734 



Fishery Bulletin 102(4) 



65°N 



60°N 



55°N 



50°N 



45 N 



40° N 



35°N 



180 W 



"I T 



170°W 160 : W 150'W 140 W 130"W 120 W 



Figure 1 



Sampling stations in the northeast Pacific where Berryteuthis 

 anonychus were collected during May 1999. Numbers indicate 

 station numbers. 



Marine Fisheries Service (NMFS) survey of salmon in 

 the northeast Pacific (Carlson et al., 1999; Bower et al., 

 2002). Samples were collected during 6-17 May 1999 

 at seven stations between 145-165°W and 39-49°N 

 (Fig. 1). At each station, a midwater trawl modified to 

 fish at the surface was towed for 1 hour. The trawl was 

 198 m long and had hexagonal mesh in its wings and 

 body, and a 1.2-cm mesh liner was used in the codend. 

 Trawling speeds were 7-9 km/h, and the average net 

 dimensions while fishing were 16 m vertical spread and 

 45 m horizontal spread. 



Squid samples were frozen on board to -20°C and 

 preserved in 50% isopropyl alcohol in the laboratory. 

 The mantle length (ML) of each squid was measured 

 to the nearest 0.1 mm, and each squid was weighed to 

 the nearest 0.01 g. The stomach contents of 338 squid 

 (167 males, 144 females, 27 undetermined) ranging in 

 ML from 10.3 to 102.2 mm (Fig. 2) were examined un- 

 der a stereomicroscope. A total of 359 squid were col- 

 lected during the survey (Bower et al., 2002), but 21 of 

 these specimens were either damaged or lost, and thus 

 excluded from our analyses. Most prey items were frag- 

 mented; therefore prey identification was usually based 

 on diagnostic body parts as described in Brodsky (1950), 

 Miller (1988), Baker et al. (1990), and Vinogradov et al. 

 (1996). and by comparison with zooplankton specimens 

 collected in the same area. The prey items were counted 

 and weighed to the nearest 0.01 mg. These wet mass 

 measurements presumably underestimated the initial wet 

 masses because mass loss occurs in invertebrate samples 

 preserved in isopropyl alcohol (e.g., Howmiller, 1972), 

 and it was assumed all prey taxa were equally affected 

 by the preservation. The numbers of individuals of each 



6CH 



50- 



40- 



Z 30- 



20- 



10-| 

 



n = 338 



10 20 30 40 50 60 70 80 90 100 

 Mantle length (mm) 



Figure 2 



Length-frequency distribution for Berryteuthis 

 anonychus. 



prey taxon were estimated from the numbers of prey 

 parts, such as copepod mandibles, amphipod heads and 

 chaetognath seizing hooks. Because of the difficulty in 

 distinguishing the copepods Neocalanus plumchrus and 

 N. flemingeri, they were grouped as a single taxon, N. 

 plumchrus+flemingeri. Some calanoid copepods that could 

 not be identified to genus level were identified as either 

 a "specialized form" or a "generalized form"; characters 

 of the specialized form included appendages that were 

 greatly enlarged or strongly developed with chelae, spines 

 on the posterior corners of the terminal thoracic segment, 



