might be desirable to allow tor short-term rearing ot 

 hatchery tr>' until physical and biological conditions in 

 the lake nursery waters become suitable. Although some 

 physical factors favor a hatchery system, spawning chan- 

 nels would obviate some of the biological problems of 

 hatcheries — especially genetic selection (matings occur 

 naturally in spawning channels) and reduction in spread- 

 ing of diseases. For example, IHN {infectious hema- 

 topoietic necrosis) virus is present in most stocks of sock- 

 eye salmon in Bristol Bay and will be an important factor 

 in the success or failure of artificial enhancement proj- 

 ects in the area (Grischkowsky and Amend 1976). 



North Arm 



About 90' f of the natural spawning in North Arm 

 occurs in Bay of Islands Creek (Fig. 1) which drains a 

 high tundra lake (Idavain Lake) and runs 27 km to North 

 Arm. Upstream migration of salmon in Bay of Islands 

 Creek is blocked by a waterfall 14 km from North Arm. 



Lack of suitable natural spawning area is most likely 

 the principal factor limiting production of sockeye 

 salmon in North Arm. Nevertheless the present avail- 

 able natural spawning area (7.5 ha) should support up to 

 100,000 spawners of both sexes or about 40,000 females — 

 recent escapements have been only about 20' r of this 

 number. 



Construction of a fish passage facility at the waterfall 

 on Bay of Islands Creek would provide salmon access to 

 an additional 13 km of stream and could increase the 

 available spawning area' in North Arm by about 50' c. 

 The feasibility of laddering the waterfall should be 

 investigated because of its potential for a significant low- 

 cost increase in natural production of fry. 



If the waterfall could be laddered and escapement of 

 sockeye salmon spawners to Bay of Islands Creek in- 

 creased to 150,000 adults, fry production should be about 



150,000 spawners x 0.4 ^male 

 spawner 



X 4,000 -^ESl. X 0.09 ^ = 21.6 million fry. 



fomalo c^aa 



female 



egg 



The recruitment of fry to North Arm would be increased 

 to 119,(XJ0 fry/HX) ha, whereas the suggested target re- 

 cruitment is 278,000 fry/100 ha (Table 10). 



It seems doubtful, therefore, that Bay of Islands Creek 

 has the potential to produce the additional fry needed to 

 achieve the target density even with laddering of the 

 waterfall. Therefore, consideration should be given to 

 artificial propagation of fry. The minimum required 

 capacity of either a spawning channel or a hatchery 

 would be about 28.9 million fry annually. 



A successful spawning channel or hatchery capable of 

 producing 28.9 million fry could generate an additional 



2.6 million smolts in the annual outmigration from North 

 Arm. At least a 3 yr full-scale operation would be re- 

 quired to realize maximum smolt production from the 

 lake. Should marine survival average 15*^0 of the ad- 

 ditional fish from North Arm leaving Naknek Lake as 

 smolts (average survival of natural smolts from the 

 Naknek system from 1956 to 1969 was about 19'( and for 

 the nearby Ugashik system 12'() (Pella and Jaenicke'), 

 an additional 390,000 sockeye salmon adults would be re- 

 cruited to the Bristol Bay fishing grounds. Three addi- 

 tional years would be needed after maximum smolt 

 production is achieved before these artificially produced 

 fish would become fully recruited to the fishery. It is like- 

 ly that about 200,000 to 300,000 (50'r to 70%) of the fish 

 produced artificially in the Naknek system and return- 

 ing to Bristol Bay would be caught in the fishery. This 

 means that 117,000 or more of them would escape the 

 fishery and return to Bay of Islands Creek, i.e., to the site 

 of the incubation facility. However, <30,000 of these 

 returning adults would be needed to restock a hatcher\' 

 facility (more would be needed for a spawning channel 

 because of lower efficiency), and the remainder could be 

 allowed to spawn in Bay of Islands Creek. This would en- 

 sure almost full utilization of the natural spawning area 

 in addition to the artificial facility. 



Northwest Basin 



Natural spawning areas are too limited in Northwest 

 Basin to accommodate increased escapements of wild 

 fish, and there are no opportunities to provide wild fish 

 access to potential new spawning areas. The only obvious 

 course of action for increasing recruitment of sockeye 

 salmon fry to Northwest Basin is through hatchery 

 propagation, because creeks entering Northwest Basin 

 are too small to satisfy the water requirements of a 

 spawning channel. 



About 11 million hatchery-produced fry (see Table 10) 

 would have to be added to the Northwest Basin to 

 achieve a target recruitment of 278,000 fry/km- of lake 

 nursery area. This would require a hatchery similar to 

 the facility already described for North Arm but about 

 one-third as large. However, costs of constructing and 

 operating such a facility on Northwest Basin would be 

 considerably more than one-third the cost of a larger 

 hatchery for North Arm. It would probably be more eco- 

 nomical to enlarge a hatchery at North Arm to raise 40 

 million fry instead of 30 million and to transplant 10 mil- 

 lion fry annually to Northwest Basin. To reduce possible 

 changes in genetic makeup of stocks of Northwest Basin, 

 only adult fish randomly selected from Northwest Basin 

 should be used to produce fry for that basin. Based on the 

 same calculation used for North Arm, the 11 million 

 hatchery fry could be expected to yield about 75,000 to 



''Unpublis)ied notes and stream survey data, Salmon Investigations 

 (1961-1963). Unpaginated. Northwest & Alaska Fislieries Center Auke 

 Bay Laboratory, Natl. Mar. Fish. Serv., NOAA, P.O. Box 155, Auke Bay, 

 AK 99821. 



'Pella, J. J., and H. W. Jaenicke. 1975. Some observations on the biol- 

 ogy- and variations of populations of sockeye salmon of the Naknek and 

 Ugashik systems of Bristol Bay, Alaska, 1956-69. Processed report, 133 p. 

 Northwest & Alaska Fisheries Center Auke Bay Laboratory-, Natl. Mar. 

 Fish. Serv., NOA.A. P.O. Box 155, Auke Bay, AK 99821. 



