ductive, and has made up most of the Naknek- 

 Kvichak commercial catch. The true size of the 

 Naknek run in any one year is difficult to assess 

 because that portion of the run taken in the com- 

 mercial fishery intermingles in the Naknek- 

 Kvichak fishing district (fig. 1) with sockeye 

 salmon bound for several of the other rivers 

 entering Bristol Bay. In most years the total 

 catch of sockeye salmon in this district has 

 equaled or exceeded the total spawning escape- 

 ment to these rivers. Spawning escapements in 

 excess of 2 million have been estimated for the 

 Naknek in recent years, giving some indication of 

 the productivity of this system. 



Commercial fishing for sockeye salmon in 

 Bristol Bay is done almost entirely by a gill net 

 fishery which is intense and efficient and capable 

 of taking most of the fish in a district during an 

 open fishing period, essentially eliminating spawn- 

 ing escapement. In the present management of 

 the Naknek stocks the entire run is treated as a 

 homogeneous mixture; therefore, to allow spawn- 

 ing escapement from all parts of the run, the 

 fishery is regulated by periodically opening and 

 closing the Naknek-Kvichak district to fishing. 



The spawning grounds of the Naknek River 

 system include a complex of four lakes, Naknek, 

 Brooks, Grosvenor, and Coville, and intercon- 

 necting and tributary streams (fig. 2). The 

 annual sockeye salmon migration to the Naknek 

 includes fish destined for interconnecting streams, 

 the tributary stream, and beach spawning areas 

 of all four lakes. Before this study, it was not 

 known if spawning groups could be identified by 

 time of migration. 



Figure 2. — Naknek River system, showing the location 

 of tagging site, weirs, and observation towers. 



The Naknek run is of relatively short duration, 

 normally occurring between mid-June and late 

 July, however, spawning takes place over a con- 

 siderably longer period of time. Depending on 

 the area utilized, spawning may begin as early as 

 late July or as late as early October. The peaks 

 of spawning activity occur about mid-August on 

 the lake tributary streams and during the latter 

 part of September on the interconnecting streams 

 and lake beaches. 



Segregation of populations by age groups by 

 time of occurrence in the run and on the spawning 

 grounds has been reported to occur in other river 

 systems, but before this study, little was known 

 of the extent to which this occurred in the Naknek 

 River system. 



MATERIALS AND METHODS 



Of the various methods now used to identify 

 races of salmon, the tag and recovery technique 

 supplemented by age analysis was considered to 

 be the most direct means for accomplishing the 

 purposes of this study. 



TAGGING OPERATIONS 



Salmon were captured and tagged daily in 1962 

 by Bureau of Commercial Fisheries personnel at 

 a site on the south bank of the Naknek River 

 24 miles above the mouth (fig. 2). Most of the 

 upstream migration in the vicinity of the tagging 

 site occurs along the south bank of the river. 



Sockeye salmon ascending the trunk streams 

 characteristically migrate in a narrow band close 

 to shore. Specimens for tagging were caught in a 

 "seine trap" (fig. 3), consisting of a 400- by 12- 

 foot beach seine having 3-inch mesh (stretch 

 measure). The seine was set by boat from shore 

 and attached to a steel stake driven into the river 

 bottom 150 feet offshore. The remaining 250 

 feet of seine was allowed to trail downstream with 

 the current, forming a partial rectangular enclosure 

 of about 38,000 square feet open on the down- 

 stream side. The free end of the net was attached 

 to shore by a rope. The upstream portion of the 

 seine attached to the stake was fitted with a trip 

 lever that could be released by a rope leading to 

 shore. When an observer located in a tower on 

 the river bank saw fish entering the enclosure, 

 the lever was tripped, releasing the net from the 

 stake and allowing it to be carried downstream 

 around the fish. Meanwhile, the free downstream 



SALMON SPAWNING POPULATIONS IN NAKNEK RIVER 



463 



