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Distribution–abundance relationships for North Sea Atlantic cod (Gadus morhua): observation versus theory

journal contribution
posted on 2023-05-18, 10:06 authored by Julia BlanchardJulia Blanchard, Mills, C, Jennings, S, Fox, CJ, Rackham, BD, Eastwood, PD, O'Brien, CM
Density-dependent habitat selection has implications for fisheries management and for the recovery of depleted fish populations. According to ideal free distribution theory, populations contract into areas of highest habitat suitability as their abundance decreases. This can increase their vulnerability to fishing and predation. We detected density-dependent habitat selection by juvenile Atlantic cod (Gadus morhua) (ages 1 and 2) in the North Sea and compared the observed distribution–abundance relationships with those predicted from a model based on ideal free distribution theory and knowledge of optimal temperatures for growth, where temperature was used as a measure of suitability. As predicted by the model, in years when stock size was low, the catches were largely confined to regions with near-optimal bottom temperatures. Conversely, when population size was high, catches were spread across a larger area including regions with suboptimal temperatures. The spatial extent of optimal habitat appears to have decreased from 1977 to 2002, reflecting a gradual warming of the North Sea. The combined negative effects of increased temperature on recruitment rates and the reduced availability of optimal habitat may have increased the vulnerability of the cod population to fishing mortality.


Publication title

Canadian Journal of Fisheries and Aquatic Sciences










Institute for Marine and Antarctic Studies


Natl Research Council Canada

Place of publication

Research Journals, Montreal Rd, Ottawa, Canada, Ontario, K1A 0R6

Rights statement

Copyright 2005 NRC Canada

Repository Status

  • Restricted

Socio-economic Objectives

Assessment and management of terrestrial ecosystems

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