peak counts and partly due to the incom- 

 plete coverage of spawning grounds be- 

 cause of certain conditions. For instance, 

 Lake Clark and many of its tributaries, 

 important as they are as spawning areas, 

 were not surveyed because of their turbid 

 glacial water. Comparative sampling data 

 on the spawning grounds are shown in 

 table 2. 



Only the more important spawning areas 

 were sampled each year. An area im- 

 portant as spawning grounds in one year 

 may not be so in another. Also, owing to 

 weather or other difficulties, even locali- 

 ties that were important as spawning 

 grounds were not visited in some years. 

 Therefore, not all localities sampled in 

 the first year were sampled in succeed- 

 ing years. Of the 16 localities sampled 

 in the 3 years, only 3 were sampled 

 consistently in all 3 years; 6 in 2 years, 

 and 7 in 1 year (table 3). The names and 

 locations of the sampling areas are shown 

 in figure 1. In 1956, the summed peak 

 count of the scale sampling areas (marked 

 by X in table 3) was about 81 percent of 

 the total from all localities; in 1957, 56 

 percent; and in 1958, 73 percent. 



General Methods 



All scales were removed from a speci- 

 fied area on the body about midway between 

 the dorsal and adipose fins and within 5 

 scale rows above or below the lateral 

 line. They were mounted on gummed cards, 

 and impressions were made on cellulose 

 acetate for examination under the micro- 

 scope and projector after the method 

 described by Koo (1955).' Scales with 



^Biology of the red salmon, Dncorhynclius nerhn (Walbaum) 

 of Bristol Bay. Alaska, as revealed by a study of their scales. 

 Ph.D. Thesis. University of Washington, Seattle. 164 pp. 

 (Available on interllbrary loan or by microfilm service.) 



regenerated nuclear areas were dis- 

 carded. Those collected from the Kvichak 

 River were read by one author and those 

 from spawning grounds by the other. A 

 certain portion of the samples were read 

 by both authors to determine whether the 

 two authors agreed, in general, in their 

 interpretation of scale marks. The validity 

 of scale markings read as annuli is not 

 discussed here because it is not important 

 to this study. Table 4 shows the percentage 

 of agreement in the two readings. 



Only freshwater age was determined, 

 and only two age groups were involved, 

 either one annulus (designated here as 1.), 

 or two annuli (designated here as 2.). Two 

 types of errors resulted in disagreement 

 between readers: (1) Scales read as 1. by 

 the first reader and 2. by the second, and 

 (2) scales read as 2. by the first reader 

 and J., by the second. For the 23 dis- 

 agreements encountered over the 3-year 

 period (table 4), 12 were errors of the 

 first type, and 1 1 were errors of the second 

 type. Disagreements between reader s thus 

 tended to average out. 



Comparative readings by the two authors 

 indicate a high degree of agreement. 

 Therefore, any major difference in age 

 composition between Kvichak River and 

 spawning ground samples cannot be 

 attributed to difference in interpretation 

 of scale marks. 



FRESHWATER AGE COMPOSITION OF 



KVICHAK RIVER AND SPAWNING 



GROUND SAMPLES 



In Kvichak River samples, percentages 

 of age groups \. and 2. were calculated 

 for each day a sample was taken. They 

 were then weighted according to the daily 



Table 2. — Samples of adult red salmon from the Kvichak spawning grounds, 1956-58 



Year 



Peak population 



estimate from 

 aerial surveys 



Number of 



scales 

 collected 



Scale sample 



Percent 



of total 



escapement 



1956 

 1957 

 1958 



1, "440, 000 



301,000 



96,000 



1,050 

 910 



0.011 

 0.031 

 0.159 



