7IMtc<U 



SAMPLING FOR WATER CHEMISTRY ANALYSIS 



Water samples were collected from the Tongue River Reservoir on a biweekly 

 basis from icemelt until freeze-up (Whalen and Leath 1976). Samples were taken 

 at three sites in the reservoir (figure 29), from the river above and below the 

 mine discharge, and below the dam. Mine discharge samples were also taken. Re- 

 servoir samples were collected at two-meter intervals throughout the water col- 

 umn at all three stations with a four-liter Van Dorn Bottle. Additionally, sam- 

 ples were collected at one-meter intervals throughout the euphotic zone for phy- 

 toplankton standing crop and primary production estimates. Whalen and Leath 

 (1976) summarize the analytical procedures used for water chemistry analyses. 



FISH SAMPLING 



Fish were collected using: 4-foot-by-6-foot frame trap nets with 1/2-inch 

 and 1/4-inch mesh webbing and 50-foot leads; 125-foot experimental gill nets; a 

 100-foot, 1/4-inch-mesh beach seine; and a 50-foot, 1/4-inch-mesh bag seine. An 

 electrofishing boat equipped to provide an output of 0-500 volts variable direct 

 or alternating current was used to sample shoreline areas. Fish were also taken 

 with a hook and line. Lengths and weights of captured fish were recorded, and 

 sport fish were tagged with numbered Floy anchor tags. Scales were taken for 

 analysis of age and growth. 



POPULATION ESTIMATES 



Population sizes of black and white crappie and northern pike were esti- 

 mated from fish captured during the spring trap-net season. The modified 

 Schnabel estimator was used (Chapman and Overton 1966), employing the expression: 



N=i: 



CtMt 



t 



Rt + 1 



where: N = estimated fish population 

 C^ = number of fish caught 

 M^ = marked fish at large 

 R^- = number of recaptures 



Confidence limits (a = 0.05) were computed according to the formula: 

 p {X < V ^tMt < X }= 1 - a 



where x^ and x are the lower and upper confidence limits, respectively, of the 

 Poisson variable, obtained from the table of expectations of Poisson variable 



83 



