Mackay et al. (1990). I also attempted to classify origins of rainbow trout (hatchery vs. 

 wild) by following procedures reported in Oswald et al. (1990). They reported that 

 hatchery fish "showed a strong 'stocking check' on the scales, generally about 8 circuli 

 out from the focus" (Oswald et al. 1990). Using this as a guideline, I reclassified the 

 same scales used by Oswald et al. (1990) and compared their results to mine. My results 

 concurred with previously reported classifications in 75% of scale samples. Each scale 

 set collected by creel clerks was similarly classified and results were compared to creel 

 clerk's classification by fin erosion and to results of tetracycline marks in rainbow trout 

 when a vertebra was collected. 



Since the mid-1990's, all rainbow trout stocked into Hebgen Reservoir have been 

 exposed to oxy-tetracycline in the hatchery to create a mark in bony structures. 

 Vertebrae were collected by creel clerks, dried, cleaned of tissue, and held under a black 

 light to detect marks. A positive "tet-mark" is a ring that glows under black light. Thus, 

 each trout's length, weight, fin erosion, tet-mark, and age were recorded and tabulated. 

 Unique identification codes assigned to each fish enabled comparisons of methods for a 

 given fish. 



RESULTS 



Fishing Pressure Estimates 



Fishing pressure was highest between May and August (Fig. 2). Of the 64,81 1 angler- 

 hours estimated for the creel period, 80% occurred during these late spring and summer 

 months (Table 1). The winter fishery was limited, although February supported over 

 2,500 angler hours of ice fishing pressure. However, during winter months the South half 

 of the reservoir was inaccessible except by snowmobile and sampled on a limited basis. 

 Limited winter counts of the south half may have biased winter pressure estimates. 



Over the course of the entire creel period, angling pressure was evenly distributed 

 between the North and South halves (46.5% and 53.5%, respectively. Fig. 2). However, 

 pressure exerted by shore (including ice fishing) and boat anglers differed between the 

 two sections. The North half of the reservoir received 40.5% of the pressure by shore 

 anglers, while 59.5% was boat anglers. On the South side, with more limited shore 

 access, boat anglers dominated pressure 82.2% to 17.8% by shore anglers. Over both 

 sections and the entire period, boat fishing comprised 71.6%) of all fishing pressure. 

 About 25% of total shore fishing pressure could be attributed to ice fishing. 



Fishing Catch-per-Effort and Harvest 



Analysis of catch rates and harvest was made difficult by creel clerks failing to record 

 trips of non-successfijl anglers fi"om June through September 2000. Of the four data sets 

 created, catch rates varied between data sets for rainbow trout but harvest was similar 

 between data sets (ANOVA; p=0.5262). For brown trout, neither catch rates (ANOVA; 

 p=0.0847) nor harvest (ANOVA; p=0.99385) varied significantly among datasets. 



