5.0 Discussion 



Available creel survey data from the 1970's and 1981 allow some comparisons among these 

 years and the more recent 1990's data for the Madison River fishery. In addition, the 

 introduction of whirling disease increases the importance of the early data in evaluating the 

 status of Madison River fish populations. Historic creels were not as exhaustive as the 1995 full- 

 river creel, but catch rate and pressure information are comparable and are examined in relation 

 to the more recent data with some caveats. Much of the earlier creel data were limited to the 

 Pine Butte and Snoball sections; therefore, these sections have been used whenever possible 

 when making direct comparisons. The intent is not to focus just on these sections, but to take 

 advantage of the continuity in data and use them as an index to the overall fishery on the 

 Madison River. 



5.1 Historic Creel Comparisons 



The Madison River rainbow trout population declined significantly after whirling disease was 

 first diagnosed in 1994. The decline is evident in catch rate data, population estimates, and angler 

 satisfaction surveys. The changes in the proportion of each species in the fish assemblage also 

 indicate an unequal effect consistent with the relative resistance of rainbow trout, brown trout, 

 and mountain whitefish to whirling disease. 



5.1.1 Catch Rates and Composition 



Catch rates for the two primary game fish in the Madison, rainbow and brown trout, were lower 

 at both Snoball and Pine Butte sections in 1996 than in 1975 (Figures 10 and 1 1). For the years 

 examined on the Snoball section, rainbow trout catch rates peaked in 1976 at 1.09 fish per hour 

 and declined to 0.74 fish per hour in 1981, the last year for creel data in this section (Figure 10). 

 However, Snoball was also open to both boat and shore fishing in 1976, and the catch rate for 

 1981 and 1975 may be skewed by the limitation to shore fishing for those years. Catch rates were 

 higher in 1976 and 1981 than 1975, when rainbow trout were caught at 0.55 fish per hour (Figure 

 10). 



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

 In the Madison River, Montana 



22 



Montana Fish, Wildlife and Paries 

 March 12, 2002 



