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Rapid Stable Isotope Turnover of Larval Fish in a Lake Superior Coastal Wetland: Implications for Diet and Life History Studies
Citation:
HOFFMAN, J., A. M. COTTER, GREG S. PETERSON, T. D. CORRY, AND J. R. KELLY. Rapid Stable Isotope Turnover of Larval Fish in a Lake Superior Coastal Wetland: Implications for Diet and Life History Studies. Aquatic Ecosystem Health and Management. Taylor & Francis, Inc., Philadelphia, PA, 14(4):403-413, (2011).
Impact/Purpose:
To research results
Description:
Trophic linkages of larval fish in Lake Superior coastal wetlands, rivers and embayments can be identified using naturally occurring differences in the stable isotope ratios of nitrogen (15N:14N, ?15N) and carbon (13C:12C, ?13C). We sampled pelagic fish larvae weekly during spring run-off (late-April to mid-July) in the hydrologically complex drowned river mouth of the St. Louis River, the second largest tributary to Lake Superior. Common species were analyzed for whole-fish ?13C and ?15N values. For all species, stable isotope signatures were growth dependant. The ?13C value of larvae was increasingly negative with increasing weight as the fish developed from the yolk-sac stage, during which they possess a maternally-derived isotopic signature, to an exogenously feeding larvae. Trends in the ?15N value of fish varied; an increase, decrease, and no change in ?15N with increasing weight were observed. A growth-based stable isotope turnover function modeled well the observed changes in ?13C and ?15N. In general, fish obtained a constant signature after a 10-fold gain in body mass, implying their tissue was at isotopic equilibrium with their natural diet. Stable isotope tracking of larval fishes revealed ecologically significant movements and trophic linkages. Difference between yolk-sac and larvae ?13C and ?15N revealed distinct patterns in larval origin and settlement. Stable isotope differences among species indicated that multiple diet sources support pelagic YOY fish production in this coastal wetland.