Reproductive biology of Mithrax forceps (A. Milne-Edwards, 1875) (Crustacea : Decapoda : Majidae)

Some aspects of the reproductive biology of Mithrax forceps were studied ba sed on 580 specimens (380 males and 200 females) collected at Chacachacare, Margarita Island, Venezuela, from April 1984 to March 1985 and from July t o November 1991. During the sampling period, males outnumbered females in t he catch by almost two to one. Sex ratio was different from 1:1 in May, Jun e, October, December, February and March. Male and female crabs attained se xual maturity at a size of 7.15 and 11.20 mm carapace length, respectively. Size at maturity for 50% of the population was 19.28 and 16.64 mm carapace length for males and females, respectively. As indicated by the presence o f ovigerous females during the whole sampling period, the population can re produce continuously during the year. Fecundity estimates of ovigerous fema les ranged from 34 to 4777 eggs (average = 1024 +/- 93). Relative fecundity was 1.90 to 207.00 (average = 58.96 +/- 4.54) eggs/mm carapace length, 1.8 2 to 200.29 (average = 56.32 +/- 4.37) eggs/mm carapace width, and 12.19 to 1656.07 eggs/g (average = 465.16 +/- 36.67). Fecundity was linear and posi tively related to carapace length and width, total weight and ovigerous mas s weight. Embryonic development was divided into three stages according to the color of the ovigerous mass and the characteristics of the embryo.