Columbia River Project water use plan: Mid Columbia River sturgeon incubation and rearing study (Year 1)

This report describes the results from the first year of a three-year investigation on the effects of different thermal regimes on incubation and rearing early life stages of white sturgeon. The Columbia River has been significantly altered by the construction of dams resulting in annual flows and water temperatures that differ from historical levels. White sturgeon have been demonstrated to spawn in two very distinct sections of the Columbia River in British Columbia, Canada, which are both located immediately downstream of hydropower facilities. The thermal regimes differ substantially between these two areas. The general approach of this study was to incubate and rear white sturgeon early life stages under two thermal regimes; one mimicking the current, cool water regime of the mid Columbia River downstream from Revelstoke Dam, and one mimicking a warmer regime similar to conditions found on the lower Columbia River at the international border. It describes the development of thermal profiles to be used in laboratory experiments from historic Columbia River temperature data. First-year results suggest that thermal regimes during incubation influence rate of egg development and size at hatch. Eggs incubated under the warm thermal regime hatched sooner than those incubated under the cool thermal regime. Mean length of free embryos at hatch was significantly different between thermal regimes with free embryos from the cool thermal regime being larger at hatch. However, free embryos from the warm thermal regime had a significantly higher mean weight at hatch. Mortality between hatch and initiation of feeding was extremely high in both treatments and virtually all fish reared under the warm thermal regime died prior to initiation of feeding. A proportion of the fish reared under the cool thermal regime did begin feeding; however, growth rates were extremely low as the onset of feeding corresponded with decreasing thermal regime temperatures. Chronic low levels of mortality resulted in few fish remaining when the growth trials were terminated at 154 days after egg fertilization. The starvation trials showed that the fish in the warm thermal regime exhausted their yolk reserves faster than fish in the cool thermal regime. The ability to resist starvation may be important in dispersal to downstream rearing areas.