Reproductive Biology of the Blue Crab, Callinectes amnicola (De Rocheburne) in the Lagos Lagoon, Nigeria

Sex ratio, fecundity, maturation development and oogenesis of Callinectes amnicola (De Rocheburne) in the Lagos Lagoon, Nigeria were investigated. The male/female ratio was 1:0.96. Fecundity estimates ranged between 478,400 and 4,480,500 eggs with a mean of 780,480 eggs. The diameter of the eggs varied between 0.25 and 0.35 mm with a mean of eggs 0.29 mm. A low positive correlation existed between fecundity and weight (r = 0.247) of the crab. Maturity was attained between 6.2 and 16.5 cm carapace width (CW) for the females and between 7.3 and 15.3 cm CW for the males. Fifty percent maturity (TL50) was attained at 10.8 cm CW in the males and 11.0 cm CW in the females. Five maturity stages of gonads were identified. Three major developmental stages of oocytes were observed. Immature and mature crabs were obtained in the lagoon throughout the year indicating that this species breeds throughout the year with a peak between March and June.