Possible Management Procedures for Increasing 



Production of Sockeye Salmon Smolts in the 



Naknek River System, Bristol Bay, Alaska 



ROBERT J. ELLIS and WILLIAM J. McNEIL' 

 ABSTRACT 



About .'t.^'/r of the Naknek River system is greatly underutilized by juvenile sockeye salmon, 

 Oncorhynchtts nerka. In two basins the cause seems to be a lack of spawning grounds, and in a third 

 basin the cause may be too few spawners or poor quality spawning grounds. The annual yield of adult 

 sockeye salmon to the fishery could probably be increased by about 200, 000 to ;i(M).OlM) fish by increas- 

 ing the production of smolts. Artificial production of fry. along with improving or increasing the 

 spawning environments, is recommended. The numbers of adult females, eggs, and fry required to ful- 

 ly seed the three underutilized basins are discussed. Attempts lo Increase the production of sockeye 

 salmon in the Naknek Kiver system must be accompanied by detailed biological studies to determine 

 optimum seeding levels and establish cause-and-effect relations. 



INTRODUCTION 



The sockeye salmon, Oncorhynchus nerka, resources of 

 Bristol Bay, Alaska, are large and valuable and have 

 been heavily fished since about 1900 (Burgner et al. 

 1969). The National Marine Fisheries Service (under 

 various names) began research on the freshwater and 

 early marine life of the sockeye salmon in Bristol Bay 

 before 1920, and since the early 1940's much of this work 

 has been done in the Naknek River system. 



The studies on sockeye salmon of the Naknek system 

 have included most aspects of their freshwater biology, 

 both biological and physical. Much is known about fac- 

 tors that appear to limit the number of young salmon 

 produced by the system and the number of returning 

 adults (Burgner et al. 1969). Within broad limits, the 

 number of returning adults produced in seawater in- 

 creases as the number of young leaving freshwater as 

 smolts increases. In contrast, above a certain minimum, 

 the number of smolts produced in freshwater appears to 

 be independent of the number of parent spawners — 

 smolt production is limited by freshwater spawning or 

 nursery areas. 



In this paper we briefly review information available in 

 the literature on 1) physical aspects and relative pro- 

 ductivity of the various lakes of the Naknek system, 

 2) abundance and distribution of spawning grounds and 

 spawning adults, and 3) abundance, distribution, and 

 growth of young sockeye salmon and associated species of 

 fish. We then consider factors that appear to be limiting 

 production of juvenile sockeye salmon in the Naknek 

 system and suggest management procedures that might 



'Northwest and Alaska Fisheries Center .^uke Bay Laboratory'. 

 National Marine Fisheries Service, NOAA, P.O. Box 155, Auke Bay, 

 AK 99821. 



significantly increase the production of smolts (juveniles 

 going to the ocean). 



PHYSICAL ASPECTS AND PRODUCTIVITY 

 OF LAKES 



In freshwater, juvenile sockeye salmon typically 

 occupy four successive habitats for varying 

 periods: spawning gravels of streams or lake beaches for 

 several months, littoral of lakes for a few weeks, open- 

 water areas of the lakes for several months to 2 or 3 yr, 

 and an outlet river through which the smolts travel for a 

 few hours or days to reach the ocean. Two factors seem 

 most likely to limit the production of smolts: the quan- 

 tity and quality of spawning grounds, which may limit 

 the number of fry produced, and the productivity of the 

 pelagic waters of the lakes where juvenile salmon do most 

 of their feeding and growing. 



The Naknek system consists of four major lakes — 

 Coville, Grosvenor, Naknek, and Brooks — and an outlet 

 stream that connects these lakes to the ocean — Naknek 

 River (Fig. 1). Naknek Lake differs from the others in 

 that it consists of five regions which appear to be phys- 

 ically and biologically discrete. These regions are treated 

 as separate basins in our research — Iliuk Arm, South 

 Bay, West End, North Arm, and Northwest Basin. 

 Because of their relative locations and to facilitate our 

 discussion in this paper, we designate five of these lakes 

 or basins as main-stem basins and three as external 

 basins (Table 1). Two high mountain lakes, Hammersly 

 and Murray, are tributary to Coville Lake and receive 

 only a few adult sockeye salmon each year so they are not 

 considered here. In general the lakes of the Naknek 

 system are deep, have little littoral area, and are oligo- 

 trophic (Burgner et al. 1969). The portion of each lake 



