224 



Fishery Bulletin 92|2), 1994 



coastal waters of Alaska during 

 spring and examines diel differences 

 in these patterns in relation to en- 

 vironmental and biotic factors. 



Materials and methods 



Samples examined were collected 

 from two cruises of the NOAA ship 

 Miller Freeman in the area south- 

 west of Kodiak Island in the north- 

 ern Gulf of Alaska (Fig. 1). During 

 May 1986 and 1987, 22 depth-strati- 

 fied tows were made with a 1-m 2 

 Multiple Opening/Closing Net and 

 Environmental Sensing System 

 (MOCNESS) (Wiebe et al., 1976) 

 equipped with 153-um mesh. The 

 net was towed obliquely and nets 

 were opened sequentially at the de- 

 sired depth strata. The primary pur- 

 pose of the sampling was to collect 

 information on the vertical distribu- 

 tion of walleye pollock larvae, which 

 are generally found in the upper 50 m 

 (Kendall et al. 1 ), and their prey. 

 Therefore, the emphasis during the 

 sampling was on the upper part of 

 the water column. The nets sampled 

 the following nominal depths: 0-15, 

 15-30, 30-45, 45-60, 60-80, 80-100, 

 and >100 m. Maximum sampling 

 depth varied (range 150-252 m) depending on the 

 depth of the water column at a particular station. 

 There were eight depth strata sampled at most sta- 

 tions but the cutoff depth between the seventh and 

 eighth net was variable. Therefore, we pooled the 

 catches from these two nets into a single depth stra- 

 tum (>100 m) for analysis. The actual sampling 

 depths are given in Table 1. More complete station 

 and catch information is given in Siefert et al. 2,3 



1 Kendall, A. W., Jr., L. S. Incze, P. B. Ortner, S. R. Cummings, 

 and P. K. Brown. In review. The vertical distribution of eggs 

 and larvae of walleye pollock {Theragra chalcogramma i in 

 Shelikof Strait, Gulf of Alaska. Submitted to Fish. Bull. 



2 Siefert, D. L. W., L. S. Incze, and P. B. Ortner. 1988. Vertical 

 distribution of zooplankton, including ichthyoplankton, in 

 Shelikof Strait, Alaska: data from Fisheries Oceanography 

 Coordinated Investigations (FOCI) cruise in May 1986. 

 NWAFC Processed Rep. 88-28, 232 p. 



1 Siefert, D. L. W., L. S. Incze, and P. B. Ortner. 1990. Vertical 

 distribution of zooplankton, including ichthyoplankton, in 

 Shelikof Strait, Alaska: data from Fisheries Oceanography 

 Coordinated Investigations (FOCI) cruise in May 1987. 

 NWAFC Processed Rep. 90-05, 129 p. 



The 22 tows were grouped into five collection se- 

 ries (Table 1) based upon date and location of sam- 

 pling (see Kendall et al. 1 ) and included two complete 

 diel series. The first diel series (Series 4) attempted 

 to sample the same body of water over a four day 

 period during 1986 by following a radar-tracked 

 drifter drogued at 35 m (Incze et al., 1990). The 

 second diel series (Series 9) sampled the same loca- 

 tion on three successive days during 1987. Other 

 collections (Series 5, 6, and 7) were taken at vari- 

 ous times of the day but in the same general area 

 as these two series (Fig. 1, Table 1). 



Retrieved nets were thoroughly washed and con- 

 tents were preserved in 5% buffered formalin. 

 Samples were sorted to the lowest possible taxon 

 and life history stage at the Polish Sorting Center 

 in Szczecin, Poland. The volume filtered was esti- 

 mated from a mechanical flowmeter mounted on the 

 MOCNESS frame and abundances were converted to 

 number per 1000 m 3 . Up to 50 preserved larvae of each 

 taxon from each net were measured to the nearest 0. 1 

 mm standard length. Net depth, temperature, and 



