Current velocity and injection of GnRHa affect reproductive behavior and body composition of captively reared offspring of wild chinook salmon (Oncorhynchus tshawytscha)

Abstract

Captively reared adult Pacific salmon (Oncorhynchus spp.) released for natural spawning exhibit deficiencies in reproductive behavior. The effects of water current velocity in rearing tanks and gonadotropin-releasing hormone analogue (GnRHa) treatment on reproductive behavior of captively reared chinook salmon (Oncorhynchus tshawytscha) were examined. Treatment of females with GnRHa resulted in a significantly greater degree of nest guarding, earlier (more natural) onset of spawning, and higher frequency of aggression towards males. Current velocity did not significantly affect the female reproductive behaviors examined. Males reared under high current velocities (HV) spawned for the first time 2.4 days earlier, and alpha males reared in HV tanks defended their access to spawning females better than alpha males reared in low velocity (LV) tanks. Males reared in HV tanks had 34% lower protein content at the time of death than fish reared in LV tanks. Females reared in HV tanks had 38% lower lipid content, but the effects of current velocity were nonsignificant when accounting for significant random variation among tanks within treatments. Identifying and modifying environmental conditions that control hormonal changes during final maturation may lead to further improvements in reproductive performance of captively reared salmon.