Effects of Salinity Fluctuation on Growth in Juvenile Spot (Leiostomus xanthurus)
The effects of fresh water run-off on growth of juvenile spot (Leiostomus xanthurus) were investigated by conducting an enclosure study in tidal creeks of Rose Bay, North Carolina. Estuarine areas intercepted by drainage canals were found to have higher salinity fluctuation than undisturbed areas. These changes appear to affect post larval spot populations in several ways: 1) Increased osmotic stress affects the fish directly, resulting in high mortality percentages. 2) Reduction of prey populations in these areas affects the fish indirectly. Where food is less abundant the fish are forced to expend more metabolic energy in feeding. Growth was surprisingly unaffected by differences in salinity variations. A "threshold" model for growth and mortality was proposed in an attempt to explain this phenomenon. It is apparent from these results that juvenile fish are incapable of tolerating the environments of disturbed areas and, probably avoid them in situ.