. The Canadian field-naturalist. 1998 KoEL AND Peterka: Fishes of the Red River of the North 633 Manitoba North Dakota Minnesota. 100 km South Dakota Figure 1. Streams in the Red River of the North basin in the United States for which fish survey records were obtained. Orfe, Leuciscus idus) introduced from local aquaria and likely not part of naturally reproducing popula- tions, and hybrid fishes, most of which were centrar- chids. Also not included were species which were determined to be recorded in error in the literature. In cases where species were reported that had not been found histori
. The Canadian field-naturalist. 1998 KoEL AND Peterka: Fishes of the Red River of the North 633 Manitoba North Dakota Minnesota. 100 km South Dakota Figure 1. Streams in the Red River of the North basin in the United States for which fish survey records were obtained. Orfe, Leuciscus idus) introduced from local aquaria and likely not part of naturally reproducing popula- tions, and hybrid fishes, most of which were centrar- chids. Also not included were species which were determined to be recorded in error in the literature. In cases where species were reported that had not been found historically in the Red River basin and appeared erroneous, the primary investigators of the reports were contacted to determine if voucher speci- mens of the species had been collected. Most errors were due to misidentification of fishes in the field. Common and scientific names of fish species fol- lowed those of the American Fisheries Society (Robins etal. 1991). Mapping of Fish Distribution Stream digitizing: All nonintermittent streams and lakes in the Red River basin were digitized from USGS 1: 250 000 scale quadrangle maps using a Summagraphics Microgrid II digitizer and TOSCA (1993) software. Streams were entered as lines and lakes as polygons with separate files created for each quadrangle map. The VCONCATE module of TOSCA was then used to combine all stream files and all lake files into two complete coverages (lay- ers). These layers then served as the base map upon which species distribution points were plotted. Species distribution: For each fish species, a file containing the year and coordinates in latitude and longitude of all sites where the species occurred was created from the Quattro Pro database. The coordi- nates were then sorted by year into three time peri- ods (early, middle, and late), saved as separate files, and downloaded into an IDRISI (1993) geographic information system (GIS). In IDRISI the files were saved as vectors in binary data format using the CONV
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