River.* Therefore, weighting by the daily 

 counts should be reliable. 



3. The sampling locality: Ideally fish 

 should be seined from both shores in any 

 day of sampling in order to avoid any 

 possible selection of segregated groups 

 of fish. Seining on both shores with equal 

 effort was not achieved because of the 

 difficulties mentioned earlier, and there- 

 fore may be a source of error. However, 

 from tagging studies, the junior author 

 (unpublished study) found that there was 

 no evidence of stratification of fish on the 

 spawning grounds, and at the same tinne 

 individual areas contained tagged fish 

 from each shore about in proportion to the 

 numbers tagged there. 



4. The sampling gear: Is it possible 

 that the beach seine might be selective 

 so that more 2. fish avoid the net and 

 appear on the spawning grounds ? This 

 might happen if 2. fish were larger than 

 1. fish, either by their original difference 

 in size or by their differential associa- 

 tion with marine age, namely 63 and 42- 

 The original difference in length, which 

 amounts to about 20 percent during smolt 

 stage, diminishes rapidly in the adults 

 because of the overwhelming marine 

 growth. Therefore, it is improbable that 

 net selection could result on that account. 

 The possibility of differential association 

 of marine and freshwater ages can be 



ruled out since in 1956 the escapement 

 was composed almost entirely (99 per- 

 cent of 3} fish. 



Fron-i the above considerations, we 

 conclude that sampling in the Kvichak 

 River was probably adequate, and the 

 discrepancy in age composition between 

 Kvichak River and spawning ground 

 samples must be traced to the latter. 



Spawning Ground Sampling 



Possible sources of sampling error are 

 as follows: 



1. Although the sampling crew had tried 

 to cover most major spawning areas, a 

 number of places were left unsurveyed, 

 either because of time and personnel 

 limitations or because of practical diffi- 

 culties. In 1957, for instance, sampling 

 areas accoxinted for only 56 percent of 

 the peak population estimated from aerial 

 surveys. 



2. Only a small portion (10 to 18 per- 

 cent, table 2) of the actual escapement 

 could be accounted for by spawning ground 

 estimates. The weighting of age groups 

 by localities was done according to rela- 

 tive population estimates, the accuracy 

 of which could not be measured. 



•4 The following is quoted from "Progress Report and Recommendations for 1957"byAdministrationof Alaska Fisheries, Juneau, 

 Alaska, November 1956, p. 19: 



"2. Evaluation of Towers for Counting Adult N4igrant Red 

 Salmon in Bristol Bay. 



"A critical comparison of weir and tower counts was made 

 on the Egegil< River during the period July 12 to July 30 when 

 somewhat more than a million adult fish migrated upstream 

 (Figure 34). 



"After finding out the habits of the fish and locating towers 

 in the proper places, a completely satisfact jry count of the 

 migrants was obtained. On two days during the early part of 

 the run, fish by-passed the towers which were not located 

 properly. During the balance of the migration, estimates of the 

 total run from tower averaged only 1.6 percent lower than 

 estimates made at the weir." 



EGEGIK RIVER RED SALMON 

 ENUMERA TION — 1956 



WEIR COUNTS 

 UPSTREAM TOWER 

 COUNTS 



12 14 16 18 20 22 24 26 28 30 

 JULY 



