Some effects of temperature on zygote and alevin survival, rate of development and size at hatching and emergence of Pacific salmon and rainbow trout

This study provides comparative data on the effects of temperature on zygote and alevin survival, rate of development to 50 percent hatching and emergence, and alevin and fry size for five species of Pacific salmon (Oncorhynchus) and for rainbow trout (Salmo gairdneri). Fertilized eggs from each species were incubated in controlled temperature baths at five constant temperatures (2°, 5°, 8°, 11° and 14°C). At 2°C, survival for coho salmon zygotes was high (85 percent), moderate for sockeye salmon zygotes (40 percent) and low for chinook salmon zygotes (4 percent). No pink and chum salmon or rainbow trout zygotes survived at 2°C. However, at 14°C survival for chum salmon and rainbow trout zygotes was high (67 and 85 percent), moderate for chinook and pink salmon zygotes (50 and 55 percent) and low for sockeye salmon zygotes (10 percent). No coho salmon zygotes survived at 14°C. The same general pattern for temperature and survival holds for alevins. These data suggest that coho and sockeye salmon are adapted to lower incubation temperatures than the other species. All six species showed an inverse relationship between temperature and incubation time to 50 percent hatching and emergence. The data were analysed using linear regression but, even after a series of transformations, the relationship between temperature and development time remained curvilinear. The only exceptions were for chum salmon at hatching and pink salmon at emergence. Incubation temperature also influences both alevin and fry size. In general, low incubation temperatures produce larger alevins and fry than high incubation temperatures. In addition to data on constant incubation temperatures, the effects of varying temperature regimes on the survival, rate of development and size of coho salmon and rainbow trout alevins and fry were also documented. Fertilized eggs from coho salmon and rainbow trout were incubated at two varying temperature regimes. The varying temperature regimes either gradually increased from 5° to 14°C (the spring regime) or gradually decreased from 14° to 5°C (the fall regime). The increasing temperature regime produces higher survival in rainbow trout zygotes and alevins than the decreasing temperature regime. However, in coho salmon there was no clear difference in zygote and alevin survival with either regime. The rate of development to hatching for zygotes incubated at either varying temperature regime was similar within a species because of similar mean incubation temperatures between regimes. But, the rate of development to emergence for alevins incubated at either varying temperature regime was different because of different mean temperatures between regimes. The linear regressions to hatching and emergence for coho salmon and rainbow trout were used to predict rates of development for zygotes and alevins incubated with each varying temperature regime. The actual and predicted rates of development to hatching and emergence are similar within a species. Varying temperature regimes also affect both alevin and fry size. The decreasing temperature regime produces larger alevins and fry in coho salmon and rainbow trout than the increasing temperature regime.Science, Faculty ofZoology, Department ofGraduat