Effects of prey density on growth and survival of white sucker,Catostomus commersoni, and pumpkinseed,Lepomis gibbosus, larvae

Abstract

Growth and survival of white sucker and pumpkinseed larvae were examined in the laboratory in relation to prey density. Mortality of both species was greatest during the transition from endogenous to exogenous nutrition. Mortality prior to yolk absorption was substantial for white suckers and was not related to prey density whereas, pumpkinseed mortality during the same period was low. After yolk absorption, however, pumpkinseed suffered considerably higher mortality rates than white sucker larvae and, in both species, mortality and growth were directly related to prey density. The minimum prey density supporting 10% survival of pumpkinseed larvae was estimated at 0.16 plankters ml-1 whereas, for white suckers it was 0.15 plankters ml-1. Significant growth of both white sucker and pumpkinseed larvae, however, occurred only at prey densities higher than 0.25 plankters ml-1. We suggest that since egg size and yolk reserve are greater in sucker larvae, suckers are better adapted to survive short term declines in prey abundance during the transition to exogenous feeding than pumpkinseed larvae. The reproductive strategies of each species seems to reflect this, with suckers spawning over a short time interval, but producing young with large yolk. Pumpkinseed, in contrast, spawn intermittently over an extended period but produce young with relatively small volk reserves.