1201 - Laserfiche WebLink

Home Browse Search

::~: i3 /lu-1U€.Ai 17'(,tno.;rel Transactiolls of thl' American Fishnil's 50rl('lJ 112:601-607, 1983 O/~OI - Temperature Preference and A voidance by Adult Razorback Suckers ~ R. V. BULKLEY AND R. PIMENTEL Utah Cooperative Fishery Research Unit, Utah State University Logan, Utah 84322 Abstract Final thermal preferendum for the razorback sucker Xyrauchen texanus, a rare endemic species of the Colorado River basin, was estimated to lie between 22.9 and 24.8 C based on electronic- shuttlebox studies, Estimates of upper and lower avoidance temperature ranged from 27.4 to 31.6 C and from 8,0 to 14,7 C, respectively, Lower, bilt not upper, avoidance temperature was positively correlated with acclimation temperature, Results indicated that new water-control structures on the upper Colorado River drainage should be designed to provide summer water temperatures between 22 and 25 C if preservation of habitat for this species is a consideration, Received November 12, 1982 Accepted June 5, 1983 .. ~ In recent years, the abundance of several en- demic fish species of the upper Colorado River has decreased to the extent that four have been formally recognized as endangered. Among the most evident reasons for the decline are the effects of impoundments, water withdrawals, and effluent returns on the aquatic environment; among the former, changes in river tempera- tures downstream from large dams are partic- ularly conspicuous (Hubbs and Pigg 1976; Ed- ,wards 1978; Behnke and Benson 1980). The numerous proposed development projects in the upper Colorado River basin could further alter river environment and jeopardize the contin- ued existence of these rare native fishes. Information on the thermal requirements of native fishes is especially important in view of the effects of reservoir construction and other water developments on river temperatures. We report here the results of temperature prefer- ence and avoidance research conducted on the razorback sucker Xyrauchen texanus, a rare species endemic to the Colorado River. Objec- tives of our study were to determine final ther- mal preferendum of the species and upper and lower avoidance temperatures, The final ther- mal preferendum was originally defined as the temperature around which all individuals of a species ultimately congregate regardless of pre- vious thermal experience, and the level at which preferred temperature equals acclimation tem- perature (Fry 1947), More recently, it has gen- erally been assumed that the final preferendum is the optimal temperature for most of the phys- '\ iological functions of fish (Coutant 1975; Craw- shaw 1977; Beitinger and Fitzpatrick 1979; Jo- bling 1981; Giattina and Garton 1982). The final preferendum seems to be innate and species-specific (Reynolds and Casterlin 1976, 1979; Magnuson and Beitinger 1978). Methods Experimental razorback suckers were off- spring from a single female spawned in 1974 at the Willow Beach (Arizona) National Fish Hatchery. The progeny were reared in concrete outdoor raceways and fed commercial trout feed. Seven hundred of the fish (15-30 cm long) were transported to the Utah Water Research Laboratory, Logan, in June 1980. Experimen- tal fish were mature and in their seventh year of life when tested. Fish were held in 833-liter circular tanks under a 14-hour-light, 10-hour- dark photoperiod and acclimated to watertem- peratures of 8, 14,20, or 26 C. Water temper- ature was changed 1 C per day until the accli- mation temperature was reached. Fish acclimated to a temperature lower than the original holding temperature were held 30 days at that temperature before they were tested; fish acclimated to a higher temperature were held for at least I week. Dry, pelleted (3-mm diam- eter) trout feed was fed ad libitum once per day. Fish were not fed during tests in accordance with guidelines established by Richards et al. (1977), Terramycin was added to the feed (4- 10 mg/kg) for two, 7-day periods to control Flexibacter columnaris infection. Fish exposed to 601