Age Class 



U 



m 



IV 



V 



VI 



Table 13. Calculated total lengths, in inches, by age classes, a 



at the end of each year's growth for 36 whitefish in the 

 Madison River. Collected in 1956 and 1957. 



Number 

 of fish 



11 

 9 

 5 

 3 



Average calculated total 

 lengths at each annulus 



16.9 



found that planting large numbers of rainbows 

 apparently had no effect on wild fish populations . 

 Holloway and Chamberlain (1942) found that 

 planting large rainbow trout for the creel exerted 

 less pressure on the wild trout populations than 

 did fingerling plantings since there was no com- 

 petition for food as there is during the growth 

 period for fingerling fish. Neither wild brown 

 nor rainbow trout in the Madison and Firehole 

 Rivers seemed to be adversely influenced by the 

 plantings of large numbers of fish in 1954 and 

 1955. The catch of brown trout increased due 

 to heavier fishing pressure, but the wild rainbow 

 catch was remarkably stable during the study 

 (fig. 3). A heavier harvest of brown trout was 

 not overexploiting the population . Growth rates 

 did not change on either wild brown or wild rain- 

 bow trout when no stocking was carried out in 

 1956 and 1957. 



ADULT FISH PLANTING EXPERIMENTS 



Many agencies periodically determine the 

 return of planted catchable-size hatchery fish to 

 evaluate their stocking programs. Such manage- 

 ment research is wise because of changing 

 environments and fishing pressure. Frequently 

 it is not possible to mark every planted fish and 

 to observe the catch of each angler, and certain 

 problems in carrying out such studies are fre- 

 quently overlooked. The original research plan 

 on this investigation called for the marking by 

 fin clipping of approximately 40 percent of the 



fish planted and to assume that the marked- 

 unmarked ratio would be the same in the catch 

 as in the plants. Fortunately, scale samples 

 were taken from all fish checked by creel clerks. 

 As illustrated earlier in this paper, adult planted 

 hatchery fish can be easily distinguished from 

 wild fish by the pattern of circuli . Chapman 

 (1958) tested the use of scale pattern character- 

 istics to segregate hatchery steelhead from 

 wild stock and reached an accuracy of almost 

 100 percent. Our recovery results would have 

 been greatly different from the true results if 

 we had used fin clips to estimate recovery rates 

 rather than the scale sample method (table 15) . 

 The hatchery life of a fish is permanently 

 marked on the scale, and it is suggested that 

 this method be used unless it is possible to mark 

 every hatchery fish planted. 



MANAGEMENT 



The fish management policy of the 

 National Park Service, dated June 17, 1954, 

 states that native fish species should be encour- 

 aged and that the stocking of catchable-size fish 

 should be avoided if possible. The three prin- 

 cipal trouts in this stream system, the brown, 

 rainbow, and brook, are all introduced species 

 and our management must only consider these 

 well-established species. We have shown 

 that the planting of fingerling rainbow and brown 

 trout does not contribute to the catch and such a 

 planting program should be avoided in the future . 



24 



