Temperature effects on green sturgeon bioenergetics

The green sturgeon Acipenser medirostris is relatively rare, and little is known about the effects of important habitat-related influences on its life history. Temperature directly or indirectly impacts the distribution of fish as well as their physiological and behavioral processes. Because the Klamath and Rogue rivers may reach 24-25degreesC and egg and embryo incubation temperatures above 22degreesC are associated with deformities in juvenile green sturgeon, data on the temperature-related bioenergetic responses of these juveniles would be especially useful in designing effective conservation and management strategies. We measured the food consumption, growth, food conversion efficiency, oxygen consumption, volitional activity, ventilatory frequency, thermal preference, and swimming performance of juveniles at several temperatures spanning their warm-season temperature range (11-24degreesC). Food consumption, growth, and food conversion efficiency generally increased with temperature between 11degreesC and 15degreesC but stayed constant between 15degreesC and 19degreesC. Growth increased and food conversion efficiency decreased with ration size. Oxygen consumption, volitional activity rate, and ventilatory frequency generally increased with temperature, while preferred temperature increased and swimming performance decreased with temperature from 19degreesC to 24degreesC. Relative to other sturgeon species, the green sturgeon has high growth and oxygen consumption rates. Overall, we found that bioenergetic performance was optimal between 15degreesC and 19degreesC under either full or reduced rations, thus providing a temperature-related habitat target for conservation of this rare species.