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Natural chemical markers identify source and date of introduction of an exotic species: lake trout (Salvelinus namaycush) in Yellowstone Lake

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Exotic species invasions pose a pervasive threat to aquatic ecosystems worldwide, yet fundamental questions about the geographic origin and timing of invasions or introductions are frequently difficult to answer. We used natural chemical markers (Sr:Ca ratios) in otoliths to identify probable source and date of introduction of exotic lake trout (Salvelinus namaycush) into Yellowstone Lake, Wyoming, USA. Otolith Sr:Ca ratios were significantly different among lake trout known to have reared in three different Yellowstone National Park lakes (Yellowstone, Heart, and Lewis lakes) and showed little variation along the otolith axis, indicating that lake trout within each lake experienced a similar, and consistent, environmental history. In contrast, suspected transplants showed a large and rapid increase in otolith Sr:Ca ratios indicative of a marked shift to water of differing chemistry. Timing of the abrupt change in Sr:Ca ratios indicated that some lake trout were introduced into Yellowstone Lake during the late 1980s, but more recent transplants also occurred. A discriminant model identified Lewis Lake as the likely source lake for lake trout transplanted into Yellowstone Lake. Our results demonstrate that chemical signatures within otoliths can serve as an important forensic tool for identifying the probable source and date of exotic fish introductions.

Bien que l'invasion d'espèces exotiques soit une menace omniprésente dans les écosystèmes aquatiques à l'échelle de la planète, les questions fondamentales concernant l'origine géographique et la date des invasions et des introductions restent souvent difficiles à résoudre. Nous avons utilisé des marqueurs chimiques naturels (rapports Sr:Ca) dans les otolithes pour identifier la source probable et la date d'introduction des touladis (Salvelinus namaycush) exotiques du lac Yellowstone, Wyoming, É.-U. Les rapports Sr:Ca des touladis élevés dans trois lacs différents du parc national de Yellowstone (Yellowstone, Heart et Lewis) sont significativement différents et ils affichent peu de variation le long de l'axe de l'otolithe, ce qui indique que les touladis de chacun des lacs y ont vécu une histoire environnementale semblable et uniforme. En revanche, les poissons soupçonnés d'avoir été transplantés montrent une augmentation rapide et importante des rapports Sr:Ca dans leurs otolithes, ce qui indique un passage subit dans une eau de caractéristiques chimiques différentes. La détermination de la date de ces changements abrupts des rapports Sr:Ca indique que certains touladis ont été introduits dans le lac Yellowstone à la fin des années 1980, mais qu'il y a eu aussi des introductions plus récentes. Un modèle discriminant identifie le lac Lewis comme la source probable des touladis introduits dans le lac Yellowstone. Nos résultats montrent que les signatures chimiques des otolithes peuvent être des outils de recherche intéressants pour identifier la source et la date probables d'introduction de poissons exotiques.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: January 1, 2005

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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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