9REPRODUCTIVE PHYSIOLOGY OF ADULT SPRING CHINOOK SALMON DURING THE FIVE MONTHS PRECEDING SPAWNING

Captively reared Snake River spring chinook salmon generally spawn two to six weeks later than returning wild fish of the same stock. This de-synchronization in spawning time presents problems to captive broodstock programs that reintegrate captive animals into the wild through releases of captively reared adults and/or the cross fertilization of wild and captively produced gametes. Delayed ovarian development may be due to rearing conditions early in the life cycle, during the final year prior to spawning when secondary oocyte growth is occurring, and/or during the final stages of maturation prior to ovulation. For example, the seasonal delay in ovulation could be caused by inappropriate environmental cues, such as temperature, altering the rate of oocyte 10 development. The goal of this study was to determine at what stage the captively reared fish are delayed. Gonadal maturation in a hatchery stock of Snake River spring chinook salmon, after their upstream migration, was compared to that of captively-reared fish. In addition, it has been shown that temperature can dela