Assessment of Bycatch and Discards in Shrimp Trawl Fisheries Operating off the Nigerian Continental Shelf

Industrial shrimp trawling on the Nigerian continental shelf produces large quantities of incidental bycatch, including juveniles of commercially important finfish, sea turtles, and invertebrates, with significant ecological and economic consequences. This study assessed the composition, quantity, and value of bycatch and discards associated with industrial shrimp trawling operations off the Nigerian coast. Fisheries observers were deployed on 18 commercial shrimp trawlers for a total of 94 sea days over a six-month period. All catch was sorted, identified, weighed, and recorded before sorting decisions were made by the fishing crew. Discard rates and the bycatch-to-shrimp ratio were calculated. Sea turtle interaction rates were recorded separately. The condition of discarded organisms was assessed at the point of return to sea. The overall mean bycatch-to-shrimp ratio was 4.8 to 1 by weight, indicating that for every kilogram of shrimp retained, 4.8 kilograms of bycatch were caught. Finfish constituted 73 percent of total bycatch by weight, dominated by Pseudotolithus spp. and Brachydeuterus auritus juveniles. Discard rate was 84 percent of total bycatch, with low survival rate of returned fish estimated at 15 percent. Sea turtle interaction was recorded on 6 occasions, involving 4 olive ridley and 2 leatherback turtles, all returned alive. The study recommends mandatory fitting of Turtle Excluder Devices, adoption of Bycatch Reduction Devices, and revision of the national bycatch policy to set legally binding discard limits. Keywords: bycatch, discards, shrimp trawl, Nigerian continental shelf, sea turtle interaction.