River, Copper River (see figure 4 for location), 

 Knutson Complex, and lliamna River, though 

 the lliamna River had inadequate recoveries 

 in 1957. These four areas received 70 to 80 

 percent of the spawning populations actually 

 counted on lliamna Lake from 1957 to 1959. 

 Above lliamna Lake, only the Newhalen-Non- 

 dalton recovery point was adequately repre- 

 sented each year, and it was tested with the 

 lliamna Lake points each year. 



In addition to the separate recovery points 

 mentioned, the two principal geographic di- 

 visions of the system, lliamna Lake and Lake 

 Clark, were compared. This provided a clue 

 to the extent of segregation of spawning groups 

 within the two lake systems and showed 

 whether as units lliamna Lake and Lake 

 Clark fish were segregated in time of occur- 

 rence. If segregated, they might be inde- 

 pendently manageable. In this comparison all 

 recoveries in Newhalen River and above were 

 considered to be bound for Lake Clark. Ac- 

 tually, some, particularly those recovered 

 from Newhalen village, probably would have 

 spawned in Newhalen River, but most were 

 probably bound for Lake Clark. 



In applying chi-square tests to these data, 

 probability levels were interpreted in the 

 conventional manner. Compared groups which 

 yielded probability values less than p=0.05 

 were considered to have independent features 

 and consequently to be segregated in time of 

 occurrence at Igiugig. 



RESULTS AND DISCUSSION 



Recoveries from days of tagging in 

 each of the 3 years are shown in tables 

 1, 2, and 3. Recovery points which in- 

 clude personal-use fisheries are footnoted, 

 and consolidated recoveries appear as de- 

 scribed in the list of collective recovery 

 points, except in the case of Knutson Complex. 

 There a breakdown was warranted because 

 large numbers of recoveries were taken from 

 one or more of the constituent groups each 

 year. A few recoveries were received after the 

 principal analyses were complete. They are 

 grouped under an appropriate heading each 

 year, but enter into one calculation only — the 

 yearly recovery percentage. 



The tagging results will be shown and dis- 

 cussed in the sections dealing with (1) the 

 visual comparison and (2) the statistical analy- 

 ses, but the import of the personal-use fishery 

 in all these data warrants a section by itself. 

 It was instrumental in raising the total recovery 

 percentage from 6.9 percent in 1957 to 18.1 

 percent in 1958 and 18.3 percent in 1959. Our 

 own recoveries meanwhile accounted for a 

 relatively constant percentage; 3.2 percent 

 in 1957, 4.1 percent in 1958, and 6.5 percent 

 in 1959. The larger increase in 1959 was 

 probably the result of improved knowledge of 

 the spawning grounds of the system, or per- 

 haps the result of improved tagging and 

 handling techniques which resulted in fewer 

 tag losses and tagging mortalities. 



Effect of Personal- Use Fishery 



Personal-use recovery data seldom differ- 

 entiated between tags taken from fish captured 

 for personal use and those taken incidentally, 

 so it is not possible to give the exact recovery 

 percentages of fish taken in nets. Nevertheless, 

 personal-use recoveries rose from about 3.5 

 percent in 1957 to well in excess of 10 percent 

 in 1958 and 1959. 



Several factors were instrumental in in- 

 creasing the percentage returns. In probable 

 decreasing order of importance they are: 

 (1) A smaller tagged to untagged ratio, (2) a 

 better advertised tagging program, (3) better 

 communication with fishermen, (4) greater 

 familiarity with methods of handling tags and 

 therefore greater effort, to forward tags after 

 the season ended, and (5) an increase in the 

 rewara offered from 50 cents per tag in 1957 

 to $1 per tag in the other 2 years. 



Since personal-use fisheries contributed 

 substantially to the total of recoveries each 

 year, it is important that if inaccurate re- 

 covery locations are given or differential 

 fishing effort exists, they are recognized as 

 possible sources of error. 



If recovery locations are incorrectly re- 

 ported and a segregation of spawning groups 

 in time materializes, bias will result. Many 

 of the people who recovered these tags are 



10 



