radius (log) on fish length (log) was used to estimate average size at time of each annulus formation for each age group. Because the two groups of scales (1969 and 1970) were interpreted at different magnification, separate regressions were used.

Stomach contents were examined from the region between the esophagus and the pylorus. Food items were identified and counted, although numbers of Some items such as carpenter were visually estimated when over about 25. When the food items were fish, they were measured for length whenever possible.

RESULTS

In the fall of 1969 and spring of 1970 scale samples of 349 fish were collected from the sport fishery on Great Central Lake. The species b~eakdown was:

Cutthroat Rainbow Dolly Varden (Salmo clarki) (Salmo gairdneri) ( malma) -----Total 1969 124 19 0 143 1970 200 4 2 206 324 23 2 349

Stomach samples were collected from 60 of the 200 cutthroat in 1970 and none in 1969. The sex ratio of these 60 fish was 25 d and 35 ~ (41.7:58.3%).

Age and size

The 324 cutthroat trout sampled ranged in length from 197 to 598 mm (x = 366), in weight from 017 to 2.1 kg, and in age from 1+ to VII+. Of this sample, 240 had no scale regeneration and thus were suitable for age and growth interpretation.

The sample consisted mainly of fish of age groups III, IV and V (Table 1) . In fact 86% of the 1969-1970 sample was of these age groups with age IV fish being the most common at 34%. -3-

There was considerable difference in the age-mean length relation­ ships of the fall 1969 and spring 1970 groups of cutthroat (Fig. 1). In the three mos t common age groups in 1969 (Ill, IV and V) mean length was greater than the same age groups in 1970. The mean lengths of these fish for 1969 and 1970 respectively were 305 and 274 mm for age 111, 414 and 341 mm for age IV and 474 and 423 mm for age V (Append ix 1 and 11). This age-spec Hic difference in size between the fall 1969 fish and the spring 1970 fish is because the former had an additional 2 or 3 months of growth.

The growth patterns of cutthroat trout throughout the sample were remarkably uniform (Fig" 2). The first two or occasionally three annuli were separated by relatively small growth zones characterized by narrow spacing of circuli. This was usually followed by a broad growth zone of widely spaced circuli and then by growth zones (years) that generally decreased progressively in size.

The estimated mean length at time of each annulus formation shows the above pattern: slow growth during each of the first 2 years, about twice as much annual growth during the third and fourth year, and less growth there­ after (Table 1, Fig. 1). From these data the best estimate of average length at time cif annulus formation is 45 mm for age 1, 94 for age 11, 206 for age Ill, 319 for age IV, 405 for age V and 465 for age VI.

The difference beDveen the estimated lengths at annulus formation and the actual mean lengths of fish decreases with age (Fig. 1). There are two explanations for this difference: one is the "plus" growth included in the actual fish length and the other is the probable bias in the sport fishery for larger, faster growing fish. A Rosa Lee phenomenon is well demonstrated in the length by age estimates for annulus I through VI (Table 1):. a decreasing size at any age group (annulus) with increasing specific age (Chugunova 1959). One explanation of this phenomenon is that the fastest growing individuals are removed earliest by the fishery (or by natural causes).

The weight-length relationship for this sample of Great Central Lake cutthroat trout is: W = .000053293L2 .5852 (Fig. 3). Some examples of average trout lengths and weights are : 350 mm-.52 kg, 400 mm-.67 kg, 500 mm-l.33 kg, and 600 mm-2.ll kg.

The two Dolly Varden included in the sample were caught June 6, 1970 at the powerhouse. They were 457 and 483 mm (1.12 and 1.38 kg) and both contained unidenLifiable fish.

The 23 rainbow ranged in length from 240 to 548 mm and ranged from age II to VI. The age-mean length relationship for those 1969 fish with usable scales were:

Age II III IV V VI n 1 2 3 7 4 Mean length (mm) 241 238 301 432 489 -4-

Food habits

Thirteen categories of food items were identified during the analysis of the 60 samples of cutthroat trout stomachs (Appendix III). In most cases stomach contents were seriously decomposed; this was mainly related to fish not being cleaned until hours after capture when the angle~ returned to the Ark Resort. In terms of percent occurrence the major food items were juvenile sockey e salmon, threespine stickleback, carpenter ant and cicada (Table 2).

Fish occurred in Some stomachs in all sampling periods with an overall occurrence of 35% and a mean of .8 fish per stomach (Appendix III). Sockeye were important only in the earliest sampling periods (May 24-31 and June 6-13) corresponding to the main smolt outmigration. This was after the thermocline was established at about 11-14 m but before surface waters reached 16 C (Parsons et al. 1972). Mean length of sockeye occurring in the stomachs was 58.6 mm (range 40-110). The most sockeye contained in one fish was 4 (45-55 mm) in a 546 mm cutthroat trout. Stickleback occurrence was rather low throughout the sampling periods at 8%. The mean length of 23 stickleback that occurred in the stomachs of three cutthroat was 50.4 mm (range 30-75). A cutthroat, 476 mm in length, contained 10 stickle­ back.

Terrestrial insects, mainly winged carpenter ants and cicada, were extremely common with an overall occurrence of 73%. Some individual fish during May 24-31 had as many as 150 ants in their stomachs (Appendix III). One individual caught during June 6-13 contained 181. The nuptial flight of the carpenter ant is apparently earlier than that of cicada with an overlap during June 20-23, 1970 (Table 2). The incidence of nonfish, aquatic food items in the stomachs was relatively low (15%) and the occurrence of empty stomachs was even lower (10%). Some annelida were probably earthworms lost from the hooks of anglers but some were leeches--decomposition made identif ication difficult.

The lure used in was noted for 55 of the cutthroat sampled. Worms and flat fish used behind a lake troll were evenly split at 26 fish each. The only other lures noted were spoon (one fish) and flashtail and dodger (two fish in August).

DISCUSS 100

The general scale pattern of Great Central Lake cutthroat trout indicates 2 or 3 years of slow growth followed by years of more rapid growth but decreasing with each successive year. This pattern suggests that of a "sea-run" salmonid. In fact the age designation for the age V cutthroat in Fig. 2 could be in the anadromous form of 3 . 2+. However it is the common pattern in in large lakes such as Babine (Griffiths 1968). To what degree this pattern represents stream and lake growth respectively or a change in diet is not known. Griffiths did show that the Babine rainbow utilized more fish (mainly sockeye fry) and fewer insects after they were age III and older than when they were younger. -5-

In the case of Gr eat Central Lake cutthroat, the first 2 or 3 years are probably spent in streams--primarily Drinkwater and McBride creeks at the head of t he lake. However, this growth difference could also be a result ofa major change i n food habits at a certain size or age, i.e. zooplariktiverous changing to pisciverous.

Unfortunately, not enough small trout have been captured by electro­ fishing in tributaries or by beach seining or trawling in the lake to make any conclusions as to life history. Only 1 day was spent electrofishing tributaries while extensive trawling and beach seining was conducted for more than 2 years. Intensive trawling at all depths throughout the lake under all light, weather and seasonal conditions with a large net having a 3 X 6 m opening resulted in no trout although kokanee and adult sockeye salmon were captured (W.E. Barraclough, personal communication). From late 1969 through 1971 229 beach seine sets throughout the lake resulted in 11 rainbow, 5 cutthroat and 2 unidentified trout--the largest was 23 cm in length but most were under 13 cm (J.I, Manzer, personal communication). The beach seine used was 39 m in length and 4.5 m deep (Manzer 1971).

There is considerable variability in the estimated lengths at annulus formation between the 1969 and 1970 samples (Appendix I and II). This may be due to variability in scale sampling techniques. If salmonid scales are not taken in the preferred region (where the scale platelets are first laid down within three scale rows of the lateral line between the dorsal and anal fins) the first growth zone will not correctly reflect the fishes' growth (Narver 1968). This will reduce the estimate of the fishes' length at all annuli but most s e r iously at the first. I have combined the 2 years' data and used it as the best estimate of growth of cutthroat in Great Central Lake (Table 1).

There is little data with which to compare the growth of Great Central Lake cutthroat with those in other lakes. Back-calculated lengths at the end of the first 2 years (Table 1) are about the same as that for cutthroat length in several small unproductive west coast Vancouver Island streams (Narver and Andersen 1974). Great Central Lake cutthroat have first and second year lengths slightly shorter than those for rainbow trout in Babine Lak~ but age-specific lengths of Great Central Lake cutthroats exceed that of older Babine rainbows (Griffiths 1968). Trout in these two big lakes are s low growing compared with more produc t ive lakes such as Kootenay Lake (cartwright 1961): . Back -ca lc ulated length at annulus formation (mm) I II III IV V VI VII VIII Great Central cutthroat 44.6 93.8 205 319 404 464 428 Babine rainbow 48.5 94.1 192 283 331 380 436 467 Kootenay rainbow 63.6 144 286 448 606 726 752

It is not possible to estimate how important sockeye are in the diet of cutthroat with the limited available data. Of the six trout containing at least one juvenile sockeye, the average number of sockeye was 2.3 . It may b e that sockeye are only available as smolts in the spring. At this time they occur in near-surface schools and in littoral areas where thtj may be more -6-

susceptible to predation. By late May, when the lake becomes thermally stratified, the non-migrant sockeye (age 0 and I) are almost exclusively limnetic and undertake a diel verticai movement (Barraclough and Robinson 1972), which places them in near surface waters for only the hours of darkness. It may be that this behavior pattern of sockeye substantially reduces predation in addition to a possible savings in energetics (Narver 1970). -7-

LITERATURE CITED

Barraclough, W.E., and D. G. Robinson. 1972. The fertilization of Great Central Lake , III. Effect on juvenile sockeye salmon. Fish. Bull. U.S. Dep. Commer. 70: 37-48.

Cartwright, JoW. 1961. Investigations of the rainbow trout of Kootenay Lake , British Columbia. Management publication No.7. British Columbia Fish and Game Branch. 46 p.

Clutter, RoL, and L.E. Whitesel. 1956. Collection and interpretation of sockeye salmon scales. Int. Pac. Salmon Fish. Comm. Bull. 9: 159 p.

Chugunova, N. 1. 1959. Age and growth studies in fish. Israel Prog. Sc. Trans 1. , Nat. Sci. Found., Wash., D.C. 132p.

Griffiths, J.S. 1968. Growth and feeding of the rainbow trout, Salmo gairdneri, and the lake trout, Salve linus namaycush, from Babine Lake, British Columbia. B.Sc o Honours Thesis, U. Victoria. 56 p ,

Koo, T oS.Y o 1962. Age in growth studies of red salmon scales by graphical means, p. 51-100. In T.S oY. Koo (ed o) Studies of red salmon, Univ. Wash. Press, Seattle.

Manzer, J.I. 1971. Data on catches, size, and food of the three-spined stickleback in Great Central Lake, British Columbia in 1970. Fish. Res. Board Can. MS Rep. 1145: 43 p.

Narver, D.W . 1968 . Identification of adult sockeye salmon groups in the Chignik system by lacustrine scale measurement, time of entry, and time and location of spawning, p. 113-148. In R.L. Burgner (ed.) Further studies of Alaska sockeye salmon. Univ. Publ. in Fish., New Series, Vol o III ,

1970. Diel vertical movements and feeding of underyearling sockeye salmon and the limnetic in Babine Lake, British Columbia. J. Fish o Res. Board Can. 27: 281-316.

Narver, D.W . , and B. C. Andersen. 1974. Fish populations of Carnation Creek and other Barkley Sound streams--1970-l973: data record and progress report. Fish. Res. Board Can. MS Rep. 1303: 115 p.

Parsons, T.R., K. Stephens, and M. Takahashi. 1972 . The fertilization of Great Central Lake. I. Effect of primary production. Fish. Bull. U.S. Dep. Commer. 70: 13-23. -8-

Table l. Mean (mm) cutthroat trout lengths as determined by back-calculation to each annulus, Great Central Lake, October 1969 and May to July 1970.

Annuli Age group (n) I II III IV V VI VII

I (1) 50

II (13) 52 108

III (62) 51 99 218

IV ( 83) 48 100 209 322

V ( 61) 45 93 202 330 415

VI (18) 46 88 169 283 409 523

VII ( 2) 36 72 107 229 305 355 428

Mean (240) 44 , 6 93.8 205.5 319.4 404.5 464 , 5 428,0 Table 2. Percent occurrence of major food items in stomachs from Great Central Lake cutthroat trout, May-August 1970 (from Appendix III).

Total Unident. Stick1e- Terrest. Carpenter Misc. Sample period n fish fish Sockeye back insects ant Cicada aquatic Empty

May 24-31 24 50 20 21 8.3 83.3 83.3 0 16. 7 4.2

June 6-13 10 30 10 10 0 60 60 0 10 10

June 20-23 10 20 0 0 20 100 100 90 20 10

July 1-12 14 14.3 14.3 0 0 57.1 0 57 14.3 28.6

August 10 2 100 50 0 50 0 0 0 0 0

Total 60 35 15 10 8 73 60 28.3 15 10 r \D r

I I 9MAY-JULY 1970 I +OCTOBER 1969

60 & ESTIMATED LENGTH AT ANNULUS FORMATION

I I I 50 I I I I • I 0

I I t- 0I I 0 I I ~ : I ~ 40 I I I E I I I S I I I :I I I 0 I I l- I & I I I I I I" I ~' t!) 30 o I I I ~ z I I I W -1 I I T I 201- • ~:

10 &

~

I 11 ill LV y ~ VII AGE GROUPS

Fig. 1 . Mean and range of leng ths of cutthroat trout by age group, Great Central Lake, October 1969 ce) and May-July 1970 (0) .

-13-

Fig. 2. A photomicrograph of a scale from a Great Central Lake cutthroat trout age V.

23 24 25 25 27 28 29 30 31 32 33 34 35 35 37 38 39 40 42 44 45 48 50 52 54 55 58 50

WEIGHT (KG) LENGTH (OM) RELATIONSHIP OF CUTTHROAT TROUT

IN GREAT CENTRAL LAKE, 1959 AND 1970 2·5 2·5 WT= 0.000053293 • LN2.5852 .. J • 1·8 ..~ I- 1·8 r--'>. • , LJ ~ 1·4 ~.. I- 1·4 .. J '-" I • .. • .. • J j: 1·0 ~ . .. ttty : .. 1·0 LJ H 0·8 0·8 I t-' W Vl 3: 0.5 -j . . ...r .... 0·5 0·5 . .. /.!.. . 0·5 1 ...... tit 0·4 0·4

0·3 0·3 ~. .. ./ 0·2 l 0·2 / . ..

23 24 25 25 27 28 29 30 31 32 33 34 35 35 37 38 39 40 42 44 45 48 50 52 54 55 58 60 LENGTH (eM)

Fig. 3 . Weight-length (log-log) relationship of cutthroat trout in Great Central Lake, fall of 1969 and spring-swmner. 1970.

-17-

Appendix I. Mean and range (mm) of 111 cutthroat trout lengths and of lengths back-calculated to annuli, Great Central Lake, October 1969. Differences between estimated length at last annuJus and fork length are due to "plus" growth.

Age group Fork Annuli (n) length I II III IV V VI

a 1 (1) 197 SO

2 ( 13) 237 52 108 210-267 31-76 84-126

3 (38) 305 49 100 218 216-375 26-91 70-192 108-312

4 (31) 414 56 106 227 343 317-571 37-83 67-144 114-311 211-495

5 ( 22) 474 48 97 217 341 424 305-584 32-72 65-152 110-297' 215-460 275-532

6 ( 6) 435 41 77 142 240 319 386 406-457 35-48 60-99 102-212 186-112 283-399 362 -418

Mean 367 50 . 7 94 . 8 215 . 9 331.8 401.5 386

a All fish had much "plus" growth. -18-

Appendix II. Mean and range (rom) of 129 cutthroat trout lengths and of estimated lengths back~ca1cu1ated to each annuli, Great Central Lake, May to July 1970. Differences between estimated length at last annulus and fork length are due to "plus" growth.

Age group Fork Annuli (n) length I II III IV V VI VII

3 (24) 274 42 96 217 197-349 22-80 63-225 113-296

4 ( 52) 341 40 95 197 306 235-522 20-84 49 -211 89-308 173 ~428

5 (39) 423 36 90 192 318 402 254 - 546 20-74 54-192 99-321 179-480 259 -592

6 (12) 451 43 89 176 290 430 558 286-598 24-68 61-143 108-330 179-489 278-710 342-892

7 ( 2) 489 36 72 107 229 305 355 428 470-508 33 -38 70-72 102 -113 178-283 263-342 322 :"'390 427~432

Mean 366 39.4 92.7 195.8 307.2 404.7 529 428 Append ix 111. Incidence of food itemS oc("urrin~ in cutthroat trout stomachs, Great Central Lake, May-Au~lls l 19 70.

Stomach con tentS Fish Te rrestrial insects Agu.t r i..: misc . Unid€'nt. Empty Date Leng th Sex Loca t ion Gear Total l!nident. Sock. SOI..' K ~~ .,h.' Thre~ spine Total See tie Ant Cicada Be~ l\, t .J I :""",'P 1 . An t! I i ds. Odona t ~ insectG SmoltS i r ~' st ick leback

May 2" - 31 "2.5 Powerhouse \.,lor m 35 . 6 Worm 3". 3 Brown's Ck. Flatfish 7 7 "1.9 ""arm 62 60 5".6 Po .... erhouse Worm 100 100 "0.6 \.,lorm 10 LO 36.8 F la t fish 20 20 2". S Brown's Ck. Flatfish L5 L5 52.1 Powerhouse \.Jorm 10 10 "".5 Brown's Ck. Flatfish "9.5 Worm 61.0 Powerhouse Worm L 25. " Powerhou se "'orm 2 2 7.9 " Powerhouse Worm 5 5 3S.1 Fawn Pt. Flatfis h 150 150 3'''.9 pOlJ e rhouse 101 LOO "S.3 Far end L5 0 L50 53.3 Flatfish LOO 100 27.9 Worm + + 29. S Powerhouse l.lo rm 50 50 31. 7 flat fis h 3".3 52.3 Spoon 2.L1 1e ng t h "0.6" items 26 12 0 79!.. 79 2 0 0 occur 12 ) 0 20 20 0 0 0 occur 50.0 20.0 l6. 0 0 8.3 83. S. 83.3 0 !. . 2 16. , C. 2 8. 0 0 " .2 >-' items'iish 1.1 .2 . 5 . 1}.- 0 .3 33 . . 1 33.0 0 .0" .0" .1 0 0 .0" '"I June 6- 13 26.7 \.Jorm 1 1 35.6 Worm 10 LO ~ 3.:2 Flatfish 11 10 36. \"'orm 21 20 4).2 "0 "0 "0. 6 \"'o rm 1. 3 . 2 Powerhouse Tro 11, worm LOO 100 56.5 Tro 11, t;,Jorm 50 . 2 lIorm ~ " \"'orm length "1." 7 : itemS IS3 L LSL I occ ur 1 1 1 6 I 6 L occur 30 10 10 10 60 10 60 10 10 10 items if ish .3 . 1 .1 .1 18 . .1 IS. 1 .1 .1 .1

June 20 -23 · 52. 7 Flatfish 7 5 "7.6 Flatfish 10 10 13 LO 27.3 Flatfi.sh 22 10 12 38.1 Flatfish 15 15 "5.7 natflsh 17 10 26.0 lIorm 10 5 "2.5 Flatfish 17 10 "6 3S.7 Flatfish 36 25 10 "3.8 Flatfish 27 15 12 ~3. 2 Flatfish 18 10 8 leng th 1.0.56 .- ite:ns 12 12 L82 L15 59 occur 2 2 LO 4 LO 9 occur 20 20 100 40 LOO 90 20 LO items/fish 1. 2 1.2 L8.2 S. 1l.5 5.9 .2 .1 Append ix II 1. ( cont'd)

Stomach con t .... ntS Fish Terrestrial in sects Aguatic misc . Un iden t. Empty Date Leng th Sex Loea t ion Cear Tota 1 linident. Sock. Sock. Coho Threes pine Tota l Ant C icadu Bee To ta 1 Zoop 1. Ane 1 ida ():jona ta insec ts smolt 5 fry stickleback

July 1-12 31.7 :f Flatfish 26.8 . Flatfish 2" _ 1 Flatfish 2".8 c< 26.7 :" Flatfish 33 .0 Flatfish, .... orm II 10 23.5 9 Flatfish, worm 26.7 o· Flatfish, .... orm 38 _ I 9 F la t fish, .... orm 50.8 , Flatfish, worm 9 "0.6 :: FlatfiSh, worm 12 12 36.8 9 Flatfish, .... orm 1L.Q FlatfiSh, ..... orm I l c ng rh 31.89 N ite ms ,. 30 29 6 0 oc cur 8 8 2 1 ucc.: ur 1·.3 1".3 57. I 7. I 57. 1".3 1".3 1".3 28.6" x it~ms / ~ish . 3 .3 2. 1 .1 2. .2 .2 .3

.!!.ugu s t 10 "0.5 ,. 2l.,.l ? Flashtail x \C! ng th "6.3 I it t: c5 11 L occur 2 occ ur 100 SO 50 items / fish 5.5 2 3.5

Grand tota 1 n - 60 I items "9 1" 13 27 1 .. 189 12 1.088 88 2 10 6 6 r occur 21 9 5 5 8 36 17 2 9 5 2 6 occur 35 1 5 8 2 8 ""73 1 3 60 28.3 3 .3 15 8.3 3.3 10 x items/fish . 8 .2 .2 .02 .02 " 19. .2 18: I 1.5 .03 .2 .. 02 .1 .02 .1 . 1