412 U. S. BUREAU OF FISHERIES 



to the phytoplankton in the lake. Samples taken on September 6 

 showed 6 one-thousandths of a milligram of phosphorus, and one- 

 half a milligram of silicon per liter. Plankton samples showed less 

 plankton in the water than was present earlier in the summer. Thus 

 some other factor, probably the amount of light, was acting as a 

 limiting factor at this time, and was allowing the gradual accumula- 

 tion of phosphorus and silicon in the lake water. 



Other fish inhabiting this lake naturally have some effect on the 

 population of young red salmon. Present in the lake are young 

 silver and king salmon, a small population of young steelliead trout, 

 cottoids, sticklebacks, and Dolly Varden trout.' It i"s considered that, 

 only the two last-named species may have an important effect on the 

 survival of the red-salmon fingerlings. The sticklebacks, due to their 

 abundance, are possible competitors for food, and the Dolly Varden 

 trout are predators. Dolly Varden trout were caught in a gill net, 

 at ail depths down to 521^ meters (175 ft.) . Salmon eggs were found 

 to be present in the stomachs of trout taken in depths down to 46 

 meters (151 ft.) indicating that these trout alternate between shallow 

 and deep water in a relatively short period of time, or else that red 

 salmon may spawn in deeper water than previously supposed. Adult 

 red salmon were taken in the net in depths down to 41 meters (134 ft.) 

 and appeared to be quite abundant in depths down to 241/^ meters 

 (80 ft.). Of the trout caught between July 19 and July 30, stickle- 

 back eggs and snails were the main articles of diet, salmon eggs 

 making up only 7.5 percent of their food. Of the trout taken between 

 August 17 and September 9, salmon eggs made up 35 percent of the 

 diet, with sticklebacks and snails next in importance. 



Trout take a heavy toll in the early spring when the salmon fry 

 are migrating down stream into the "lake. However, stomach con- 

 tents of trout taken during the summer months showed very few 

 remains of salmon fingerlings, none being found in the July samples, 

 and only 1.2 percent in August and September. 



Data on the returns from known escapements were collected, escape- 

 ment and catch records were compiled, and scale samples taken 

 throughout the season for the purpose of age determination. Com- 

 plete returns from the 1929 spawning are now at hand with the ex- 

 ception of the few 7-year fish which will return in 1936. The 1929 

 escapement was 900,519 and the return per fish from this escapement 

 will be approximately 1.6 to 1.0, as compared with 2.2 to 1.0 for the 

 1928_ escapement and 1.8 to 1.0 for the 1927 escapement. There is 

 considerable evidence toward the belief that these returns are below 

 normal and are, in the main, caused by unfavorable environmental 

 conditions existing in Karluk Lake during the time these fish were 

 residents there. 



CHIGNIK RIVER RED SALMON 



This investigation was continued in 1935 on a much reduced scale. 

 As in 1934 a temporary assistant was stationed at Chignik from May 

 until October for the purposes of collecting fish scale samples, and 

 of observing the commercial catches for marked fish. The data 

 <iollected have been filed for future use. 



