PACIFIC SALMON FISHERIES 417 



natural, iiiaKinucli as growth may be checked by other causes than the purely 

 seasonal one. Also a considerable experience is requisite for the correct inter- 

 pretation in many cases, and a small residue of doubtful significance has always 

 remained. This element is too small to affect the general results, and further 

 investigation will almost certainly eliminate the doubtful cases altogether.-' 



As a result of his investigations up to this point, Doctor Gilbert 

 presented the following conclusions drawn from the data collected: 



1. The sockeye spawns normally either in its fourth or fifth year, the king 

 salmon in its fourth, fifth, sixth, or seventh year, the females of both species 

 being preponderatingly 4-year fish. 



2. The young of both sockeye and king salmon may migrate seaward shortly 

 after hatching, or may reside in fresh water until their second spring. Those of 

 the first type grow more rapidly than the second, but are subject to greater 

 dangers and develop proportionately fewer adults. 



3. Coho salmon spawn normally only in their third year. The young migrate 

 either as fry or yearlings, but adults are developed almost exclusively from those 

 which migrate as yearlings. 



4. Dog [chum] salmon mature normally either in their third, fourth, or fifth 

 years, the humpback always in their second year. The young of both species 

 pass to sea as soon as they are free swimming. 



5. The term "grilse," as used for Pacific salmon, signifies conspicuously under- 

 sized fish which sparingly accompany the spawning run. They are precociously 

 developed in advance of the normal spawning period of the species. So far as 

 known, the grilse of the king salmon, coho, and dog [chum] salmon are 

 exclusively males; of the sockeye, almost exclusively males, except in the 

 Columbia River, where both sexes are about equally represented. The larger 

 grilse meet or overlap in size the smaller of those individuals which mature 

 one year later at the normal period. 



6. Grilse of the sockeye are in their third year, of the king salmon in their 

 second or third year, of the coho and the dog [chum] salmon in their second year. 



7. The great differences in size among individuals of a species observed in the 

 spawning run are closely correlated with age, the younger fish averaging con- 

 stantly smaller than those one year older, though the curves of the two may 

 overlap.^ 



Since 1910 Doctor Gilbert devoted much of his time to inves- 

 tigations ^ along this line, especially on the sockeye, with most 

 interesting and valuable results. 



His observations on the sockeye runs of British Columbia indicate 

 that they consist principally of four and five year fish and that these 

 two classes appear during successive seasons in widely differing pro- 

 portions; that each stream has its distinctive race of sockeye, the 

 progeny returning at maturity to the parent stream; that sockeye 

 fry rarely survive when they proceed to sea within the year in which 

 they are hatched; and that sea feeding, with the consequent rapid 

 growth, is the most important factor in producing early maturity, 

 an equal number of years in fresh water producing comparatively 

 little effect. 



» Age at Maturity of the Pacific Coast Salmon of the Genus Oncorhynchus. By Charles H. Gilbert. 

 Bulletin, U. S. Bureau of Fisheries, 1912, Vol. XXXII, pp. 4, 5. Washington, 1913. 



« .'i.ge at Maturity of the Pacific Coast Salmon of the Genus Oncorhynchus. By Charles H. Gilbert. 

 Bulletin, U. S. Bureau of Fisheries, 1912, Vol. XXXII, pp. 21, 22. Washington, 1913. 



' Contributions to the Life History of the Sockeye Salmon. (No. 1.) By C. H. GUbert. Report of 

 British Columbia Commissioner of Fisheries for the year ending Dec. 31, 1913, with Appendices, pp. 

 R53-78. Contributions to the Life History of the Sockeye Salmon. (No. 2.) By C. H. Gilbert. Report 

 British Columbia Commissioner of Fisheries for the year ending Dec. 31, 1914, with Appendices, pp. 

 N45-75. Contributions to the Life History of the Sockeye Salmon. (No. 3.) By C. H. GUbert. 

 Report British Columbia Commissioner of Fisheries for the year ending Dec. 31, 1915, with Appendices, 

 pp. 827-64, fi p!s. Contributions to the Life History of the Sockeye Salmon. (No. 4.) By C. H. Gilbert. 

 Report British Columbia Commissioner of Fisheries for the year ending Dec. 31, 1917, with Appendices, 

 pp. Q33-80, 14 pis. Contributions to the Life History of the Sockeye Salmon. (No. 5.) By C. H. Gilbert. 

 Report British Columbia Commissioner of Fisheries for the year ending Dec. 31, 1918, with Appendices, 

 pp. X26-,'i2, 24 pis. Contributions to the Life History of the Sockeye Salmon. (No. 6.) By C. H. Gilbert. 

 Report, British Columbia Commissioner of Fisheries for the year ending Dec. 31, 1919, with Appendices, 

 pp. U35-68, 6 pis. Victoria, British Columbia. 



