Rapid stable isotope turnover of larval fish in a Lake Superior coastal wetland: Implications for diet and life history studies

Joel C. Hoffman, Anne M. Cotter, Gregory S. Peterson, Timothy D. Corry, John R. Kelly

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Trophic linkages of larval fish in Lake Superior coastal habitats can be identified using naturally occurring differences in the stable isotope ratios of nitrogen ( 15N: 14N, δ 15N) and carbon ( 13C: 12C, δ 13C). We measured 13C and 15N values in common 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. For all species, δ 13C 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 δ 15N with increasing weight varied among species; an increase, decrease, and no change in δ 15N were observed. A weight-based stable isotope turnover function modeled well the observed changes in δ 13C and δ 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 diet. Difference between yolk-sac and larvae δ 13C and δ 15N revealed distinct patterns in larval origin and settlement. Based on the species analyzed, we identify two specific Lake Superior coastal wetland-dependent fish early life histories that incorporate habitat use, movement, and trophic dynamics. This study thus provides a methodological approach that can potentially help resolve interactions between watershed character, coastal productivity, and Lake Superior that are of significance to the lake's fisheries.

Original languageEnglish (US)
Pages (from-to)403-413
Number of pages11
JournalAquatic Ecosystem Health and Management
Volume14
Issue number4
DOIs
StatePublished - Oct 1 2011

Keywords

  • St. Louis River
  • foodweb
  • δ C
  • δ N

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