AN ICHTHYOLOGICAL SURVEY OF THE FORKS OF THE PLATTE RIVER IN WESTERN NEBRASKA

摘要

An ichthyological survey (1989-1995) of 31 sites on the North Platte and South Platte rivers and immediately below the North Platte diversion dam (junction of the North Platte and South Platte rivers) resulted in the captures and distributional documentation of 46 species of fishes. Four other species, found in the drainage, were captured in tributary streams only. Preserved voucher records are based on 49 sampling visits (1989-1995) to the 32 localities (approximately 55,000 specimens). An additional 42,000 nonvouchered specimens were taken, identified, and released at 17 of the localities (1980-1995). Above Lake McConaughy, the North Platte River is dominated by five species (Cyprinella lutrensis, Hybognathus hankinsoni, H. placitus, Hybopsis dorsalis, and Notropis ludibundus), whereas below Lake McConaughy the fish fauna is dominated by only four species (Catostomus commersoni, Cyprinella lutrensis, Hybopsis dorsalis, and Notropis ludibundus). The South Platte fish fauna is dominated by six species (Cyprinella lutrensis, Hybopsis dorsalis, Notropis ludibundus, Pimephales promelas, Semotilus atromaculatus, and Fundulus zebrinus). The two units on the North Platte River are each divisible into eastern and western sections, based on the compositions of the fish faunas. The eastern and western divisions are attributed to effects of the impoundment of the North Platte River by Lake McConaughy. Recent (1995) work on the South Platte River also suggests the existence of eastern and western subdivisions, but those subdivisions were not evident 10-20 yr ago. Including nonvouchered records obtained by ichthyology classes, the twelve sites on the North Platte River above Lake McConaughy harbor 15-29 species of fishes (39 species taken in total), whereas the eight sites on the North Platte River below Lake McConaughy harbor 17-29 species (34 species taken in total) and the twelve sites on the South Platte River harbor 19-33 species (37 species taken in total).