216 U. S. BUREAU OF FISHERIES 



Marking experiments at Karluk. — In connection with the intensive 

 investigation of the Karhik River red salmon that is being carried on 

 by Dr. C. H. Gilbert and Dr. W. H. Rich, 50,000 seaward migrants 

 were marked during June, 1927. This phase of the work was begun 

 in 1926 and has as its purpose the ultimate determination of the num- 

 ber of seaward migrants each year. Future runs of adult fish will 

 be sampled, and from the samples the percentage of marked fish in 

 each age group will be determined. At the same time the total 

 number of fish of each age group will be determined by scale readings. 

 With these data at hand, the number of seaward migrants may be 

 determined by means of the following proportion : The percentage of 

 marked fish in a given age group is to 100 as the number of fish 

 marked is to the total number migrating seaward. Twenty-four of 

 the fish marked in 1926 were recovered as adults (grilse) in 1927. 

 These formed 0.357 per cent of the total number of grilse. As 47,000 

 seaward migrants were marked in 1926, the proportion becomes: 

 0.357:100: : 47,000 :x (the total number of migrants in 1926). Ac- 

 cording to this calculation, there were about 13,000,000 seaward 

 migrants in 1926, but the probable error of this determination neces- 

 sarily is large because of the comparatively few marked gi^ilse recov- 

 ered. It is expected that more adequate returns will be secured in 

 1928, when most of the fish that migrated in 1926 will return, and that 

 a more accurate calculation of the number of seaward migrants in 

 1926 can be made then. 



Observations on the spavMing grounds at Karluk Lake. — These 

 were continued by Doctor Rich, assisted by S. P. Smith, temporary 

 assistant. Conditions on the spawning grounds and in the lake were 

 strikingly different from those found in 1926. Tlie summer of 1927 

 was much colder, with a heavier rainfall. As a result, the water in 

 the spawning streams remained high throughout the summer and 

 apparently provided more favorable spawning conditions. At the 

 same time the spawning escapement was much lower than in 1926, 

 as a result of which the spawning beds never were crowded and there 

 was no such mortality of unspawned fish as was recorded in 1926. 

 Conditions in the lake were equally different. The surface tempera- 

 ture of the lake remained below 12° C, which was about 5° C. below 

 the maximum surface temperature recorded in 1926. No thermo- 

 cline was established, while in 1926 a well-defined thermocline was 

 maintained throughout the summer. Further investigations will be 

 necessary in order that the efi^ect such varied conditions have upon 

 the hatching of the eggs and the survival and growth of the young 

 salmon during their life in the lake may be determined. A good col- 

 lection of young salmon was made in Karluk Lake with a special net. 

 It never has been possible before to secure young red salmon during 

 their sojourn in the lake, and this collection should be valuable in 

 solving some of the difficult problems that arise in reading adult 

 scales. Dr. George Kemmerer, of the University of Wisconsin, made 

 a chemical survey of Karluk Lake and the tributary streams as a 

 . basis for a more thorough understanding of the ecological conditions 

 that apparently make this lake especially favorable for the growth 

 of young red salmon. 



Tagging red salmon in Uganik Bmj. — ^Another experiment was 

 made in Uganik Bay, Kodiak Island, Alaska, where Doctor Rich 



