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Disentangling local from macroenvironmental effects: quantifying the effect of human encroachments based on historical river catches of anadromous salmonids

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Abstract:

In this paper, we use dynamic factor and intervention analysis to identify and quantify the effect of human encroachments on anadromous salmonid catches in 22 Norwegian rivers over a 128-year period. In particular, we address effects of hydropower development, gravel removal, and stock enhancement (fish ladder construction and stocking). The methods allow for quantification of perturbation effects in the river environment on the annual catch, after removing long-term temporal trends at the appropriate spatial scale. The estimated effects of the encroachments differed among rivers, indicating that the mechanisms differ among rivers even for the same type of encroachment. In three rivers where hydropower development and stock enhancement had occurred, a significant increase of 0.8–9.8 tonnes (t) (34%–44%) was estimated, whereas a significant reduction of 11.2 t (38%) was estimated for the river where gravel removal had taken place. For rivers with additional biological information available, we find support for our estimated effects. In general, removal of gravel significantly reduced catch and there were positive effects of fish ladder constructions and variable effects of hydropower development and stocking (both positive and negative coefficients).

Nous utilisons l'analyse factorielle dynamique et l'analyse d'intervention pour identifier et quantifier les effets des empiétements humains sur les captures de salmonidés anadromes dans 22 rivières de Norvège sur une période de 128 ans. En particulier, nous nous intéressons aux effets des développements hydroélectriques, des enlèvements de gravier et des améliorations de stock (constructions d'échelles à poissons et empoissonnements). Les méthodes permettent de quantifier les effets de perturbations dans l'environnement de la rivière sur la récolte annuelle, après avoir retiré les tendances temporelles à long terme à l'échelle spatiale appropriée. Les effets estimés des empiétements diffèrent d'une rivière à une autre, ce qui indique que les mécanismes varient en fonction des rivières pour un même type d'empiétement. Dans trois rivières (développement hydroélectrique, amélioration de stock), nous évaluons l'accroissement à 0,8–9,8 tonnes (t) (33–44 %), alors que dans la rivière d'où on a retiré du gravier, nous calculons une réduction significative de 11,2 t (38 %). Dans les rivières pour lesquelles il existe des informations biologiques additionnelles, nous obtenons des données qui appuient nos conclusions. En général, le retrait du gravier réduit la récolte de manière significative, la construction d'échelles à poissons a des effets positifs, alors que le développement hydroélectrique et l'empoissonnement ont des effets variables (coefficients positifs et négatifs).[Traduit par la Rédaction]

Document Type: Research Article

Publication date: October 1, 2006

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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