ABSTRACT 



Hebgen Reservoir provides a popular fishery for Southwest Montana. While wild 

 rainbow and brown trout are the basis for the fishery, Montana Fish, Wildlife, and Parks 

 (FWP) annually stocks approximately 100,000 Eagle Lake strain rainbow trout. The 

 management goal for the Hebgen Reservoir fishery is to establish a self-sustaining trout 

 fishery. However, little was known about the contribution of hatchery rainbow trout to 

 the angler's creel. This creel survey was designed to quantify angling pressure, catch 

 rates, angler characteristics, and to better define contribution of hatchery rainbow trout to 

 the creel. For the period from June 12, 2000 to June 10, 2001, we estimated fishing 

 pressure to be 64,8 1 1 angler hours, concentrated from May to August. Catch rates of 

 rainbow trout averaged 0.31 per hour, which were considerably higher than the estimated 

 0.09 brown trout caught per hour. Mountain whitefish and Utah chub are common in the 

 reservoir, but rarely caught by anglers. Total harvest was estimated to be between 9,303 

 and 1 1,345 rainbow trout and from 2,958 to 3,571 brown trout. 



Rainbow and brown trout caught by anglers were of similar average length and weight, 

 averaging 16.4 inches, 1.45 lbs and 16.1 inches, 1.54 lbs, respectively. Age 3 and 4 

 rainbow and brown trout comprised 68% of trout in the creel, hi general, hatchery 

 rainbow trout grew slightly faster than wild rainbow trout, but wild rainbow live longer. 

 Age 1 rainbow trout were rare in the creel and in gill nets, suggesting that wild rainbow 

 rear in tributaries. Only hatchery age 1 rainbow trout were in the creel. 



Rainbow trout origin was difficult to assess. We used dorsal fin erosion, presence of a 

 "stocking-check" on scales, and tetracycline marks to indicate whether or not rainbow 

 trout were of hatchery origin. Each method had biases and results ranged from 30% by 

 dorsal fin erosion to 3% by tetracycline marks. Scale analysis was the most subjective, 

 estimating that 47% of rainbow trout were of hatchery origin. 



