The data discussed are from the commercial 

 catch and the spawning grounds in the areas 

 and years as follows: 



1. Alaska Peninsula commercial catch, 

 1951-57, 



2. Kodiak Island commercial catch, 1948-51 

 and 1955-57. 



3. Prince William Sound commercial catch, 

 1952-53 and 1956-58, and spawning grounds, 

 1952-57. 



DATA COLLECTION 



The commercial catch samples were 

 obtained chiefly at salmon canneries, but a 

 small number were taken on the Prince 

 William Sound fishing grounds during tagging 

 operations. The spawning ground samples were 

 collected during stream surveys and tag 

 recovery programs in Prince William Sound. 



Fish sampled at the canneries were caught 

 by traps, purse and beach seines, and gill nets. 

 The gear type was recorded, since certain 

 types, particularly gill nets, were probably 

 selective for size of fish and for sex. 



The length from mideye to fork of tail was 

 determined in millimeters by one of two 

 instruments devised by the Institute's staff for 

 measuring salmon in the field. These are 

 described by Duncan * and Thompson. ' Both 

 machines give a straight line measurement and 

 avoid much of the bias inherent in simple tape 

 measurements. 



For salmon taken on the spawning grounds 

 the mideye-fork measurement had to be re- 

 placed by a mideye to hypural plate measure- 

 ment because of eroded caudal fins on many of 

 the fish. All measurements were converted to 

 mideye-fork length by the formula 



Ye 1,1048 X- 1.1052 



where Y is the mideye-fork measurement 

 and X the hypural plate measurement. The 



1 Duncan, Rea E. 1956. Two measures of the length 

 of red salmon, Oncorhynchus nerka (Walbaum), their 

 relation and application in the study of the catch and 

 escapement in Bristol Bay, Alaska. M.S. Thesis, Uni- 

 versity of Washington, Seattle, 92 p. 



'Thompson, William F. Report in preparation at 

 Fisheries Research Institute. 



formula was calculated from paired measure- 

 ments obtained from 228 chum salmon taken 

 in traps on the Alaska Peninsula from June 20 

 to July 30, 1951. 



Scales for age determination were taken 

 from at least 20 percent of the fish measured 

 in each sample. In small samples, propor- 

 tionately more scales were taken. 



Sex ratios were obtained from counts of 

 fish as they passed along the cannery conveyor 

 belts, or from piles of fish in the cannery 

 bins. The number of fish used in determining 

 sex ratios was usually more than the number 

 measured for length. Fish in small deliveries 

 were frequently canned before a large sample 

 could be obtained. 



DATA ANALYSIS 



Data on length, age, and sex ratio were 

 arranged by date and locality of catch. 



Length measurements, recorded to the 

 nearest millimeter in the field, were grouped 

 in 1-cm. intervals. Some workers began their 

 groups with even centimeters, e.g., 570 mm.; 

 others began them 1 mm. larger, e.g., 571 mm. 

 Since the corresponding centimeter groups 

 would be 570-579 and 571-580, the midpoints 

 574.5 and 575 fell one-half millimeter apart. 

 This minor discrepancy was not considered in 

 analyzing the data. 



To determine age, plastic impressions suit- 

 able for microprojection were made from 

 scales that were mounted sculptured side out 

 on gummed cards. The procedure is outlined 

 by Koo (in press). Most of the scales were 

 read by Thorsteinson and Noerenberg, but a 

 few were read by Smith and other members of 

 the FRl staff. Agreement in scale interpretation 

 was tested by an independent reading of a set 

 of 200 scales by each author. Eight scales 

 were regenerated and judged unreadable by 

 each reader. Some disagreement existed in 

 interpreting the scales: 15 (7.5 percent) were 

 read as different ages by one or more readers. 

 In view of the difficulty in establishing the 

 position of chum salmon scale annuli (Henry, 

 1953), this disagreement may not be excessive. 

 It does suggest a need for standardizing 

 methods of interpreting chum salmon scales 

 and investigating patterns of scales from fish 

 of known ages. 



