Abstract.- The feeding habits 

 of late-larval and early-juvenile wall- 

 eye pollock Theragra chalcogramma 

 from a coastal nursery habitat in the 

 western Gulf of Alaska were exam- 

 ined in relation to fish size (10.0-29.9 

 mm SL) and site of collection. Pseu- 

 docalanus sp. was the dominant prey. 

 Copepod nauplii and Pseudocalanus 

 copepodids decreased in importance 

 in the diet as fish size increased, con- 

 comitant with an increase in impor- 

 tance oi a.du\t Pseudocalanus sp. and 

 Calanus spp. Other prey showed no 

 clear relation to fish size. A compari- 

 son of diet between collection sta- 

 tions revealed considerable variabil- 

 ity. Along two transects perpendicu- 

 lar to the Alaska Peninsula, between- 

 station diet overlap was observed to 

 be high for one transect, and low for 

 the other. Along a transect parallel 

 to the Alaska Peninsula, some adja- 

 cent stations yielded high diet over- 

 lap, and other yielded low overlap, 

 while the most distant stations pro- 

 duced high diet overlap. Patchiness 

 of food resources likely contributed 

 subtantially to these patterns. One 

 possible consequence of the ingestion 

 of different prey in different locales 

 is that differential growth rates could 

 result. 



Feeding Ecology of Late-Larval 

 and Early-Juvenile Walleye Pollock 

 Theragra chalcogramma from 

 the Gulf of Alaska in 1987* 



Jill J. Grover 



College of Oceanography, Oregon State University 

 Hatfield Marine Science Center, Newport, Oregon 97365 



The recent discovery of large spawn- 

 ing aggregations of walleye pollock 

 Theragra chalcogramma in Shelikof 

 Strait from late March to mid-April 

 suggests that this is the principal 

 spawning center for the species in 

 the Gulf of Alaska (Dunn et al. 1984, 

 Kendall et al. 1987). The concentrated 

 mass of eggs produced in Shelikof 

 Strait in early spring and the ensu- 

 ing dense patch of larvae provide un- 

 common access to the early life his- 

 tory of the species. The spawning 

 aggregations produce distinct cohort 

 patches (20 x 50 km or larger) of eggs 

 at depths greater than 150 m (Incze 

 et al. 1989). After about 14 days, the 

 eggs hatch (Dunn and Matarese 

 1987, Kim 1989) and larvae ascend to 

 the upper 50 m (Incze et al. 1989). 

 The larval patches can be followed 

 for up to 30 days as they drift with 

 prevailing currents to the southwest 

 (Kendall et al. 1987, Hinckley et al. 

 1989, Incze et al. 1989). The cohesive- 

 ness of the patches likely results from 

 the restricted spawning area within 

 Shelikof Strait (Hinckley et al. 1989) 

 as well as Alaska Coastal Current cir- 

 culation patterns (Incze et al. 1989). 

 Ichthyoplankton has been surveyed 

 regulai'ly in and around Shelikof Sti'ait 

 since 1979, and much is known re- 

 garding the early life history of wall- 

 eye pollock in this area (e.g., Kendall 

 et all 1987, Incze et al. 1989, Kim 

 1989, Yoklavich and Bailey 1989). 

 However, considerably less is known 



Manuscript accepted 7 May 1990. 

 Fishery Bulletin, U.S. 88:463-470. 



•Contribution FOCI-0105 to Fisheries-Ocean- 

 ography Coordinated Investigations, NOAA. 



about life history of late-larval and 

 juvenile stages within nursery habi- 

 tats in the western Gulf of Alaska. A 

 survey in June and July 1987 col- 

 lected late-larval and early-juvenile 

 pollock from a coastal nursery area 

 over the continental shelf along the 

 Alaska Peninsula (Hinckley et al. 

 1989). While the center of distribu- 

 tion was between the Shumagin and 

 Semidi Islands, a large number of late 

 larvae and juveniles were collected 

 over a broad area running nearly the 

 length of the Alaska Peninsula. The 

 broad distribution enabled us to ex- 

 amine whether diet varied along the 

 length of the Alaska Peninsula and 

 along a nearshore-offshore transect. 

 Although the feeding habits of the 

 late larvae have been previously re- 

 ported from several locations, in all 

 cases results have been pooled across 

 collection stations (Kamba 1977, 

 Clarke 1978, Cooney et al. 1980. Lee 

 1985, Kendall et al. 1987). In the 

 present study, feeding habits of late 

 larvae were analyzed by size and 

 these data are compared to previous 

 reports. Further, diet was analyzed 

 by collection station, and between- 

 station differences were examined 

 using a measure of diet overlap. 



Materials and methods 



Pollock larvae were collected in the 

 Gulf of Alaska during June 1987 by 

 the RV Miller Freeman. Collections 

 were made using a 5-m- Methot 

 frame trawl (Methot 1986) (2 x 3 mm 

 oval mesh) that was fished obliquely 



463 



