HABITAT PREFERENCE 



Daily catch rates were totaled for each week of the sampling season. The 

 data were analyzed in two ways: by catch/kilometer and catch/trip. Calcula- 

 tion of discharge vs. catch rates was performed as discussed above for 

 shovelnose sturgeon. The number of fish sampled in certain flow regimens 

 (discharge-frequency histogram) is graphed in figure 23. The data points 

 form only one side of the graph, but, since it can be assumed that there would 

 be zero fish at zero flow, the other side can be interpolated. It is possible, 

 however, that there would be zero fish before the flow reaches zero. 



The quadratic regressions of trip and linear catch rates in relation to 

 the discharge resulted in an optimum passage flow estimate of 13.6 m^/sec 

 (430 cfs) for both catch rates. Figure 24 indicates very little passage 

 occurring at flows less than 8 m-^/sec (280 cfs). 



Temperature 



The temperature graph (number of fish caught within a specified range of 

 temperatures) shows a near-normal distribution of sauger moving into the 

 Tongue River (figure 25). A regression was run between the two catch rates 

 and maximum and minimum temperatures as was done for the shovelnose sturgeon 

 (see page 40 for model). A hyperbola with optimum values of 12.4°C (54°F) and 

 9.4°C (49OF), respectively, for the trip catch rate resulted. For linear catch 

 rates, the maximum and minimum optimum temperatures were 12.3°C (540F) and 

 9.30c (490F), respectively (figure 26). The preferred temperature regimens 

 found in the Tongue River during the spawning migration correspond to those 

 found in other areas (Brown 1971, Scott and Grossman 1973). 



TAGGING STUDIES 



A total of 646 sauger were tagged with Floy anchor tags in 1976. Of 

 these, 22 (3.4 percent) were returned by anglers. The majority of the tags 

 (81.8 percent) were returned from the Tongue River. Some local movement was 

 shown, with many fish moving upstream to the T&Y diversion, 24 to 29 km 

 (15 to 18 mi) upstream from where they were tagged. Four sauger were caught 

 in the Yellowstone River, three moving upstream. The downstream migrant 

 moved about 28 km (17.6 mi) in 50 days. Upstream movement ranged as follows: 

 1.6 km (1 mi), 19 days; 84 km (52.4 mi), 78 days; and 164 km (102 mi), 

 87 days. The range of movement demonstrated by the small sample suggests a 

 mobile sauger population inhabiting the Yellowstone River. The low tag return 

 rate by fishermen indicates that the fishery is not being utilized to its 

 potential . 



CHANNEL CATFISH 



The channel catfish (Tatalurus punatatus) is probably the most sought- 

 after game fish in the lower Yellowstone River Basin. The channel cat, native 

 to Montana, was first reported by the Lewis and Clark Expedition. Preferred 



52 



