Reproductive analysis of southern and Gulf flounders ( Paralichthys lethostigma and P. albigutta) in South Carolina based on scuba surveys.

摘要

Specimens of southern and Gulf flounders were collected by SCDNR and recreational divers off the South Carolina coast using scuba from 2007--2010. Reproductive development was analyzed using histologically prepared gonad tissues. Interviews were conducted with recreational divers to examine local ecological knowledge of flounder spawning. A drifter release experiment was conducted to determine surface water movement patterns as a proxy for potential larval dispersal. Long--term datasets from SCDNR were analyzed for flounder catches. The effect of freezing on histological sections of gonad tissues was investigated, and data suggested maximum oocyte diameters may provide a rapid means to stage tissues with freezing damage. Gulf flounder with hydrated oocytes were collected using scuba gear at five artificial reefs off SC during January--March at 18--29 m depth and 12--15°C bottom temperature. Observations suggested that flounder spawning behavior includes "stacking" and that Gulf flounder spawn during late afternoon, evening, or night. Spawning frequency of Gulf flounder was estimated to be 2--3 days from January through March. Southern flounder were rarely observed during the spawning season (December--March). Bottom temperatures at dive sites remained less than 17°C during these months. Recreational divers collected the majority of southern flounder in October and in May off Little River Inlet, SC. Data suggested that southern flounder were migrating through those sites to spawning locations elsewhere. Southern flounder likely spawn in deeper water, beyond the safe depth limits of recreational scuba diving or migrate further south to warmer waters to spawn.