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.

Abundance and population structure of the Atlantic horseshoe crab Limulus polyphemus in Pleasant Bay, Cape Cod

“…Since we cannot be certain when each molt occurred in Pleasant Bay, our assessment is the parsimonious and conservative given the distinctiveness of the cohorts and the relative increase in size from one cohort to the next. The mean prosomal widths of successive juvenile cohorts are similar to those reported for juveniles reared continuously in the laboratory (Sekiguchi et al 1988), for a few horseshoe crab cohorts previously measured in Pleasant Bay (Shuster 1982) (Table 4), and for snow crabs (Comeau et al 1998 159.7 ± 5.1 Table 4. Limulus polyphemus.…”

“…Juvenile females would have to make a 44 to 92% prosomal increase in a single molt. These seem dauntingly large given that a prosomal increase of approximately 20% has been suggested as the largest possible for adult snow crabs, a species with a mean size of instars and size at sexual maturity almost identical to those of horseshoe crabs (Dawe et al 1991, Comeau et al 1998. Even sea spiders, the taxon that has the largest reported % increase associated with a single molt to maturity (41.5 ± 6.2% for males and 57.2 ± 3.1% for females), do not achieve the size increase necessary to account for the largest horseshoe crabs in the Bay (Tomaschko et al 1997).…”

Small-scale non-linear geostatistical analysis of Liocarcinus depurator (Crustacea: Brachyura) abundance and size structure in a western Mediterranean population

“…Sediment characteristics have been found to strongly influence occurrence and distribution of many benthic decapod crustaceans, especially of those with burrowing and burying habits (Atkinson & Taylor 1988, Pinheiro et al 1996, Comeau et al 1998. In this study, the use of geostatistical procedures was fundamental in identifying which sediment variables may influence the distribution of Liocarcinus depurator.…”

“…Abelló et al 1990, Ardizzone et al 1990, Rossi & Costantini 2000, although it has received less research effort within the field of geostatistics (Comeau et al 1998, Lembo et al 2000a. However, some studies suggest that different scales of spatial structuring (e.g.…”

“…However, some studies suggest that different scales of spatial structuring (e.g. by geographic sectors, latitude or depth) may exist for a given species, as shown for the snow crab Chionoecetes opilio, for which an important spatial segregation was detected by sex and size in the Gulf of Saint Lawrence using geostatistics (Comeau et al 1998). The spatial structure of the shrimps Parapenaeus longirostris and Aristeus antennatus was studied by Lembo et al (1999Lembo et al ( , 2000a in the Tyrrhenian Sea from stratified, random, bottom-trawl data.…”