The biology of the smooth swim crab, Portunus validus (Herklots) off Lagos coast, Nigeria.
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Lawal-Are, A. O.
The size composition, growth pattern, food and feeding habits, fecundity and sex ratio of the smooth swim crab, Portunus validus (Herklots) off the Lagos Coast, Nigeria were investigated. The carapace length of the 618 specimens examined ranged between 4.5cm and 11.4cm (carapace width 9.2cm to 19.5cm) and weighed 82.3g to 694.0g. The crabs exhibited negative allometric growth in both sexes. There was high correlation between carapace width and body weight of the crabs with correlation coefficient (r) ranging between 0.889 and 0.911. The condition factor ranged between 3.78 and 5.46 with a mean of 4.85. The condition factor decreased with increase in crab size. The crabs fed mainly on fishes, molluscs, crustaceans, plant parts and algae. There were distinct differences in the feeding habits in relation to size. The small crabs fed mainly on shrimp appendages while larger crabs fed mostly on fishes and molluscs. The sex ratio was 1: 2.2 which was significantly different from the expected 1: 1 ratio. The fecundity ranged between 806,000 and 6,240,000. The average fecundity was 2,200,310. The egg diameter ranged from 0.28mm to 0.45mm. The mean egg diameter was 0.34mm.
distribution , feeding hablt , growth pattern , carapace length , Lagos Coast , Portunus validus
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