Modeling connectivity of walleye pollock in the Gulf of Alaska: Are there any linkages to the Bering Sea and Aleutian Islands?

Authored by Carolina Parada, Sarah Hinckley, John Horne, Michael Mazur, Albert Hermann, Enrique Curchister

Date Published: 2016

DOI: 10.1016/j.dsr2.2015.12.010

Sponsors: North Pacific Research Board

Platforms: No platforms listed

Model Documentation: ODD

Model Code URLs: Model code not found

Abstract

We investigated the connectivity of walleye pollock in the Gulf of Alaska (GOA) and linkages to the Bering Sea (BS) and Aleutian Island (AL) regions. We used a spatially-explicit Individual-based model (IBM) coupled to 6 years of a hydrodynamic model that simulates the early life history of walleye pollock in the GOA (eggs to age-0 juveniles). The processes modeled included growth, movement, mortality, feeding and the bioenergetics component for larvae and juveniles. Simulations were set to release particles on the 1st of the month (February to May) in fourteen historical spawning areas in the GOA up to the 1st of September each year. Model results reproduced the link between the Shelikof Strait spawning area and the Shumagin nursery region for March and April spawners, besides other Potential Nursery Areas (PNAs) found in the GOA. A prominent finding of this study was the appearance of the BS as important PNAs for several GOA spawning grounds, which is supported by a consistent flow into the BS through Unimak Pass. The simulations showed the highest density of simulated surviving pollock in the western Bering Sea (WBS) region with the lowest coefficients of variation of the whole domain. Three spawning sectors were defined, which aggregate multiple spawning areas, in the eastern (EGOA), central (CGOA) and western Gulf of Alaska (WGOA). A connectivity matrix showed strong retention within the CGOA (25.9\%) and EGOA (23.8\%), but not in the WGOA (7.2\%). Within the GOA, the highest connectivity is observed from EGOA to CGOA (57.8\%) followed by the connection from CGOA to WGOA (24.3\%). Overall, one of the most prominent connections was from WGOA to WBS (62.8\%), followed by a connection from CGOA to WBS (29.2\%). In addition, scenarios of shifting spawning locations and nursery sectors,of GOA, BS and AL are explored and implications for walleye pollock stock structure hypotheses are discussed. (C) 2015 Elsevier Ltd. All rights reserved.

Tags

Individual-based model Vertical-distribution Spatially explicit Early-life history Population connectivity Kokanee oncorhynchus-nerka Theragra-chalcogramma Western gulf Shelikof strait Mitochondrial-dna