We calculated average annual fry recruitment per 100 

 ha of lake area by dividing estimates of annual fry 

 recruitment (Table 9) by surface area (Table 1). The es- 



Table 9. — Approximate number of fry reeruited annually to lake 

 basins in the Naknek River system, assuming that 4()7o of the spawn- 

 ers were females with an average of 4,000 eggs/female. 



timates for the combined main-stem lakes and for each 

 of the external basins are: 



A first approximation of the desirable number of addi- 

 tional fry that could be supported in the Naknek system 

 is obtained by determining the number of fry needed to 

 bring the average annual recruitment of fry in North 

 Arm, Northwest Basin, and Brooks Lake up to the level 

 estimated for the main-stem lakes, i.e., 278,000 fry/100 

 ha (Table 10). 



Table l(). 



-.Additional soekeye salmon fry that are desirable for lake 

 basins in the Naknek River system. 



Additional Spawners Required 



With natural spawning, approximately 532,000 addi- 

 tional adults would be required in the combined escape- 

 ments to North Arm, Northwest Basin, and Brooks Lake 

 to generate the potential for an additional 76.6 million 

 fry recruits, i.e., 



North Arm 

 Northwest Basin 

 Brooks Lake 



Total 



331,000 



77,000 



124,000 



532,000. 



Adequacy of Natural Spawning Grounds 



Up to 5,(X)0 female soekeye salmon spawners can be 

 accommodated on 1 ha of good quality spawning ground 

 (Burgner et al. 1969). With a sex ratio of 40 females/100 

 spawners, 1 ha of spawning ground would accommodate 

 up to 12,500 spawners (both sexes). Thus, at least 42.6 ha 



of spawning ground would be required for an additional 

 532,000 adults in the Naknek .system. Under this 

 assumption, the existing and required number of spawn- 

 ers and natural spawning areas in North Arm, North- 

 west Basin, and Brooks Lake (Table 11) lead us to con- 

 clude that: 



1) The available natural spawning areas are inade- 

 quate for North Arm and Northwest Basin to meet the 

 stated goals of fry recruitment, even if the desired 

 spawner escapements could be provided. 



2) The available natural spawning areas are adequate 

 for Brooks Lake to meet the stated goals of fry recruit- 

 ment. Factors which may now be limiting fry recruit- 

 ment to Brooks Lake are underescapement of spawners 

 and poor survival conditions in existing spawning areas 

 or both. 



Table II. — Total existing and required number of spawru-rs 

 and spawning area for soekeye salmon in North Arm, North- 

 west Basin, and Brooks Lake. 



Basin 



Number ot spawners Spawnmgarea (ha) 

 .Additional Total 



Existing required Existing required 



North. Arm 20.000 331.IXH) 7.5 28.1 



.Northwest Basin 2,000 77,000 0.7 6.3 



Brooks Lake 21.000 124,000 18.0 11.4 



RECOMMENDATIONS AND CONCLUSIONS 



Any plan to increase recruitment of soekeye salmon fry 

 to North Arm, Northwest Basin, and Brooks Lake must 

 satisfy the requirements of soekeye salmon for repro- 

 duction and time of entry of juveniles into the lake 

 nursery area. Furthermore, such a plan should be eco- 

 nomically feasible and will have to be integrated with 

 resource management programs of the U.S. Park Service 

 and the Alaska Department of Fish and Game. We 

 consider four currently used methods to increase fry pro- 

 duction in each of the three external basins: 1) In- 

 crease the escapement of spawners into already accessi- 

 ble spawning grounds, 2) provide spawners access to 

 presently inaccessible stream areas by laddering impass- 

 able waterfalls, 3) construct spawning channels, and 

 4) construct hatcheries. Because of probable need to 

 revise any method undertaken, all attempts to enhance 

 the present stocks in the Naknek system should be care- 

 fully documented and evaluated. 



Spawning channels to supplement natural recruitment 

 of soekeye salmon fry to lakes have shown promise in 

 some instances in British Columbia, and should be con- 

 sidered in the Naknek system. Assuming a satisfactory 

 egg-to-fry survival of 70'^c in spawning channels (versus 

 9' c in natural spawning grounds), channels with a capac- 

 ity of approximately 27,000 female spawners (or about 

 67, .500 total spawners with a 40:60 sex ratio) would be re- 

 quired. This would mean about 5.4 ha of spawning sur- 

 face. 



A hatchery capable of producing 76.6 million fry would 

 probably cost less to construct than a spawning channel 

 and would require much le-ss space. A building to house 

 the required incubators would encompass about 1,300 

 m.- Provision of about 1,800 m- of exposed raceways 



