old fish are more abundant. Connnnercially 

 caught sockeye salmon range from "jacks" 

 which return to spawn after 1 year at sea as 2- 

 or 3- year olds to 5-, 6-,orrarely7-year olds. 

 Three-year-old sockeye salmon (in their fourth 

 year) with 2 years at sea predominate in the 

 Fraser and Columbia Rivers, but the 5- and 

 6-year olds are more abundant in Alaskan and 

 Asian waters. Commercially caught pink sal- 

 mon are almost invariably in their second 

 year, with only one winter zone on 

 the scales. 



Although coho and chinook salmon and steel- 

 head trout are often caught on their spawning 

 migrations, they are also taken at any age up 

 to nnaturity in coastal waters by trolling with 

 baits and lures. Coho salnnon usually mature 



after 1 year at sea--in their third year in the 

 southern areas and in their fourth year in the 

 northern localities. Some chinook salmon ma- 

 ture after one or two summers at sea ("jacks" 

 as 2- or 3-year olds). Others may require as 

 many as 6 or 7 years to reach maturity. 

 Steelhead trout of any age up to a maximum 

 of 5, 6, or even 7 years old may be caught. 



In the Japanese offshore commercialfishing 

 and in research fishing by Canada, Japan, and 

 the United States, fish of all ages and stages 

 of maturity are now caught from soon after 

 they reach the sea to just before they enter 

 their natal streams on the spawning migration. 

 Ages may not be as important a diagnostic 

 feature of species for these fish as for adults 

 taken inshore. 



SPECIES IDENTIFICATION FROM SCALES 



This section of the paper is divided into 

 3 parts: 



1. Descriptions and photographs of the 

 scales of each species. Differences among 

 species are noted, including those which 

 are not diagnostic enough to enter into the 

 dichotomous key, but which may assist 

 in identification of species, especially 

 when the differences between species are 

 small. 



2. A key to the species identification 

 of scales of salnnon and steelhead trout 

 taken in the ocean or in fresh water in the 

 year of spawning. 



3. A section on the species identifica- 

 tion of scales of juvenile fish. 



DESCRIPTION OF THE SCALES OF THE 

 VARIOUS SPECIES 



Pink Salmon (fig. 3) 



Pink salmon scales are easily distinguished 

 by their snnall size relative to the size of the 

 fish, single winter zone or year mark, and 

 absence of a fresh-water nucleus. Scales of 

 pink salmon are more variable in their pos- 

 terior field than the other species; only a small 

 percentage, however, have radial striations, 

 circuli in the posterior field, or have more 

 than six complete circuli below the focus of 

 the scale. 



Chum Salmon (fig. 4) 



Scales of chum salmon can be distinguished 

 from those of the other species by the absence 

 of a fresh-water nucleus, less than seven 

 circuli complete below the focus (usually 

 to 3), heavy granular reticulations between 

 the two fields, rough sculpturing of the posterior 

 field with radial striations, and no circuli or 





m 





i^^.^..^^ 



Figure 3. — Scales of pink salmon, age 0.1. 



segments of circuli in the posterior field. In 

 addition they usually have large scales for the 

 size of the fish. The whole scale has a "bolder", 

 more open appearance, with broader shoulders 

 than the scales of the other species. 



Sockeye (Red) Salmon (fig. 5) 



Scales of sockeye salmon generally have a 

 pronounced fresh- water nucleus often with one 

 or more winter marks. The ocean zone has 

 two or three winter marks as a rule, except 

 for the "jacks" which have one. Generally, no 

 more than six circuli are complete below the 

 focus. The circuli are generally not as bold or 

 distinct as those of chum salmon; thus, sockeye 



