348 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Hours 



18 28 

 September 



Period ending 



Figube 30. — Total number of hours (by 10-day periods) spent on Grebe Lake by fishermen during 1953 and 1954. 



satory reaction on the part of fishermen to fill out 

 forms only if they caught fish. 



More fish were taken from Grebe Lake by 

 fishermen using flies than by any other method. 

 However, the number of fish taken by any one 

 group of fishermen depended not so much on the 

 type of gear they used as it did on the number 

 of anglers in that group ; the percentage of fisher- 

 men using any one lure or combination of lures 

 agreed closely with the percentage catch by that 

 respective method (table 30). Since tabulations 

 are not for individual fishermen, but for parties, 

 the combinations occurred where one person in 

 a party would use spinners and another flies, or 

 other lure. The average number of people per 

 party was 2.5 in 1953 and 2.9 in 1954. 



Fishing yield from Grebe Lake was low (table 

 29) . There was a harvest of only about 6 pounds 

 per acre in 1953 and 8 pounds per acre in 1954. 

 In contrast, a trout lake in Oregon of similar 

 size and also having a creel limit of five fish pro- 

 duced more than 50 pounds per acre of trout 

 each year between 1945 and 1947 (Holloway 

 1947). In a series of trout lakes on Grand Mesa 

 in Colorado, anglers were removing an average 

 of 63 pounds per acre per year with two of the 



lakes yielding an average of 106 pounds per acre 

 per year (Lyall 1941). 



PREDATORS AFFECTING GREBE LAKE 

 POPULATIONS 



The removal of fish from Grebe Lake by pred- 

 atory birds and mammals is a factor that affects 

 the size and composition of the population. 

 However, measurement of the effect of predation 

 is difficult. Black bear, Ursus americanus Pallas, 

 mink, Mustela vison Schreber, and river otter, 

 Lutra canadensis Schreber, were seen on Grebe 

 Lake between 1952 and 1954, but they were not 

 numerous, and actual evidence of predatory 

 activities was small. The osprey, Pandion haliae- 

 tus, however, took fish throughout each season. 



Table 30. — Use of lures and effectiveness on Grebe Lake 

 in 1953 and 195/, 



