[mcmurrich] pacific COAST SALMON 25 



relatively far from the sea, is still greater, even without the evidence 

 presented by their scale markings. 



The occurrence of a grilse spawning mark even in a single fish is, 

 however, of interest as showing that grilse occur in the Dog Salmon, 

 as well as in 0. nerka and 0. tschawytscha. I did not succeed in obtain- 

 ing any grilse Dog Salmon, nor was their occurrence known to those 

 fisherman whom I questioned This lack of knowledge of them may 

 have been due, however, to the fact that my inquiries were made in 

 districts where seine fishing alone is practised, since by this method 

 the small grilse would be apt to escape capture. Since they occur in 

 the other two species with a four-year cycle they are certainly to be 

 expected in 0. keta, especially since the fact that the Coho and Hump- 

 back never pass beyond the grilse stage seems to indicate that this is 

 an important stage in the life-history of the genus. 



Since this paper was written I have received by the courtesy of 

 the author a copy of a paper by Professor Gilbert •• on the ''Age at 

 Maturity of the Pacific Coast Salmon of the Genus Oncorhynchus. ' ' 



Professor Gilbert's results, which were also based on a study of 

 the scales, differ greatly from those I obtained, inasmuch as he main- 

 tains that the Sockeye reaches maturity in either its fourth or fifth 

 year, the grilse being in their third year; that the Spring Salmon spawn 

 normally in either the fourth, fifth, sixth or seventh year, the grilse 

 again being in their third year; that the Coho spawn only in the third 

 year; the Dog Salmon in either their third, fourth or fifth year; and the 

 Humpback only in their second year. Thus his results show an inde- 

 finiteness in the age at maturity, except in the cases of the Coho and 

 Humpback, which contrasts strongly with the definiteness of my 

 interpretations. 



Professor Gilbert was fortunate in having a much larger supply 

 of material for study than that at my disposal and some of the discre- 

 pancies in our results may be due to this, since variations are to be 

 expected in all biological phenomena. But I still believe that the 

 definiteness I described is the typical condition; it alone will har- 

 monize with the conditions shown, for example, by the Fraser River 

 Sockeye. The most definitely established fact with regard to these 

 fish is the four-year periodicity in their runs and the conclusion seems 

 to be inevitable that the ova from the fish of any big run furnish the 

 fish for the big run of four years later. Professor Gilbert, however, 

 maintains that of the fish developed from the ova of a given year a 

 little more than one-half run as mature individuals in their fourth year 

 and a little less than one-half in their fifth year. Such a state of affairs 

 would inevitably and quickly obliterate any such definite periodicity 

 *Bull. U.S. Bureau o'" Fisheries, XXXII. 1913. 



