Population biology of the spider crab, Mithraculus forceps (A. Milne-Edwards, 1875) (Majidae, Mithracinae) on the southeastern Brazilian coast

Abstract

This investigation provides information on the biology of the spider crab, Mithraculus forceps, on the southeastern coast of Brazil. Monthly collections were carried out from January to December 2000, by SCUBA diving off Couves Island (23 degrees 25'25"S 44 degrees 52'03"W). A total of 436 crabs was obtained: 248 males and 188 females, with 108 females carrying eggs. The population showed a normal structure, and the sex ratio was 1 : 0.76 in favour of males. Individuals reached morphological maturity over a wide size range, between 6.7 mm and 13.9 rum carapace width (CW) for males and between 8.5 mm and 16.0 mm CW for females. Ovigerous females and recruits were recorded during the entire study period. No correlations were detected between the frequency of individuals and the selected environmental factors of water temperature, salinity, and light.