Evaluation of the Sustainability of Shrimp Trawl Fisheries in Delta State: Bycatch and Habitat Impacts

Shrimp trawl fisheries in the coastal waters of Delta State, South South Nigeria, are economically important but have faced increasing scrutiny for their ecological impacts, including bycatch of juvenile fish and damage to benthic habitats. This study evaluates the bycatch composition, bycatch-to-shrimp ratio, size structure of discarded fish, and trawling ground characteristics in shrimp trawl operations observed aboard six commercial vessels operating from Warri, Delta State, over a four-month period. Bycatch was sorted, identified, weighed, and measured for all hauls observed. Benthic sediment and habitat data were collected at 24 trawled stations using grab samplers and underwater video. Bycatch-to-shrimp ratios averaged 5.8:1 by weight, indicating that nearly six kilograms of non-target organisms were discarded for every kilogram of shrimp retained. Juvenile Ethmalosa fimbriata, Pseudotolithus spp., and Cynoglossus spp. constituted the dominant bycatch components. Over 60% of discarded finfish individuals were below minimum landing size. Trawling ground benthic habitats showed evidence of significant physical disturbance, with reduced macrofaunal diversity in repeatedly trawled areas. The study provides empirical evidence of the ecological costs of current shrimp trawl practices in Delta State coastal waters and recommends the mandatory adoption of bycatch reduction devices, seasonal trawl closures during peak juvenile recruitment periods, and stronger enforcement of existing mesh size regulations by the Federal Department of Fisheries.

Keywords: shrimp trawl, bycatch, Delta State, coastal fisheries, sustainability