David Janetzki

Project Title:" Pollutant transport by introduced salmon and implications for dam removal in Great Lakes tributary streams "

External Partnership: Lindsay Chadderton, Aquatic Invasive Species Director The Nature Conservancy and Mark Fedora, Hydrologist USFS and The Nature Conservancy

Intentional species introductions are often performed to provide societal benefits, although introduced species often bring with them a variety of ecological impacts.  In the Great Lakes region of the upper Midwest, U.S.A., Pacific salmon have been intentionally introduced from the Pacific Northwest for recreational fishing.  This species introduction has significantly contributed to the $4 billion Great Lakes fishery, but the potential ecological impacts of salmon, especially in their spawning streams, have been only sporadically addressed. 

One potential impact of introduced salmon is the transfer of pollutants to streams during annual spawning migrations.  In the lakes, salmon are fish-eating predators and therefore accumulate pollutants at much higher concentrations than what are found in their prey.  Subsequently, when salmon migrate to tributary streams to spawn, stream-resident fish feed on pollutant-laden salmon eggs and incorporate pollutants into their body tissues.  This ‘biotransport’ of pollutants to stream fishes is well-documented, but the magnitude and spatial variability associated with this process remains poorly understood and has not been related to key issues in stream restoration, such as dam removal. 

In his CAC research, David assessed the magnitude of pollutant transfer from salmon to native fishes in Great Lakes tributary streams.  Specifically, he focused on quantifying pollutant levels in native brook trout (Salvelinus fontinalis) and sculpin (Cottus spp.) above and below barriers to migrating salmon in six Great Lakes tributary streams—three from Lake Michigan and three from Lakes Superior and Huron.  This provided a contrast between a relatively ‘pristine’ system, Lakes Superior and Huron, and a historically more polluted system, Lake Michigan.  Fish tissues were analyzed for concentrations of polychlorinated biphenyls (PCBs) and heavy metals, both of which are harmful to wildlife.

      Through cooperation and coordination with The Nature Conservancy and Michigan Department of Natural Resources, David's research greatly impacted stream conservation and restoration. It also provided great lakes fisheries with responsible management strategies.  This study has established a precedent for future research to assess pollutant levels in native fish, as well as for studying the physiological effects of pollutants on native fish.  The results of this project have informed biologists about how dam removal may or may not spread pollutants upstream.  This is an important consideration because restoring natural flow regimes and reconnecting populations by removing dams is considered essential for restoring ecosystem health and integrity.  The information generated by this research has provided biologists and policymakers with a more complete picture of the ecological impacts of introduced salmon.

Distinctive Outcomes: David is currently working with TNC and the US Forest Service to develop new guidelines for the management of dams.