An evaluation of Florida, northern, and hybrid largemouth bass Micropterus salmoides under intensive culture conditions

Typescript (photocopy).Two populations of largemouth bass, electrophoretically identified as representing the northern (N) Micropterus salmoides salmoides and Florida (F) M. s. floridanus subspecies, were used to produce four experimental crosses, two parental and reciprocal hybrids (NF and FN, female parent first). The four strains were reared and evaluated under uniform hatchery conditions to determine relative performance for production characters: trainability on pelleted food; growth, feed efficiency, and survival in ponds; and response to a stress test. Northern fish were more successfully trained to eat pelleted food than Florida fish. The hybrids were intermediate in performance. Growth rate in replicated ponds was compared among strains. In ponds that were stocked separately and communally by strain, the northern fish grew fastest. Performance for growth rate in decreasing order was N > NF > FN = F with both stocking strategies. Northern fish had higher feed efficiency (80%) than the Florida fish (58%). Feed efficiency for the hybrids was 64% (NF) and 57% (FN). Pooled data showed Florida and FN hybrid fish had better total survival (98% and 97%, respectively) than the NF hybrid and northern fish (95% and 94%, respectively). Pooled data for proportionate survival of feeding fish showed the hybrids (95%) performed better than the parental strains (F = 94% and N = 93%). There were strain differences in response to net-confinement stress based on blood glucose, plasma chloride, and mortality values. Florida and hybrid strains began to die before net-confinement ended. Florida fish were the least tolerant of all strains, regardless of rearing or experimental conditions. After 7 d recovery from net-confinement, 12% of Florida fish were alive compared to 96% of the northern fish. Hybrids were intermediate in performance with survival values for NF and FN fish, 31% and 81%, respectively. Results of hatchery largemouth bass strain evaluation trials showed that differences in performance among the strains had a genetic basis. Environmental and genotype by environment interaction effects, observed in this study, indicate that strain performance in different environments may be difficult to predict