Author(s): Ambrose Eyo, Ukpatu John, Udoh James

Abstract: Wet and dry season variations in shrimps and bycatch compositions were surveyed in the Nematopalaemon shrimp fishery in the near shore water (<35 m depth and <5 nautical miles) in the Okoro River estuary, Southeastern Nigeria. The catch composition included: 46 species from 27 families in the wet season and 35 species from 23 families in the dry season. Total catch consisted 39.3% shrimp, 7.55% bycatch, 0.15% crabs/squids in the wet season and 46.37% shrimp, 6.61% bycatch and 0.05% crabs/squids in the dry season. Finfish, crabs and squids were higher in wet season than dry season, while shrimp catch was higher in the dry season than wet season. Significant variabilities in shrimp and bycatch compositions were detected at these temporal scales, shrimps-bycatch ratio of 5: 1 and 7:1 were obtained respectively at wet and dry seasons. Bycatch species were juveniles with a total length range of 4 to 30 cm in the wet season and 4 to 56 cm in the dry season. Majority of the bycatch species occurs throughout the year, few have seasonal occurrence and showed progressive increase in mean total lengths and weight from wet to dry season; Arius latiscutatus, Trachinotus teraia, Alpheus pontederiae and Callinectes amnicola in the wet season while Sardinella aurita, Chloroscumbrus chrysurus and Pseudotolithus typus showed progressive increase in mean total and weight from dry to wet season. The comparison of multi-species composition of the fishery revealed that only 15 out of the 48 species recorded showed significant difference between seasons (p<0.05). These species are: N. hastatus, P. atlantica, Pellonula leonesis, Pseudotolithus elongates, Trichurus lepturus, Lutjanus endecacanthus, and Ethmalosa fimbriataa. The total quantity of shrimps and bycatch landings combined were significantly higher in dry season (39,164.73kg) than in wet season (34,798.15kg) (p<0.005). The Nematopalaemon shrimp fishery is characterized by wet and dry season variations in catch composition. Thus, pragmatic management strategy is hereby recommended to reduce bycatch problems in the artisanal shrimp fishery.

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