Executive Summary 



The parasite that causes whirling disease was first discovered in Montana in rainbow trout in the 

 Madison River in December 1994. It was discovered during an investigation into the cause of a 

 major decHne in the rainbow trout population in the upper Madison River. Part of FWP's 

 response to these findings was an intensive creel survey in 1995 and 1996. In 1995, the creel 

 survey covered the entire Madison River from Quake Lake downstream to the headwaters of the 

 Missouri River at Three Forks; and in 1996, the section from Slide Inn downstream to Windy 

 Point (approximately 20 river miles) was surveyed. The results from these two surveys, when 

 compared with historical creel surveys, provide a great deal of insight into the effects of the 

 disease on the fishery. 



The Madison River rainbow trout fishery declined significantly from the late 1970's and early 

 1980's to the period after whirling disease was first diagnosed in 1994. The decline is evident in 

 angler catch rate data, trout population estimates, and angler use surveys. Catch rates for rainbow 

 trout were much lower in 1995 than in earlier surveys, but the catch rates for brown trout did not 

 show a similar pattern, and actually increased from 1977 to 1995. It appears that as whirling 

 disease was reducing the numbers of rainbow trout, the brown trout population became 

 proportionately more available for capture by anglers. Changes in FWP's annual population 

 abundance estimates for rainbow and brown trout have mirrored changes in catch rates in the 

 upper Madison River over the years, and the 1995 and 1996 surveys were no exception. Rainbow 

 trout population declines as measured by the annual electrofishing surveys paralleled the rinbow 

 trout catch rate declines recorded in the creel surveys. 



Despite these declines, the anglers who chose to fish the Madison River were generally satisfied 

 with their fishing experience according to the 1995 angler satisfaction survey. However, FWP's 

 biennial mail-in surveys showed a slight decrease in angler use of the Madison River in the mid- 

 1990's. Nearly 90% of all anglers surveyed on the Madison in 1995 and 1996 were non- 

 residents, which may explain why many anglers also responded that they had fished the area for 

 one year or less. The upper reach of the river was frequented almost exclusively by fly anglers, 

 and had a higher proportion of guided trips than the lower reach. In addition, the upper river 



Evaluation of 1995 and 1996 Creel Data and its Implications related to Whirling Disease Montana Fish, Wildlife and Paries 



In the Madison River, Montana March 1 2, 2002 



