Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8538
Title: Factors affecting summer distributions of Bering Sea forage fish species: assessing competing hypotheses
Author: Sandra L. Parker-Stetter, Samuel Urmy, John K. Horne, Lisa B. Eisner, Edward V. Farley
Publication Year: 2016
Journal: Deep Sea Research Part II: Topical Studies in Oceanography
Volume: 134
Pages: 255-269
Keywords: capelin,Walleye pollock,Pacific cod,distribution,Bering,information theoretic approach,

Hypotheses on the factors affecting forage fish species distributions are often proposed but rarely evaluated using a comprehensive suite of variables.  Using 24 predictor variables, we compared competing hypotheses and calculated average models for the distributions of capelin, age-0 Pacific cod, and age-0 pollock in the eastern Bering Sea from 2006-2010.  Distribution was described using a two stage modeling approach: probability of occurrence (“presence”) and density when fish were present.  Both local (varying by location and year) and annual (uniform in space but varying by year) variables were evaluated, the latter accounting for the possibility that distributions were random but that overall presence or densities changed with annual conditions.  One regional variable, distance to the location of preflexion larvae earlier in the year, was evaluated for age-0 pollock.  Capelin distributions were best predicted by local variables such as bottom depth, temperature, and salinity.  Annual climate (May sea surface temperature (SST), sea ice extent anomaly) and wind (June wind speed3) variables were often important for age-0 Pacific cod in addition to local variables (temperature and depth).  Surface, midwater, and water column age-0 pollock distributions were best described by a combination of local (depth, temperature, salinity, zooplankton) and annual (May SST, sea ice anomaly, June wind speed3) variables.  Our results corroborated some of those in previous distribution studies, but suggested that presence and density may be influenced by different factors.  Even though there were common environmental factors that influenced all species’ distributions, it is not possible to generalize conditions for forage fish as a group.


This manuscript evaluates support of hypotheses relating the distributions of Bering Sea forage fish to oceanographic conditions

Theme: Ecosystem approach to improve management of marine resources
Foci: Characterize the interaction between marine, freshwater and terrestrial ecosystem components.
Official Citation:

Parker-Stetter, S, S Urmy, J Horne, L Eisner & E Farley. 2016. Factors affecting summer distributions of Bering Sea forage fish species: assessing competing hypotheses. Deep Sea Research II, 134: 255-269.