between the dorsal and adipose fins and three 

 rows up from the lateral line. The scale was 

 placed sculptured side up on a numbered spot 

 on a strip of gummed tape. The numbers on 

 the tape corresponded to numbers on water- 

 proof record sheets. Scales were not collected 

 after August 13 when scale resorption became 

 pronounced. Plastic impressions were later 

 made of the scales, using the method described 

 by Clutter and Whitesel (1956). Ages were 

 interpreted by viewing the impressions on a 

 scale projector. 



Most of the fish sampled (97.2 percent) were 

 in three age categories: 52, 27 percent; Sg, 

 8.1 percent; and 6o, 62.1 percent. The first 

 numeral denotes the total age of the fish and 

 the subscript the number of years in fresh 

 water, including the brood year as 1 year. For 

 instance, a 63 fish would have spent two grow- 

 ing seasons in fresh water and three in the sea. 

 Its scales would have five annuli, two formed 

 during its fresh-water life and three during 

 its ocean life. 



70 



60 



)i:5SS7CM. 



50 



"xn" 



25 30 35 40 45 50 55 60 65 70 

 MIDEYE FORK LENGTH (CM.) 



Figure 5. — Mideye-fork lengths ofadultsockeye salmon 

 sampled at Brooks Lake weir in 1957. 



Sex was determined by external characters. 

 Accurate determination was difficult early in 

 the season but became easier as fish matured. 

 The sex ratio indicated by samples from the 

 trap was 1:1 (328 males and 324 females). The 

 ratio did not change significantly through the 

 season. 



Snout-fork and mideye-fork lengths were 

 taken to the nearest one-half cm. by placing 

 the fish in a cradle on which metric tapes 

 for each type of length were mounted. Snout- 

 fork length was determined by placing the 

 fish in the cradle and measuring the distance 

 from the snout to the fork of the tail. Mideye- 

 fork length was taken by zeroing the tape at a 

 reference point about 10 cm. from the anterior 

 end of the cradle, sliding the fish backwards 

 until its eye was opposite the zero point, and 

 recording the distance on the tape at the fork 

 of the tail. Mideye-fork lengths are generally 

 preferred in salmon length analyses because 

 of the rapid growth of the snouts of salmon as 

 the fish approach maturity, particularly the 

 males. 



Mideye-fork lengths of females ranged from 

 39 to 62 cm., with a mean of 55.4; and of 

 males, from 29 to 66 cm., with a mean of 

 55.9 (fig. 5). Length distributions of sexes 

 were different: females were considerably 

 more uniform in size and were more closely 

 grouped around the mode than males. Both 

 sexes were made up two size groups, reflect- 

 ing an ocean life of either 2 or 3 years. 



Potential egg deposition was calculated from 

 counts of eggs from females selected from the 

 range of sizes in the run (table 1). Initially, 

 females were taken from the trap at the weir; 

 later those that died in gill net sampling were 

 also used. To insure a full complement of 

 eggs, females whose ovaries were sexually 

 mature were not used. The ovaries were 

 hardened in 10 percent formalin for 48 hour?. 

 At first one ovary per female was preserved; 

 the total volume by water displacement was 

 measured; and the three samples from that 

 ovary were counted and their volume meas- 

 ured by displacement. The ratio of number 

 of eggs to volume in the small samples was 

 then applied to the entire ovary and doubled 

 to estimate total number of eggs in both 

 ovaries. It soon became apparent that this 

 method produced erratic results, and an ac- 

 tual count of all eggs in one ovary from each 

 fish was begun. The procedure was again 

 modified when a difference was noted between 

 the numbers of eggs in the right and left 

 ovaries — a difference not always closely re- 

 lated to the size of the ovary — and all eggs 

 in both ovaries were subsequently counted. 

 Thirty-eight were counted in this manner to 

 provide an accurate basis for calculating total 



