Distribution, reproduction and moulting of the rock crab,Cancer irroratus Say, 1917, in the mid-Atlantic Bight

Abstract

Summary Rock crabs, Cancer irroratus, were collected in October 1971, and April and June 1973 during trawl surveys of the continental shelf of the mid-Atlantic Bight. More than 1700 rock crabs were captured in 58 trawls. They were contagiously distributed within a depth range of 18–390 m. Maximum abundance occurred within 40–60 m and 6–9·9°C. Male crabs ranged from 8 to 127 mm in carapace width, females from 11 to 113 mm. Two modal size groups for males and females were recognized: less than 50 mm and 51–100 mm. There was a third group of male crabs over 100 mm width. Crabs less than 50 mm were more abundant than larger crabs at depths from 15 to 150 m; they were most abundant at 40–60 m. Crabs 51–100 mm were more abundant than other size groups in the 150–400 m depth stratum. Males greater than 101 mm were most abundant at 20–60 m. Male crabs predominated in June. Sex ratios (M : F) ranged from 1·2 to 1·9 : 1. In October the ratios ranged from 1 : 2·1 to 4 : 1. In April the ratio was 1·7 : 1. The ratios ...