15 NOVEMBER 1999
Y. Narimatsu, H. Munehara-1999
Canadian Journal of Fisheries and Aquatic Sciences, 56(10): 1849-1855
Abstract:
The effects of spawn date on survival and growth during the embryonic, larval, and juvenile stages of a coastal fish, Hypoptychus dybowskii (Gasterosteiformes), were examined. Monitoring of embryos using SCUBA showed that the embryonic period decreased as the season progressed and the hatching rate was lowest for the early-spawn cohort (EC). Analysis of otolith daily growth increments indicated that EC larvae had much lower survival and growth rates than larvae of middle-spawn (mc) and late-spawn (lc), but there were no large differences in either rate among juveniles of the three cohorts. EC suffered the highest mortality rates in the embryonic and larval stages; these high rates were linked with slow development and growth, probably caused by below-optimum water temperatures. EC fish grew over a longer period and reached larger body size than MC and LC fish. These results suggest that intra-annual variations in growth pattern and survival rate in the embryonic and larval stages were caused by spawn date differences, which favored the LC in the study year, but the EC might have a size-dependent advantage in survivorship and reproductive success during the postjuvenile stages.