was sufficiently large to account for a substantial 

 portion of the 5 2 age group represented in the 

 Naknek River samples, but lacking in the samples 

 from the other spawning grounds. 



Other probable spawning areas in the Naknek 

 system include the turbid Savonoski River (fig. 

 2) and most of its clear-water tributary streams 

 and deepwater beach spawning areas as yet un- 

 known. None of these were sampled in 1962. 



Regardless of the spawning areas left un- 

 sampled, it seems clear from the evidence pre- 

 sented that there is segregation by age on the 

 spawning grounds of the Naknek River system. 

 This agrees with the conclusion reached by Koo 

 and Smith (1960) for various spawning areas of 

 the Kvichak River system in Bristol Bay. 



Theoretically this segregation could be of great 

 importance in managing individual spawning 

 populations as they pass through the fishery. 

 If certain spawning grounds are characterized by 

 populations composed predominantly of fish of 

 2-ocean age and others of 3-ocean age, the effects 

 of the gill net fishery, which is selective for large 

 fish, would be unequal for each group. A knowl- 

 edge of any consistencies in the age structure of 

 individual spawning populations would, therefore, 

 provide those charged with managing the Naknek 

 sockeye salmon stocks with a means of gaging the 

 possible effects of the fishery on these populations. 

 Many years of data, however, will be required 

 before consistencies in the age structure of indi- 

 vidual spawning populations could show up. 



The results presented above suggest two im- 

 portant lines of future investigation: (1) A com- 

 plete survey of all beach and turbid water areas of 

 the Naknek system for spawning areas that were 

 previously undetected, and (2) continued study 

 of segregation by age on the spawning grounds to 

 uncover any consistencies in the age group struc- 

 ture of individual spawning populations. 



SUMMARY 



1. Tag and recovery techniques were used to 

 determine the extent of segregation by time of 

 occurrence for the individual spawning populations 

 in the sockeye salmon run of Naknek River, 

 Alaska. Salmon were tagged daily on the Naknek 

 River at a site located about 24 miles above the 



mouth of the river. A different tag color combina- 

 tion was used to identify each day of tagging. 

 Subsequent recovery or observations of tagged 

 fish on the spawning grounds and the relative 

 abundance of each color combination present 

 provided the basis for determining the extent of 

 segregation. 



2. Results lead to the following conclusions: 

 (a) Segregation of individual Naknek spawning 

 populations by the time of occurrence in the trunk 

 stream was minimal. As a consequence, most 

 spawning grounds derived their fish from all parts 

 of the run and, generally, in proportion to the 

 size of the daily escapement. Exceptions were 

 Brooks River, which received a disproportionate 

 share of early-run spawners, and Grosvenor 

 River, which seemed lacking in early-run fish. 

 (6) The short duration of the Naknek run is 

 probably the most reasonable explanation for the 

 intermingling of most spawning groups, (c) Be- 

 cause of the lack of segregation in time, it is un- 

 likely that spawning populations can be managed 

 on an individual basis in the fishery. The Naknek 

 sockeye salmon stocks will probably be most 

 effectively managed, as a whole, by securing 

 spawning escapement proportional to the daily 

 abundance of fish in the fishery. 



3. No seasonal trends in age composition could 

 be described as characteristic of the Naknek run, 

 probably because of intermingling of most of the 

 spawning populations during the run. 



4. Fish from all known spawning grounds of the 

 Naknek system were sampled to determine the 

 age composition of populations associated with 

 the separate spawning areas. Spawning popula- 

 tions have age characteristics that differ signifi- 

 cantly from one to another and, therefore, show 

 segregation by age on the spawning grounds of the 

 Naknek River system. Continued study of 

 segregation by age on the spawning grounds is 

 necessary for a number of years to determine if the 

 age structure of specific spawning populations 

 conforms to specific patterns. It is likely that 

 major spawning population's as yet undetected 

 and, therefore, not sampled in this experiment 

 exist in the Naknek system. A thorough survey 

 to locate and determine the magnitude and age 

 characteristics of these populations, if any, is 

 needed for a complete understanding of segrega- 

 tion and the productive importance of individual 

 spawning areas within the Naknek system. 



SALMON SPAWNING POPULATIONS IN NAKNEK RIVER 



477 



