FISH SPECIES-RICHNESS TRENDS IN THE NIOBRARA RIVER, NEBRASKA, BELOW THE SPENCER DAM

Nebraska Public Power District (NPPD) has monitored fish populations annually (except 1998) since 1993 on the Niobrara River in Nebraska, in the vicinity of Spencer Hydropower Project before and after flushing or sluicing activities. These activities could alter water quality in the river downstream, which can negatively impact fish populations. Intensive sluicing-monitoring studies coupled with operational adjustments indicated minimal impacts were occurring to fish populations in the vicinity of the hydro. Long-term diversity and abundance of fish species has been a historical concern, so annual fish sampling has continued through the present. Of the 13,063 fishes in 26 species sampled below the hydropower complex, six species composed approximately 96.5 percent of the total sample. The most common species sampled were sand shiner, Notropis ludibundus (38.6%); red shiner, Notropis lutrensis (34.0%); flathead chub, Hybopsis gracilis (12.2%); carpsuckers, Carpiodes spp. (5.6%); bigmouth shiner, Notropis dorsalis (3.9%); and channel catfish, Ictalurus punctatus (2.2%). Over the nine-year period, catch-per-unit-effort trends indicated no significant increases or decreases among years sampled and the respective species collected. Fish CPUE was not significantly affected by short-term annual sluicing