Evaluating Turtle Excluder Devices with Reduced Bar Spacing for Bycatch

Evaluating Turtle Excluder Devices with Reduced Bar Spacing for Bycatch Reduction in the Penaeid Shrimp Fishery of the Gulf of Mexico

Dominy Hataway – NOAA Fisheries, Southeast Fisheries Science Center – Pascagoula, MS  

Lee Saxon - NOAA Fisheries, Southeast Fisheries Science Center – Pascagoula, MS

Keywords- Bycatch, reduced bar spacing, bycatch reduction device (BRD), turtle excluder device (TED), shrimp, Gulf of Mexico.                                                                        

Measures to reduce finfish bycatch in the Southeastern U.S. shrimp fishery have led to the development of bycatch reduction devices (BRDs). Currently approved BRDs rely on the swimming behavior of fish to affect escapement through the device and out of the trawl.  Due to differences in the swimming behavior of bycaught finfish and elasmobranchs, current BRD designs do not effectively exclude all species.  The turtle excluder device (TED), a required component of most shrimp trawls fished in the Southeastern U.S., is effective in eliminating larger fish from the catch. However, exclusion may be enhanced with reduced deflector bar spacing.  

We conducted comparative tows between a TED with 2 inch bar spacing vs. a traditional TED with 4 inch bar spacing as a means of assessing differences in bycatch and shrimp catch rates.  This study used one inshore commercial shrimp trawler working in Mississippi and Louisiana waters and one shrimp trawler working primarily in inshore Alabama waters. Additionally the project is utilizing the shrimp trawl observer program of the Galveston, Texas laboratory to collect comparative catch data from an offshore shrimp trawler in Texas.

Traditional TEDs have bars spaced 4 inches apart and work as a sorting device in the trawl to exclude larger bycatch species such as sharks and rays, jellyfish, and large bony fishes. By decreasing the distance between the bars additional bycatch species could be excluded. As of October 2010, there has been 40 comparative tows conducted with the 2 inch bar spacing and an identical curved bottom flatbar TED with 4 inch bar spacing.  The TED with 2” bar spacing had bycatch reduction rates for all sharks combined of 72.3% and reduction of the catch of rays by 59.5% by number. The most prevalent bycatch species in these inshore tests was the Atlantic croaker Micropogonias undulatus,  the TED with 2 inch bar spacing reduced the Atlantic croaker catch by 37.5% by weight. The shrimp loss for the 2 inch bar spacing TED is 4.95 percent by weight which was not significant at alpha <.05 level.