The Behavioral Response of Juvenile Red Snapper (Lutjanus campechanus) to Shrimp Trawls that Utilize Water Flow Modifications to Induce Escapement

Abstract

Clear differences in swimming ability between finfish and shrimp in trawls have been utilized in the Southeastern U.S shrimp fishery to reduce the by catch of finfish. The Jones/Davis device which has been mandated for use in the Gulf of Mexico shrimp fishery uses four windows to provide an escape path for fish while a funnel keeps the shrimp away from the windows, reduces water flow around the windows, and acts as a leading panel to guide the fish out of the trawl. Observations of fish behavior showed that finfish generally reacted to the slack water flow created by the funnel by swimming towards the lowest water flow area. The escape rate of finfish such as juvenile red snapper (Lutjanus campechanus), however, was low and random during towing when no net surging and fish crowding occurred. The highest escape rates occurred during slow down prior to haulback, but were dependent on the haul back procedure. This may help explain the haul-to-haul variation in escapement documented for the Jones/Davis device. Modifications and techniques to improve escape rates during towing are discussed.