Ecological Connectivity Between Shallow Coastal Habitats and Offshore Fishing Grounds for Juvenile Fish in the Bight of Benin

Coastal nursery habitats including estuaries, seagrass beds, and mangrove creeks are widely recognised as essential juvenile fish production areas, but the quantitative contribution of these habitats to offshore adult populations in West African waters remains poorly established. This study investigated the ecological connectivity between shallow coastal nursery habitats and offshore fishing grounds in the Bight of Benin using otolith microchemistry as a natural tag. Adult individuals of three commercially important species (Pseudotolithus elongatus, Galeoides decadactylus, and Brachydeuterus auritus) were collected from offshore trawl surveys, and their sagittal otoliths were sectioned for life history reconstruction. Strontium-to-calcium and barium-to-calcium ratios were measured along otolith transects using laser ablation inductively coupled plasma mass spectrometry. Elemental profiles were compared against otolith chemical signatures of known-origin juvenile individuals from candidate coastal nursery habitats. Discriminant function analysis correctly assigned 81 percent of juveniles to their natal coastal habitat based on otolith chemistry. Retroactive assignment of adults revealed that 60 to 75 percent of the offshore adult populations originated from estuarine nursery habitats along the Nigerian coast. Mangrove creek habitats showed the highest nursery production contributions for Pseudotolithus elongatus. Seagrass bed origin individuals showed significantly better body condition at capture, suggesting a habitat quality effect. The study provides the first quantitative habitat connectivity data for the Bight of Benin and strongly supports the conservation of coastal nursery habitats as a prerequisite for sustainable offshore fisheries. Keywords: otolith microchemistry, habitat connectivity, nursery habitats, Bight of Benin, coastal fisheries.