they did not want to spread the disease or because they were concerned that might not catch 

 many fish. 



90,000 



80,000 



70,000 

 « 60,000 

 •S 50,000 



be ' 



•3) 40,000 



•5 30,000 



20,000 



10,000 







%<^* s<=0^ \9%^ \<)%'^ \9%* vc.%^ x^"^ xcp^ vcp"^ xSP^ -.ii'^ \# 



Year 



Figure 15. Angler days fished from 1968-1999 on the section of the Madison River from Ennis Lake to 

 Hebgen Reservoir, Montana. Data were collected via mail-in surveys distributed by FWP to randomly 

 selected Montana fishing license holders. 



5.2 Population Estimates 



Changes in rainbow and brown trout population abundance have mirrored changes in catch rates 

 in the upper Madison River over the years. FWP conducts annual electrofishing and Peterson- 

 type mark-recapture population estimates to assess the fishery and estimate trout species 

 populations. Three marking runs are followed by three recovery runs, 10 to 14 days after 

 marking. The ratio of marked to unmarked fish in the recovery sample is used to estimate 

 abundance according to FWP's computerized Mark-Recapture Log-likelihood Model. 



Population assessments are completed each fall and occasionally in the spring. Fall estimates 

 were used in this report to evaluate how the actual number of fish present compared with the 

 number offish being caught by anglers because the data set is continuous, and fall estimates are 



Evaluation of 1995 and 1996 Creel Data and its Implications related to Whirling Disease 

 In the Madison River, Montana 



27 



Montana Fish, Wildlife and Paries 

 March 12.2002 



