Development and use of the Wetland Fish Index to assess the quality of coastal wetlands in the Laurentian Great Lakes

We use fish and environmental data from 40 wetlands of the Laurentian Great Lakes to develop the Wetland Fish Index (WFI), a tool that can be used to assess the quality of coastal marshes. A partial canonical correspondence analysis was used to ordinate fish species along multidimensional environmental axes that accounted for anthropogenic disturbance based on temperature, conductivity, and the presence of pollutants (e.g., suspended solids and primary nutrients). Compared with other measures of fish habitat quality (e.g., Shannon–Wiener diversity index and species richness), the WFI was the only index that was significantly related to the degree of water quality degradation and wetlands condition, as indicated by an independent index of wetland quality, the Water Quality Index (WQI). WQI ranks sites according to deterioration in water quality and is statistically related to the degree of land-use alteration in wetland watersheds. We demonstrate the usefulness of the WFI for detecting intrawetland variation between two sites in a degraded urban wetland, Frenchman's Bay, Lake Ontario, and to distinguish the heavily impacted wetlands in lower Green Bay from the less-impacted marshes in middle and upper Green Bay, Lake Michigan. This was accomplished by using only published fish data without corresponding environmental variables.