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Predicting the location of optimal habitat boundaries for lake trout (Salvelinus namaycush) in Canadian Shield lakes

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The optimal habitat boundary for lake trout (Salvelinus namaycush Walbaum) has been defined as that portion of the lake having both more than 6 mg·L–1 oxygen and temperature less than 10 °C. Here we use an existing hypolimnetic oxygen model to define the lower boundary of the optimal habitat by identifying the depth at which 6 mg·L–1 oxygen occurs at the end-of-summer stratification period. Then we develop a new model to predict the 10 °C depth or upper habitat boundary for the same date. These two boundaries can be used in conjunction with measured individual strata volumes to calculate the optimal habitat volume. Parameters needed for the models include lake morphometry, total phosphorus (TP) concentration, and Secchi depth or dissolved organic carbon (DOC) concentration. Thus, the optimal habitat model can be used to predict the effects on optimal habitat volumes of changes in trophic status (increases or decreases in TP), or changes in light transmission (caused by changes in DOC or its surrogate in these lakes, i.e., Secchi depth) that result from changes in climate, land use, acid–base status, or incident ultraviolet radiation levels.

L'habitat optimal du touladi (Salvelinus namaycush Walbaum) a été défini comme la portion du lac qui possède simultanément une concentration d'oxygène supérieure à 6 mg·L–1 et une température inférieure à 10 °C. Nous utilisons un modèle déjà existant de l'oxygène de l'hypolimnion pour définir la frontière inférieure de l'habitat optimal en déterminant la profondeur à laquelle se situe la concentration d'oxygène de 6 mg·L–1 à la fin de la période de stratification estivale. Nous avons ensuite mis au point un nouveau modèle pour prédire la profondeur de la température de 10 °C, soit la frontière supérieure de l'habitat, pour la même date. Ces deux frontières combinées aux mesures des volumes des différentes strates peuvent servir à calculer le volume de l'habitat optimal. Les variables requises pour ces modèles sont la morphométrie du lac, la concentration de phosphore total (TP) et la profondeur de Secchi ou alors la concentration de carbone organique dissous (DOC). Ainsi, le modèle d'habitat optimal peut servir à prédire les effets sur le volume de l'habitat optimal de changements dans le statut trophique (accroissements ou réductions de TP) ou de changements dans la transmission de la lumière (causés par des changements dans le DOC, ou son substitut dans ces lacs, c'est-à-dire, la profondeur de Secchi) qui résultent de modifications du climat, de l'utilisation des terres, du statut acide–base ou des intensités de radiation ultraviolette incidente.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2003-08-01

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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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