Distribution-abundance relationships for North Sea Atlantic cod (Gadus morhua): observation versus theory. Canadian Journal of Fisheries and Aquatic Sciences 62
Abstract: Density-dependent habitat selection has implications for fisheries management and for the recovery of de-pleted fish populations. According to ideal free distribution theory, populations contract into areas of highest habitat suitability as their abundance decreases. This can increase thei...
| Main Authors: | , , , , , , |
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| Format: | Text |
| Language: | English |
| Published: |
2005
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.460.2358 http://uncover-nscs-report.googlecode.com/svn/trunk/stuff_from_jp/Blanchard ideal free distribution.pdf |
| Summary: | Abstract: Density-dependent habitat selection has implications for fisheries management and for the recovery of de-pleted 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 com-pared the observed distribution–abundance relationships with those predicted from a model based on ideal free distribu-tion 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 in-cluding 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. Résumé: La sélection de l’habitat en fonction de la densité a des conséquences sur l’aménagement des pêches et la récupération des populations de poissons décimées. Selon la théorie de la distribution idéale libre, les populations se concentrent dans des zones d’habitats les plus adéquats à mesure que leur taille diminue, ce qui peut augmenter leur vulnérabilité à la pêche et à la prédation. Nous avons détecté une sélection de l’habitat en fonction de la densité chez de jeunes morues (Gadus morhua) (âges 1 et 2) de la mer du Nord et nous avons comparé les relations répartition– abondance observées à celles prédites à partir d’un modèle basé sur la théorie de la distribution idéale libre et les connaissances des ... |
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