Kendall and Picquelle Egg and larval distributions of Theragra chalcogramma 



135 



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Figure 1 



Gulf of Alaska showing the six strata used to analyze distribution of walleye pollock eggs and larvae. Gridded area was used in detailed analyses 

 of the Shelikof Strait region. 



The 32 cruises were conducted for a variety of pur- 

 poses, so not all station patterns are ideal for the pres- 

 ent analysis. Some results from these cruises have been 

 reported elsewhere (Bates and Clark 1983, Dunn et al. 

 1984, Kendall and Dunn 1985, Bates 1987, Kendall 

 et al. 1987). Although several ships were used, stan- 

 dard MARMAP oblique tows with 60-cm bongo nets 

 (Smith and Richardson 1977) were. conducted at all sta- 

 tions, with two exceptions: smaller bongo nets (20 cm) 

 were used in 1984 aboard the NOAA ship Chapman 

 and in April 1985 aboard the Miller Freeman. Mesh 

 size was generally 505 j^m, although 333-/jm mesh was 

 used aboard the NOAA Ship Miller Freeman in 1985 

 and 1986. On most cruises, sampling was conducted to 

 a maximum depth of 200 m, as water depth permitted, 

 but on the Miller Freeman in 1985 and 1986 sampling 

 was conducted to within about 10 m of the bottom. 

 Data collected from flowmeters in the mouth of the 

 nets and bathykymograph records (for most tows) 

 allowed us to determine the maximum depth and 

 volume of water filtered for each tow. More details of 

 the conduct of these cruises are found in Dunn and 

 Rugen (1989). 



Samples were preserved at sea in a 5% buffered for- 

 malin/seawater solution and returned to shore for pro- 

 cessing. All fish eggs and larvae were then sorted from 

 the samples, identified, counted, and the larvae were 

 measured (mm standard length, SL): total sample when 

 larvae numbered fewer than 50, or a random subsam- 

 ple of at least 50 when more than 50 larvae were in 

 a sample. In each sample, developmental stages were 

 determined for 100 randomly selected walleye pollock 

 eggs according to the scheme of Matarese (Alaska Fish. 

 Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand 

 Point Way NE, Seattle, WA 98115-0070, unpubl. 

 manuscr.) (see Kendall and Kim 1989). Egg develop- 

 ment data were then grouped into the six age groups 

 used by Kendall and Kim (1989). Numbers of eggs and 

 larvae in the tows were standardized to numbers per 

 10-m- sea surface by calculating the volume of water 

 filtered during the tow and dividing this number by the 

 maximum depth of the tow. 



Since most tows were taken to a maximum depth of 

 200 m, and substantial numbers of eggs occurred below 

 this depth, we adjusted catches of eggs, based on data 

 in Kendall and Kim (1989), to account for eggs below 



