Section IV., 1913. • [23J ■ Trans. R.S.C. 



Some Further Observations on the Life Histories of the Pacific Coast 

 Salmon as Revealed by their Scale Markings. 



By J. Playfair McMurrich, M.A., Ph.D., LL.D. 



(Read May 28, 1913) 



At the last meeting of the Royal Society of Canada I presented 

 an account of"" observations upon the scale markings of the various 

 species of Oncorhynchus occurring upon the Pacific Coast, and pointed 

 out the conclusions as to the life cycles of these fish that were to be 

 deduced from the markings. During the summer of 1912, while 

 acting as Director of the Biological Station at Departure Bay, B.C., 

 I was able to obtain additional material for the confirmation and ex- 

 tension of my earlier observations, and for the opportunity for so doing 

 I am especially indebted to the courtesy of Rear-Admiral Kingsmill 

 and Captain Holmes Newcomb and to the managers of the various 

 canneries that I was able to visit. 



In my former paper I showed that the scale markings of the various 

 species of Oncorhynchus indicate that the members of this genus may 

 be divided into two groups, according to the typical lengths of their 

 life-cycles. Thus the markings indicate that the Spring Salmon (0. 

 tschawytscha) , the Sockeye (0. nerka), and the Dog Salmon (0. kefa) 

 have a typical four year life-cycle, a few individuals of at least the 

 first two species, however, becoming precociously mature and returning 

 to the spawning grounds in the second year as grilse. On the other 

 hand the Coho (0. kisutch) and the Humpback (0. gorbuscha) all return 

 to the spawning grounds in their second year; their life-cycle is one of 

 two years and they do not pass beyond the grilse stage. 



My conclusions as to the age of the spawning Coho have been 

 criticized on the ground that while the fish studied may all have been 

 in the grilse stage, they did not represent fully grown individuals, and 

 it was therefore possible that these latter may really have a four-year 

 cycle. My original observations were made on fish varying in length 

 from 44 cm. to 69.5 cm., the measurements being taken from the tip 

 of the snout to the root of the tail in each case, and since the major- 

 ity of the fish examined were over 60 cm. in length the suspicion of 

 immaturity seems to be unfounded. To make the matter more certain, 

 however, I obtained scales during the past summer from ten additional 



*McMurrich, J. P. — The Life Cycles of the Pacific Coast Salmon Belonging to 

 the Genus Oncorhjmchus, as Revealed by their Scale and Otolith Markings, in Proc. 

 and Trans. Roy. Soc. Canada. 3rd Ser. Vol. VI. 1912. 



