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Fish Larvae as Indicators of Cross-Ecosystem Subsidies in Great Lakes Coastal Embayments

Project Summary

Tucker trawl for sampling fish larvae deployed in Duluth, MN harbor from the MED's R/V Prairie Sounder.

Great Lakes coastal tributaries and their associated vegetated, shallow, protected embayments connect coastal watersheds to fisheries by serving as nursery grounds for migratory fishes – their young rely on these habitats for feeding and refuge – and by supporting a forage base for predatory fishes. The water quality and fish habitat in these coastal ecosystems, however, are highly vulnerable to degradation from human activities. Our goal is to help restore healthy Lake Superior fisheries by identifying, conserving, and maintaining the connections between coastal landscapes and coastal fishes.

We are interested in whether changes in the watershed alter how coastal habitats support the production and growth of fishes. Our research uses chemical biomarkers in fish larvae to describe the flow of energy and nutrients from the land to the coastal aquatic food web. We are comparing six southwest shore river-embayment systems – the St. Louis River and Duluth/Superior Harbor (MN), Pokegama River and Pokegama Bay (WI), the Nemadji River and Allouez Bay (WI), the Amnicon River (WI), and Fish Creek and Chequamegon Bay (WI). These river-embayment ecosystems provide critical nursery habitat for priority Great Lakes fish such as lake sturgeon and walleye. Due to their relatively fast response to environmental conditions (i.e., days to weeks), their fish larvae could be used to test differences with respect to landscape character, time, or hydrology. As indicators, fish larvae could provide information on contributing sources (e.g., specific biomarkers reflect anthropogenic or terrestrial origins) and demonstrate population-level responses (e.g., nutritional status of early life stages, a potential indicator for population success).

A burbot larva (length 5mm) caught in the St. Louis River, MN.
A yolk-sac stage walleye larva (length 9 mm) caught in the St. Louis River, MN.

Key products

Hoffman, J.C., J.R. Kelly, G.S. Peterson, A.M. Cotter, M. Starry, and M.E. Sierszen. Using d15 N in fish as an indicator of watershed sources of anthropogenic nitrogen: Response at multiple spatial scales. Estuaries and Coasts (submitted).

Hoffman, J.C., A.M. Cotter, G.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. Journal of Aquatic Ecosystem Health and Management, Special Issue, in press.

Project personnel


Name E-mail Phone
Joel Hoffman hoffman.joel@epa.gov 218-529-5420
Jack Kelly kelly.johnr@epa.gov 218-529-5119
Anne Cotter    
Mike Knuth    
Greg Peterson    
Tim Corry    

Research project update date

January 23, 2012

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