Modification of an index of biotic integrity and development of reference condition expectations or dunal, palustrine wetland fish communities along the southern shore of Lake Michigan

Abstract

Abstract I modified and calibrated an index of biotic integrity (IBI) to assess wetland quality of dunal, palustrine wetlands along the southern shore of Lake Michigan. Fish communities were sampled using a combination of electrofishing and seining techniques to collect a representative sample. A combination of 50 historical and recent sites were sampled from northeast Illinois and northwest Indiana to develop reference expectations for dunal wetlands less than 35 ha surface area. I examined 36 attributes of wetland fish communities to derive a dunal, palustrine IBI. Several metrics from the original IBI were retained including: total number of species, number of sensitive species, and percent tolerant species. Trophic composition characters included the percentage of omnivores and insectivores. Fish condition was evaluated using the catch-per-unit of effort and the percentage of deformities, eroded fins, lesions, and tumours (DELT). Several metrics were modified from the original IBI to better reflect water resource quality in dunal wetlands. The number of darter species was replaced by a combination of the ecologically similar number of darter and madtom species; number of sunfish species was modified to the number of centrarchid species, which included the black bass species; number of sucker species was replaced by the number of minnow species since few sucker species were anticipated in dunal wetlands; and I substituted percent carnivores with percent pioneer species. Pioneer species reflect wetland stability and water permanence. Hybrids were not important constituents of wetland communities and did not show a relationship with wetland degradation, so I substituted the percentage of lake-obligate species to reflect species that were dominant in lentic waters.