Montz, G.R. 1993. Aquatic macroinvertebrates of the Pigeon River, MN. Final report to the Minnesota Department of Natural Resources. Unpaged.
Aquatic macroinvertebrates were collected from the Pigeon River between Partridge Falls and the mouth of the river during summer 1992 and 1993. A total of 163 taxa (genus or species) were identified from qualitative and quantitative samples. Insects comprised the majority of the taxa (151) with mollusks (8) and crustaceans (4) comprising a small part of the community. Ephemeroptera, Plecoptera, and Trichoptera were well represented (71 taxa) in the invertebrate community, and several uncommon taxa were collected. Functional group community composition varies little from Partridge Falls down to the rapids below Pigeon Falls. There is a surprisingly large predator component throughout the river, comprising up to 30W of the taxa at a given site. Collector/gatherers and scrapers dominate the remainder of the community, indicating that particulate and diatom food sources are most important in the river, while shredders are nearly absent.
The water quality appears to be very good to excellent, with little or no evidence of organic enrichment detected. While water clarity is very good up at Partridge Falls, there appears to be more particulate matter in the river further downstream (below Horn Falls). This may be a result of input from the Arrow River in Canada.
The occurrence of numerous taxa intolerant of organic . degradation highlights the need for careful planning of: park improvements. Nutrient enrichment, siltation, and runoff must be avoided to prevent impact to the invertebrate community. Routine monitoring should be used to determine if impacts are occurring.