Conservation of native fish communities in tributaries to the Great Lakes: Predicting the impacts of contaminants delivered by spawning pacific Salmon

Grant: # 1244

Grant Amount: $222,115.00

Board Decision Year: 2012

University of Notre Dame (Notre Dame)

Chaloner, Dominic ( 574-631-2441

GLFT - Ecosystem Health and Sustainable Fish Populations-C - Ecological and biological fisheries research to inform management

Project Details

Dominic Chaloner, a research associate professor at the University of Notre Dame, led a team of scientists to assess the extent to which Pacific salmon migrating from the Great Lakes into tributaries during their spawning runs increase contaminant levels in local fish populations. The team focused on mercury and persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), given their prevalence in the Great Lakes basin.

The team reached four principal conclusions regarding the role that Pacific salmon play in moving contaminants from one location to another and transferring those contaminants to local fish populations.

  • Different chemicals have significantly different biotransport rates. Mercury, for example, is present in the Upper Great Lakes at relatively consistent levels and introduced through atmospheric deposition, which was determined to have a larger role in depositing pollutants locally than salmon-mediated biotransport. When it comes to POPs, however, biotransport can be a significant contributor.

  • Salmon eggs, rather than tissue, appear to be the most likely source of POP transfer to local fish. The amount of POPs that build up in local fish populations depends on diet and physiology. Of the species studied, brown trout were most susceptible to increased pollutant concentrations, followed by brook trout because they eat more salmon eggs. Mottled sculpin, on the other hand, were the least susceptible.

  • POP contaminant levels at the lake basin scale influence local fish contaminant levels—even in more pristine tributaries with salmon runs. In other words, in lake basins with generally higher PCB levels, like Lake Michigan, local fish, in what might be regarded as otherwise unpolluted tributaries, often have higher POP concentrations from salmon-mediated biotransportation.

  • Biological variables such as diet and growth rates, rather than physical and chemical variables, appear to influence POP levels in local fish populations.

GLFT policy enables grantees to hold the release of the final project report while publications are pending. The final progress report will be added at a later date.