Natural Diet, Feeding and Predatory Activity of the Crabs Callinectes arcuatus and C. toxotes (Decapoda, Brachyura, Portunidae)

Abstract

The natural diet of Callin~ctes arcuatlls Ordway in the Huizache-Caimanero lagoon system (W. Mexico) was detern~~ned and several aspects of its feeding and predatory activity were investigated. Limited observations ware also made on the dlet of C. toxotes Ordway. The diets of the two crabs were similar, but thdt of C. arcuatus appeared more varied; it consistc:d nla~nly of bivalve molluscs, crabs and fish. D~ffrrences in the diet of C. arcuatcls in different areas of the lagoon system and at different times of the year reflected differences in prey availability rather than In prey selt>ctlon. Small crabs (below 60 mm breadth) were basically detritivores and scavengers, whilst larger crabs were scavengers and predatory feeders. They were not found to be major preddtors of penacs~d shrimp, and C arcclatus was shown not to 1x1 an elficlent predator of highly rnob~lc an~ni~~ls such as shrimp. Feedlng occurred mainly at night, especially around dusk.