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Establishment Patterns of Non-native Fishes: Lessons from the Duluth-Superior Harbor and Lower St. Louis River, an Invasion-prone Great Lakes Freshwater Estuary
Citation:
PETERSON, G. S., J. HOFFMAN, A. S. TREBITZ, C. W. WEST, AND J. R. KELLY. Establishment Patterns of Non-native Fishes: Lessons from the Duluth-Superior Harbor and Lower St. Louis River, an Invasion-prone Great Lakes Freshwater Estuary. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, 37(2):349-358, (2011).
Impact/Purpose:
Although our data cannot address trends, our results suggest that despite frequent recent invasions, current populations of native fishes remain viable. This study provides a model for assessing current status of non-native fishes in Great Lakes coastal ecosystems. Our results reinforce the view that using a single gear, metric, or location to describe non-native species prevalence may result in a biased or incomplete assessment.
Description:
The St. Louis River freshwater estuary which drains into western Lake Superior and includes the Duluth-Superior (MN-WI) harbor, has a long history of non-native fish introductions. From 1985 to 2002, seven new fishes were identified in the estuary, an unprecedented rate of non-native establishment for the Laurentian Great Lakes. We conducted a comprehensive multi-gear survey of the fish assemblage in the St. Louis River estuary in 2006 and 2007. Ten non-native fishes were captured; they were found in 84% of samples in our study and comprised 15% of the total fish abundance captured amongst four different gears. Non-natives made up a higher proportion of the total fish abundance and biomass for all gears in the lower, urbanized portion of the estuary. Using an invasion stage framework, we classified the status of non-native fishes with respect to their relative abundance and distribution. Eurasian ruffe (Gymnocephalus cernuus) and round goby (Apollonia melanostomus) have become abundant and widespread in this system while threespine stickleback (Gasterosteus aculeatus) and freshwater drum (Aplodinotus grunniens) remain relatively uncommon and localized. Invasion status of the remaining non-native fishes was generally intermediate or exhibited characteristics of both extremes. Tubenose goby (Proterorhinus semilunaris) were widespread but numerically rare while white perch (Morone americana) were locally dominant. Although our data cannot address trends, our results suggest that despite frequent recent invasions, current populations of native fishes remain viable. This study provides a model for assessing current status of non-native fishes in Great Lakes coastal ecosystems. Our results reinforce the view that using a single gear, metric, or location to describe non-native species prevalence may result in a biased or incomplete assessment.