Chipmunk and Grouse Creeks have supported egg- taking activities 

 for several years, but their fish are subjected to only moderate fish- 

 ing pressure in the South Arm. It is knoi^m from tagging operations that 

 many Chipmunk Creek adults move into West ITiumb after spawning in Chipmunk 

 Creek, but tagging also suggests that most post=spawners from this stream 

 remain in the South Arm, 



Pelican Creek has for many years provided spawn for culture^ and has 

 contributed fish to the center of the area of greatest fishing pressure on 

 Yellowstone Lake. Declines have been measured in numbers and sizes of 

 spawners on Pelican Creek in the past five years. 



Arnica Creek falls into another category. No egg-taking has occurred 

 on Arnica Creek for many years, but fishing in the West Thumb area, to 

 which Arnica Creek contributes a large share of its fish, has become very 

 intense (see Moore, Cope, and Beckwith, 1952) » 



It might appear, then, that Chipmunk and Grouse Creek^ with moderate 

 egg-taking and low fishing pressure, have not yet been seriously affected 

 with respect to decrease in sizes and numbers of spai^mers. Pelican Creek, 

 with heavy egg-taking and heavy fishing pressure, has suffered significant 

 declines in size of fish and numbers of spawners. Arnica Creek, with no 

 egg-taking, but with heavy fishing pressure,, has undergone a decrease in 

 spawner size. 



Fish in the Fishing Bridge Fishery Area have decreased in size. This 

 is the most heavily fished part of Yellowstone Lake and contributes more 

 fish to the creel than any other part of the lake. The area receives many, 

 if not most, of its fish from northern streams,, such as Pelican Creek, 

 which are undergoing decreases in fish size, in the West Thumb Fishery, 

 where angling pressure is second in intensity, a decrease in size has been 

 measured. This area also receives fish from streams, such as Arnica Creek, 

 whose spawners are decreasing in size. The combined lake fishery, being a 

 mixture of fish from population units that show decreases in size, as well 

 as from other areas, showed a decrease from 1951 to 1952 because of the 

 large proportion of north em -caught fish in the catch. 



The fishery appears to have suffered a steeper and more definite decline 

 in fish length than have the spawning runs. The probable reason for this is 

 that the fishery has penetrated deep into the younger age groups (two-and 

 three-year-olds), a condition which is immediately manifested in fishery 

 length measurements. The spawners measured in streams have been made up of 

 disproportionately large numbers of younger age groups, but not to the extent 

 seen in the fishery. Practically no two-year-olds enter streams for spawn- 

 ing, and those few that do ascend streams probably do not contribute to the 

 spawning. With the usual paucity of two-year-olds, ypawners in streams do 

 not have the opportunity for rapid declines in mean total length that la 

 afforded the fishery. 



Ih 



