Reducing bycatch in the United States Gulf of Mexico shrimp trawl fishery with an emphasis on red snapper bycatch reduction

Abstract

Bycatch, the capture of non-targeted species during commercial fishing, is a global problem that may require novel solutions. The nested cylinder bycatch reduction device (NCBRD), developed using laboratory behavioral studies (Parsons and Foster, 2007; Parsons et al., 2012), was herein evaluated for reducing bycatch in shrimp trawl fisheries and for its application in the U.S. Gulf of Mexico (GOM) fishery. We examined the efficacy of the NCBRD for retaining shrimp, for reducing total bycatch, and for reducing bycatch of juvenile red snapper (Lutjanus campechanus), a species that is presently over-fished in the GOM. Using paired trawling on-board leased, commercial fishing vessels, shrimp catch, total bycatch, and the catch of red snapper juveniles were compared from trawls equipped with an NCBRD and control trawls without. Depending upon configuration, trawls with an NCBRD captured about 46–100% of shrimp taken in controls, reduced total bycatch by 26–60% and, of particular note, reduced red snapper bycatch by about 50%. When catch rates were compared, 2.29 (±0.38 s.e.)snapper/h/trawl were taken with an NCBRD and 6.11 (±0.93 s.e.)snapper/h/trawl without, a highly significant (ANOVA, P=0.0032, F=9.39, d.f.=1, 64) effect. Finally, using only red snapper captured in control trawls, we observed a significant effect of depth on red snapper capture with decreasing numbers of red snapper captured with increasing depth. In waters south of Galveston shallower than about 55m, catch rates ranged from 4.5 to 23.4snapper/h/trawl and in deeper water ranged from 0.3 to 2.4snapper/h/trawl. We identified a highly significant relationship (P<0.001, R2=0.685) between red snapper catch and depth. We estimate that use of the NCBRD would reduce juvenile red snapper bycatch in the northern Gulf of Mexico by about 50%. These results suggest that the NCBRD may find application in trawl fisheries worldwide.