The Effect of Thermal Overwintering Conditions of Spawners on Duration of Egg Incubation and Holding of Yolk Sac Larva in Sturgeons

Abstract

The goal of this research is to determine temperature threshold limits and duration of overwintering in spawners of beluga (great sturgeon) and Russian sturgeon in the aquaculture farms that would preclude impairment of the generative function. The study performs the assessment of temperature conditions and outcome of overwintering of spawners, egg incubation, and holding of yolk sac larva in beluga and Russian sturgeon in the farms using the warm discharge water from power-producing facilities. The examined parameters have been compared with data obtained from spawners from natural populations in the lower reaches of the Volga River. It has been established that spawners of studied species can survive up to 9 months under conditions of food deprivation at a mean water temperature of 2.2–2.4°С. Both studied species have exhibited an increase in duration of incubation to 24 h and longer compared with individuals from natural populations under conditions of shortened and “comfortable” warm-water overwintering. The duration of egg incubation and holding of yolk sac larva nearest to the conditional norm has been obtained under more severe overwintering conditions of spawners. Desirable conditions include mean water temperature of 3°С and duration of 3–6 months for overwintering of beluga spawners and gradual increase in water temperature from 11 to 14°С and holding of yolk sac larva from 14 to 18°С for the egg incubation. Preferable conditions for overwintering of spawners of Russian sturgeon are mean water temperature of 4°С and duration of 4.5–6.5 months. Preferable conditions for egg incubation of the latter are gradual increase in water temperature from 13 to 16°С and holding of yolk sac larva from 16 to 20°С.