The vast majority of theses in this collection are open access and freely available. There are a small number of theses that have access restricted to the WWU campus. For off-campus access to a thesis labeled "Campus Only Access," please log in here with your WWU universal ID, or talk to your librarian about requesting the restricted thesis through interlibrary loan.

Date Permissions Signed

11-28-2022

Date of Award

Fall 2022

Document Type

Masters Thesis

Department or Program Affiliation

Marine and Estuarine Science Program

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

Sobocinski, Kathryn L.

Second Advisor

Sandell, Todd A.

Third Advisor

Olson, M. Brady (Michael Brady)

Abstract

Pacific Herring play a critical role in the food web of the Salish Sea. The Cherry Point stock, centered 30 miles north of Bellingham Bay, has declined roughly 97% since the 1970s. This massive decline is a point of concern for environmental and fishery managers and has led to research into both the initial decline and the stock’s inability to recover. One key data gap in need of research is whether the Cherry Point herring stock is experiencing increased predation from the nearshore fish, bird, and invertebrate community due to its unique late spawn timing and spawning behavior. To that end, I investigated predation on herring spawn by deploying predator exclusion enclosures and remote underwater time lapse cameras at spawning locations of both the declining Cherry Point stock and Semiahmoo Bay, a nearby stock with stable population trends. Bird surveys in 2021 indicate that avian abundance was highest before spawning occurred and that most birds had left the spawning area before eggs were deposited. The exclusion of avian, large fish, and invertebrate predators from accessing the eggs did not significantly affect the survival of eggs when compared to areas exposed to predation from these groups. There was significant egg mortality in both the control and excluded plots over the spawning period. Remote underwater time-lapse cameras showed higher abundances of fish predators and greater predator diversity at the Cherry Point spawning site compared to Semiahmoo Bay, but this could be driven by seasonal differences. A non-metric multidimensional scaling analysis of the time-lapse data showed slight differences between pre-spawn predator assemblages and predator assemblages during and after the incubation period. This study shows that while predation from larger fauna did not have a significant impact on Pacific Herring egg survival for the years of 2021 and 2022, egg mortality was high and is likely influenced by a multitude of factors including spawning time and habitat, water temperature, and numerous smaller fish and invertebrate species that take advantage of the lipid-rich food source.

Type

Text

Keywords

Pacific Herring, forage fish, fish recruitment, food web, Salish Sea, fish assemblages, early-life history

Publisher

Western Washington University

OCLC Number

1352092499

Subject – LCSH

Pacific herring--Spawning--Salish Sea (B.C. and Wash.); Pacific herring--Mortality--Salish Sea (B.C. and Wash.); Pacific herring--Predators of--Salish Sea (B.C. and Wash.); Bird populations--Salish Sea (B.C. and Wash.)

Geographic Coverage

Salish Sea (B.C. and Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Download

Share

COinS