[mcmurRicH] LIFE CYCLES OF THE PACIFIC COAST SALMON ILI 
in several species of Clupeidæ and was employed by Maier! in his 
determination of the age in Pleuronectes and Gadus. Fryd’s observa- 
tions (1901),? extended over a large number of species belonging to the 
various orders of Teleostei, are also of interest as showing that in the 
majority of cases there is a possibility of determining from the otoliths 
the age of the individual fish. 
In what follows I shall present the evidence that has been gathered 
from both the scales and the otoliths regarding the age of the various 
species of Oncorhynchus when they return from the sea on their way to 
the spawning grounds. And since our knowledge of the life-cycle of 
O. nerka is the most complete and may, therefore, be taken as a basis 
for the interpretation of the markings on the two structures under 
consideration I shall begin the account of my results with this species. 
I. Tue Sockeye (O. nerka) WALBAUM. 
The life-cycle of the Sockeye Salmon is apparently one of four 
years. This conclusion is based upon the cyclic nature of the runs of 
the fish in the Fraser River, it being a well-known fact that a “big 
run” occurs every four years, the intervening three years being 
characterized by “poor runs.” It is supposed that the fish composing 
a big run of one year are the descendents of those which formed the big 
run of the fourth preceding year, and if this be true of the fish of the big 
runs, it is in all probability also true of those of each of the three inter- 
vening poor runs. Furthermore it seems to be pretty well established 
that very few, if any, of the fish that have reached the spawning grounds 
ever return to the sea; they spawn but once in their lives and then die. 
Consequently the fish of each year of the four year cycle represent a 
generation whose duration is four years. Assuming the correctness of 
this deduction the life history of a Sockeye may be supposed to be as 
follows. The eggs are spawned during the autumn in the “riffles” of 
streams leading from fresh-water lakes, and the young fish hatch out 
in the early winter months. For several months after hatching the 
fry remain in fresh water, but in the succeeding late spring or early 
summer they migrate to the sea, where they remain for three years, 
returning as full grown fish in the latter part of the summer of their 
fourth year to seek the spawning grounds, where they die. 

1Maier, H. N. Beitrage zur Altersbestimmung der Fische. Wissensch. Me- 
eresuntersuch. Abth. Kiel. N.F. Bd. VIII. 1906. 
*Fryd, C. Die Otolithen der Fische in Bezug auf ihre Bedeutung für Syste- 
matik und Altersbestimmung. Inaug. Dissert. Altona. 1901. 
