8145 - Laserfiche WebLink

Home Browse Search

IOjQ 0 fut;~0t ctf. Enl'im",,,rlltaJ Riology of 1.1...hr... 27: 255-263. I '}<Xl. @ 19'X1 Klllwrr Academic Pllhli.<h('f"S. Printrd in thr Nrthrrland.\'. Effects of ambient Lake Mohave temperatures on development, oxygen consumption, and hatching success of the razorback sucker Michael A. Bozek'. Larry J. Paulson & Gene R. Wilde:! IAk~ M~ad Umllological Research Center, Univenity of Nevada-Las Vegas, Las Vegas, NY 89154, U.S.A.; I Pr("Selll address: Department of Zoology and Physiology, Univcrsity of Wyoming, Box 3/44. lAramie, WY 82071, U.S.A.; 1 Present address: Department of Zoology, Oklahoma State Unb'enity, Stillwater, OK 74074, U.S.A. Reccj,'cd 4.8.1~ Accepted 26.5.1m Key K'ord.{: Xyroucl,elrtcxanll,f, Incubation. Respiration, Embryo, Eggs. Larvae Synopsis Spawning of razorback suckers. Xyrauchen texallUS, in Lake Mohave occurred from lQ-220C and larvae were collected at water temperatures from lQ-150C in 1982 and 1983. In the laboratory. hatching success was similar from 12-200C. but reduced hatching success was found at 1000C while none hatched at Jr'C. Development rate and oxygen consumption were positively related to incubation temperature. Direct effects of ambient Lake,Mohave water temperatures on hatching success of razorback sucker embryos arc consid- ered minimal. Historical spawning temperatures for the species arc hypothesized ba~d upon successful incubation temperatures and comparison to the white sucker, Catostomus commersonJ. Introdudion Lowcr-than-historic. water temperatures from hy- polimnetic discharges of dams on the Colorado Rivcr ha\'c been implicated as a factor contributing to the decline of razorback suckers. X)'rallchen texamls (Vanied: et al. 1970. Johnson & Rinnc 1982, Marsh 1985. Tyus 1987). Thermal cycles un- der which nalive specics evolved have been altered by thc~ disch:tr!!cs. which increase winter temper- atures and decrease those in summer (Paulson et :11. 19Xtla). Reduced tcmperatures during incuba- tion O1:'y din:ctly rcsult in egg mort.llity or increase the Icn~th of exposure of cmhryos :lOd larval..' to othl'r sources of mortality such as watcr Icvel nuc- tuations, predation. and severe wavc action. Initiation of spawning by fishes is usually limed with optimal survival temperatures. Naturally- spawned egg.s should be cxpected to emerge as larvae at ambient temperatures as long as seasonal thermal trends continue (McCormick el al. 1977, Alabaster &. Uoyd 1980). Spawning of razorback suckers has been documented in nature at water temperatures from 6-2Z0C (Douglas 1952, McAda & Wydoski 198f)' Bozek 19M, Tyus 1987). In the laboratory. Marsh (1985) found that 2O"C was the optimal incubation temperature for razorback suckers. with lower hCllching success at 150C and complete mortality at 5 and 10"C. It appears. therefore. that poor reproductive success in the Colorado River may be duc to incomp<ltible in- cuhation temperatures from cold hypolimnetic dis- charges of reservoirs. Lakc Mohave contains the largcst known pop- ulation of razorback suckers (Minckley 1983, Bo- zek 1984). The species is rare in other lower river