Effectiveness of bycatch-reduction devices in roller-frame trawls used in the Florida shrimp fishery

Abstract

High rates of fishery discards have been noted for penaeid shrimp fisheries worldwide and especially for the shrimp trawl fisheries of the southeastern U.S.A. Selective fishing gear, such as bycatch-reduction devices (BRDs), can significantly decrease bycatch and discards in shrimp trawl fisheries. The roller-frame trawl, a type of gear unique to Florida, is used in seagrass beds to harvest food shrimp and bait shrimp. No BRD is required for roller-frame trawls, although bycatch can be significant. We tested the effectiveness of two BRDs – the Florida fisheye (FFE) and the large-mesh extended-mesh funnel (EMF) – in reducing bycatch in roller-frame trawls. Tests were conducted at two Florida locations: the nearshore waters off Tarpon Springs, where food shrimp are harvested, and Biscayne Bay, where bait shrimp are harvested. At Tarpon Springs, each device was tested independently and with the addition of a stimulator cone; the cone was not tested at Biscayne Bay. We tested each BRD configuration using a paired trawl design; a BRD-equipped net was deployed off one side of the boat, and a control net with no BRD was deployed off the other side of the boat. The effectiveness of the BRD configurations in retaining shrimp while reducing bycatch varied considerably. Although some significant species-specific reductions were observed in the FFE, that BRD did not significantly reduce overall finfish bycatch, but it did retain shrimp. The EMF performed well, but only at Tarpon Springs. Bycatch reduction was significant, albeit low, and shrimp loss was low. At Biscayne Bay, both bycatch and shrimp loss were significantly reduced in the EMF. Use of the stimulator cone with the FFE and the EMF resulted in significant bycatch reduction but also significant shrimp loss. Modification of the gear may improve their performance in roller-frame trawls.