Population Structure and Exploitation Rate of Blue Crab (Callinectes sapidus) in the Estuary of Bight of Benin, Edo State

Blue crabs (Callinectes sapidus) are commercially and ecologically important crustaceans that support significant artisanal fisheries along the Nigerian coast. This study evaluated the population structure, sex ratio, size-at-maturity, and exploitation rate of blue crabs in the estuarine waters adjacent to Benin River, Edo State, South South Nigeria. Crabs were collected monthly for five months from artisanal fishing grounds using crab pots and collapsible traps at three stations. Carapace width, total weight, and sex of each individual were recorded. Length-frequency data were analysed using FiSAT II software to estimate growth parameters and exploitation rate. Gonad condition was assessed visually to determine maturity status. A total of 672 individuals were sampled. Females constituted 54 percent of the catch. Mean carapace width was 10.4 centimetres, with significant differences between sexes. Size-at-50-percent maturity was estimated at 8.7 centimetres carapace width for females. Von Bertalanffy growth parameters were: L infinity = 18.2 centimetres, K = 0.61 per year. The estimated exploitation rate (E = 0.68) exceeded the optimal reference point of 0.5, indicating overfishing. The dominance of small, immature individuals in catches confirmed excessive harvest of recruits. Monthly catch trends at all sites showed consistent decline over the sampling period. The study recommends minimum legal carapace width limits, restrictions on berried female harvest, and gear type regulation to rebuild blue crab stocks in the Bight of Benin estuarine system. Keywords: Callinectes sapidus, population structure, exploitation rate, Benin River, crustacean fisheries.