1909.] The Life History of the Pacific Salmon. 37 



Columbia they are known as Little Redfish or Kennerley's salmon and 

 were for a time regarded as permanent residents in fresh water, but ac- 

 cording to Jordan they have been observed by Gilbert in the lower reaches 

 of the Columbia and are probably anadromous. 



If this be the case they probably correspond to the grilse of the At- 

 lantic salmon and, like these, are fish that have returned to fresh water 

 earlier than usual, perhaps as the result of a precocious maturing of their 

 reproductive organs. It is worthy of note that these fish show less of the 

 red colouration than the adult males and the beak formation, so character- 

 istic of the latter, is much less developed. More information is needed 

 concerning these grilse and while it would be interesting to correlate their 

 occurrence with that of the yearlings, such a suggestion would be at present 

 too much in the nature of pure speculation. 



But while it is possible that some fish may delay their return to fresh 

 water until the fifth year and others may hasten it, yet it seems, from 

 the facts that have been presented that the upward migration of the im- 

 mense majority of fish takes place in the fourth year of their life. And I 

 have recently been able to obtain confirmatory evidence of this from a 

 structural peculiarity presented by certain organs of the fish. In 1899 

 Hoffbauer* showed that the age of Carp could be determined by a study 

 of the concentric rings on their scales, and later Thomsonf found that 

 this was true also for several members of the Cod family. In 1906 MaierJ 

 extended the observation to the Flat-fishes and found further, that the 

 so-called ear bones or otoliths of these fishes showed series of concentric 

 rings similar to those occurring in the wood of exogenous trees and like 

 these indicating the age of the fish. Recalling this fact and in the hopes 

 that the otoliths of the salmon might show a similar structure, I obtained 

 through the kindness of Inspector Sword of New Westminster, B.C., the 

 heads of six Sockeyes taken in September on their way up the Fraser 

 River, and on examining the otoliths of four of these fish I was delighted 

 to find that they all showed growth rings and, furthermore, there were 

 in each case four such rings. Sketches of the right otoliths of these four 

 fish are here shown (Fig. 2) and it will readily be perceived that in each 

 four distinct growth lines occur. The observation requires repetition on 

 a much larger number of fish and the otoliths of fry, yearlings and grilse 

 ought also to be examined before this present finding can have full value, 



*Jahresbericht des Schlesischen Fischerei-Vereins. 1899. 



tj. S. Thomson. Journ. Marine Biological Assoc. Vols. VI and VII. 1902 

 and 1904. 



|H. N. Maier. Wissenchaftl. Meeresuntersuchungen. Abth. von Kiel. VIII. 

 1906. 



