Release of Juvenile Mussels into a Fish Hatchery Raceway: a Comparison of Techniques
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Offspring of four, gravid female L. fasciola were tested to evaluate the extent of variability in growth and survival among brood stock. Comparison of growth and survival of progeny showed significantly lower performance of only one female (p < 0.05). Although results indicate variability in growth and survival among broods, it is not known whether heritabilities or physiological fitness caused this variability.
Infested fish (IF), newly metamorphosed juveniles (NMJ) and juveniles cultured for 1 month (CJ) were released to a fish hatchery raceway in order to determine the most appropriate developmental stage to release juveniles. Significant differences were recorded among the three release methods, with CJ attaining the greatest growth (2.47 mm plus/minus 0.02), NMJ with the next best growth (1.86 mm plus/minus 0.02), and IF exhibiting the least growth (1.34 mm plus/minus 0.02) (p < 0.0001). Survival among release methods was not statistically different because of high variability within each release method. High mortality from predacious fish was presumably the cause of this variability. With minimal predation, L. fasciola experienced 82.2% (plus/minus 3.6) survival at 90 days. Survival of hatchery-reared juveniles was comparably higher than laboratory-reared juveniles, suggesting that culturing freshwater mussels in a hatchery raceway is a preferable alternative to laboratory culture.
An experiment was conducted to compare growth of confined and unconfined juvenile L. fasciola released to a fish hatchery raceway. After 72 days, juveniles confined to small open dishes within the raceway (1.04 mm plus/minus 0.08) exhibited significantly less growth than juveniles released to the raceway that were not held in containers (2.15 mm plus/minus 0.07) (p < 0.0001). Results of additional comparisons with compiled growth data suggest that juvenile growth is retarded when cultured in small dishes.
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