Abstract:
Available data on the ecology of aquatic organisms in the Red River of the North Basin, a study unit of the U.S.
Geological Survey's National Water-Quality Assessment program, were collated from numerous sources. Lack of
information for invertebrates and algae precluded a general summary of distribution and ecology throughout the
basin. Data on fish species distributions in the major streams of the Red River of the North Basin were analyzed based
on the drainage area of the stream and the number of ecoregions the stream flowed through. Species richness
increased with both drainage area (log drainage area in square kilometers, R2=0.41, p=0.0055) and the number of
ecoregions a river flowed through. However, theses two factors are autocorrelated because the larger the drainage, the
more likely that the river will flow through more than one ecoregion. A cluster analysis identified five river groups
based on similarity of species within the fish community. Analysis of trophic and taxonomic composition provided
justification for the cluster groups. There were significant differences (p=0.05) in the trophic composition of the river
cluster groups with respect to the number of predator species, omnivore species, benthic insectivore species, and
general insectivore species. Although there were no significant differences in the number of species in the bass and
sunfish family or the sucker family, the number of species in the minnow family and the darter subfamily were
different (p=0.05) among the groups identified by cluster analysis. Data on contaminant concentrations in fish from
the Red River of the North indicated that most trace elements and organochlorine compounds present in tissues were
not at levels toxic to fish or humans. Minnesota and North Dakota have issued a fish consumption advisory based on
levels of mercury and (or) PCBs found in some species.
