Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8617
Title: Variability in species composition and distribution of forage fish in the Gulf of Alaska
Author: David W. McGowan, John K. Horne, Sandra L. Parker-Stetter
Publication Year: 2017
Journal: Deep Sea Research Part II: Topical Studies in Oceanography
Keywords: capelin,Gulf of Alaska,forage fish,Pacific herring,Walleye pollock

In the Gulf of Alaska (GOA), forage fish species, such as age-0 walleye pollock (Gadus chalcogrammus), capelin (Mallotus villosus), Pacific herring (Clupea pallasii), and mesopelagic fishes, are ecologically important as both consumers of zooplankton, and prey to fish, seabirds, and marine mammals.  Characterization of spatial and temporal variability in forage fish distributions is needed to improve understanding of how changes in biomass and availability potentially impact predators.  As part of the GOA Integrated Ecosystem Research Program, an acoustic-trawl survey was conducted in the summer and fall of 2011 and 2013 to quantify variability in species composition, density, and distributions of forage fish over the continental shelf and slope in the central and eastern regions of the GOA.  The forage fish community in 2011 can be characterized by the absence of age-0 pollock and lower densities of capelin, herring, and mesopelagics compared to observations in 2013.   Seasonal changes in community composition are attributed to the transport of age-0 pollock from offshore waters in summer 2013 to nearshore nursery areas in fall, and to immigration of herring over the eastern GOA shelf in fall of both years.  Forage fish distribution patterns varied within and between regions due to intra- and interspecific differences in horizontal and vertical distributions that were correlated with bottom depth.  Observed spatial and temporal variability in community composition and distributions of forage fish species may potentially impact predator foraging in the GOA, as well as the effectiveness of monitoring to detect changes in forage fish biomass.

Theme: Ecosystem approach to improve management of marine resources
Foci: Assess ecosystem status and trends.