Habitat Preferences of the Snow Crab, Chionoecetes opilio: Where Stock Assessment and Ecology Intersect

Habitat Preferences of the Snow Crab, Chionoecetes opilio: Where Stock Assessment and Ecology Intersect

J.S. Choi

Habitat Preferences of the Snow Crab, Chionoecetes opilio: Where Stock Assessment and Ecology IntersectThis is part of Biology and Management of Exploited Crab Populations under Climate Change
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Description

The Scotian Shelf ecosystem (SSE) represents the southernmost distribution limit of snow crab in the northeast Atlantic. As a result, temperature variations can be expected to be an important factor in determining their spatial distribution. Temperature data from 1950 to the present were modeled as generalized additive models (GAMs) and used to reconstruct spatially explicit annual bottom temperatures. The influence of such temperature variations relative to other habitat factors such as substrate grain size, depth, and bottom slope and curvature is described with a binomial GAM and a 13-year data series of snow crab trawl surveys. Two main considerations result. First, explicit knowledge of habitat bounds must inform biomass estimation/stock assessment; otherwise, habitat bounds are implicitly assumed to be fixed and only density estimates are modeled. For the SSE, this type of assumption can result in errors of ±30% in biomass estimates relative to a methodology that accounts for environmental/habitat variations. Second, suitable habitat for snow crab has existed for many years prior to the late 1990s proliferation of snow crab in the SSE. It is hypothesized that alterations in food web structure, particularly the recent demise of demersal fish, was a primary factor in the recent expansion of the snow crab population. This potentially antagonistic relationship between demersal fish and snow crab provokes difficult questions for resource managers as the successful management of one species may have deleterious effects on others.

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