Effects of summer upwelling on the abundance and vertical distribution of fish and crustacean larvae off central Florida's Atlantic coast

Abstract

The abundance and vertical distribution of various fish and crustacean larvae in response to seasonal upwelling at a study site off the east central Florida coast were examined. Upwelling was recorded at the site from mid July to late August 1986 during which the intruded water was confined to near-bottom layers with a well-defined thermocline present near mid-depth. Near-bottom temperatures of 20–23°C were generally 3–6°C below temperatures recorded near the surface during this time. Densities of larval fish, penaeid shrimp, stomatopods, brachyuran zoeae, brachyuran megalopae and porcellanid zoeae were quantified at near-surface and near-bottom levels prior to, during and following the upwelling event. Densities of brachyuran zoeae and penaeid larvae dominated the other four groups in both levels of the water column throughout the 14-week study. Only brachyuran megalopae and penaeid larvae occurred in significantly higher numbers in upwelled water. All six larval groups were found in higher densities near the bottom through most of the study period. Combining these results with findings from related physical studies suggests that upwelling may play an important role in transporting these and other larval forms shoreward in this region.