Snow Crab (Chionoecetes opilio) Distribution Limits and Abundance Trends on the Scotian Shelf
The distribution and abundance of snow crab (Chionoecetes opilio) near its southern limit of the Scotian Shelf is characterized from commercial fishing locations and from groundfish trawl surveys. Groundfish surveys also provide data on bottom temperature. Snow crab are most abundant on the eastern...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.518.6490 http://journal.nafo.int/J21/tremblay.pdf |
| Summary: | The distribution and abundance of snow crab (Chionoecetes opilio) near its southern limit of the Scotian Shelf is characterized from commercial fishing locations and from groundfish trawl surveys. Groundfish surveys also provide data on bottom temperature. Snow crab are most abundant on the eastern Scotian Shelf where bottom temperature is generally <3°C even in summer; they are absent from the deep central Shelf, "Scotian Gulf", which has access to warmer offshore waters. West of the Scotian Gulf snow crab abundance is low, likely ephemeral, and limited to pockets of cold bottom water. The fishery exploits most of the areas where snow crab are expected to be abundant on the Scotian Shelf. Mean annual catch rate by trawls was correlated with mean annual commercial catch rate for the 1980–94 period. There is some evidence of an endogenous cycle in recruitment, but other factors such as changes in bottom temperature appear important to snow crab production on the eastern Scotian Shelf. It cannot be resolved whether the high biomass at the beginning of the fishery resulted from a peak in a recruitment cycle, or from the accumulation of biomass of the virgin population. Year-classes that originated in the mid-1970s and those that entered the fishery from 1982–86 were small; those that supported high landings in the late-1980s and early-1990s may have been larger because of increased survival of early life-history stages, but the reasons for any increased survival are not clear. Lower temperatures after 1984 appear to have contributed to expanded habitat, and reduced predation from groundfish may have increased the survival and growth of juvenile and adolescent snow crab on the eastern Scotian Shelf. |
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