Removal of Black Drum on Louisiana Reefs to Increase Survival of Eastern Oysters Crassostrea virginica

Abstract

Black drum Pogonias cromis are large, molluscivorous fish that severely limit the abundance of eastern oysters Crassostrea virginica in the northern Gulf of Mexico. In field experiments, we tested two fish removal methods—baited trot lines and gill nets—near commercial oyster leases to determine whether the removal of black drum would increase eastern oyster survival. Both methods removed fish and increased oyster survival in the spring but not in the fall, when little mortality occurred. The numbers and biomass of black drum caught varied with gear type: 10‐cm (bar mesh) gill nets landed the most fish, while trot lines and 10‐cm gill nets were equally effective in landing the greatest biomass. Eastern oysters were more common in the diet of black drum in the spring than in the fall and increased in importance with fish size. Fish of 70–75 cm (standard length) had the greatest impact on oyster production. These fish can be removed most effectively with 12.5‐cm gill nets, though trot lines are preferable because they require less effort and produce less bycatch. The removal techniques used here may also be successful in aiding other bivalve fisheries suffering from predation.

Oyster Reefs Are Reservoirs for Potential Pathogens in a Highly Disturbed Subtropical Estuary

“…Human infections from consuming pathogen-contaminated oysters are well documented [19,[41][42][43], and this is concerning since oysters are farmed for food on leased plots in the IRL [44] and can be recreationally harvested in certain areas [45]. But infections from contaminated oysters may occur in other predators such as fishes [46] and large crustaceans [47] as well. Oysters can also transport suspended pathogens to the benthos in their biodeposits [48,49], likely turning oyster reefs into PPM reservoirs as excreted biodeposits accumulate in reef crevices and sediments.…”