Habituation to Captivity and Controlled Spawning of White Bass

Abstract

We successfully spawned white bass Morone chrysops that had been habituated to captivity in indoor tanks for over 1 year and whose cycles were entrained by simulated temperature and light regimes. In summer (1990) 300 white bass (300–600 g) of an approximately even sex ratio were distributed into three 10,000-L water-recycle systems. One system was maintained under an ambient photoperiod and temperature regime, one was maintained under a regime that simulated a 9-month (compressed) annual cycle of changing photoperiod and temperature, and one was held at a temperature range at or above spawning temperature (15–25°C) and constant photoperiod (14 h light: 10 h darkness). By human chorionic gonadotropin (hCG) injections (1,100 IU/kg for female fish; 275 IU/kg for males), we induced the compressed-cycle fish to spawn in March 1991 and the ambient-cycle and constant-cycle fish to spawn in May 1991. Constant-cycle fish injected with hCG in March 1991 failed to spawn. Male white bass continuously held at water temperatures within the 15–25°C range constantly spermiated. Percent hatch rates were similar whether the eggs were fertilized by sperm from males subjected to the same photothermal regime as the female spawners or to a different regime. Annual rhythms of serum levels of estradiol-17β and testosterone, as well as gonadal growth and histology of the wild and the three captive populations of white bass were documented and correlated with actual spawning events. We demonstrated that wild adult white bass can readily be domesticated to serve as broodstock, and that they are amenable to manipulation of spawning time.