Preliminary observations on the effects of holding temperature on reproductive performance of female white sturgeon, Acipenser transmontanus Richardson

Commercial sturgeon farms in California have observed poor spawning perform ance and ovarian regression in fish maintained at constant 16-20 degrees C water temperatures. The effects of the pre-spawning thermal regime on oocyt e germinal vesicle migration (GVM), in vitro maturation (GVBD), plasma conc entrations of reproductive hormones, and hormonally-induced ovulation in wh ite sturgeon females were examined. Gravid females were exposed to three te mperature treatments (seasonal 10-15 degrees C, constant 15 degrees C, and constant 18 degrees C), and ovulation was induced when females reached the responsive stage. While all females (n = 5 per treatment) in the seasonal t emperature treatment ovulated and produced fertile eggs, oocyte development (GVM) and ovulation were inhibited in the constant temperature treatments, and follicular atresia ensued in three out of five females exposed to 18 d egrees C water temperature. Temperature treatment did not have a significan t effect on plasma hormone concentrations throughout the pre-spawning and s pawning periods, but plasma concentrations of androgens and oestradiol decl ined in females that experienced developmental arrest and atresia. The spaw ning results provided empirical evidence for the negative effects of elevat ed temperatures on ovulatory response and egg quality. The pre-spawning the rmal regime appears to be an important environmental factor for normal ovar ian development in cultured white sturgeon and should be considered in mana gement of wild stocks reproducing in rivers with regulated water flows. (C) 1999 Elsevier Science B.V. All rights reserved.