56 U. S. BUREAU OF FISHERIES 



the Hot Creek Rearing Ponds Project were concluded June 30, and 

 investigations on the survival rates of hatchery-planted trout by 

 means of the Convict Creek experimental stream, operated in co- 

 operation with the U. S. Poorest Service, were substituted as a major 

 project. 



Twenty-three plants of brook, brown, and rainbow trout were 

 made during the season of 1937 in the experimental stream. Va- 

 rious age groups were used, and plantings were made under vary- 

 ing predator conditions to determine survival rates over varying 

 intervals of time. Several of the experiments were failures because 

 of faults in the physical set-up, such as holes under dams and 

 clogging of screens. The information obtained during this first 

 year has pointed the way for future operations and the biological 

 data have provided definite guides for stocking programs. From 

 the successful experiments it was determined that hatchery-reared 

 advanced fry suffer great losses in wild waters, but that hatchery 

 fish from three to four inches long show a high survival. Brown 

 trout did better than the other species with rainbow trout next in 

 order of success in the experimental plants. Studies of condition 

 factors showed that hatchery-reared fish lost weight after planting 

 and a measure was determined for the optimum stocking intensity 

 in relation to the food supply. 



In one section a survival of 100 percent was obtained following 

 a plant of rainbow trout based on the table developed by Dr. G. C. 

 Embody. In another section, stocked with 1,000 advanced cut- 

 throat fry, only 34 fish survived to the end of the season. The 

 presence of 10 wild predatory trout was responsible for the heavy 

 losses. 



In future operation it is ]:>lanned to divide the experimental 

 stream into a smaller number of sections. Em])hasis will be placed 

 on ]:)lanting experiments with rainbow and l)rown trout. 



Boat catch records were again obtained from anglers fishing 

 Convict Lake. The catch per unit of effort rose slightly from 0.21 

 fish per hour in 1935 to 0.27 fish per hour in 1936. A total of 365 

 trout were reported by 286 anglers in the 1936 season while 184 

 anglers took only 167 trout in 1935. 



Of the trout cauglit in Convict Lake in 1936, over 49 percent were 

 unmarked rainbows and approximately 48 percent were brown trout. 

 Only seven marked rainbows from the plant of 2,014 (average length 

 5.67 inches) planted in July 1935, were reported caught by boat 

 fishermen in 1936, while 349 of these fish were caught in the season 

 of 1935. Therefore, in 2 seasons' fishing a total of only 356 trout, 

 or ajiproximately 18 percent, of the 2,014 planted in 1935 have been 

 re])orted caught. However, such a low survival may prove to be 

 more apparent than real, since fish planted in the lake can easily 

 leave through either the inlet or outlet. Several reports were ob- 

 tained of marked rainbow being caught as much as one-half mile 

 below the lake. 



Cooperative investigations with the U. S. Forest Service were 

 continued in the national forests of California, Oregon, and Washing- 

 ton. A survey was completed and stocking policies were developed 

 for the headwaters of the South ITmpqua River above Tiller, Oreg., in 

 the Umpqua National Forest. In addition, complete angling catch 

 records were taken on Fish Lake by the Forest Service. Fish Lake, 



