Raceway Spawning of Largemouth Bass

Abstract

Largemouth bass (Micropterus salmoidesl were spawned in outdoor raceways during three spawning seasons. During the first season, limited spawning success was achieved using year-class 4 Marion largemouth bass due to the late start of the experiments in the normal spawning season. During the second season, Florida largemouth bass (M. salmoides floridanus) were allowed to acclimate for 0-8 weeks. There was an inverse relationship between the length of the acclimation period and latency to first spawn, however, once spawning began the rate of spawning was similar across treatments. The second experiment was designed to test for differences in spawning success of acclimated bass treated with human chorionic gonadotropin (hCG; 4,000 IU/kg BW), [D-Ala6Pro9-N-ethylamide]-luteinizing hormone releasing-hormone (LHRH-A; 0.1 mg/ kg BW), salmon gonadotropin-releasing hormone (sGnRH; 0.1 mg/ kg BW), and Ovaprim (0.5 ml/ kg BW). The best hormone treatments in this study appeared to be hCG, Ovaprim, and sGnRH. The third experiment of the season involved treatment of unacclimated bass with hCG and LHRH-A. Due to the late start of this experiment, spawning success was low and no comparative information could be obtained. During the third season, unacclimated and 2-week acclimated Florida largemouth bass were treated with hCG or LHRH-A (0.5 mg/kg BW). Injections of hCG induced spawning quicker, produced more spawns and more fry than injections of LHRH-A or saline treated controls. Spawning success of acclimated bass was greater than that of unacclimated bass in all hormone treatments. Acclimation periods may have allowed stress associated with common fish culture practices to diminish and may have provided time for syncrony to develop between male and female largemouth bass. In the last experiment, injections of hCG in females resulted in spawns within 48 hours; however, spawns did not produce fry. This was attributed to overripeness of ova or a lack of syncrony with males. These results show that optimum spawning can be achieved when largemouth bass are allowed to acclimate to raceway conditions for 2 weeks, and that hCG treatment of both sexes is the preferred hormone treatment for induction of spawning.