Growth, spatial distribution, and abundance of benthic stages of the snow crab (Chionoecetes opilio) in Bonne Bay, Newfoundland, Canada

Abstract

The growth and spatial distribution of postlarval snow crab (Chionoecetes opilio) from a relatively unexploitated stock in Bonne Bay, Newfoundland (Gulf of St. Lawrence), were described from the analysis of size distributions from trawls and a dredge sampled between 1988 and 1993. Immature crabs molted twice a year for instars I-V and then molted annually until females reached a terminal molt at maturity (instar X or XI) and males a juvenile stage (instar VIII). Thereafter, juvenile males could molt to another juvenile size, skip a molt, or achieve a terminal molt at the onset of the morphometric differentiation of their claws depending on the relative abundance of mature males. The life expectancy of females and males was 13 and 19 years, respectively. Males should recruit to the commercial size of 95 mm carapace width at instar XII, 9 years or more after settlement. Relative abundance of early benthic to commercial-size individuals suggests that small immature crabs (instar V) migrate from shallow rocky to deep muddy bottoms. The patchy spatial distribution observed for the snow crab appeared to be determined more by substrate and intraspecific factors than by depth. Seasonal movements to shallow waters by larger animals was related to density- and temperature-dependent factors associated with the reproductive and growth cycle.