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Date of Award

Winter 2023

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Sciences, Marine and Estuarine Science Program

Degree Name

Master of Science (MS)


Environmental Sciences

First Advisor

Sobocinski, Kathryn L.

Second Advisor

Loew, Ellis

Third Advisor

Bodensteiner, Leo R., 1957-


Walleye pollock (Gadus chalcogrammus) and Chinook salmon (Oncorhynchus tshawytscha) are economic and cultural resources in Alaska. Chinook salmon bycatch is a large concern within the pollock fishery. Current strategies to reduce salmon bycatch include modifying trawl gear by implementing artificial light near or on escapement panels to increase salmon escapement. The visual characteristics of pollock and Chinook salmon were investigated to understand the perception of trawl gear. The visual pigments of each species were measured using microspectrophotometry (MSP). Pollock were dichromats with spectral sensitivity ranging from 449nm–518 nm and Chinook salmon were trichromats with sensitivity ranging from 436 nm–545 nm. The green opsins within Chinook salmon will activate when stimulated by wavelengths that are outside of the spectral sensitivity of pollock. Microspectrophotometry data defining pollock and Chinook salmon visual pigments, spectral irradiance data from the Bering Sea, and spectral reflectance of commonly used trawl components were input into two visual models, VPModel® and the R package pavo. Visual models predict how the organism’s visual system responds to visual stimuli. Modeling the spectral distribution and physiological visual characteristics predicts how fish interact and adapt to the changing light environment. Spectral irradiance availability decreased with depth and increasing chlorophyll a concentration. Target contrast against the background space light was dependent on the light environment characteristics including depth. Using the physiological data and theoretical model output provides spectral range and intensity limitations to behavior experiments aiming to increase the escapement potential of Chinook salmon in the pollock fishery




Alaska, Chinook salmon, walleye pollock, fishing, trawl, vision


Western Washington University

OCLC Number


Subject – LCSH

Walleye pollock fisheries--Bycatches--Bering Sea; Chinook salmon--Alaska; Trawls and trawling--Bycatches--Bering Sea; Bycatches (Fisheries)--Bering Sea

Geographic Coverage

Bering Sea; Alaska




masters theses




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