Determining Winter flounder Spawning Sites in Two Connecticut Estuaries

Winter flounder (Pseudopleuronectes americanus) come inshore during the late winter and early spring to lay their eggs in shallow bays and estuaries along the coast. Unlike most fish eggs, which are buoyant, these eggs are demersal and sink to the seafloor. This makes them vulnerable to burial from various types of natural and human caused disturbances (e.g., storms, mobile fishing gear, maintenance dredging). Our objective was to map spawning areas in two harbors and search for generalities among these sites that would allow us to predict where winter flounder might spawn in other areas. This would allow managers to avoid permitting activities for those times and locations where winter flounder spawn. We used a modified demersal plankton net (a benthic sled) to collect winter flounder eggs in New Haven and Milford harbors and map their distributions. Most of the eggs were collected at the end of March, when water temperatures were 4-6° C. This could vary from year to year depending on temperature. The distributions of eggs were not correlated with sediment type or depth but were related to the prevailing tidal currents in the area sampled. Since the eggs are present in low-current depositional areas, they are vulnerable to burial. Our observations suggest that winter flounder either do not deposit eggs in high current areas, or if eggs are deposited there, they are swept away. Since early stage embryos (morula, blastula, gastrula) were found in low current areas, it seems unlikely that they were transported there from some other location. These findings have important management implications because any activities (dredging, building breakwaters, installing docks) near spawning areas could have adverse effects if they change the prevailing currents in the area