Consistent yearly appearance of 



age-0 walleye pollock, 



Theragra chalcogramma, 



at a coastal site 



in southeastern Alaska, 



1973-1994 



H. Richard Carlson 



Auke Bay Laboratory, Alaska Fisheries Science Center 



National Marine Fisheries Service, NOAA 



1 1305 Glacier Highway, Juneau, AK 99801-8626 



Walleye pollock, Theragra chalco- 

 gramma, are found throughout the 

 North Pacific Ocean; their abun- 

 dance is centered in the Bering Sea 

 and Gulf of Alaska, where they are 

 of great economic importance and 

 a key species in the ecosystem. Pol- 

 lock presently support the world's 

 largest single-species fishery, aver- 

 aging over 5 million metric tons (t) 

 annual catch since the early 1980's 

 (Lloyd and Davis, 1989). They made 

 up 5% (4.9 million t) of the total 

 world catch of all species in 1991 

 (FAO, 1993). 



Adult pollock are found over the 

 continental shelf, mainly in the 

 mid-range of the water column; the 

 greatest biomass has been found be- 

 tween 100 and 300 m deep (Smith, 

 1981). Most spawning takes place 

 in spring (Kendall and Picquelle, 

 1990), during late March and April 

 in the Gulf of Alaska (Kim, 1989). 

 Spawning pollock broadcast pe- 

 lagic, nonadhesive eggs in mid-wa- 

 ter (Serobaba, 1974). 



Larval pollock are found near the 

 surface and in mid-water, above 

 100-m depths and they make diel 

 vertical migrations (Serobaba, 

 1974; Kamba, 1977; Pritchett and 

 Haldorson, 1989). In Southeast 

 Alaska, abundant larvae (5-7 mm 

 standard length [SL]) were found 



during mid-May in Auke Bay; peak 

 hatching occurred about 28 April 

 (Haldorson et al., 1990). Later- 

 stage larvae (4-17 mm SL) were 

 found throughout the water column 

 from near surface to 55 m depths 

 during June and July in Auke Bay; 

 they became demersal (absent from 

 the plankton, found only near the 

 bottom during day) after reaching 

 20-30 mm SL (Salveson, 1984). 



The presence of young pollock 

 has been documented from mid- 

 water and near bottom depths dur- 

 ing summer (Smith, 1981; Krieger 

 and Wing, 1986; Hinckley et al., 

 1991) and fall (Carlson et al. 1 ). 

 Available information on their dis- 

 tribution generally covers only a 

 few years or wide geographic areas. 

 During August-December trawl 

 surveys from 1969 through 1981, 

 age-0 pollock were taken near the 

 bottom at 30-60 m depths at vari- 

 ous bays and inlets in southeast- 

 ern Alaska (Carlson et al. 1 ). 



Although general distribution of 

 some young pollock is documented, 

 patterns of long-term use of specific 

 sites by successive generations of 

 young-of-the-year (age-0) pollock 

 are little known. Because pollock 

 year-class strength can be estab- 

 lished after the larval stage (Bailey 

 and Spring, 1992), sampling these 



sites may provide useful informa- 

 tion for establishing an index of 

 population characteristics. 



This paper documents the yearly 

 first appearance, from 1973 through 

 1994, of newly metamorphosed juve- 

 nile walleye pollock at a specific site 

 in Auke Bay, Southeast Alaska, and 

 describes the young fish living near 

 bottom during their initial growing 

 season. 



Methods 



The 1,344 diving observations re- 

 ported in this study took place in 

 or near northeastern Auke Bay 

 (Fig. 1), 20 km west of Juneau, 

 Alaska, and focused on two adja- 

 cent, submerged (20-25 m depths) 

 rocky ledges at a site within 200 m 

 of the Auke Bay Laboratory. The 

 diving effort included sites within 

 a 15-km radius of Auke Bay that 

 were surveyed periodically to ex- 

 plore possible presence of age-0 

 pollock elsewhere in the area. 



Conventional scuba gear was 

 used and no decompression proce- 

 dures were followed. I averaged 8.8 

 (range 0-17) diving days per month 

 from June through December and 

 covered intertidal to 20-30 m 

 depths for 22 consecutive years 

 (Table 1). Nearly all dives took 

 place during daylight until Novem- 

 ber and December, when night 

 dives became equally routine. Most 

 diving days involved a single dive; 

 an average dive was made to a 

 depth of 23 m and lasted 25 min- 

 utes. On each dive, I routinely 

 swam the equivalent of transects 

 over a set of underwater landmarks 

 (e.g. rock ledges, cobble slope), 

 noted and later recorded all identi- 



1 Carlson, H. R., R. E. Haight, and K. J. 

 Krieger. 1982. Species composition and 

 relative abundance of demersal marine 

 life in waters of southeastern Alaska, 

 1969-81. U.S. Dep. Commerce, NMFS, 

 NWAFC Processed Rep. 82-16, 106 p. 



Manuscript accepted 7 November 1994. 

 Fishery Bulletin 93:386-390 ( 1995). 



386 



