RACEWAY SPAWNING OF FLORIDA LARGEMOUTH BASS - EFFECTS OF ACCLIMATION TIME AND HORMONE-TREATMENT ON SPAWNING SUCCESS

Several acclimation periods and hormone treatments were tried to deter mine their effects on controlled spawning of 2-year-old Florida largem outh bass (Micropterus salmoides floridanus). During the first season, fish were acclimated to raceways for 0-8 weeks before spawning; males and females were separated during acclimation. There was an inverse r elationship between the length of the acclimation period and latency o f first spawn after the sexes were mixed. The longest acclimation peri ods resulted in the shortest latencies; however, once spawning began, the rate of spawning (interval between spawns) was similar across trea tments. During the second season, unacclimated and 2-week-acclimated l argemouth bass were injected with saline, human chorionic gonadotropin (HCG; 4,000 IU/kg body weight) or [D-ala6pro9-N-ethylamide]-luteinizi ng hormone releasing hormone (LHRH-A; 0.5 mg/kg body weight). Injectio ns of HCG induced spawning quicker, and produced more spawns and fry, than injections of LHRH-A or saline. Acclimated largemouth bass produc ed more spawns than did unacclimated largemouth bass in all treatments . Acclimation periods may have allowed stress associated with common f ish culture practices to diminish and may have provided time for synch rony to develop between male and female largemouth bass. In the last e xperiment, injections of HCG in females alone resulted in spawns withi n 48 h; however, spawns did not produce fry. This was attributed to a lack of synchrony with males, possibly resulting in overripeness of eg gs. These results show that optimum spawning can be achieved when larg emouth bass are allowed to acclimate to raceway conditions for 2 weeks , and that HCG treatment of both sexes is the preferred hormone treatm ent for induction of spawning.