|Feeding habits, prey fields, and potential competition of young-of-the-year walleye pollock (Theragra chalcogramma) and Pacific herring (Clupea pallasi) in Prince William Sound, Alaska, 1994-1995|
Sturdevant, M.V.; Brase, A.L.J.; Hulbert, L.B. (2001). Feeding habits, prey fields, and potential competition of young-of-the-year walleye pollock (Theragra chalcogramma) and Pacific herring (Clupea pallasi) in Prince William Sound, Alaska, 1994-1995. Fish. Bull. 99(3): 482-501
In: Fishery Bulletin. US Government Printing Office: Washington, D.C.. ISSN 0090-0656, more
Baltic Sea; Baltic sea; Marine
|Authors|| || Top |
- Sturdevant, M.V.
- Brase, A.L.J.
- Hulbert, L.B.
Diets of young-of-the-year (YOY) walleye pollock (Theragra chalcogramma) and Pacific herring (Clupea pallasi) were compared between seasons (summer and autumn), years (autumn), and allopatric and sympatric fish aggregations (autumn) in Prince William Sound (PWS), Alaska. Fish were collected principally by mid-water trawl 20 July-12 August 1995, 5-14 October 1995, and 7-13 November 1994. Prey fields were assessed fi-om zooplankton samples in 1995.During the summer, the principal prey of allopatric pollock and herring was small calanoids and diet overlap was high (R-0>0.76). During the autumn, diets were composed of large calanoids, larvaceans, and euphausiids. Diet overlap between sympatric species was greater in November 1994 (R(0)l ess than or equal to 0.94) than in October 1995 (R(0) less than or equal to 0.69). The seasonal diet shift to larger prey coincided with larger fish size and with decreased abundance and proportions of the principal zooplankter, small calanoids, and increased abundance and proportions of large calanoids and larvaceans in zooplankton tows. However, feeding decreased in autumn, compared with summer, especially for herring. Sympatric fish had higher rates of nonfeeding than allopatric fish, and subtle differences in prey selection existed between the aggregations, but sampling variation could explain these feeding differences.The similarity in diets of YOY pollock. and herring indicate the potential for competition, These species are important to commercial fisheries and as forage for marine birds and mammals. An understanding of their trophic interactions could help to explain shifts in fish community structure and bird predation. If sympatry increases as prey resources decline, competition in autumn may be particularly important in regulating populations.