Effects of variation in the visual environment on the feeding and catchability of Alaska fishes

• Main Author: Rohan, Sean Khosuke
• Other Authors: Essington, Timothy E
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: fisheries; light and turbidity; marine ecology; ocean optics; predator-prey interactions; visual foraging; Aquatic sciences; Bering Sea; Chukchi Sea; Chukchi; Subarctic; Alaska; Copepods
• Online Access: http://hdl.handle.net/1773/47543

Thesis (Ph.D.)--University of Washington, 2021 Aquatic animals use vision to perform tasks such as feeding, threat detection and avoidance, orientation, and social behavior. Thus, changes in light and water clarity can disrupt processes that affect the biological productivity of marine populations and alter visual interactions between fish and fishing gear. In the Bering Sea and Chukchi Sea, unprecedented warming due to climate change has enabled a poleward range expansion of historically subarctic fishes, which is likely to alter conditions for visual foraging and visual interactions between fish and fishing gear in fisheries independent surveys and commercial fisheries. In this dissertation, I examine the extent to which variation in light, depth, and water clarity influence visual foraging and catchability in the Bering Sea and Chukchi Sea. In Chapter 1, I develop a new generalized visual reaction distance model that predicts the reaction distance of fish to prey. In Chapter 2, I develop a novel method to monitor subsurface water clarity using bottom-trawl mounted archival tags equipped with a photodiode that measures irradiance. Using the method, I generate a time series of downwelling diffuse attenuation coefficient and optical depth for the eastern Bering Sea, which I use to characterize spatial-temporal variation in light and water clarity from 2004 to 2018. In Chapter 3, I use a deterministic simulation model to evaluate the extent to which latitudinal variation in light regime affects the catchability of semi-pelagic and demersal fishes in the Bering Sea and Chukchi Sea. In Chapter 4, I characterize the extent to which visual foraging opportunity varies over space and time for a walleye-pollock-like predator visually searching for Calanus spp. copepods and juvenile walleye pollock during summer on the eastern Bering Sea continental shelf.