Limited behavioural thermoregulation by adult upriver-migrating sockeye salmon (Oncorhynchus nerka) in the Lower Fraser River, British Columbia

Abstract

The objective of this study was to combine radio telemetry with individual thermal loggers to assess the extent to which adult migrating sockeye salmon (Oncorhynchus nerka (Walbaum in Artedi, 1792)) behaviourally thermoregulate during their migration through the Fraser River mainstem, British Columbia. The Fraser mainstem represents a region of the migration route that contains some of the highest mean temperatures encountered by sockeye salmon during their life history. We found that throughout the study area, individual sockeye salmon body temperatures occasionally deviated from ambient temperatures (DT), yet individuals maintained a DT of -1 8C or cooler for only 5% of their migration through the study region. There were moderate mean deviations of DT in two segments that are known to contain thermally stratified waters. In one of the study segments with the greatest DT, mean body temperatures decreased as river temperatures increased and DT became increasingly positive with higher river discharge rates, but these relationships were not observed in any of the other study segments. No relationship existed between DT and migration rate. While periodic associations with cool water were evident, mean body temperatures were not significantly different than mean river temperatures throughout the lower Fraser mainstem. This finding raises further conservation concerns for vulnerable Fraser River sockeye stocks that are predicted to encounter increasing peak summer river temperatures in the coming decades.Résumé : L'objectif de notre recherche est de combiner l'utilisation de la radio-télémétrie et d'enregistreurs individuels de température afin d'évaluer dans quelle mesure les saumons rouges (Oncorhynchus nerka (Walbaum in Artedi, 1792)) adultes sont capables par leur comportement de faire de la thermorégulation durant leur migration le long du cours principal du Fraser, Colombie-Britannique. Le cours principal du Fraser est une portion de la route de migration qui contient quelques-unes des températures moyennes les plus élevées que connaît le saumon rouge durant son cycle biologique. Dans l'ensemble de la région d'étude, la température corporelle des saumons individuels diffère à l'occasion de la température ambiante (DT); néanmoins, les individus maintiennent un DT de -1 8C ou davantage durant seulement 5% de leur migration à travers la région d'étude. Il y a des différences moyennes modérées de DT dans deux sections connues pour posséder des eaux à stratification thermique. Dans l'une des sections d'étude qui possède le DT le plus important, la température corporelle moyenne diminue à mesure que la température du fleuve augmente et DT devient de plus en plus positif en fonction de l'augmentation du débit de la rivière; ces relations ne s'observent cependant pas dans aucun autre segment étudié. Il n'existe pas de relation entre DT et le taux de migration. Tandis que les associations periodiques avec d'eau frais était évidentes, les températures corporelles moyennes ne diffèrent pas significativement des températur...

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Tracking animals in freshwater with electronic tags: past, present and future

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Aerobic scope increases throughout an ecologically relevant temperature range in coho salmon

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