66 SALMON AND TROUT IN ALASKA. 



AGE OF ADULT SALMON. 



The age of the sockeye at maturit}^ is yet not absokitely determined. 

 It is unnecessary to do more than refer to the four-year theory based 

 on the quadrennial increase in the Fraser River run. There seems to 

 be sufficient reason for believing four years to be the usual term of life 

 for the socke3^e and the king salmon, but experiment has pretty con- 

 clusively shown that they may mature in less time or may be retarded 

 beyond that term. 



It is possible that the humpback reaches maturity in less time. The 

 rapid growth of the young and the biennial occurrence of the species 

 in Puget Sound may be noted in support of this belief. The small 

 size and irregular number in certain localities may be adduced also. 

 A fish of a short growth-period would be more apt to show rapid 

 fluctuation in numbers than a form overlapping a variable series of 

 years. At Yes Bay in 1903 many very large males occurred, in some 

 cases reaching a weight of 11^ pounds. These were already much 

 "humped" and advanced in sex maturity, whereas the main body of 

 fish were still bright. Their occurrence was unusual and the size 

 extraordinary. The fishermen believed them survivors of a previous 

 season. The grilse form has not been noted among the humpbacks 

 or dogs." It has been reported for the coho by Mr. Patching, but 

 not seen by the writer. 



SALMON-MARKING EXPERIMENTS. 



Methods. — In an effort to determine the exact age of maturity, fish 

 have been variously marked. As against the results thus obtained it 

 has been asserted that any mutilations can be of no value, since the 

 mutilated part will regenerate. There have been a number of trials 

 of marks. Hubbard, experimenting in the Clackamas River, by re- 

 moval of the adipose fin is supposed to have determined maturity to 

 arrive in the king salmon at three, four, and five years — mainly at 

 three. Richardson, at Karluk, by removing the dorsal fin in the same 

 manner, arrived at four years as the average age of the sockeye. In 

 August, 1903, 1,600 sockeye fry, reared for the purpose at the Fort- 

 mann Hatchery from the 1902 eggs, were marked by excising both 

 ventrals with fine curved scissors. The fry were released at a point 

 in the Naha just above Heckman Lake as soon as marked, at which 

 time they were about 3 months old. In 1906 between 50 and .100 

 adult sockeyes with ventral fins missing were reported by the super- 

 intendent of the hatcher}^ at Yes Lake from the spawning beds 

 there. Some had also the adipose fin removed; this mark in addition 

 had been used on some of the fry mentioned above. At the Fort- 



aSee p. 9. 



