3. The important spawning streanns 

 are quite long, often 10 to 20 miles, and 

 have fish distributed over the entire 

 length. Ground surveys and sampling 

 could normally cover only relatively short 

 sections. If distribution of age groups 

 was uneven over the whole length of the 

 river, then sampling one or two sections 

 could lead to biased results. 



4. In some areas spawning took place 

 over a long period of time, and there 

 were instances of early and late popula- 

 tions. Owing to practical difficulties,, re- 

 peated visits to a spawning ground were 

 not made, and therefore the data used 

 may be representative of one population 

 but not the other. 



5. The two age groups were not evenly 

 distributed over all spawning grounds. 

 While 1. fish predominated in one local- 

 ity, 2. fish predominated in another 

 (table 6). 



listed were not representative of the 

 population; they could have been selective 

 in favor of Z, fish because of timing, 

 selection of a certain section of a stream, 

 or other reasons. 



1957 Samples . --Samples from only two 

 spawning ground areas, Nick G. Creek 

 and Belinda Creek, had significantly higher 

 percentages of I. fish than samples from 

 the Kvichak River (table 6), but both 

 these localities are insignificant spawn- 

 ing creeks (table 3). Unless the population 

 in these creeks had been grossly under- 

 estimated, which is improbable, weighting 

 cannot be a main cause for the discrep- 

 ancy here. 



The two factors that caused nonrepre- 

 sentative samples in 1956 might also have 

 caused them in 1957. Kokhanok Creek and 

 ELiamna River, for instance, while both 

 important as spawning areas, were not 

 sampled. 



The variable ratios of the two age groups 

 on the spawning grounds occur in each of 

 the 3 years and are occasionally extreme. 

 This fact, coupled with the uneven distribu- 

 tion of population size on the various 

 spawning grounds, makes proper sampling 

 and weighting extremely difficult, if not 

 impossible. 



The above are general considerations 

 of some theoretical factors that may 

 cause spawning ground sampling to be 

 nonrepresentative of the escapement pop- 

 ulation. Let us now examine each year 

 individually. 



1956 Samples . --Samples from only one 

 spawning grovind area, Tazimina River, 

 has a higher percentage of 1_. fish than 

 samples from the Kvichak River (table 6), 

 but Tazinnina River was relatively unim- 

 portant as a spawning area (table 3). 

 Therefore, weighting cannot be considered 

 here as the main cause of the discrep- 

 ancy between spawning ground and Kvichak 

 River sampling. 



Other factors that could have caused 

 the discrepancy are: (1) Localities not 

 sampled for scales had large populations 

 with higher than 84 percent 1_. fish. 

 (2) The samples obtained from localities 



1958 Samples . - -Age composition of 

 spawning ground samples agreed with 

 that of Kvichak River samples. While in 

 2 previous years most spawning localities 

 had higher percentage of Z. fish than 

 Kvichak River samples, in 1958 most 

 spawning localities had higher percentages 

 of 1_. fish (table 6). In fact, the unweighted 

 mean is 21 percent for J_. fish in 1958, 

 compared with the weighted nnean of 11. 

 Obviously then, weighting here has played 

 a big role in bringing about the agreement 

 between spawning ground and Kvichak 

 River samples. This can be noted espe- 

 cially in the case of Newhalen River 

 (table 3). 



Only 8 locations were sampled in 1958 

 compared with 10 in either 1956 or 1957, 

 and the sampling areas in 1958 were, in 

 general, quite different from those of the 

 other 2 years (table 3). Three new areas. 

 Flat Islands, Surprise Creek, and 

 Lonesome Bay, which were insignificant 

 producers, were added in 1958, while 

 some of the more important areas, Iliamna 

 River, Kijik Lake, and Finger Beaches, 

 were not sampled. Therefore, the excellent 

 agreement between Kvichak River and 

 spawning ground samples in 1958 is 

 probably a fortuitous occurrence rather 

 than a result of more representative 

 sampling. 



