Figure 4. — Scale of a chum salmon, age 0.3. 



f'^^-'y' -V^=^^:^' g0f^^. 



as those of the chum salmon scales. The pos- 

 terior field is clear; it has no prominent 

 markings. Any markings that do occur are 

 faint and ill-defined and tend to be concentric 

 with the scale margin, but not circuluslike. 

 See Mosher (1968) for additional information 

 on sockeye salmon scales. 



Occasionally sockeye salmon go directly to 

 the sea after emerging from the gravel; these 

 fish are called "ocean-run sockeye." Their 

 scales can be distinguished from the scales of 

 chum and ocean- run chinook salmon (the only 

 other species with which they might be con- 

 fused) by the difference inthe posterior field of 

 the three species: chum and chinook salmon 

 scales have strong radial striations; they are 

 absent on sockeye salmon scales (fig. 6). 



Coho (Silver) Salmon (figs. 7 and 8) 



Coho salmon scales are generally large 

 for the size of the fish. The fresh-water zone 

 varies in size and usually has 1 or 2 annual 

 marks. The large ocean zone generally has 

 only 1 annual mark, but occasionally two occur 

 in Alaskan and Asian fish. The circuli are 

 fairly distinct, as a rule. Often the scales are 

 pinched-in at the base of the anterior field. 



The scales of this species are fairly distinct 

 from those of the sockeye salmon and may be 

 distinguished from them by: 



1. More than six complete circuli (often 

 many) below the focus. 



Figure 5. — Scale of a sockeye salmon, age 2.3. 



salmon scales usually lack the "open" ap- 

 pearance of the chum salmon scales. Usually, 

 the anterior field is not as broad at the base, 

 where it joins the posterior field, and the 

 shoulders of the scale are not as prominent 



Figure 6. — Scales of ocean-run sockeye 

 salmon, ages 0.3 and 0.2. 



