8145 - Laserfiche WebLink

Home Browse Search

~l- 10- .ke the related white sucker. Caloslomlls commersolti (McCormick et a!. 1m) may allow us to hypothe- size on potential pre-historiC.ll !'pawning and rear- ing tempcnlturcs for this species. The minimum viable incubation temperature of razorback sucker embryos appears to be similar to that of the white sucker. The maximum viable in- cubation temperature for razorback sucker.;. how- ever. is warmer. Successful hatching in white suck- ers occurred from 9.0 to 20.8" C with high percent- ages of. normal embryos hatching from 9.0 to 17.20 C. We found !'uccessful hatching of razorback suckers from 10.0 to 2O.00C and Mar.o.h (1985) found the apparcnt upper limit of razorback sucker hatching success occurring between 25 and 30" C. White !'uckers initiate spawning from 1_2 to 11.""'(' (Raney & Wchl;tcr 1942. Geen et OIl. 19M. Corhett & Powles 1983). The razorback !'ucker has been reported !'pawning in free-nowing reaches of the upper Colorado River basin at temperature!' as low as 60C (McAda & Wydoski 1980). This is the lowest temperature reported for spawning by this spccic,;. Both spedes. therefore. seem to initiate Sf1<1wning helow temperatures required for succns- ful incubc~tion. Spawning prior to optimal incuba- tion temperatures is common in freshwater fish (Alabaster & Lloyd 1980). Our comparison of the white sucker with the razorback sucker indic.ltes that spawning is initiated at similar temperaturcs :lOd th:lt both have similar succcs."ful minimal in- cubation tempcmtures. Based on this cumparison. initiation of spawning for the razorback sucker at flOC could. thereforc. reasonably be near the his- turica) tempcraturCl\ that initiated spawning in this species. Whik incubation is sllcccs."ful at some lower temperatures, highcr temperatures appear to be hencr for larval growth. Growth in whitc suckers is extremely slow at lO? C nut is maximized at 26.90 C ("IcCormick el al. J97il. Mo\'cment to warmer ~h:lllllw watl'r l'>~' white sucker I~HY:le is l'>c1ie\'cd tu IX-Ctlf ((1 Orlimi7.l' ~rowth :lnd thcrdllrc !'uT\"i,';,1 I \k<.'tlflllil-k l't al. IQTi). R,wlrba\.'k ~1Il"kl'r dl','d- l"lpmcnt i~ ,lI!'o extremely !-klW at ur C t>ut incrca~l'~ wilh increasing temperature as demon!'trated in our ('xpcriment~. Optimal dc\'clupmenl temper- ature" could he higher than 2ff C nut were not ..:r Ill- tis of "C- 'l,f fI). ;Ih i(lr 'ld ,'re ,.t- ,.cs ..:r- ~'Iy .to ... "'- he .10 -'c- :'ic illS t!Jg :11- ,..c . ,:\." 'i..l ':c r. :....... ,- . . 'I. .'n 'j':: 261 determined because our highest test temperature was only 20" C. As in white suckers. movement to warmer water to optimize growth might he cxpect- ed in razorback suckers as well. S)'nthesis No one temperature is best suited for aJllife stages of a given species. McCormick et al. (1977) found an JI.'PC temperature increase from the optimal embryonic incubation tem~rature to the optimal larval growth rate temperature. They suggested that fish have adapted the timing of incubation and emergence to increase hatching succes." and larval growth rates to water temperatures in the 5ystems whcre they occur. Fa5ter dcvcklpmcnt rates of em- bryos result in earlicr hatching which enables lar- vae to begin foraging earlier. attain greater size, and compete better for available food resources. Increased size of young fish increases their surviv- ability and therefore recruitment into the popula- tion (Mason & Chapman 1965. Fausch & White 19M. Chandler & Bjornn 1988). Tempcrdtures available for larval and juvenile growth in the upper Colorado River may inOuence survival of the razorback sucker. Kaeding & Os- mundson (1988) suggest that recruitment of Col- orado River squawfish. Plychochrilu.f IlIci".~. in the uppC'r rivcr may be limited by tempcmture that reduces growth mtes nceded to secure a minimum overwintering size, Minimum size for 0'" fish is critical to their survival through the first winter (Gutreuter & Anderson 1985, Wicker & Johnson 1987). Similarly. reduced growth in razorback suckers may also reduce their survival in thc upper fiver. In Lake Mohavc, reduced temperaturcs may bc less of a problem. Incubation temperatures in basin area~ of Lake Moha\'e (10-~2('C) appear to be compatiNe with successful incubation temper- ;lfllrl'~ that \\'l' found in the lat-oratory and e\"i- dl'necd in fidd collections. The protracted spawn- ing !'...,,~on in Lake Moha\'e also may reduce the effect of lower spawning tcmpcraturcs th..t occur during the early season. While this suggests that direct mortality from lower temperatures ma~' he