823 



Abstract— Effects of year and region 

 on young-of-the-year (age-0) walleye 

 pollock abundance and size were exam- 

 ined by using bottom and midwater 

 trawl collections made during 1985-88. 

 Samples were collected from shelf and 

 coastal areas in three adjacent regions 

 of the western Gulf of Alaska. The pri- 

 mary focus was to examine regional dif- 

 ferences in recruitment prediction and 

 annual differences in fish distribution. 

 Fish density was used to indicate abun- 

 dance, and length was included as a 

 relevant factor in fish production. Year 

 and region significantly interacted as 

 effects on age-0 density. Recruitment 

 prediction was best in the Kodiak Is- 

 land region, upstream of the main 

 spawning area, where fish densities 

 were high during 1985 and 1988 in 

 relation to 1986 and 1987. On a large 

 scale, fish were evenly distributed every 

 year, except during 1987 when their 

 density increased strongly from east to 

 west . Age-0 length also varied with year 

 and region. This was apparent after 

 accounting for daily increases in mean 

 length (0.09 cm/d). Fish were compar- 

 atively small during 1986. intermedi- 

 ate during 1985, and large during 1987 

 and 1988. Regional differences in fish 

 length were due to a relative abundance 

 of large-size fish around Kodiak Island 

 where the average size was about 0.75 

 cm larger than elsewhere. Thus, a rela- 

 tive abundance of large individuals in 

 this region was associated with good 

 recruitment prediction. These results 

 are discussed in terms of their rele- 

 vance to spatial variation in the pro- 

 duction of recruits. 



Effects of year and region on the abundance 

 and size of age-0 walleye pollock, 

 Theragra chalcogramma, in the 

 western Gulf of Alaska, 1985-1988* 



Matthew T. Wilson 



Alaska Fisheries Science Center 

 National Manne Fisheries SeiA/ice, NOAA 

 7600 Sand Point Way NE 

 Seattle, Washington 98115 

 E-mail address matt wilsoniaJnoaa gov 



Manuscript accepted 5 April 2000. 

 Fish. Bull. 98:823-834 (2000). 



Young-of-the-year (age-0) fish abun- 

 dance is used in managing temperate 

 marine resources (Goodyear, 1985; 

 Bailey et al., 1986; Johannessen and 

 Tveite, 1989; Sundby et al., 1989; Gal- 

 aktionov, 1993; Corteni). Estimating 

 the abundance of age-0 fish, however, is 

 complicated by their broad and some- 

 times variable spatial distributions. 

 This variability, which can obscure 

 shifts in distribution from changes in 

 abundance (Olsen and Soldal, 1989; de 

 LaFontaine et al., 1992; Polacheck et 

 al., 1992; Anderson et al., 1995), may 

 affect survival. 



Walleye pollock, Theragra chalco- 

 gramma, are semidemersal gadids that 

 reside in the North Pacific Ocean 

 (Lynde, 1984; Springer, 1992; Wolotira 

 et al., 1993). The National Oceanic and 

 Atmospheric Administration (NOAA) 

 has sought to understand and predict 

 pollock recruitment better because of 

 the commercial importance and recruit- 

 ment variability of the species (Kend- 

 all and Duker, 1998; Hollowed et al.2; 

 Wespestad et al.'^ ). Much of the research 

 on pollock recruitment has been done 

 in the western Gulf of Alaska (GOA) as 

 part of NOAA's Fisheries Oceanography 

 Coordinated Investigations (FOCI) pro- 

 gram (Schumacher and Kendall, 1991; 

 Kendall etal, 1996). 



In the GOA, many pollock spawn 

 during early April in southwestern 

 Shelikof Strait (Picquelle and Megrey, 

 1993 ) ( Fig. 1 ). This spawning is believed 

 to be primarily responsible for replen- 

 ishing the GOA pollock stock (Kendall 

 and Picquelle, 1990; Hollowed et al.-). 

 FOCI researchers have devised a trans- 

 port paradigm for young pollock of She- 



likof Strait, in which they move with 

 the prevailing currents from the main 

 spawning area in the Strait to shelf 

 and coastal nurseries farther southwest 

 (Schumacher and Kendall, 1995; Kend- 

 all et al., 1996). Although some individ- 

 uals may be carried beyond the shelf, 

 the oceanic North Pacific is not consid- 

 ered an important pollock nursery area 

 (Smith et al., 1984). This pattern of 

 dispersal, hereafter referred to as the 

 FOCI recruit-pathway paradigm, was 

 demonstrated in 1987 (Hinckley et al., 

 1991), and it has been simulated by 

 a model of lai^val transport that incor- 

 porates detailed physical and biologi- 

 cal information (Hermann et al.. 1996a, 



* Contribution 0262 of the Fisheries Ocean- 

 ogi-aphv Coordinated Investigations, 7600 

 Sand Point Way NE, Seattle. WA 98115. 



' Corten, A. 1986. Application of the re- 

 sults from international young fish sur- 

 vevs in fisheries management in recent 

 years. ICES, Doc. CM. 1986/0:54, 26 p. 



-' Hollowed, A. B., E. Brown, J. lanelli, P. Liv- 

 mgston, B. Megi'ey, and C. Wilson. 1997. 

 Walleye pollock. In Stock assessment and 

 fishery evaluation report for the gi'ound- 

 fish resources of the Oulf of Alaska, p. 

 31-119. Prepared by the Oulf of Alaska 

 Groundfish Plan Team, North Pacific Fish- 

 ery Management Council, P.O. Box 103136, 

 Anchorage, AK 99510. 



' Wespestad, V. G., J. N. lanelli. L. Fritz, T. 

 Honkalehto, N. Williamson, and 0. Wal- 

 ters. 1997. Benng Sea-Aleutian Islands 

 walleye pollock assessment for 1998. In 

 Stock assessment and fishery evaluation 

 report for the groundfish resources of 

 the Bering Sea/Aleutian Islands regions, 

 p. 35-102. Prepared by the Bering Sea/ 

 Aleutian Islands Plan Team, North Pacific 

 Fishery Management Council, P.O. Box 

 103136, Anchorage, AK 99510. 



