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St. Louis River fish migrations: Gains and losses of ecosystem services
Hoffman, J., A. Trebitz, L. Burkhard, T. Hollenhorst, A. Cotter, Greg Peterson, AND M. Pearson. St. Louis River fish migrations: Gains and losses of ecosystem services. Minnesota Chapter of the American Fisheries Society, St. Cloud, MN, February 21 - 23, 2017.
A widely distributed and economically important ecosystem service associated with coastal wetlands is producing commercially- and recreationally-harvested fishes. In this presentation, we present recent research that reveals the economic impact of coastal wetland fishes in the Great Lakes and uses novel approaches to measure how the presence of contaminated sites changes the nature of the fishery by increasing contaminant residues in high-value fishes.
The Twin Ports fishery has undergone change from a migratory fish-based fishery to a Lake Superior-based fishery, and is now returning to a diverse fishery that includes fish of both life histories. These changes reflect past disturbances to the Great Lakes ecosystem as well as recent water quality improvement and efforts to restore habitat in the St. Louis River. Migratory fishes are an important ecosystem service for the St. Louis River, and improvements to the ecosystem quality within the St. Louis River Area of Concern has benefited migratory fishes. The coastal wetlands within the lower river provide direct support to a variety of high-value, recreationally-important fish species, including walleye, northern pike, and bass. Moreover, these wetlands serve as nursery habitat for a broader suite of high-value, commercially-important species. Restoration has likely improved the value of these coastal wetlands because low-value rough species tend to be more prevalent in degraded coastal wetlands, whereas high-value commercial and game fishes are more prevalent in high-quality coastal wetlands. There have been losses in ecosystem services, as well. Owing to legacy contamination of mercury and PCBs, migratory fishes in the St. Louis River have sufficiently high contaminant burdens to warrant consumption advisories, and recent movement research demonstrates that there is a positive relationship between increased use of St. Louis River habitat (versus Lake Superior) and tissue contaminant burden. From a resource management perspective, this represents a complex value function, wherein there is growing interest in catching and consuming these high-value, game fishes even though the greater access to St. Louis River habitat creates a public health risk. Future sediment remediation and concurrent habitat restoration will be able to enhance the value of migratory fishes if it is effective at reducing contaminants in the food web.