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BULLETIN OF THE BUREAU OF FISHERIES. 



and of the fifth. Slow growth and smaller size mean deferred maturity in all years 

 except the first and the second. 



The failure of similar results to appear in Doctor Fraser's article, above referred to, 

 may be due to the mixed nature of his material. His second, third, and fourth year 

 classes are not composed of fish maturing in their second, third, or fourth years, but are 

 accidental assemblages of fish that were in their second, third, and fourth years at the 

 time they came into his hands. His second-year class doubtless contained individuals 

 that would eventually mature variously in their second, third, fourth, and fifth years; 

 and his third-year class, fish that woidd mature in their third, fourth, and fifth years. 

 Under such conditions differential methods of growth of year classes could not be dis- 

 covered, even if they should exist. In Doctor Fraser's 1915 material it was indicated 

 that the 4-year fish that were preparing to spawn were larger than those of equal age 

 that would remain in the sea for another year. That result was in harmony with 

 our present findings but was not verified by him in the material of 1916. 

 Table 4. — Calculated Growth of Yukon King Salmon. 



In the following table (5) is given the average weight for all specimens of a given 

 length, the males and females being stated separately. The weights were taken with 

 an ordinary spring-balance scales reading to pounds and half pounds. No high degree 

 of accuracy can be claimed for this method, but the results present interesting terms 

 of comparison with the king salmon races of other rivers. The number of records 

 available for each length is insufficient for a wholly reliable average, a fact that will 

 explain irregularities in progression in the table. It will be noted that females of equal 

 length with males average slightly heavier than the latter. There was no noticeable 

 elongation of the jaws in the males at the time this material was examined. 



Table 5. — Average Weights by Units of Length, Yukon King Salmon, 1920. 



