101 



with five 25-foot panels of different mesh size: 3/4, 1, 1%, 1% and 2-inch. 



Trap nets were 4 x 7-foot frames covered with 1-inch mesh net; leads were 

 approximately 25 yards. The nylon seine was 100 x 12 ft. 



A percentage of the hatchery rainbow trout stocked in Clark Canyon 

 were marked for future identification using fin clips. Clips used were: 

 adipose-- 1970, left pelvic-- 1971, and adipose— 1972. Rainbow trout in 

 creels of reservoir fishermen were checked for these marks and also were 

 identified as wild or hatchery by the appearance and shape of the fins. 

 Hatchery fish had fins with bent rays and rounded tail fins. 



Fish from Red Rock River and Horse Prairie Creek were sampled using 



boat electrofishing gear as described by Vincent (1971). Fish population 



estimates were made using the mark and recapture method as expressed by 



(M+l) (C+l) where M is the number of fish marked, C is the number of 

 (R+l) 



fish recaptured, and R is the number of marked fish recaptured. Population 

 estimation calculations were done on a hand calculator prior to 1969. The 

 1969-1972 fish population calculations were done on a computer using the 

 most recent Montana F1sh and Game computer format. 



Fishing pressure on Clark Canyon Reservoir was determined in 1971 

 using pressure curves as outlined by Peterson (1970). In 1972, fishing 

 pressure was determined using the method of Neuhold and Lu (1957). This 

 method is based on a stratified random sample. The year was stratified 

 into 4-week periods starting March 15 and further stratified into week- 

 days and weekend days. Two weekdays per week were selected at random with 

 subsequent weekdays in "the following 3-week period selected such that each 



