ocean age of the fish, but only those that were 

 replaced before the first winter reveal the total 

 age. 



Regenerated scales may be used to back-calcu- 

 late the year of scale loss; for instance, scales 

 taken from scars on the body of the fish may 

 show the number of years since the injury. This 

 technique can be applied to fish with gill net 

 marks. 



The scales on plate 17 are arranged to show 

 increasing amounts of regeneration. Figures A 

 and B, D and E, and F and G are pairs; the 

 large scale of each pair shows about the same 

 amount of regeneration of the fresh-water zone 

 as the small scale of the pair. To illustrate how 

 regenerated scales may be used to date an in- 

 jury that removed the original scale, I arbitrar- 

 ily assume that all the scales from adult fish on 

 this plate were collected in the summer of 1965. 



Scale A. A scale from an adult cockeye salmon 

 shows regeneration of only a few cen- 

 tral circuli ; the fish spent one winter 

 in fresh water and two winters in the 

 ocean. This scale replaced one lost in 

 1962, a short time after the original 

 scale was foi-med. 



Scale B. A scale from a young sockeye salmon 

 taken in fresh water shows regenera- 

 tion that involves only a few circuli. At 

 adult size the scale of this fish would 

 look much like scale A. 



Scale C. A scale from a young sockeye salmon. 

 This scale shows a larger area of re- 

 generation. 



Scale D. A scale from a young sockeye salmon 

 shows regeneration of about half of 

 the scale. 



Scale E. A scale from an adult sockeye salmon 

 shows regeneration that involves about 

 half of the fresh-water zone ( scale D ) . 

 This scale shows that the fish spent 

 two winters in the sea and at least 

 one in fresh water. This fish also lost 

 the original scale in 1962; the age of 

 the fish at tliat time could have been 

 from a few months to over a year. The 

 total age of the fish cannot be deter- 

 mined from this scale. 



Scale F. A scale from a young sockeye salmon 

 shows regeneration of most of the 

 scale. 



Scale G. A scale from an adult sockeye salmon 

 shows regeneration of the entire fresh- 

 water zone ( scale F ) . This scale shows 

 only that the fish spent three winters 

 in the ocean and tliat the scale re- 

 placed one lost in 1962. 



Scale H. A scale from an adult sockeye salmon 

 shows regeneration of fresh-water 

 growlh and most of the first summer 

 at sea. This scale shows that the fish 

 spent two winters at sea after it lost 

 the original scale in the summer of 

 1963. 



Scale I. A scale from an adult sockeye salmon 

 with only the winter and last sum- 

 mer's gro\\d;h completed before cap- 

 ture. Because of extensive regenera- 

 tion, even the ocean age of this fish 

 cannot be determined. The scale is of 

 slightly atypical shape; it replaced 

 one lost in the summer of 1964. 



Scale J. A scale from an adult sockeye sal- 

 mon with only a few months' growth 

 complete. The scale is atypical in size 

 and shape; it replaced one lost in the 

 spring of 1965 and is unusable for age 

 or racial studies. 



RESORBED SCALES (Plate 18) 



At some time during the migi'ation toward 

 their spa\raing streains, sockeye salmon stop 

 feeding and subsist on stored fat and other body 

 materials. As they v/ork their way up the 

 streams, the material in the scales is resorbed. 

 Resorption generally starts along the lateral mar- 

 gins of the scale near the base of the anterior 

 field and progi-esses until the whole scale margin 

 is affected. Scales taken from spa-wning fish may 

 have only a small central portion left. On most 

 resorbed scales taken from spawning fish the 

 fresh-water gro-wih may still be present, but 

 usually the ocean growth zones are too badly 

 eroded to pei-mit determination of total age with 

 confidence. With greatly resorbed scales, study 

 of otoliths or length frequencies may be required 

 to estimate the age of the fish. 



270 



U.S. FISH AND WILDLIFE SERVICE 



