Pattern of Sex Steroid Concentrations in Relation to the Annual Reproductive Cycle of Wild and Captive Black Rockfish

Abstract

Gonadal development and plasma steroid hormone concentrations of wild (N = 73) and captive (N = 65) black rockfish Sebastes melanops were examined over 1 year. Seasonal variation was observed in the concentrations of testosterone and estradiol in the plasma of wild female black rockfish, the highest concentrations of each occurring in October. Male black rockfish exhibited the highest testosterone concentrations during the summer (July 29–August 9). Gonadosomatic index (GSI) and estradiol concentration were highly correlated for wild female black rockfish sampled in the fall, demonstrating the utility of this nonlethal approach for evaluating gonadal status during this species' vitellogenic period. No relationship between testosterone concentrations and GSI was observed in male fish. Hormone concentrations in captive female black rockfish were depressed throughout the year, illustrating that maintenance conditions were not conducive to the normal progression of reproductive events for this species.