Twenty-one fish (8.6 percent of the total sample) that had been tagged 

 in 1974 with monels were recaptured in 1976. A weight loss of 0.62 kg (1.37 lb) 

 per fish (p = 0.19) was demonstrated. Monel tags were not used in 1975; 

 however, by considering the weight at recapture in 1975 as the tagging weight, 

 weight loss or gain from 1975 to 1976 could be determined. Thus, monel- 

 tagged fish lost an average of 0.10 kg (0,22 lb) per fish (p = 0.05) from 

 1975 to 1976. Twenty-two sturgeon (3.1 percent of total) tagged with the 

 anchor tag in 1975 and recaptured in 1976 displayed a significant weight 

 gain of 0.06 kg (0.13 lb) per fish (p = 0.01). Total returns in 1976 were 

 9.4 percent (67 of 709) of those tagged in 1975. The 1975 and 1976 rates of 

 return are comparable. 



The regression plot of weight at recapture versus weight at tagging 

 reveals the significance of the weight loss or gain associated with the two 

 tagging methods (figure 19). All regression lines for anchor-tagged fish 

 fell above the equilibrium line (that line showing no weight gain nor loss), 

 indicating that fish gained weight over the period shown. Monel-tagged 

 sturgeon fell below the equilibrium line, suggesting weight loss over the 

 time period. It is apparent that the monel tag caused a physiological stress 

 in the sturgeon which resulted in a significant weight loss. 



Movement . Of the 94 shovel nose sturgeon tagged and recaptured in 1976, 

 the majority were recaptured in the same section in which they had been tagged. 

 Time between tagging and recapture ranged from 1 to 60 days. The sampling 

 period was stratified into monthly segments to detect differences in movement 

 with time. As shown in table 8, upstream movement was greater than downstream 

 movement in May and June. The differences were not considered significant 

 because of the small sample size. In July, upstream and downstream movements 

 were nearly equal . 



In 1975, 90 percent (45 of 50) of the sturgeon tagged and recaptured 

 that year showed no detectable movement. Six percent (3 of 50) showed 

 upstream movement, while 4 percent moved downstream. 



Comparisons were made between tagging locations and recapture location 

 for fish recaptured in subsequent years. A fish was considered to be in a 

 different location if there was a difference greater than 1.6 km (1 mi). No 

 sturgeon tagged in 1974 and recaptured in 1975 was recaptured downstream from 

 where it was tagged (table 9), and of those fish tagged in 1974 and recaptured 

 in 1976, the majority (89.2 percent) were recaptured either upstream or in 

 similar locations to where they were tagged. From 1975 to 1976, the sturgeon 

 exhibited a strong tendency to return to the same place (75.0 percent). 



Angler Returns . The shovel nose sturgeon provides an excellent spring 

 fishery for those anglers who pursue them. Returns of tagged sturgeon by 

 fishermen show a light harvest (table 10). Returns of 1974-tagged fish 

 totaled 1.67 percent by 1975; 1975-tagged fish were returned at a rate of 

 1.41 percent (0.71 percent/year). Overall returns totaled 1.11 percent, 

 indicating a lightly-utilized resource. An exploitation rate of 5.0 percent 

 was considered an acceptable level for lake sturgeon on the Menominee River 

 in Wisconsin (Priegel 1973). The lake sturgeon is a slow-growing, late- 

 maturing fish which does not survive high levels of exploitation. The 

 current exploitation rate for shovelnose sturgeon on the Tongue River is not 

 excessive. 



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