An habitat types at eac 

 Samples from any one site on 

 qualitative analysis of the s 

 in a formalin solution. In t 

 a US Series 30 mesh screen an 

 lowest taxa possible without 

 then preserved in 50 percent 

 identification. The Nematoda 

 by Richard Oswald of Rozeman, 

 identified by Barbara Marback 



h section were sampled for aquatic invertebrates, 

 any one day were combined to give an overall 

 amplinq. All samples were fixed in the field 

 he laboratory, bottom samples were washed through 

 d all organisms picked and sorted to the 

 the aid of magnification. Specimens were 

 alcohol solutions and saved for further 

 , Oliqocheata and Diptera were identified 



Montana, while all other organisms were 



Roth of Hillsboro, Oregon. 



'I 



Several sampling techniques were used to collect and sample fish 

 populations. Electrofishing qear using a mobile positive from the bank 

 or a stationary boom positive on a small fiberglass boat was used during 

 early sampling periods. Seining was conducted with a 25-foot, 1/4 inch mesh 

 bag seine and a 10', 1/4 inch mesh seine. A fine mesh dip net was utilized 

 when sample site consisted of a small trickle of water. Gill nets (125' 

 experimental and 100', 2-inch bar mesh gill nets) were either drifted 

 through deep holes or dead-set. Traps made of reinforcing bar and covered 

 with chicken wire were baited and fished for channel catfish. Setlines were 

 fished overnight during early spring of 1978, however, they were unsuccessful 

 in capturing any game fish. 



All game fish were weighed, measured, fin clipped (walleye and sauger) 

 and marked with numbered Floy tags. Scale samples were taken beneath the 

 pectoral fin from the left side. The number of fish of each species was 

 recorded for most samples but when this was not done, relative abundance 

 of each species was recorded. Lengths and weights were not measured on all 

 fish since many of them, particularly cyprinids, are small. Length frequency 

 analyses were completed for those species where such data was taken. Species 

 diversity indicies were calculated for each season according to Newell (1977). 



RESULTS 



Physical and Chemical Parameters 



The runoff pattern of Beaver Creek is typical of a prairie stream, 

 with a bi-modal discharge (Figure 5). Peak runoff occurs in March , 

 followed by a smaller peak in June. Flows then taper off to minimal for 

 the remainder of the year. Maximum discharge for the thirty-year (1938- 

 1968) period of record at Wibaux was 107 m^/sec (3780 cfs). Historic 

 records indicated flood stages in 1929 and 1872 reaching about 850 m3/sec 

 (30,000 cfs) . Periods of no flow occur regularly. Mean flow at Wibaux 

 (1938-1968) was 0.63 m3/sec (22.3 cfs). 



General chemical features of the Beaver Creek drainage are shown 

 in Table 1, which summarizes measurements taken during the field study. 

 Alkalinity was high in comparison to other streams, averaging 240 mg/1 

 at the three stations, reflecting the chemical nature of the drainage. 

 Specific conductance increased with progression downstream, from an 



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