Michael P. Gutzmer, Nebraska Public Power District (NPPD), 1414 15th Street, Columbus, Nebraska 68601, (402) 563-5742, and Mark M. Peyton, Central Nebraska Public Power and Irrigation District (Central), P.O. Box 188, Gothenburg, Nebraska 69138, (308) 537-3582.

INTRODUCTION

Prior to 1987 there was very little information concerning the abundance and diversity of fishes in the Platte River. Since that time work conducted by the Nebraska Game and Parks Commission and the University of Nebraska-Lincoln (UNL) on the Lower Platte, Chadwick Ecological Consultants, Inc. (Chadwick's) and work by the Platte River Whooping Crane Habitat Maintenance Trust (Trust) on the Central Platte, the U.S. Geological Survey's National Water Quality Assessment program on the Platte, and recent UNL work on the North and South Platte rivers, has resulted in an extensive data bank concerning fish species composition and abundance within the system.

One area that received limited study and therefore has little diversity data available is that portion of the river beginning at Central's Tri-county Diversion located at the confluence of the North and South Platte Rivers east of North Platte, Nebraska, and ending approximately 120 kilometers downstream at the J-2 River Return, east of Lexington (the Upper Platte River).

PURPOSE OF THE STUDY

This study documents the species richness for the Platte River between the confluence of the North and South Platte Rivers and the J-2 River Return and compares this data to other fisheries data from the Central Platte, North Platte, and South Platte Rivers.

METHODS

Fish were sampled at six sites on the upper Platte River between Maxwell and Lexington (Figure 1) in July and five were sampled a second time in October 1996. Sampling was done using a 6 meter, 5mm mesh seine and a Smith-Root Model 15-C backpack shocker.

Samples were taken by pulling the seine downriver through a minimum of four 15 meter lengths at each site. Snags, pools, and bank habitat were sampled at three sites in October using the backpack shocker. Fish collected were identified, counted, and returned to the river. Voucher specimens were collected.

The resulting collection data and species list were compared to species lists generated from studies by Chadwick Ecological Consultants, Inc. (1996) in the central Platte River, and by Lynch and Roh (in press) in the North Platte and South Platte Rivers.

RESULTS

Two sampling efforts at six sites in the Platte River between Maxwell and Lexington, Nebraska resulted in the collection of 3,626 fish representing 30 species.

The five most abundant species were bigmouth shiners (Notropis dorsalis), sand shiners (N. stramineus), red shiners (Cyprinella lutrensis), creek chubs (Semotilus atromaculatus), and stoneroller (Campostoma anomalum). These five represented 79% of all fish collected. Five species (western silvery minnow, shorthead redhorse, channel catfish, yellow bullhead, and stonecat) were represented by a single specimen each. A list of species, the number of fish collected, and the number of sites where those fish were collected is given in Table 1.

Nineteen fish representing five species (walleye, northern pike, yellow perch, freshwater drum, and shorthead redhorse) were identified from a pool in the recently drained Gothenburg Irrigation Ditch immediately downstream, and during the summer, connected to, the Brady collection site.

In total 30 species were collected from these six sites on the upper Platte River. An average of 14 species were collected per site with the Brady site having the highest species richness, 21, and the Maxwell and Cozad sites the lowest species richness, 10.

DISCUSSION

The portion of the Platte River located between the confluence of the North and South Platte Rivers and Lexington, Nebraska, has changed over the course of the past 100 years. There was little or no information pertaining to historical species diversity and/or fish abundance within this stretch to use in determining icthyodiversity and/or fish abundance. The objectives of this study were to document species richness (diversity) and abundance of fish at six locations spaced throughout this reach of the river and to compare that with diversity and abundance of fish above and below this reach.

Chadwick's studies from 1990 to 1995, investigated species richness, abundance, and habitat use in the Platte River. Their studies were in the Central Platte River between the J-2 River Return and Phillips, Nebraska. From these sites, and the collection of over 92,500 specimens, they were able to document the presence of 47 species of fish. The number of species collected in a single year ranged from 28 to 39 (Chadwick, 1996).

In an extensive investigation of 31 sites on the North and South Platte Rivers from 1989 to 1995, Lunch and Roh (in press) collected over 97,000 specimens representing 46 species of fish.

A comparison of species lists generated from these two extensive studies and the present preliminary investigation of the Upper Platte, an area bordered by these studies, is given in Table #2.

Whittaker's Coefficient of Community (1975) shows a similarity between Chadwick's and Lynch & Roh's studies of 73%, between Chadwick's and this study of 68%, and between this study and Lynch & Roh's of 60%. The similarity between the Chadwick and Lynch & Roh studies is quite high despite the geographic difference in the study areas. The similarity of species richness documented in the upper Platte and that of the central Platte and on the North and South Platte Rivers is surprisingly high given the one year effort, and the other two studies which sampled for five and six years respectively.

Another method for evaluating similarities and differences in species abundance between the river reaches is to compare which species are most abundant in each of the areas.

With greater effort, more species are likely to be sampled at any given location. Those species that are most abundant, however, are usually identified in the initial sampling episodes (Chadwick's, for example, have the same five species as most common in four of the six years in which data is available). Table 3 shows the most abundant species found in this study compared to their abundance in both the Chadwick and Lynch & Roh reports.

In comparing the most abundant species there is a strong correlation between the 1996 data collected in the Upper Platte and that reported by Lynch & Roh (r = 0.87). A weaker correlation exists between this data and that reported by Chadwick's (r = 0.62).

The major differences in this study and the other two are brassy minnows (H. hankinsoni) and plains minnows (H. placitus) accounted for 21% of the fish collected in the North Platte and South Platte Rivers, while on the upper Platte brassy minnows accounted for 5% of the fish collected and no plains minnows were found. In the central Platte mosquitofish (G. Affinis) and the plains killfish (F. zebrinus) accounted for 40% of the fish sampled while in the upper Platte they accounted for less than 1%.

CONCLUSION

Prior to this investigation there had been limited effort to document species richness and diversity of the fish community in the Platte River in Nebraska between the Central Diversion Dam located east of North Platte, Nebraska, and the confluence of the Platte River and the J-2 River Return east of Lexington, Nebraska.

The data from this study and the two used for comparison show a strong similarity between the species composition and richness found in the upper Platte and that of the central Platte and North Platte and South Platte Rivers. Relative abundance between this study and the other two also showed a strong correlation between the most abundant species in the upper Platte and that of the North and South Platte Rivers, and a weaker, but still compelling correlation with that of the central Platte.

Spatial and temporal variations in our sampling may account for differences in the species collected and the abundance of fish when compared to the other studies. Additionally, level of effort and flow rates during sampling periods play a role in the successful collection of fish at any given site.

LITERATURE CITED

Chadwick Ecological Consultants, Inc. Fish Monitoring Study Central Platte River, Nebraska 1995. A report to the Nebraska Public Power District and the Central Nebraska Public Power and Irrigation District.

Lynch, John D. and Brian R. Roh. An ichthylogical survey of the forks of the Platte River in western Nebraska. In press.

Whittaker, R.H. 1975. Communities and Ecosystems. 2nd Edition. MacMillian Publishing Co., NY.

Return to 1997 Platte River Basin Ecosystem Symposium

Last updated by Darren A. Jack on 4/28/97