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The control of point-source contaminants and regulations designed for specific waste discharges have reduced incidents of fish kills. These actions, however, do not protect fish like salmon, which encounter many different contaminants during extensive migrations. Attempts to document pollutant-associated toxicity is challenging in migratory salmon, although a few laboratory and field studies have produced a convincing body of evidence that lifelong contaminant exposure can contribute to the demise of fish. The case of the decline of Fraser River sockeye salmon (Oncorhynchus nerka) in British Columbia, Canada, brought into sharp relief the difficulty of assigning a specific cause (e.g., climate, disease, or contaminants) to a diffuse problem (i.e., low fish returns). Determining the effects that pollutants have on wild salmon requires study designs that consider life history, habitat, and the real world of complex contaminant exposures. In the absence of evidence from such study designs, the future survival of salmon may hinge on the application by managers of the precautionary approach to stressors that are within immediate jurisdictional control, such as toxic chemicals. Le controle des contaminants de source ponctuelle et la reglementation visant les rejets de dechets precis ont reduit l'incidence de mortalites massives de poissons. Ces mesures ne protegent toutefois pas des poissons comme le saumon, qui est confronte a de nombreux contaminants differents durant ses grandes migrations. Si la documentation de la toxicite associee aux polluants chez les saumons migrateurs n'est pas chose facile, quelques laboratoires et etudes de terrain ont produit des preuves convaincantes du lien entre l'exposition soutenue aux contaminants et la mortalite des poissons. Le cas du declin du saumon sockeye (Oncorhynchus nerka) du fleuve Fraser, en Colombie-Britannique (Canada), a mis en evidence la difficulte d'attribuer a une cause precise (p. ex. climat, maladie, contaminants) un probleme diffus (c.-a-d. baisse du nombre de poissons revenant au cours d'eau d'origine). La determination des effets des polluants sur le saumon sauvage necessite une methodologie d'etude qui tienne compte du cycle de vie, de l'habitat et de la realite de la complexite de l'exposition aux contaminants. En l'absence de preuves decoulant d'etudes ainsi con^ues, la survie du saumon pourrait dependre de l'application d'une approche prudente a la gestion des stresseurs pouvant faire l'objet d'un controle etroit, tels que les produits chimiques toxiques. [Traduit par la Redaction], 'For life and death are one, even as the river and sea are one.' --Khalil Gibran 1883-1931 Introduction Belly up It was 7:20 am on 5 August 2005, and the [...]

Although concentrated pollution has been eliminated from most waterways, low levels of pesticides and other chemicals still end up in streams. A new study replicated typical trace concentrations of 10 [...]

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