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Home , Cutthroat trout, Lahontan cutthroat trout, Lake trout, Pyramid Lake (Nevada), Tahoe sucker, Tui chub

Naturalist

Volume 43 Number 1 Article 1

1-31-1983

Life history of the Lahontan cutthroat , clarki henshawi, in Pyramid ,

William F. Sigler W. F. Sigler and Associates, Inc., Logan, Utah

William T. Helm Utah State University

Paul A. Kucera Tribe, Lapwai,

Steven Vigg University of Nevada System, Reno

Gar W. Workman Utah State University

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Recommended Citation Sigler, William F.; Helm, William T.; Kucera, Paul A.; Vigg, Steven; and Workman, Gar W. (1983) "Life history of the Lahontan , Salmo clarki henshawi, in , Nevada," Great Basin Naturalist: Vol. 43 : No. 1 , Article 1. Available at: https://scholarsarchive.byu.edu/gbn/vol43/iss1/1

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. The Great Basin Naturalist Published at Provo, Utah, by Brigham Young University

ISSN 0017-3614

Volume 43 January 31, 1983 No. 1

LIFE HISTORY OF THE , SALMO CLARKI HENSHAWI, IN PYRAMID LAKE, NEVADA

William F. Sigler', William T. Helm^ Paul A. Kucera\ Steven Vigg*, and Gar W. Workman'

Abstract.— The Pyramid cutthroat trout (Salmo clarki henshawi) population was sampled on a monthly basis from November 1975 through December 1977. A subsample of 676 trout, stratified by size and lake habitat, provided biological data. The entire population is presently derived from hatchery production, stocked at lengths of approximately 75 to 300 mm. Peak annulus formation occurs in March and April, followed by the peri-

od of maximum growth. Scale patterns illustrate a variable growing season. Maximum growth in length is in the first

three years of life; after that males begin to grow faster than females. Males attained a greater age in our sample; i.e., the oldest male was seven years old compared to six years for females. The Pyramid Lake Lahontan cutthroat trout exhibit nearly isometric growth. The legal sport fishery removed <20,000 adult fish in 1977 (>380 mm); other decimating factors are poorly un- derstood. No evidence of the following diseases or pathogens was found in the Pyramid Lake population, presuming a carrier incidence of 2 percent at the 95 percent confidence level: infectious pancreatic necrosis, infectious hemato- poietic necrosis, viral hemorrhagic septicema, bacterial kidney disease, enteric redmouth, furunculosis, whirling dis- ease, blood fluke; however, 7 of 235 (=:;3 percent) adults sampled at the Marble Bluff fish way were positive for furunculosis. Small trout feed primarily on and benthic invertebrates; cutthroat trout >300 mm are piscivorous, feeding almost exclusively on {Gila bicolor). The spawning migration of Pyramid Lake cutthroat trout to the Marble Bluff egg taking facility in spring 1976 and 1977 peaked in April and May. Females mature at three or four

years (352-484 mm), and males mature at two or three years (299-445 mm). Mean diameter of mature eggs is 4.51 mm; both ovum size and fecundity are a function of fish size. Fecundity ranges from 1241 to 7963 eggs, with a mean of 3815. Lahontan cutthroat trout comprise <2 percent of the numerical relative abundance and <7 percent of the total fish biomass. Distribution patterns vary on a seasonal basis, with maximum activity during late fall and winter. Man- agement objectives are presented and recommendations are discussed.

The Lahontan cutthroat trout (Salmo clarki The dechne and ultimate of the henshawi) is unique in its abihty to withstand original strain of cutthroat trout in Pyramid the alkaline-saline waters of remnant Great Lake was caused primarily by degradation of Basin . of Pyramid Lake spawning habitat associated with diversion of Lahontan cutthroat trout in a continuous lake water out of the Truckee -Pyramid environment for 50,000-100,000 years with Lake ecosystem (Trelease 1953). The Pyra- an abundant prey species (tui chub, Gila mid fishery has been reestablished bicolor) resulted in a unique predator— the via hatchery propagation of Heenan, Walker, world's largest cutthroat trout (18.6 kg). and Summit lake strains of Lahontan cut-

'W. F. Sigler & Associates Inc., P.O. Box 1350, Logan, Utah 84322. 'Utah State University, Logan, Utah 84322. 'Nez Perce Tribe, Lapwai, Idaho 83540. 'Desert Research Institute, University of Nevada System, Reno, Nevada 89507. 'Utah State UniveRity, Logan, Utah 84322. Great Basin Naturalist Vol. 43, No. 1

Nine now discrete basins once conjoined to form vast (area 22,300 km^; maximum depth 270 m) Lake Lahontan in the northwestern Great Basin (Hubbs and Miller 1948). Pyra-

mid Lake is the deepest remnant of this once great lake system that experienced several cycles of water level fluctuations during the Epoch (Houghton 1976). Great Basin lakes have desiccated to the present state since the last pluvial period some 10-12 thousand years before present (BP). Benson (1978) concludes via sediment analyses that Pyramid Lake was greatly reduced in size 9-5 thousand years BP, but did not become dry and had subsequently been rising until the cultural impacts of the past century.

Pyramid is a graben lake approximately 40 km long and 6.5 to 16 km wide, with a north-

south axis (Figure 2). At the mean 1976 ele- vation of 1157 m ( Geological Survey 1977), Pyramid Lake has a surface area of 446.4 km^, a volume of 26.4 km^, a mean depth of 59 m and a maximum depth of 103 m (Harris 1970). Pyramid is the deep- est and most voluminous saline terminal lake in the western hemisphere (Galat et al. 1981). Pyramid Lake, located entirely within the Pyramid Lake Paiute Indian Reservation, is the terminal water body of the endorheic system originating 193 river Fig. 1. The largest post-1943 Lahontan cutthroat trout (12.7 kg), captured by Ralston Fillmore from Pyra- km upstream at oligotrophic . mid Lake, Nevada, April 1976. Photograph courtesy of The evaporation loss is about 1.2 m annually. Alan Ruger. Due to transbasin diversion of the Truckee River, the lake level declined 23 m between throat trout, and, in the past, of cutthroat- 1905 and 1979; this amounts to a 30 percent trout {Salmo gairdneri) hybrids. The rainbow reduction in lake volume. The lake water is S. c. henshawi currently has highly ionic (Na+ > K+ > Mg2+ > Ca2+; "threatened" status (Deacon et al. 1979). CI- > HCO3 > CO32- > SO42-), with a pH Pyramid Lake presently supports a trophy of 9.2. The 1976 (TDS) sport fishery; the average trout retained by concentration was 5235 mg/1 at elevation fishermen is 500 mm in length and weighs 1 .2 1157 m. On a worldwide perspective, 71 per- kg. In 1976, a Paiute Indian, Ralston Fill- cent of some 350 saline lakes listed by more, captured a 12.7 kg Lahontan cutthroat McCarraher (1972) are more saline than trout that represents a record for the post- Pyramid, but, compared to USA saline lakes.

1943 fishery (Fig. 1). Recent catches are evi- Pyramid is in the moderate range (Galat et dence that the environment of Pyramid Lake al. 1981). is capable of supporting at least a limited During 1976 and 1977 mean surface tem- valuable and unique fishery. However, hu- perature ranged from 6.1 to 23.1 C. As winds man demands on limited Truckee River wa- subside and surface water temperature in- ter and recent droughts have jeopardized the creases, a thermocline is formed in June and trout in Pyramid Lake. The ethics and prior- lasts through December at 16 to 22 m. The ities of our society, as a whole, may ulti- lake is monomictic (Hutchinson 1957); turn- mately decide the fate of the Pyramid Lake over begins in early winter and mixing ex- Lahontan cutthroat trout. tends to spring. January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT

Fox Valley

Needles Helk Kitchen Cormorant Rock

Anderson Bay

True North

PopcortT"

Fig. 2. Bathymetric map of Pyramid Lake, Nevada; depth contours are in meters.

Physical changes, including out-of-basin Pyramid and Winnemucca lakes, Nevada, and inbasin water diversions, channelization, and spawned in the entire Truckee River and and destruction of riparian habitat, have ad- its , a total length of 525 km. They versely affected the ecology of the Truckee also moved into Lake Tahoe, Nevada-Califor- River-Pyramid Lake ecosystem. Historically nia, and spawned in its streams. the Lahontan cutthroat trout moved out of , completed in 1905, 62 km Great Basin Naturalist Vol. 43, No. 1 above Pyramid Lake, effected a transbasin Range and Distrirution diversion of much of the lower Truckee Riv- An ancestoral cutthroat trout probably in- er flow. This obstacle reduced river spawning vaded ancient Lake Lahontan from the Co- to the area below the dam. The dam not only lumbia River Basin and developed into what had the direct effect of reducing flows in the is now known as the Lahontan cutthroat lower river, but indirectly caused the buildup trout (Behnke and Zarn 1976). When the of the delta at the mouth. The numbers of great lake desiccated, two populations of La- trout diminished steadily imtil 1930, which hontans evolved, one best adapted to lakes was the last successful spawning year for the and the other to streams. The major lake original population of Pyramid Lake Lahon- populations of Lahontan cutthroat trout were tan cutthroat trout (Sumner 1939). The U.S. then in Pyramid Lake, , Donner Bureau of Fisheries (now U.S. Fish and Wild- Lake, Independence Lake, and Lake Tahoe life Service) stocked limited numbers in the (Miller 1951). The trout in some of these lake in 1931 and 1932. None was seen in lakes, which held an abundance of forage Pyramid Lake after 1943 and very few after fish, became predatory at an early age, grew 1938. However, before that time millions of fast and large, and were moderately long eggs had been taken from the Pyramid Lake lived. cutthroat and stocked elsewhere (Townley Currently, the largest population of lake- 1980). dwelling Lahontan cutthroat trout is in Pyra- In 1976 the Marble Bluff complex, con- mid Lake. Walker Lake supports a small sisting of a dam and impoundment, a build- population that has no opportunity to repro- ing, and a 5.6 km fishway ending at the lake, duce. Summit Lake and Independence Lake was completed. This facility was built so that may contain the most nearly pure strain of spawning fish could migrate upriver when the Lahontan, but both lakes are small and there was not enough water in the river del- have few (Behnke and Zarn 1976). ta. The fishway, operating at 0.85 to 1.27 A number of western lakes support reproduc- mVsec, allows fish to move upstream via four ing populations of Lahontan cutthroat trout. step-up ladders. At the upper end of the fish- Recently a small stream-dwelling population way the fish may be shunted on upstream or of Lahontan cutthroat trout, believed to have into the building. been transplanted from Pyramid Lake before 1930, was discovered near Pilot's Peak, north Importance of Wendover, Utah-Nevada (Hickman and Duff 1978, Hickman and Behnke 1979). The Pyramid Lake Lahontan cutthroat There are a number of stream-dwelling La-

trout is potentially of substantial economic hontan cutthroat trout populations in the and social importance to the Pyramid Lake Great Basin. Paiute Indian Tribe. Its adaptation to the In 1950, the Nevada Fish and Game De-

highly saline waters of the lake make it a partment initiated a small-scale stocking pro- unique natural history entity. gram of Lahontan cutthroat and other trout In 1977 an estimated 27,241 people spent in Pyramid Lake (Trelease 1969). The pro- 276,532 hours fishing for Lahontan cutthroat gram has now grown to 2.2 million 75-300 trout in Pyramid Lake. They landed 43,841 mm fish per year, supplied by two hatcheries fish, of which 19,930 or 46 percent were le- of the Pyramid Lake Indian Tribal Enter-

gal size (381 mm). This is at the rate of 0.16 prises (PLITE) and the Lahontan National fish per hour landed and 0.07 kept. at Gardnerville, Nevada.

It has been estimated that the historic an- nual production of Lahontan cutthroat trout Morphology and was at least 454,000 kg (Behnke 1974). The Pyramid Lake trout was the mainstay in the Despite the diverse evolutionary histories diet of the Pyramid Lake Paiutes and many of western trout (genus Saltno), some species other Indian tribes. They were also shipped are related closely enough to interbreed free- to mining camps and other markets as far ly and produce fertile hybrids. It is this po- away as San Francisco. tential presence of all degrees of hybrids January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT within a habitat that complicates identi- operculum and the origin of the dorsal fin. fication and evaluation of pure stock (Behnke Five scales per fish were selected and impres- and Zam 1976). The original stock of Lahon- sions made of them on plastic slides with the tan cutthroat trout was apparently resistant use of a roller press (Smith 1963). to hybridization due to its long isolation in The length-weight relationship is expressed the Lahontan basin. The present subspecies by the formula W = aL'' (Sigler 1951), where does not share this characteristic. The isola- W = weight in grams, L = fork length in tion also encouraged a high degree of adapt- cm, and a and b are constants. A log transfor- ability for lake habitat. mation of W produces a linear equation. The The following are typical meristics of the constants a and b are calculated by the meth- Lahontan cutthroat trout (Behnke and Zam od of least squares. 1976): Validity of the scale method was deter- mined by criteria suggested by Van Oosten Scale counts 1929, 1944) and Hile (1941). To avoid lateral series (1923, two rows above possible bias, scales were first read without lateral line 150-180 knowledge of the size of the fish. The scales above lateral line were read at least three times. Further (origin of dorsal checks for accuracy of age assignment includ- fin to lateral ed comparisons with known age and tagged line) 33-43 fish, Peterson's method, and use of year Vertebrae 61-63 marks on other bony parts. All scales were Gillrakers 21-28 examined with an Eberbach microprojector Pyloric caecae 40-75 at a magnification of SOX. Basibranchial teeth Numerous and The body-scale relationship was calculated well developed according to Tesch (1971). The condition fac- tor K = WxlOVL^ was calculated according The number of pyloric caecae is higher in the to Carlander (1969), where W = weight in Lahontan cutthroat than in other subspecies grams and L = fork length in mm. Calcu- of cutthroat. The large, round, rather dull lations were accomplished using an age- reddish spots that appear on the head as well growth computer program (Nelson 1976). as on the caudal peduncle and occasionally Creel census information was collected ventrally are the best field characteristic. from January 1977 to April 1978. Four week- The following data were collected as part days and six weekend days were randomly se- of a study contracted between W. F. Sigler & lected each month for censusing, with holi- Associates Inc. and the United States. This days treated as weekend days. On each study was to provide an ecological evaluation selected day a check station was manned on of Pyramid Lake and its fishery resources and the principal highway leading to Pyramid habitat. Lake and three aerial counts were made. Check stations were in operation from noon Procedures until dark, where all pertinent information was collected from fishermen. Aerial surveys

Fish life history data were taken by month- were conducted by dividing a day into three ly nettings from November 1975 through De- equal time segments and an aerial count was cember 1977. Fish were sampled by bottom made at the midpoint of each segment (Fig.

set variable-mesh gill nets, vertical set gill 3). Inclement weather caused cancellation of nets, beach seines, fyke nets, and trawls. Fish 5 percent of the flights (Kennedy 1978). were measured to the nearest millimeter in Shore fishermen and boats were counted on fork (FL), standard (SL), and total (TL) each flight, with the number of boat fish- lengths and weighed to the nearest gram (Sig- ermen obtained by multiplying the number ler and Kennedy 1978). of boats by the average number of fishermen Scale samples were collected from the left per boat on the day of the count (Johnson side in the region above the lateral line and and Wroblewski 1962). When less than 10 midway between the posterior edge of the boats were checked, the yearly mean number Great Basin Naturalist Vol. 43, No. 1

(1942) lists 40 mm (FL) as the size of Lahon- tan cutthroat from Blue Lake, , at Hells Kitchen Needles time of scale formation. Yellowstone cut- throat develop scales when they are between 40.3 mm and 42.8 mm (FL) (Brown and Bail- ey 1952). Laakso and Cope (1956) report 39.3 mm (FL) as the size of cutthroat trout at the Anderson Bay time of scale formation. Cutthroat trout sam- pled in had formed scales at 41.2 to 63.2 mm (FL) (Brown and Bailey 1952). Ir- ving (1953) reports 23.9 mm (FL) for cut- throat trout in Henry's Lake, Idaho. Rob- ertson (1947) found considerable variation in the size of cutthroat trout at the time of scale formation.

all ''aREAN- Dago Bay Nearly scales examined from Pyramid EIGHT s^ Lake fish showed early growth patterns char- acteristic of hatchery rearing. Scales also showed crowded circuli beginning in late

Depth contours (m] September 1975 and 1976 and in early No- Truckee River To Reno Nixon To vember 1977. Nearly all scales aged showed Fig. 3. Lake areas used for creel census data collec- winter bands of thin and closely spaced cir- tion and location of creel check stations. culi. Summer growth bands appear as thick and widely spaced circuli. The beginning of of fishermen per boat was used. Rate of suc- growth, the first appearance of summer cess, effort, and harvest were calculated by banding, is assumed to correspond with for- computer program (David Wheaton, pers. mation of the annulus. The period of annulus comm. 1977). All calculations were expanded formation extended from about February to a 30-day month. Mean lengths and weights through May, peaking in late April 1976 and of fish caught were also calculated. late March 1977. Food habits were determined by examining All annuli were readily visible. Check the stomachs of five fish per size group from marks that appeared throughout all fields each net catch. Food habit analyses were were prominent during the first year's conducted by percent of frequency of occur- growth for the majority of fish examined. rence and percent of total volume. These stress conditions that resulted in Fecundities were determined by actual egg growth interruptions existed during the first counts (Kucera and Kennedy 1977). Criteria (0 age) year for fish from the National Fish described Nikolsky were used for by (1963) Hatchery (Lahontan National Fish Hatchery determining stage of maturity; only ripe fe- personnel, pers. comm. 1976). This situation males and fresh ovaries were used for fecun- presumably does not occur every year. dity studies. Linear and logio (Y+1) regres- sions between fecundity, fork length, weight, age, ovum diameter, ovary weight, and net Seasonal Growth weight (body weight minus ovary weight) were used to examine the interrelationships Our analyses of age and growth for Lahon- between these variables. tan cutthroat trout from Pyramid Lake is based on scale samples from 676 specimens Age and Growth taken almost exclusively with nets from No- vember 1975 through November 1977. The Appearance of Scales and general shapes of the 1976 and 1977 growth Formation of Annuli curves (Fig. 4) were the same, but during Fork length at the time of scale formation 1977 growth was more rapid and extended for hatchery-reared Lahontan cutthroat plan- over a longer period of time than for com- ted in Pyramid Lake is 25.8 mm. Calhoun parably aged fish in 1976. Increments of January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT growth declined with increasing age of fish in AgeV 1976, but increased in 1977. Growth in- 500 creased sharply in spring, slowed in late sum- mer, and ceased during fall and winter.

Annual Growth E J. 300 Annual growth (back-calculated lengths) values were derived from the body length- i£ 200 scale radius relationship FL = A -I- B(SR); = FL = fork length in mm and SR anterior -il91_ = 273. Days Days scale radius (Table 1). Body-scale regression 100 equations, based on data collected over the entire study, were used to calculate the 1976 1977 lengths. The results for 676 fish are: for fe- FA males FL = 155.881 + 3.5364 (SR), for AJ AOD JAOD Month males FL = 79.176 + 4.2599 (SR), for in- determinates FL = 112.872 + 4.0834 (SR), Fig. 4. Seasonal growth curves, 1976 and 1977, for Lahontan cutthroat trout age groups I through V. Fish and for combined FL = 132.952 + 3.8079 were collected from Pyramid Lake, Nevada, from No- (SR). vember 1975 through November 1977. The graph ab-

Young-of-the-year Lahontan cutthroat scissa is divided into bimonthly intervals beginning with trout sampled from Lahontan National Fish April. Hatchery averaged 152 mm in length at age eight months. By the end of Year I, hatchery Lahontan cutthroat trout greater than 787 trout are approximately 203 mm FL (Lahon- mm were not sampled with our nets and thus tan National Fish Hatchery personnel, pers. do not appear in our age and growth studies; comm. 1976). These data demonstrate that however, larger ones were taken by anglers. the back-calculated lengths for age I Pyramid In the 1977 creel sample, which was about Lake trout are accurate. three times that of the net sample, 22.5 per- in Growth in length is nearly isometric from cent of the 1916 trout exceeded 600 mm the end of the first through the seventh years length; the longest one was 990 mm FL. The (S.D. = 107.0). Ei- of life. Variation by sex is evident in the average size was 505 mm growth rates of certain age groups. Annual ther these large fish grew faster than the av- increments of growth in length for males are erage in our studies, or they were older than fish. In greater than for females from age II on. Ac- the maximum ages of our net-caught Fill- cording to Irving (1953), male trout from April 1976, an Indian angler, Ralston Henry's Lake, Idaho, grow faster than fe- more, captured a 12.7 kg Lahontan cutthroat males, and Bulkley (1961) reports male trout trout, the largest recorded since December outlive females. Pyramid Lake Lahontan cut- 1925, when another Indian, John Skim- world throat trout appear to follow these patterns. merhorn, caught an 18.6 kg trout, the Others have reported no difference between record cutthroat (Wheeler 1974). There are larger the sexes in growth rates (Drummond 1966, numerous unconfirmed reports of ones turn of Snyder and Tanner 1960). than this being marketed around the The oldest male and female aged from the century. length-weight Pyramid Lake were in their seventh and sixth LeCren (1951) states the in addition to provid- year, respectively. This longevity is some- relationship equation, length to weight, what less than historical data. Sumner (1939) ing a method of converting and found the oldest age groups of trout in Pyra- also indicates taxonomic differences value of the mid Lake were the seven- to nine-year-olds. events in the life history. The growth is Studies in smaller high altitude lakes. Upper constant "B" will equal 3.0 where (Ricker 1971). Blue Lake (Calhoun 1944), and Topaz Lake symmetrical or isometrical demonstrate linear (Johnson 1958), indicate that few trout live Values less than 3.0 place faster than growth in past their sixth year (Table 2). growth is taking Great Basin Naturalist Vol. 43, No. 1 weight. Values greater than 3.0 demonstrate The length-weight curve of the Lahontan the reverse; both are allometric growth. cutthroat trout shows the importance of for- The length-weight equations calculated for age fish. In Pyramid Lake cutthroat trout Lahontan cutthroat trout show growth weight gains tend to exceed the increases in slightly exceeds the cubic relationship; this length when the diet shifts from invertebrates represents allometric growth. We combined to fish. They are in their third year and sim- all years, drawing on data from 561 trout. ilar to cutthroat trout from Independence

Sizes ranged from 189 mm (36 g) to 787 mm Lake, California (Lea 1963). Lea states the

(6163 g) (Table 3, Fig. 5). Tesch (1971) notes rate of growth for the Independence Lake allometric growth in some salmonid stocks. cutthroat trout population is only slightly

Table 1. Summary of the mean calculated fork lengths and increments of growth for Lahontan cutthroat trout collected from Pyramid Lake, Nevada, from November 1975 through November 1976.

Calculated fork lengths (mm) at end of each year of life Number Age group of fish 2 3 4 5 6

(Female)

I 42 238 II 68 236 306 III 80 233 305 374 IV 25 236 304 376 442 V 23 236 303 374 442 500 VI 15 233 306 374 447 508 580

Grand average 235 305 374 443 503 580 Increments of growth 235 70 70 68 59 72 Number of fish 253 211 143 63 38 15

(Male)

I 4

II

III IV V VI VII January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT curvilinear until age III, at which time the i.e., gravid females weigh significantly more relative weight increase accelerates greatly. just before spawning season than after. Thus Lea also reports that, for Independence Lake the K of females is more variable than males cutthroat trout less than 225 mm, forage fish on a seasonal basis. are of minor significance, but for those over A direct relationship between size and 300 mm, fish become the major forage item. condition factor of Pyramid Lake Lahontan

Hazzard and Madsen (1933) report cutthroat cutthroat trout is evident (Table 5). Lea trout from Jackson Lake, , also (1963) reports a trend of increasing condition show a definite change in diet from Crustacea factor with increasing length for Independ- to fish at a length of approximately 300 mm. ence Lake Lahontan cutthroat trout. Fleener The condition factor (K = W X 10VL^) is (1952), however, states condition factor de- used as an index of well-being or relative ro- creases with length for cutthroat trout from bustness. The average K of 561 Pyramid Beaver Creek, a small tributary of the Logan Lake Lahontan cutthroat trout, sexes and age River, Utah. Irving (1953) says size, age, and groups combined, was 1.00. A slight sexual sex are not related to condition factor for dimorphism is noted for condition factor, Henry's Lake cutthroat trout. It seems logical with males having a slightly higher K value that condition factor would be directly re- than females (Table 4). This is in agreement lated to fish size in lake environments where with results from other studies. Fleener large fish have a predatory advantage. This (1952) and Madsen (1940) also report higher situation occurs in Pyramid Lake since, at the K values for male over female cutthroat critical size of about 300 mm, Lahontan cut- trout. However, the extent of the sexual di- throat trout are able to utilize the huge for- morphism may vary with fish size and season; age base of tui chubs.

Table 2. Growth of cutthroat trout from 14 Western lakes. 10 Great Basin Naturalist Vol. 43, No. 1

6163 Graph symbol • 23456 789 A BC D

No. points represented 1 2 3 4 5 6 7 8 9 10 11 12 13

W= .0027L33271* Age 4938 + n = 561 VII

. Age VI

3712 + Age / V /..• Age

IV •4 » ? 2487 3 2

J 2 . ». X Age I 1261 + 2 . .3«'5 . I /3. Age I > ••2*32 •42** • ••7847 •* il 2 * 2^23489664222 • -Age I I , •37AC6943 2 • I 4 5638 37087^ 233 ••• 2 44494S7S732I^^2* • 26528848A94522** • + 2*26S4*3* 189* 309" 428 548 677 787

Fork length (mm)

Fig. 5. Length-weight relationship of combined data for Lahontan cutthroat trout from Pyramid Lake, Nevada, November 1975 through November 1977, with mean length-weight values by age groups. FL in cm.

Conversion Factors Hatchery-reared Lahontan Cutthroat Trout, Length-weight Relationships and Factors for converting TL to FL and SL to Condition Factors FL for cutthroat trout from Pyramid Lake, Nevada are: In 1976, 612 fingerlings were taken from the Lahontan National Fish Hatchery, Gard- TL = 1.07 FL (189 - 490 mm) TL = 1.05 FL (500 - 590 mm) nerville, Nevada, to determine length-weight TL = 1.03FL(>.590mm) relationships. The fingerlings represent wild = .888 (189 - 300 mm) SL FL Summit Lake stock ranging in fojk length SL = .893 FL (301 - 500 mm) from 57.9 to 125 (Table and La- SL = .895FL(>501 mm) mm mm 6) FL = .935 TL (202 - 524 mm) hontan fifth-generation domestic stock, origi- FL = .953 TL (525 - 620 mm) nally from Summit Lake, ranging in fork = FL .970TL(>608mm) length from 40 mm to 250 mm (Table 7). The FL = 1.13 SL (168 - 266 mm) length-weight relationships are calculated as: FL = 1.12 SL (268 -447 mm) FL = 1.12SL(>447mm) Summit Lake brood W = .00001L2-8749 Lahontan brood W = .000007L30588 The ratios vary with size, necessitating more than one set of conversion factors. Con- The K-factors for domestic stock range version factors for cutthroat trout have been from 1.01 to 1.21, the exponent indicating reviewed by Cope (1953). slightly faster growth in weight than length. January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 11

The K-factors for wild stock show sUghtly de- fishery. Walker Lake's now extinct Sacra- creasing trends; the exponent is less than 3.0, mento perch population reached its limit of

indicating these fish are getting slimmer as "alkalinity" tolerance when it could no long- they grow in length. er reproduce in the early 1950s. At that time, The Lahontan brood attain greater weight the total alkalinity was approximately 2500 per length than do Summit Lake brood. The mg/1 as HCO3 (Cooper 1978). In 1952, the weight differences can be attributed to brood TDS of Walker Lake was 6790 mg/1 (Koch spawned from wild stock being more active et al. 1979). are stressed by (wild) and domestic stock being more passive and grow poorly in Pyramid Lake water; (Lahontan National Fish Hatchery Manager, they do not survive in more concentrated al- Charles R. Messier, pers. comm. 1976). kaline waters such as Walker Lake (Knoll et al. 1979) and Omak Lake (Paul A. Kucera, Mortality and Morbidity pers. comm. 1982). Taylor (1972) notes that Various factors may cause mortality of carbonate and bicarbonate salts are more tox- Pyramid Lake's trout population, including ic to Lahontan cutthroat trout at elevated , death during stocking of hatchery TDS levels than sodium chloride alone. Ele- recruits, predation on juveniles, spawning-re- vated temperatures may have a synergistic lated deaths of adults, and disease. When effect on toxicity and vice versa other decimating factors are inoperative or (Vigg and Koch 1980). eliminated, senility must ultimately cause Mortalities range widely among fish cap- death. Among 676 Lahontan cutthroat trout tured and released. Hooking mortality of sampled from Pyramid Lake during this lure-caught cutthroat trout in Yellowstone study, no females and only four males Lake was relatively low (<6.5 percent); reached age VII. Sumner's (1939) data in- however, the combination of natural baits dicates very few of the original population of and high water temperature resulted in sig- Lahontan cutthroat trout lived beyond eight nificantly higher mortality (Mamell 1969, years, although a few may have lived to be Marnell and Hunsaker 1970). In Pyramid 11. Lake, where fish <483 mm TL are illegal (as Chemical constituents of the aquatic habi- of 1 July 1982), all types of artificial lures are tat are rarely neutral in their effects on the used. The losses from hook and release in biota. Toxic substances often first express Pyramid Lake have not been established. Le- themselves as growth suppressants, reproduc- gal sport fishing removed < 20,000 fish in tive inhibitors, increased vulnerability to dis- 1977, not a seriously decimating factor for ease, or destroyers of the most sensitive link the Pyramid Lake population. in the food chain. Increased levels of TDS Infectious disease is a potential threat to could be detrimental to the Pyramid Lake wild and cultured fish alike. Rational man-

Table 3. Length-weight relationships (linear and curvilinear) for Lahontan cutthroat trout from Pyramid Lake, Nevada, from November 1975 through November 1977.*

Log-log transformation Exponential Class (linear) (curvilinear)

(Female) logioW = -2.6218 + 3.3754 logioL W = .0023L3-3754 (i^ = .95, n = 224) F = 602.4 = (Male) logioW = -2.8052 -I- 3.4778 logioL W .0016L3'«778 (1^ = .94, n = 73) F = 1089.9

= .0042L3-2023 (Indeterminate) logioW = -2.3690 -I- 3.2023 logioL W (r2 = .92, n = 262) F = 3017.2

(Combined) logioW = -2.5531 + 3.3271 logjoL W = .0027L3-3271 (i^ = .94, n = 561) F = 9293.3

^Equations were calculated using fork length in centimeters. 12 Great Basin Naturalist Vol. 43, No. 1 agement and utilization of any fisheries must 1977, the Fish Disease Control Center, U.S. incorporate a realistic understanding of the Fish and Wildlife Service, Fort Morgan, Col- serious pathogens extant in the system. A fish orado, conducted inspections. population undergoing environmental deg- Attribute sampling for IPN in 1976 pre- radation is subjected to environmental factors sumed a 5 percent carrier incidence and that may predispose the population to dis- achieved 95 percent confidence limits. No ease. Various interstate and international evidence of any pathogen was detected in regulations have been formulated to restrict 1976 (Ferjancic 1976). Sampling in 1977 pre- movement of serious fish pathogens. sumed a carrier incidence of 2 percent and PLITE has a program to determine the achieved 95 percent confidence. Inspections presence of pathogens in Pyramid Lake conducted in 1977 (Ruger 1977) detected no trout. Particular attention is given to those evidence of IPN, IHN, VHS, bacterial kidney pathogens included in restrictive lists. A disease, enteric redmouth, furunculosis, series of inspections begun in 1976 followed whirling disease, or blood fluke, except 7 of proper procedure as specified by the Fish 235 adults sampled at the Marble Bluff fish- Health Section of the American Fisheries So- way were positive for furunculosis. ciety and The River Wildlife Coun- Sample sizes were sufficiently large to ex- cil-Fish Disease Policy (American Fisheries tend confidence beyond original required Society: Fish Health Section 1975), Con- sampling presumption. Regulation and pro- sultation and confirmation of procedure were tocol require assumption of a 2 percent car- reviewed by Ron Goede, fish pathologist of rier incidence for 95 percent confidence in the Utah Division of Wildlife Resources, and wild populations. Sample sizes in this study by Dennis E. Anderson, U.S. Fish and Wild- are sufficient at the 1 percent carrier in- life Service, Fort Morgan, Colorado. cidence to permit 95 percent confidence in The inspections in 1977 included the fol- detecting IPN and at the 2 percent carrier in- lowing diseases and/or the pathogens in- cidence to permit 95 percent confidence in ducing the diseases: detecting all other listed diseases.

Viral: IPN (Infectious pancreatic necrosis) (1976 & 1977) Food and Feeding Habits IHN (Infectious hematopoietic necrosis) VHS (Viral hemorrhagic septicemia) Lahontan cutthroat trout in Pyramid Lake Bacterial: Bacterial kidney disease {Renebacteriiirn are largely piscivorous after they reach a size salmoninarum) Enteric redmouth {Yersinia ruckerii) of approximately 300 mm. They then feed al- Funmculosis {Aeromonas sahnonicida) most exclusively on tui chubs, but they may Parasitic: Whirling disease {Myxosoma cerebralis) feed opportunistically on other fish and they Blood fluke {Sanguinicola sp.) feed to some extent on aquatic insects. Small Pyramid Lake and lower Truckee River trout feed on zooplankton and benthic in- fish populations were sampled by hook and vertebrates. From January through Decem- line, gill net, and electrofishing. Fish were ber 1976, 192 Lahontan cutthroat trout were also collected from the Marble Bluff fishway examined for food habits; 35 had not recently and the Dunn Hatchery, Sutcliffe, Nevada. fed. The highest percentage of the 35 non- The inspection in 1976 was conducted by feeders occurred during the winter and early Biometrics Inc., Tacoma, . In spring months when v/ater temperatures and.

Table 4. Coefficient of condition for Lahontan cut- Table 5. Coefficient of condition based on increasing throat trout from Pyramid Lake, Nevada, fork length in fork length (mm) for Lahontan cutthroat trout from mm, November 1975 through November 1977. Pyramid Lake, Nevada, November 1975 through No- vember 1977. January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 13 therefore, trout metabolism and feeding ac- the volume. Chironomid pupae are eaten tivity were low. nearly twice as frequently as larvae. This is The piscivorous nature of Lahontan cut- also true for Lahontan cutthroat in Blue throat trout was predictable. Fish, the most Lake, California (Calhoun 1944) and - frequent food item, was eaten by 62.4 per- sonally in Omak Lake, Washington (Paul A. cent of the trout (Table 8). Fish also account- Kucera, unpubl. data 1981). Platts (1959b) re- ed for the largest volume of food (84.5 per- ports chironomidae pupae are the most im- cent). Snyder (1917) found adults in lakes portant forage item for cutthroat trout in feed largely on minnows, with one fish from Strawberry Reservoir, Utah. Pyramid Lake described as containing three The remaining food items in the cutthroat large minnows. In Johnson's (1958) food anal- diet were of relatively minor importance yses of 20 Pyramid Lake cutthroat trout, fish compared to consumption of fish and chi- were dominant. Insects, zooplankton, and ronomids. Some of the items, however, can amphipods appear in descending order of im- be of significant value seasonally or during portance. Invertebrates rather than fish are certain life stages, such as zooplankton and the major source of food for Lahontan cut- smaller invertebrates for young-of-the-year throat trout in two Sierra lakes, presumably trout. Other food items consumed in order of because the trout occur in different areas of percent of frequency of occurrence were: the lake than other species of fish (Calhoun terrestrial insects (10.2); amphipods, both

1942). Hyallela and Gammarus (9); algae (7.6); zoo- A diet succession from invertebrates to fish (7.6); bottom substrate (4.5); He- is apparent for Lahontan cutthroat trout as mipterans (3.2); odonates (1.9); vascular they increase in size (Table 9). Invertebrates plants (1.9); coleopterans (.6); and hydracari- make up 51.2 percent and fish 38.3 percent nads (.6). of the volume of food eaten by trout 198-300 mm FL. The volume of invertebrates eaten Reproduction decreases with increasing trout size. Larger trout, 300-399 mm, consume 32.8 percent in- The Lahontan cutthroat trout spawning vertebrates and 60.8 percent fish. This is also migration into the Truckee River and Marble true for Utah cutthroat trout (Sigler 1962, Bluff fishway peaked in April and May of Sigler and Miller 1963). 1976 and 1977 at river water temperatures Chironomids, the second most important varying from 8 to 16 C (Fig. 6). Although food item, are consumed by 41.4 percent of only 563 fish were captured in 1976, the run the trout, but account for only 4.0 percent of was reported to be the largest in recent years

Table 6. Expected Lahontan cutthroat trout measurements (FL) based on measurements of 200 Lahontan cut- throat trout, Summit Lake brood. Lahontan National Fish Hatchery, Gardnerville, Nevada, 1976.

Length (L) 14 Great Basin Naturalist Vol. 43, No. 1

(U.S. Fish and Wildlife Service pers. comm. an unusual concentration of cutthroat trout 1976). In comparison with the number of fish in the lake near the Truckee River mouth at in the lake large enough to reproduce, this this time. However, large numbers of trout number is amazingly small. The 1977 creel congregated around the Sutcliffe area where census (Kennedy 1978) produced an esti- hatchery reared cutthroat are planted. As mated sport fishing catch of < 20,000 Lahon- Ball (1955) postulates, since these planted fish tan cutthroat trout >380 mm TL. This size is were not imprinted on an inflowing stream, a reasonable approximation of the average they may be milling about the area where length at reproductive maturity. It is obvious they were originally planted. that the population of mature fish must be Limited data on the maturation of female considerably greater than 563, the number Lahontan cutthroat trout in Pyramid Lake that were captured. Netting did not indicate suggest that consecutive-year spawning does

Table 7. Expected Lahontan cutthroat trout measurements (FL) based on measurements of 412 Lahontan cut- throat trout, Lahontan domestic brood. Lahontan National Fish Hatchery, Gardnerville, Nevada, 1976.

Length (L) January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 15 not occur. Judging by ovary development, four-year-old fish. If an alternate-year - several females of age groups IV and V col- ing pattern is typical, then most female La- lected prior to the spawning season were not hontan cutthroat trout in Pyramid Lake will going to reproduce the current year but spawn a maximum of twice in their lifetime. would the following spring. Similar situations If they mature at age IV, they may live to have been reported elsewhere. Some 1-15 spawn only once. Some of those that mature percent of the cutthroat in Arnica Creek, at age III may spawn again at age V. Yellowstone National Park, spawn each year The sex ratio of Lahontan cutthroat trout after reaching maturity, 10-26 percent are in our net catches was 1 male:4.23 females alternate-year spawners, and 46 percent skip (n = 455). This is not representative of the two years (Ball and Cope 1961). Seven per- population in the lake. The ratio of males to cent of the female Lahontan cutthroat trout females in the spawning runs was variable, in Blue Lake, California, spawned in con- i.e., 1.06:1 in 1976 and 1:2.35 in 1977. The secutive years, and 10.5 percent of the origi- ratios of Summit Lake Lahontan cutthroat nally marked females were in the run two trout spawning runs, from 1968 to 1975, var- years later (Calhoun 1942). ied from 1:1.3 to 1:2.2 and averaged 1:1.6 Female cutthroat trout in Pyramid Lake males to females (Rankel 1976). Angling is mature at age III or IV, when they are 352 to male-selective in Pyramid Lake. This is also 484 mm FL; males mature at ages II or III, true in Omak Lake (Paul A. Kucera, pers. when 299 to 445 mm FL. Lahontan cutthroat comm. 1981). trout in Independence Lake, California, ma- Female Lahontan cutthroat trout spawn ture at ages III or IV (Lea 1963). Lea attri- after attaining an average gonadal somatic butes the presence of small numbers of ma- index (percent gonad weight to total body ture three-year-olds to a precocial element of weight) of 11 percent. The progression in go- the population. Rankel (1976) reports spawn- nadal somatic indices, observed from October ing runs of Lahontan cutthroat trout from through December 1977, indicates a steady Summit Lake, Nevada, consist mainly of increase in germinal growth through the

Table 8. Food of 157 Lahontan cutthroat trout. Pyramid Lake, Nevada, 1976. 16 Great Basin Naturalist Vol. 43, No. 1 winter. The largest increase involves a shift Monthly progression in egg sizes from Octo- from an average value of 5.9 percent in No- ber through December 1977 indicated a con- vember to 8.1 percent in December. sistent, gradual increase in ovum size. The The diameter of mature eggs of Pyramid mean egg diameter in December was 4.11 Lake Lahontan cutthroat trout range from mm, with some eggs as large as 4.60 mm. 2.76 to 5.09 mm and average 4.51 mm. Some females may be able to spawn in

Table 9. Percentage of total volume and frequency of occurrence of food items consumed by Lahontan cutthroat trout from Pyramid Lake, Nevada, in relation to size. Trout were captured from January through December 1976 with bottom-set gill nets.

Food item January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TroUT 17

J F 1977 Month and year

Fig. 6. Mean monthly Pyramid Lake cutthroat trout catches (15 gill net sets per month) from November 1976 through December 1977, in comparison with the spawning runs at the Marble Bluff fish passage facility.

December or January. For example, as early dity from 1241 to 7963 and average 3815 as January, 1981 and 1982, mature cutthroat eggs per female. Lea (1963) reports fecun- were running up a small stream south of Sut- dities of Lahontan cutthroat trout in Inde- cliffe, Nevada, artificially produced by pendence Lake, California, vary from 669 to pumping about .057 m^/sec of lake water 2080 eggs and average 1191 eggs per female. through rearing ponds and allowing it to run back into the lake. Egg size is positively cor- HUbitat and Ecology related with fish length (r = .48; P<0.05) and weight (r = .51; P<0.05), indicating The most characteristic feature of the that egg size increases with fish size. Pyramid Lake environment is the high level The number of eggs produced by a female of salts; TDS concentration was about 5350

Lahontan cutthroat trout is significantly re- mg/1 during 1976-1977 (Sigler and Kennedy lated to age, fork length, and weight 1978). Although sodium chloride is the domi- (P<0.05). The above relationships have sig- nant salt (over 70 percent), alkalinity may be nificant linear fits with and without logio the most important constituent. The mean transformation of data. Fork length provides pH is 9.2. The historic increase in TDS levels the best predictor for fecundity, followed by was associated with the decline in lake level weight and age. Increases in fecundity corre- (Fig. 7). Since the baseload of salts is relative- the spond to increases in length and weight. The ly constant, TDS varies inversely with of the lake. Various studies, although log 10 equation for fork length and fecundity is volume logioF = 2.83 (logioFL) - 4.16, and for preliminary in nature, have demonstrated but alka- weight and fecundity is logioF = .81 that NaCl is relatively irmocuous, sahnonids (logioWT) + .92. These fish range in fecun- linity (HCO3 + CO3J is toxic to I

18 Great Basin Naturalist Vol. 43, No. 1

1 1 L. 1186 _l 1 I

1183 ^ X I \ 5500 X \ / \ 1180 x-> \" 1176 - \ 5000 E 1173 -

1170 - 4500 • • • • TDS H X -^ 1167 - — X Fragmentary record a> More complete record 5

(September altitudes are shown I 1164 < ^ - 4000

1161 -

- 1158 - 3500

1155 -

1152 3000 — 1 1 1 1 1 1 1 1 1 I 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980

Year

Fig. 7. Water level and total dissolved solids fluctuations in Pyramid Lake, Nevada, 1867-1979 (From Galat et al. 1981).

(Beatty 1959, Mitchum 1960, Taylor 1972, 23.1 C in July 1976 and August 1977, respec- Knoll et al. 1979). tively. The lake is thermally stratified from The five major species of fish in Pyramid June through December; wind-generated Lake, in order of relative abundance are: tui mixing occurs from January through May. chub, , Lahontan cutthroat The thermocline forms at a depth ranging trout, cui-ui (Chasmistes cujus), and Sacra- from 16 to 22 m. The euphotic depth aver- mento perch {Archoplites interruptus). Al- aged 11 m for 1976 and 1977, which resulted though numerous species have been in- in a trophogenic zone of about 4.67 km^ (Ga-

troduced, the current species composition is lat et al. 1981). almost exclusively represented by the original Surface-dissolved oxygen (DO) is above 8 fish species, the only exception being the Sac- mg/1, and thus not limiting to fish. Meta- and

ramento perch (Vigg 1981). This fact is prob- hypolimnetic DO depletion occurs beginning ably due to the harsh environmental condi- in July following stratification and algal de- tions of Pyramid Lake, specifically the TDS composition; maximum DO deficits occur in levels. In contrast, exotic fish introductions the profundal zone just prior to late fall mix- have nearly extirpated the native fish fauna ing. Hypolimnetic DO deficits in stratified of oligotrophic (low TDS) Lake Tahoe at the lakes are generally associated with decompo- upper end of the Truckee River (Miller sition of organic matter, which is generated 1951). by primary production in surface water, and The maximum surface (0-1 m) water tem- gradually sink to the bottom. During Decem- perature in Pyramid Lake was 21.4 and ber, the mean DO level is <4 mg/1 at depths January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 19

>61 m and <0.2 mg/1 at depths >92 m However, the relative of the Lahon-

(Vigg 1980). In contrast to the anoxic condi- tan cutthroat trout population is estimated at tions, which are very hmited on a temporal 6.4 percent. Theoretically, the biomass of a and spatial basis in Pyramid Lake, Walker primary piscivore such as cutthroat trout Lake exhibits extensive DO depletions that may be as much as 20 percent of the biomass severely restrict fish distribution (Cooper of the fish forage (McConnell et al. 1978).

1978, Koch et al. 1979). The trout population at present is far below Diatoms {Cyclotella sp. and Stephanodiscus its theoretical maximum. spp.) dominate the phytoplankton commu- Activity of the Lahontan cutthroat trout nity during winter; but the most abundant population is at a maximum from December chlorophyte, Crucigenia sp., attains max- through March. Peak spawning migrations imum abundance in spring (Sigler and Ken- occurred during April and May in 1976 and nedy 1978). Blue-green algae are by far the 1977 (Fig. 6). In 1978 the run was from dominant form in Pyramid Lake, comprising March 8 to June 13 (Wolcott 1978). The

>74 percent. Nodularia spumigena is the greatest trout activity observed in our study most abundant species; blooms begin as early corresponds very closely to the historical as July and may last as late as October. Tem- spawning period of the winter race of Pyra- poral nutrient dynamics inversely relate to mid Lake Lahontan cutthroat trout (Snyder phytoplankton abundance. Following vernal 1917). Snyder observed that the spawning increases of algal growth, orthophosphate migrations of Lahontan cutthroat occurred in and nitrate are depleted and remain at low two distinct periods. The larger winter run of lakes levels during the summer period of maximum trout out of Pyramid and Winnemucca following the rise in river flows Octo- primary production. Silica, in addition to ni- began the spawning migration ex- trate, probably limits diatom production in ber-December; tended through March. As the winter run Pyramid Lake (Galat et al. 1981). Benthic macroinvertebrates, periphyton, waned, the spring nm of the smaller, darker, and more heavily spotted trout commenced. and zooplankton all are important energy This migration peaked in April and extended sources for in Pyramid Lake. Di- to May. atom domination of the periphyton commu- The sport fishing catch was highest in win- nity is demonstrated by sampling with glass ter, corresponding to the high catches in the slides (<99 percent). The chlorophyte, 1975-1977 net sampling program (Figure 8). Cladophora glomerata, was the dominant The proportion of large trout was greatest epilithophyton in Pyramid Lake during May during winter. The high level of winter activ- and June in 1976 and 1977 (Sigler and Ken- ity of the Pyramid Lake population of La- nedy 1978). Chironomids are the lake's most hontan cutthroat trout is apparently a mani- abundant macroinvertebrates (63 percent), festation of innate spawning-related followed by Oligochaetes (33 percent), which behavior. The larger and older spawners in are especially abundant in the profundal the cutthroat trout population in Yellowstone zone (Robertson 1978). Two euryhaline am- Lake are predominant in the early part of phipods, Gammarus lacustris and Hyallela each spawning run, with the smaller spawn- azteca, are associated with tufa and rocks. ers comprising the latter part of the runs is of The zooplankton community composed (Bulkley and Benson 1962). five cladocerans, three copepods, and four The differences between the 1976-1977 rotifers (Lider and Langdon 1978). The cla- Marble Bluff spawning runs and the activity doceran, Diaptomus sicilis, is a perennial spe- patterns of the lake population of cutthroat cies and the most abundant zooplankter trout may be explained by three factors: (1) throughout the year. few Pyramid Lake Lahontan cutthroat trout The Lahontan cutthroat trout is the third were apparently imprinted on the Truckee most numerous fish in Pyramid Lake. Com- River; (2) the spawning runs were composed pared to the more abundant tui chubs and of a disproportionately large number of cut- Tahoe suckers, the trout population is numer- throat-rainbow hybrids that were raised (thus ically small, about 1.3 percent (Vigg 1981). imprinted) in the Truckee River watershed; 20 Great Basin Naturalist Vol. 43, No. 1

38- -S > -Q 36 o S 34 19 g- 32 To 96 30- i "I 28

-i 26 78 ^;^ 24 - 22-

76 20 ^ I

u> 16

3 14

12- I 152 i 10 o 92 I 8 i i I -5 6 o i i 4^ i ^ 32

S 2 14 30 35 '^ 1 ^ m i 1 DJ FMAMJ JASONDJ 1FMAMJ JASON 1976 1977

Month and year

Fig. 8. The proportion of large (>550 mm) cutthroat trout taken in the monthly bottom-set gill net catches in Pyramid Lake, Nevada, November 1975 through 1977.

and (3) Lahontan cutthroat trout are prob- stream association, streams can be lost as nur- ably genetically programmed for winter as sery areas if no natural reproduction occurs, well as spring spawning, but early winter even though mature adults are present in the peak flows are now diminished or eliminated lake. Ball postulates that nonimprinted fish, by diversions. For example, during 1976 such as gravid adults, may randomly move flows in the lower river peaked in March and throughout a lake or mill about in the area steadily decreased to the lowest annual level where they were planted. in December (U.S. Geological Survey 1977). On an annual basis the majority of Lahon- Spawning cutthroat trout instinctively re- tan cutthroat trout in Pyramid Lake occur at turn to the stream in which they were born depths <61 m (Fig. 9). Compared to other (Ball 1955, Platts 1959a, McCleave 1967, species, its depth preference is intermediate, Jahn 1969). Their olfactory development pat- and most closely associated with that of tui terns indicate cutthroat trout are capable of chub. There is a differential seasonal depth imprinting on a home stream odor at a very distribution of cutthroat trout (predator) and early age (Jahn 1972). Moreover, mature cut- tui chub (prey) in Pyramid Lake, i.e., inshore throat are able to return to home streams versus 46 m (Fig. 10). Cutthroat trout appar- even when deprived of their sense of vision ently prefer inshore areas during all seasons or smell, indicating an inborn "compass" except summer, when shallow water temper- homing mechanism. atures are high. Tui chub are generally in- Ball (1955) says, since predetermination of shore during spring and summer, inter- spawning site is established by early life mediate during autumn, and offshore during January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TroUT 21

Percent species composition

" -^ Tui chub

Mean catch Cutthroat trout ^ -A Tui chub

• • Cui-ui o o Tahoe sucker

Depth (m)

Fig. 9. Percent species composition of tui chub and percent of the mean catch of cutthroat trout, tui chub, cui-ui, and Tahoe sucker by depth in Pyramid Lake, Nevada. Data are derived from the total catch of 108 bottom gill net sets on a quarterly basis (September, December, March, and June) during 1976-1977 (Vigg 1980).

winter. Maximum overlap of the two popu- moves into cooler, deeper waters (Fig. 11). lations occurs during spring, the period of This temperature relationship clearly illus- maximum cutthroat trout growth. The two trates the habitat preference of Lahontan species are opposite with respect to depth cutthroat trout for cooler waters than their distribution during winter, when trout meta- prey the tui chub. The lowest summer den- bolism and feeding are low. sity of cutthroat trout occurs in littoral ben- high- Changes in net catch/effort and benthic thic and inshore surface waters, and the the depth distribution of cutthroat trout occurred est density in benthic waters in or below on a seasonal basis in 1976-1977 (Vigg 1978). thermocline. During the summer months, at depths of During late fall and winter, when the total cutthroat are well represented the catch rate of cutthroat trout was about 1.5 20-60 m in benthic areas, while avoiding zone. times that of other seasons, they inhabited surface waters of the offshore limnetic of the predominantly inshore areas. As surface wa- From June to October the majority with ter temperatures increase from 10 to 16 C limnetic trout are at depths of 15-28 m (Vigg during late spring, the trout population negligible ntmibers at greater depths 22 Great Basin Naturalist Vol. 43, No. 1

100 n Cutthroat trout 90 ^ Tuichub 80 n J t 70 60 w 50

40 i

30 i 20

10 i i i i

Fall Winter Spring Summer Fall Winter Spring Sumnner Fall

(N-D) (J-M) (A-J) (J-S) (O-D) (J-M) (A-J) (JS) (OD)

1975 1976 1977

Season, month and year

Fig. 10. Percent of the total seasonal variable mesh bottom-set gill net catches of cutthroat trout and tui chub taken at inshore (versus 46 m) sampling stations in Pyramid Lake, Nevada, from November 1975 through December 1977.

1980). As surface temperatures cool below 16 ciety, the secondary beneficiary, must also be C in the fall, trout return to surface waters satisfied if the goal of the tribe is to be and inshore areas. reached. This goal, as articulated by the U.S. The profundal zone of Pyramid Lake (>61 Justice Department, is to produce a viable m), which constitutes about half of the bot- fishery in Pyramid Lake. The above state- tom area and 20 percent of the volume, is ment may be assumed to be synonymous with nearly devoid of cutthroat trout in summer. or an extended definition of viable fishery. Temperatures at these depths are less than 7 As far as can be determined, there is vir-

C during all seasons, and oxygen is low dur- tually no natural reproduction of Lahontan ing the fall and early winter. Cutthroat trout cutthroat trout in the Truckee River at pres- densities are slightly higher in the profundal ent. An important aspect of the management zone during winter, but this deep area is not program should be to reestablish successful an important habitat for trout (Sigler and spawning runs in the Truckee River (Innis et Kennedy 1978). al. 1981). This will require rehabilitation to stabilize stream banks and provide shade to Management reduce water temperatures, installation of fish ladders to permit spawning adults to mi- Management of any fishery should ensure grate upriver, fish screens to keep down- that biological, social, economic and political stream migrants from entering values are given appropriate consideration so canals, and augmented stream flow during as to produce maximum benefits to society critical seasons. Sufficient water will be re- from a given stock of fish. Although the pri- quired for adults to migrate in winter and mary beneficiary of the Pyramid Lake fishery early spring; to keep temperatures below is the Pyramid Lake Paiute Indian Tribe, so- 13.3 C through the fry stage; and below January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 23

Fig. 11. Percent of the catches of cutthroat trout and tui chub taken on the surface from surface and bottom gill nets (adjusted to unit of net area) at the 23 m depth in Pyramid Lake, Nevada, from February through November 1977.

21.8 C (Vigg and Koch 1980) during juvenile Unless Lahontan cutthroat trout have been are residence. Since it will take years to restore imprinted on Truckee River water, they river habitat, the Lahontan cutthroat trout disinclined to attempt to ascend the river to population must be sustained by stocking. spawn. Some hatchery fish should be stocked The catch rate of legal size (>380 mm TL) in the lower river to initiate a spawning run. Lahontan cutthroat trout in 1977 was ap- The trout reared in the PLITE Numana proximately one fish per 14 hours of effort. Hatchery may be imprinted on the Truckee Under the minimum legal size of 457 mm the River because the hatchery outfall runs into catch rate was one fish per 18.9 hours (Alan the river. The reasons for the very substantial Ruger, pers. comm. 1982). Catch rates should spawning runs of Lahontan cutthroat trout ap- be increased five- to tenfold to fall within ac- up the Sutcliffe outflow (>9000 in 1982) beliefs ceptable limits. This will require substantially pears to contradict some long-held increased recruitment rates and the reduction and raises more questions than answers. Alan the of incidental causes of mortality. Since ma- Ruger (pers. comm. 9 June 1982) thinks odors, such as ture fish appear to congregate in the vicinity fish are returning to hatchery fish. modified an- of stocking sites in late fall, winter, and early fish feed and juvenile The in the Truckee Riv- spring, during the time when sport fishing is nual temperature regime that will be best, some of the stocking effort should be di- er, due to the regulation in flow must be rected to the vicinity of popular fishing areas necessary to provide for all uses, for the reestablish- and access points (Table 10). considered in planning 24 Great Basin Naturalist Vol. 43, No. 1 ment of natural reproduction in the river. some of the present population should and Temperatures acceptable for spawning and apparently do tend to spawn in winter. incubation of eggs exist during winter and When hatchery brood stock are to be used as early spring; thus successful natural repro- a source of eggs, a program of selective duction in the river will depend in part on an breeding utilizing early-spawning fish should early spawning migration. Behnke (1979) sug- be initiated. Stocking in the river and lake gests selecting maximum-size fish at first should be limited to Lahontan cutthroat maturity for breeding stock. He also recom- trout; hybrids should not be utilized. mends using the genetic diversity in remnant Benthic invertebrates are the major food stocks to produce the best-adapted strain to source of Lahontan cutthroat trout until they Pyramid Lake conditions. As pointed out by exceed 300 mm FL. Survival of smaller Snyder (1917), Pyramid Lake Paiute Indians stocked fish may be limited by the avail- early in the century recognized two spawn- ability of benthic invertebrates. The feasibil- ing runs of Lahontan cutthroat trout: one in- ity of stocking fish as large as 300-330 mm, volved large fish in late November, Decem- and their survival and costs in comparison to ber, and January; the other occurred in the the size conventionally stocked, should be spring when the smaller fish spawned. The evaluated. In view of the larger number of spring-spawning fish always faced the haz- trout that must be stocked, introducing larger ards of high water temperatures, but not at fish could eliminate benthic invertebrate the level that exists today. Competition for abundance as a limiting factor and thus in- river flows is much more intense in spring crease survival rates of stocked fish. than in winter. It is generally agreed that Currently all trout <483 mm TL that are some remnant of the original pool of landed must be released. The present catch

Lahontan cutthroat trout persists. Therefore, rate of undersized fish is much greater than

Table 10. Comparison of gill netting catch rate, surface water temperature, and trout fishing success during 1977 at Pyramid Lake, Nevada. January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TroUT 25 those fish longer than 483 mm. The reason the summer months, but lasts from May for releasing a fish is the assumption that it through November. Nonfishing recreationists will survive to spawn and/ or be caught later. currently represent a significant segment of This assumption should be tested, and the the lake users, almost twice the use of fishing size limit implemented accordingly. effort (Fig. 12). The Lahontan cutthroat trout now in Pyra- mid Lake probably is physiologically capable Summary of hybridizing with rainbow trout. A popu- lation of mature rainbow trout in the middle The lake form of Lahontan cutthroat trout and upper Truckee River where Lahontan is the largest of all cutthroat. Its ancestors in- cutthroat trout spawn would, therefore, po- vaded ancient Lake Lahontan from the Co- tentially threaten the maintenance of the lumbia River drainage about 70,000 years lake strain. In addition, residents BP. Before the coming of white men, the La- in the upper Truckee River will compete hontan cutthroat trout was a staple in the with and prey on young Lahontan cutthroat diet and an item of trade for the Paiute In- trout. Since a large part of the Truckee River dians of Pyramid Lake. Later, both white is managed by the Fish and Game Depart- men and Indians commercialized the trout ment of California and the Nevada Wildlife fishery in markets as far away as San Fran- Department, the decision is theirs to imple- cisco. At one time the annual production ment reduction in the nonnative resident may have been as much as 454,000 kg. In populations of the river fish. 1943 the last of the Lahontan cutthroat trout Nonfishing recreation on Pyramid Lake disappeared from Pyramid Lake. Very few represents approximately 500,000 hours of had been seen after 1938. Lahontan cutthroat use annually. This use is concentrated during and other trout were stocked in the lake

Table 10 continued. 26 Great Basin Naturalist Vol. 43, No. 1

130, Nonfishing recreation

120 Ibtol hsnermen

110

100

90

J F 1977 Month and year

Fig. 12. Hours per month of fishing and nonfishing recreation at Pyramid Lake, Nevada, in 1977-1978.

Starting in 1950. Today, there is virtually no wide, covers an area of 446.4 km^, and has a natural reproduction. mean depth of 59 m and a maximum of 103 Lahontan cutthroat trout in Pyramid Lake m. Derby Dam, completed in 1905, effects a live six to seven years. They start maturing at transbasin diversion of part of the Truckee age three to four, some as early as December River flow. The TDS of Pyramid Lake in or as late as April, May, or June. There may 1977, at an altitude of 1157 m, was 5235 be what amoimts to two potential spawning mg/1. The base load of TDS is reasonably runs. An average-size female produces about stable. Pyramid Lake stratifies into three It destra- 3815 eggs and is mature when the gonadal well-defined layers in June-July. somatic index reaches 11 percent. None of tifies in December-January. It is a midlevel the eight potential disease organisms ex- productivity lake. Pyramid Lake, a remnant plored in 1976-1977 were considered a haz- of Lake Lahontan, has a pH of 9.2 and is high ard. The fish are most active in the lake from in carbonates and bicarbonates. Summer sur- December through March, a time of most face temperatures are 21-23 C. There is fishing effort. Cutthroat <300 mm feed pri- ample dissolved oxygen in the epilimnion and marily on invertebrates; after that size they thermocline at all times. Nodularia, a blue- feed heavily on fish. Five species of fish con- green alga, dominates much of the lake from stitute >99 percent of the population. They late summer to early fall. Diatoms dominate are, in order of abundance, tui chub, Tahoe the periphyton communities. Chironomids sucker, Lahontan cutthroat trout, cui-ui, and are the most abundant macroinvertebrates. Sacramento perch. Pyramid Lake, entirely within the Pyramid Conclusions Lake Paiute Indian Reservation, is the termi-

nus of the Truckee River, which is its only The Lahontan cutthroat trout fishery in source of water except for a few desert show- Pyramid Lake is currently not a viable one. ers. The average annual loss to evaporation is The annual catch was < 20,000; the rate, one 1,2 m. The lake is 40 km long, 6.5 to 16 km fish for > 14 hours effort, when the minimum January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 27 legal size was 381 mm TL. Fishing success Literature Cited should be increased in the magnitude of five-ten times. Any adverse changes in the American Fisheries Society: Fish Health Section. 1975. Suggested procedures for detection and lake ecology may stress the fish that will in identification of certain infectious diseases of susceptible to disease. turn make them more . Amer. Fish. Soc, Washington, D.C. The 1905 diversion of the Truckee River, Ball, O. P. 1955. Some aspects of homing in cutthroat trout. Proc. Utah Acad. Sci., Arts, Lett. 32:75-80. which in dry years may take most of the Ball, O. P., and O. B. Cope. 1961. Mortality studies on flow, reduced available stream spawning area cutthroat trout in . U.S. Dept. to for the cutthroat from >500 km <62 km Inter., Fish Wildl. Serv. Res. Rep. 55. 62 pp. of substandard stream. Derby Dam, over a Beatty, D. B. 1959. An experimental study of the tox- icity of sodium bicarbonate, sodium chloride, and period of 25 years, doomed the historical cut- sodium sulfate to rainbow trout. Unpublished fishery. Successful reproduction in the throat thesis. Univ. of Wyoming. stable riparian habitat 1974. effects of project lower river demands Behnke, R. J. The the Newlands and water temperatures < 13.3 C, until after on the Pyramid Lake fishery. File Rep. 15 pp. 1979. Monograph of the native of the spawning-hatching-fry emergence and <21.8 genus Salmo of western North America. U.S. For. C thereafter. Brood stock or wild egg-pro- Serv., U.S. Fish Wildl. Serv., U.S. Bur. Land Mgt. ducing fish for hatcheries should be selected Washington, D.C. Behnke, R. and M. Zarn. 1976. Biology and manage- for large size at first maturity and for winter J., ment of threatened and endangered western early spring maturing. Part of the matur- or trout. USDA, For. Serv. Gen. Tech. Rep., Fort ing fish in the lake should be imprinted on Collins, Colorado. 45 pp. the Truckee River. Since the effluent from Benson, L. V. 1978. Fluctuations in the level of pluvial Lake Lahontan for the past 40,000 years. Quar- Numana Hatchery flows into the Truckee temary Res. 9:300-318. River, it may be these trout will be im- BjoRNN, T. C. 1957. A survey of the fishery resources of printed. The biological implications of the Priest and Upper Priest lakes and their tribu- Completion Rep. Idaho large lam of cutthroat into the Sutcliffe flow taries. Dingell-Johnson Fish Game Dep., Boise, Idaho F-24-R. 176 pp. should be explored in depth. D., E. Bailey. 1952. Time and pat- Brown, C. J. and J. Since the base load of TDS is constant in tern of scale formation in Yellowstone cutthroat Pyramid Lake, the concentration varies in- trout {Salmo clarkii lewisii). Trans. Amer. Mi- crosc. Soc. 120-124. versely to lake volume. Any significant in- 71(2): BuLKLEY, R. V. 1961. Fluctuations in age composition crease in may prove harmful to key or- TDS and growth rate of cutthroat trout in Yellowstone ganisms in the food chain and to the trout. Lake. U.S. Fish Wildl. Serv. Res. Rep. 54. 31 pp. The median level of productivity that Pyra- BuLKLEY, R. v., and N. G. Benson. 1962. Predicting year-class abundance of Yellowstone Lake cut- mid Lake currently enjoys is considered more throat trout. U.S. Fish Wildl. Serv. Res. Rep. level for Pyramid desirable than a higher 50:1-20. Lake Lahontan cutthroat trout. A. 1942. The biology of the black-spotted Calhoun, J. trout {Salmo clarkii henshawi [Gill and Jordan]) in two Sierra Lakes. Unpublished dissertation. Acknowledgments Stanford University. 218 pp. 1944. The food of the black-spotted trout {Salmo This work was performed under Bureau of clarkii henshawi [Gill and Jordan]) in two Sierra Indian Affairs contract H50C 14209487. As- Nevada lakes. California Fish Game Dep. 80-85. sistance and cooperation was provided by 30(2): Carlander, K. D. 1969. Handbook of - of F. Sigler Associates Inc. employees W. & eries biology, Iowa State Univ. Press, Ames, (WFSAI), members of the Pyramid Lake Iowa. 1:1-752. 1978. Contributions to the life history of Paiute Indian Tribe, and the U.S. Fish and Cooper, J. J. the Lahontan tui chub, Gila bicolor obesa (Gi- Wildlife Service, Fisheries Assistance Office, rard), in Walker Lake, Nevada. Unpublished Nevada. Denise Robertson and Roy Reno, thesis. Univ. of Nevada, Reno, Nevada. Whaley, formerly of WFSAI, were respon- Cope, O. B. 1953. Length measurements of Yellowstone Spec. Sci. Rep. sible for the two sections on age and growth, Lake trout. U.S. Fish Wildl. Serv. Fish. 102. 17 and food habits, respectively. The manuscript pp. Willl\ms, and S. Deacon, £., G. Kobetich, J. D. fisheries direc- J. was reviewed by Alan Ruger, Contreras. 1979. Fishes of en- tor. Pyramid Lake Indian Tribal Enterprises, dangered, threatened, or of special concern. Fish. Sutcliffe, Nevada. Bui. Amer. Fish. Soc. 4(2):29-44. 28 Great Basin Naturalist Vol. 43, No. 1

Drummond, R. a. 1966. Techniques in the collection Johnson, V. K. 1958. Fisheries management report. and mounting of trout scales. Prog. Fish Cult. Lakes— Pyramid, Walker, and Tahoe. Dingell- 28(2):113-116. Johnson Completion Rep. Nevada Fish and Echo, B. 1955. Some ecological relationships between J. Game Dept. FAF-4-R. 47 pp. yellow perch and cutthroat trout in Thompson L. 1978. creel survey of Lake, Kennedy, J. A Pyramid Lakes, Montana. Trans. Amer. Fish. Soc. Pages 414-437 in Sigler L. Nevada. W. F. and J. 84:239-249. Kennedy, eds.. Pyramid Lake ecological study. results of the 1976 I.P.N. (In- Ferjancic, K. p. 1976. The W. F. Sigler & Associates Inc., Logan, Utah. fectious pancreatic necrosis) survey conducted on Knoll, J., D. L. Koch, R. Knoll, J. Sommer, L. Lahontan cutthroat trout (Salmo clarki henshawi) Hoffman, and S. Lintz. 1979. Physiological ad- Lake, Nevada. Pyramid Lake Indian at Pyramid aptations of salmonid fishes {Salmo clarki hen- Sutcliffe, Nevada Rept. 4 Tribal Enterprises, pp. shawi, Salmo gairdneri and FiNNELL, L. M. 1966. Granby Reservoir Studies. Colo- kisutch) to alkaline saline waters and their toxic rado Div. Wildl., Fisheries Res. No. 3:4-6. effects. Report to Office of Water Research and Fleener, G. G. 1952. Life history of the cutthroat trout Technology. Desert Res. Inst. Bioresources Cen- {Salmo clarkii Richardson), in Logan River, Utah. ter Piibl. 50009. Reno, Nevada. 82 pp. Trans. Amer. Fish. Soc. 81:235-248. L., E. L. Lider, R. L. Koch, D. J. J. Cooper, Jacobson, Galat, D. L., E. L. Lider, S. Vigg, and S. R. and R. Spencer. 1979. Investigations of Walker Robertson. 1981. Limnology of a large, deep J. Lake, Nevada: Dynamic ecological relationships. North American terminal lake. Pyramid Lake, Desert Res. Inst. Bioresources Center Publ. Reno, Nevada. USA. Hydrobiologia. 82:281-317. Nv. No. 50010. 191 pp. Harris, E. E. 1970. Reconnaissance bathymetry of Pyra- Kucera, p. a., and L. Kennedy. 1977. Evaluation of a mid Lake, Washoe County, Nevada. Hydrologic J. sphere volume method for estimating fish fecun- Investigation Atlas HA-379, U.S. Geol. Surv. dity. Prog. Fish Cult. 39(3):115-117. S., 1933. Studies of the Hazzard, a. and M. J. Madsen. Laakso, M., and O. B. Cope. 1956. Age determination food of the cutthroat trout. Trans. Amer. Fish. in Yellowstone cutthroat trout by the scale meth- Soc. 63:198-207. od. Wildl. Mgt. 20(2): 138-153. A. 1978. Status of cut- J. Hickman, T. J., and D. Duff. Lea, R. N. 1963. Ecology of the Lahontan cutthroat throat subspecies in the western Bonneville Ba- trout {Salmo clarki henshawi) in Independence sin. Great Basin Nat. 38(2): 193-202. California. Unpublished thesis. Univ. of R. 1979. Probable dis- Lake, Hickman, T. J., and J. Behnke. Berkeley. covery of the original Pyramid Lake cutthroat California, 95 pp. relationship trout. Prog. Fish Cult. 41:135-137. LeCren, E. D. 1951. The length-weight and Hile, R. 1941. Age and growth of rock bass (Ambloplites seasonal cycle in gonad weight and condition in Ecol. rupestris Rafinesque) in Nebesh Lake, Wisconsin. perch {Perca fluviatilis). J. Anim. Trans. Wisconsin Acad. Sci., Arts, Lett. 20(2):201-219. 33:189-337. Lider, E. L., and R. W. Langdon. 1978. Plankton ecolo-

HuBBS, C. L., and R. R. Miller. 1948. The Great Basin gy. Pages 241-293 in W. F. Sigler and J. L. Ken- with emphasis on glacial and postglacial times. nedy, eds., Pyramid Lake ecological study. W. F. n. The zoological evidence. Univ. of Utah. Bull. Sigler & Associates Inc., Logan, Utah. 17-166. 1940. on age and growth of cut- 38(20): Madsen, M. J. Report Houghton, S. G. 1976. A trace of desert waters. The throat trout {Salmo lewisii) of Yellowstone Lake, Great Basin story. Arthur H. Clark Co., Glendale, Wyoming. U.S. Fish Wildl. Serv. Res. Rept. 12 California. 287 pp. pp. Hutchinson, G. E. 1957. Treatise on limnology: geogra- Marnell, L. F. 1969. Hooking mortality of cutthroat phy, physics, and chemistry. Vol. 1. John Wiley trout. Unpublished dissertation, Colorado State and Sons, . 1015 pp. Univ. 99 pp. Innis, G. S., D. F. Hanson, and W. Haefner. 1981. A J. Marnell, N. E., and D. Hunsaker 11. 1970. Hooking simulation of alternatives in model management mortality of lure-caught cutthroat trout {Salmo a freshwater fishery. Elsevier Scientific Publ. Co. clarki) in relation to water temperature, fatigue Amsterdam, The Netherlands. 12:267-280. and reproductive maturity of released fish. Trans. Irving, R. B. 1953. Ecology of the cutthroat trout {Salmo Amer. Fish. Soc. 99(4): 684-688. clarkii Richardson) in Henry's Lake, Idaho. Un- McCarraher, D. B. 1972. A preliminary bibliography published thesis. Utah State Agricultural College. and lake index of the inland mineral waters of 101 pp. the world. FAO. Fish. Cir. 146. Jahn, L. a. 1969. Movements and homing of cutthroat McCleave, D. 1967. Homing and orientation of cut- trout {Salmo clarki) from open-water areas of Yel- J. throat trout {Salmo clarki) in Yellowstone Lake lowstone Lake. J. Fish. Res. Bd. Can. with special reference to olfaction and vision. 26:1243-1261. J. Fish. Res. Bd. Can. 24(10):201 1-2044. 1972. Development of the olfactory apparatus of McCoNNELL, W. D. L. Galat, and K. Hamilton- the cutthroat trout. Trans. Amer. Fish. Soc. J., 1978. Potential fish production of Pyra- 101(2):284-289. Galat. mid Lake based on organic matter contributions. Johnson, M. W., and L. Wroblewski. 1962. Errors as- Collins, sociated with a systematic sampling creel census. Colorado Coop. Fish. Res. Unit. Fort Trans. Amer. Fish. Soc. 91(2):201-207. Colorado. 84 pp. January 1983 SiGLER ET AL.: LaHONTAN CuTTHROAT TrOUT 29

Miller, R. G. 1951. The natural history of Lake Tahoe Smith, S. H. 1963. Making plastic impressions of fish fishes. Unpubhshed dissertation. Stanford Univ. scales with a roller press. Prog. Fish Cult. 160 pp. 16(2): 75-78. MiTCHUM, D. L. 1960. An experimental study of the tox- Snyder, G. R., and H. A. Tanner. 1960. Cutthroat trout icity of calcium carbonate, calcium sulphate, reproduction in the inlets to Trappers Lake. Col- magnesium carbonate, and magnesium sulphate orado Div. Wildl. Tech. Bull. 7:1-85. thesis. Univ. of to rainbow trout. Unpublished Snyder, J. O. 1917. The fishes of the Lahontan system of Wyoming. Nevada and northeastern California. U.S. Bur.

Nelson, L. 1976. SHAD II. A model for analysis of fish- Fish. Bui. 1915-16(35:31-86). eries age and growth data. Wildl. Sci. Dep., Utah Sumner, F. H. 1939. The decline of Pyramid Lake fish- State Univ., Logan, Utah. 15 pp. ery. Trans. Amer. Fish. Soc. 69:216-224. NiKOLSKY, C. B. 1963. The ecology of fishes. Acad. Press, Taylor, R. E. L. 1972. The effects of increasing salinity New York. ,393 pp. on the Pyramid Lake fishery. Agric. Expt. Sta., ed. 1964. of calculated growth University of Nevada. 8 Peters, J. C, Summary pp. data on Montana fishes, 1948-1961. Dingell-John- Tesch, F. W. 1971. Age and growth. Pages 98-131 in son Completion Rep., Montana Fish and Game W. E. Ricker, ed., Methods of assessment of fish Dept., Helena, Montana. F-23-R. 76 pp. production in freshwaters. Blackwell Sci. Publ., Platts, W. S. 1959a. Homing, movements, and mor- Oxford. fishery, tality of wild cutthroat trout {Salmo clarki) TowNLEY, J. M. 1980. The Truckee Basin spawned artificially. Prog. Fish Cult. 1959 1844-1944. Nevada Historical Society in coopera- (January):36-38. tion with Desert Research Institute, Univ. of Ne- 1959b. Food habits of the cutthroat trout in vada, Reno. of lake. Strawberry Reservoir, Utah. Proc. Utah Acad. Trelease, T. J. 1953. The death a Field and Sci., Arts, Lett. 36:119-121. Stream. February. Rankel, G. L. 1976. Fishery management program, 1969. The rebirth of a lake. Nevada Outdoors 1976, Summit Lake Indian Reservation, Hum- and Wildlife Review. Nevada Dept. Fish and boldt County, Nevada. Manuscript, U.S Fish Game 4:3. Wildl. Serv., Reno, Nevada. 35 pp. United States Geological Survey. 1977. Water re- RiCKER, W. E., ed. 1971. Methods for assessment of fish sources data for Nevada, water year 1976. U.S. production in freshwaters. Blackwell Sci. Publ., Dept. Inter., Carson City, Nevada. 344 pp. whitefishes [Coregonus Oxford. 348 pp. Van Oosten, J. 1923. The Robertson, O. H. 1947. An ecological study of two high clupeaformis). A study of the scales of whitefishes mountain trout lakes in the Wind River Range, of known ages. Zoologica 11(17):380-412. Wyoming. Ecology 28(2):87-112. 1929. Life history of the lake (Coregonus

Robertson, S. R. 1978. The distribution and relative artedii LeSueur) of as revealed by its abundance of benthic macroinvertebrates in scales, with a critique of the scale method. U.S. Pyramid Lake, Nevada. Unpublished thesis, Bur. Fish. 44(1928):265-428. Univ. of Nevada. 1944. Factors affecting the growth of fish. RuGER, A. W. 1977. The results of the 1977 disease sur- Trans. Ninth N. Amer. Wildl. Conf. 9:177-183. vey conducted on Lahontan cutthroat trout (Sal- Vigg, S. 1978. Vertical distribution of adult fish in Pyra- mo clarki henshawi) at Pyramid Lake, Nevada. mid Lake, Nevada. Great Basin Nat. Manuscript, Pyramid Lake Indian Tribal Enter- 38(4):417-428. prises, Sutcliffe, Nevada. 1980. Seasonal benthic distribution of adult fish

SiGLER, W. F. 1951. The life history and management of in Pyramid Lake, Nevada. California Fish and 66(l):49-58. the mountain whitefish (Prosopium williamsoni Game J. (Girard)) in Logan River, Utah. Utah State Agri- 1981. Species composition and relative abun- Nevada. cultural College Bull. 347. 36 pp. dance of adult fish in Pyramid Lake, 1962. Bear Lake and its future, 26th Fac. Assn. Great Basin Nat. 41(4):395-408. Honor Lecture. Utah State Univ., Logan, Utah. Vigg, S., and D. L. Koch. 1980. Upper lethal temper- trout in waters 23 pp. ature range of Lahontan cutthroat eds. 1978. Pyramid of different ionic concentration. Trans. Amer. SiGLER, W. F., AND J. L. KENNEDY, Lake ecological study. W. F. Sigler & Associates Fish. Soc. 109:336-339. story of Ne- Inc., Logan, Utah. 545 pp. Wheeler, S. S. 1974. The Desert Lake: the F., composition vada's Pyramid Lake. Caxton Printers, Ltd., SiGLER, W. AND J. B. Low. 1950. Age and growth of fish and fishermen success in Caldwell, Idaho. 133 pp. Utah's high Uinta lakes. Utah Acad. Sci., Arts, Wolcott, Roger S. C, Jr. 1978. Evaluation of the 1978 Lett. 27:32-36. Lahontan cutthroat trout run to the Pyramid year. Sigler, W. F., and R. R. Miller. 1963. Fishes of Utah. Lake fishway and comparison with past Utah Dept. Fish and Game, Salt Lake City, Utah. U.S. Fish Wildl. Serv., Fish. Asst. Office, Reno, 203 pp. Nevada. 30 pp.