with the potential to act as a corridor for transmission of whirling disease. Other tributaries to the 

 Missouri have recently tested positive for whirling disease, and its downstream progression will 

 create similar concerns throughout the state's trout waters (Liknes et al. 1999). 



Stocking has been suggested as a remedy to the whirling disease dilemma. If very young fish are 

 the most susceptible, then stocking adult or sub-adult fish seems an attractive option for avoiding 

 infection. However, Montana ceased stocked its river fish populations as early as the 1970's 

 because FWP had collected data suggesting that stocking trout on top of natural populations 

 actually decreased overall fishery strength (Vincent 1996, 1987). Vincent (1987) cited 

 differences in behavior between hatchery and wild trout, lower overall health and vigor of 

 hatchery fish, and the potential for introducing other diseases as reasons for not returning to a 

 river stocking program in Montana. Other studies have confirmed these findings, and suggest 

 that hatchery fish, due to their homogeneous genetic makeup, may degrade the overall quality of 

 wild salmonid populations (Hindar, Ryman and Utter 1991). The argument against stocking 

 generally stresses the concept of "local adaptation" by which it is reasoned that as populations 

 evolve and adapt to an area, the progeny of that population become better able to cope wdth 

 conditions specific to that river, stream or lake (Hindar, Ryman and Utter 1991). Trout do not 

 rear their young, and many of their behavioral adaptations are genetically based and 

 environmentally influenced (Allendorf, Ryman, and Utter 1987). When hatchery fish with their 

 non-local gene complement are stocked on top of wild populations, the hybrids may experience 

 lower spawning success, lower survival, and reduced heahh (Hindar, Ryman and Utter 1991). 

 Therefore, stocking hatchery rainbow trout in the Madison River might actually compound the 

 impact of whirling disease rather than remedy its effects. 



The potential for lasting ecological damage from whirling disease is high, and the long term 

 preservation and enhancement of the fishery is FWP's primary concern. Therefore, FWP wants 

 to quantify the impact that whirling disease has had on the Madison River in terms of angler 

 catch rates, fishing pressure, and social perception of the river and its fishery. By fully 

 understanding how whirling disease has affected the Madison River fishery, FWP hopes to 

 determine the best management strategy to facilitate recovery. 



Evaluation of 199S and 1996 Creel Data and its Implications related to Whirling Disease 

 In the Madison River, Montana 



31 



Montana Fish, Wildlife and Parks 

 March 12, 2002 



