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The Great Basin Naturalist AGE, GROWTH, AND FOOD HABITS OFTUI CHUB, G7LA BICOLOR, IN WALKER LAKE, NEVADA James J. Cooper Abstract. —At Walker Lake, Nevada, tui chub were collected 1975-1977 for analysis of age, growth rate, and food habits. The fork length (FL)-scale radius (SR) relationship was linear and described by the equation FL = 4.44 + 3. 17 (SR). Age I, II, III, and IV chub were 1 16, 176, 218, and 242 mm fork length, respectively. Ma.ximum longevity was six years. The length weight relationship was defined by the log transformed linear equation log weight = -4.65 + 2.93 (log FL). Chub collected from pelagic regions ate mostly zooplankton, whereas chub collected from littoral areas had a diet of zooplankton and benthic organisms. Tui chub, Gila bicolor, is the most abundant of Study Area the three species of fish currently found in Walker Lake, a remnant of pluvial Lake La- Walker Lake, Nevada. It is common to the hontan, is in west central Nevada 209 km Walker, Carson, Truckee, and Humboldt river southeast of Reno. The lake has a surface area systems of the Lahontan basin (La Rivers 1962). of 15,000 ha, is 25 km long and 9 km wide, and Various subspecies of tui chub occur in other has a maximum and mean depth of 33 and 20 endorheic basins in the drainages of pluvial lakes m, respectively. It is the second largest rem- Railroad, Toiyabe, and Dixie, and lakes in the nant of Lake Lahontan. The lake's drainage White Mountains in west central Nevada. Other basin is endorheic and receives water from the forms occupy lake basins in California, south- eastern Sierra Nevada via the Walker River. eastern Oregon, and southeastern Washington Because Walker is a terminal lake, it has a (Hubbs et al. 1974). In Walker Lake tui chub are relatively high total dissolved solids (TDS) an important component of the ecosystem content of 12,500 mg/1 that has increased bioenergetics and are preyed upon heavily by rapidly in historic times. During the past 45 the piscivorous Lahontan cutthroat trout, Sahno years the lake has had an average increase in clarki henshawi (Cooper and Koch, 1984). The TDS of 152 mg/1 per year, and the cutthroat vast number of fish-eating birds that annually trout sport fishery appears to be in jeopardy. visit the lake are also predators of tui chub. The primary factor responsible for the increasing Most of the life history information reported salinity has been surface evaporation exceeding in the literature for the Lahontan form of tui tributary inflow; since 1915 the lake's elevation chub has been collected from Eagle Lake, has dropped at an average rate of 0.58 m per year California, and Pyramid Lake, Nevada. (Cooper and Koch, 1984). Agricultural and ur- Kucera (1978) and Kennedy (1983) studied the ban diversion of the Walker River is hastening reproductive biology and growth of Pyramid desiccation of the lake. Lake tui chub. Kimsey (1954) described the life history of the Eagle Lake tui chub popula- Methods tion. Cooper (1978, 1982), working on Walker Lake, described various aspects of tui chub The scale method was used to anahze the life history. Notes on the species can be found age of tui chub at various sizes (Ricker I97I, in other articles (Snvder 1917, La Rivers 1962, Everhart et al. 1975). Scales were taken from Vigg 1978, 1980, 1981, Galatetal. 1981, Galat the left side of the body above the lateral line and Vucinich 1983a, 1983b). The objectives of and below the dorsal fin. In the laboratory this study are to present data on the age, scales were placed between two plastic slides growth rate, and diet of tui chub from Walker and run through a roller press to form an Lake. impression. Scales were read using an Eber- Biological Sciences Center, Desert Research Institute, Box ri()22(), Reno, Nt 1 South Fall Street, Carson City, Nevada 89710. 784 October 1985 CoopeRiTuiChub 785 Table 1. Mean calculated fork length and moan cakiiiati-d annual growth increments for tui chub collected June-November 1976, Walker Lake, Nevada. Calculated fork length at Age No. of end of each year of life (mm) class fish I 786 Great Basin Naturalist Vol. 45, No. 4 Table 2. Tui chub growth rates in five selected waterbodies. October 1985 COOPER: Tui Chub 787 Table 3. Food of tui chub by percent frequency of occurrence id percent j^nt composition collected from tw( habitats in Walker Lake, Nevada, in 1976 and 1977*. Food item 788 Great Basin Naturalist Vol. 45, No. 4 history of the tui chub, Siphatcles La Rivers. I. 1962. Fishes and Fisheries of Nevada. Ne- KiMSEY, J. B. 1954. Life bicolor, from Eagle Lake, Cahfornia. CaHfornia vada Fish and Game Commission. 782 pp.X L. 1976. II, for analysis fish- Fish and Game J. 40:39.5-410. Nelson. SHAD A model of 1955. the eries age and growth data. Wildl. Sci. Dept., Utah KiMSEY, J B , .AND R R Bell Observations on ecology of largemouth black bass and the tui chub State University, Logan, Utah. 15 pp. in Big Sage Reservoir, Modoc County. California RiCKER, W E. 1971. Methods for assessment offish pro- Inland Fish. Branch, Ad- Dept. Fish and Game, duction in fresh waters. Inter. Biol. Programme, min. Rept. 55-15, Sacramento, California. Black-well Scientific Publ., 348 pp. KuceRA, p. a. 1978. Reproductive biology of the tui chub, Snyder, O. 1917. The fishes of the Lahontan system of Gila bicolor, in Pyramid Lake, Nevada. Great J. Nevada and northeastern California. Bull. U.S. Basin Nat. 38:203-207. Bur. Fish. 35:31-86. KuCERA, P. A.. G. W. WORK.MAN, D. ROBERTSON, S. ViGG. R. Whaley, and R. Langdon 1978. Life history of ViGG. S. 1978. Vertical distribution of adult fish in Pyra- the tui chub. In W. F. Sigler and J. L. Kennedy, mid Lake, Nevada. Great Basin Nat. 38:417-428. eds. Pyramid Lake Ecological Study. VV. F. Sigler 1980. Seasonal benthic distribution of adult fish in and Assoc. Inc., Logan, Utah. Pyramid Lake, Nevada. California Fish and Game Langdon, R. W. 1979. Food habits of the tui chub, Gila J. 66:49-58. bicolor, in Pyramid Lake, Nevada. Unpublished 1981. Species composition and relative abundance thesis. Humboldt State University, Areata, Cali- ofadult fish in Pvramid Lake, Nevada. Great Basin fornia. 45 pp. Nat. 41:.395-406..
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