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Physiological consequences of “premature freshwater return” for wild sea-run brown trout (Salmo trutta) postsmolts infested with sea lice (Lepeophtheirus salmonis)

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The physiological consequences of “premature migratory return” to freshwater for wild sea-run brown trout (Salmo trutta) smolts infested with sea lice (Lepeophtheirus salmonis) were investigated in the laboratory. Osmoregulatory, metabolic, and stress markers were analysed in order to assess the potential consequences of transfer to freshwater, 19 days after the challenge with L. salmonis. Infestation intensity was significantly reduced following transfer to freshwater, and mortality rates were markedly higher in infested fish maintained in seawater vs. fish that were transferred to freshwater. Significant sea lice effects, consistent across a number of physiological markers, were apparent once L. salmonis developed to the mobile stages. Plasma chloride, lactate, and cortisol all were significantly higher than control values, and liver glycogen concentration was significantly reduced in infested fish in seawater. After return to freshwater, these physiological measures returned to control levels, but significant lice effects persisted for fish maintained in seawater. Premature return of infested sea-run brown trout to freshwater does, therefore, confer significant short-term physiological benefits across a range of osmoregulatory, metabolic, and stress markers.

Nous avons étudié en laboratoire les conséquences physiologiques d’un « retour prématuré de migration » en eau douce chez des saumoneaux de truites brunes anadromes (Salmo trutta) sauvages et infestées de Lepeophtheirus salmonis. Nous avons analysé des marqueurs de l’osmorégulation, du métabolisme et du stress afin de déterminer les conséquences potentielles d’un transfert en eau douce, 19 jours après une confrontation avec L. salmonis. L’intensité de l’infestation est significativement réduite après le transfert en eau douce; les taux de mortalité sont nettement plus élevés chez les poissons infestés maintenus en eau salée par rapport aux poissons transférés en eau douce. Des effets significatifs des poux de mer, retrouvés dans plusieurs marqueurs physiologiques, apparaissent une fois que L. salmonis atteint les stades mobiles. Chez les poissons infestés en eau de mer, les concentrations plasmatiques de chlorures, de lactate et de cortisol sont toutes significativement plus élevées que chez les témoins et la concentration de glycogène du foie est significativement réduite. Après un retour en eau douce, les mesures physiologiques reviennent aux valeurs témoins, alors que des effets significatifs des poux persistent chez les poissons retenus en eau de mer. Un retour prématuré en eau douce des truites brunes anadromes infestées procure ainsi des bénéfices physiologiques qui sont apparents dans une gamme de marqueurs de l’osmorégulation, du métabolisme et du stress.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: October 1, 2007

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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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