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Date of Award

Summer 2025

Document Type

Masters Thesis

Department or Program Affiliation

Environmental Science

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

Kastner, Sam

Second Advisor

Hatch, Marco B. A.

Third Advisor

McPhee-Shaw, Erika E.

Abstract

Since time immemorial, the Indigenous Peoples of the Salish Sea, British Columbia, and Alaska have thrived in their environment. In these regions, the traditional practice of building clam gardens has been a central means for bivalve harvesting. These gardens are created by a low rock wall built parallel to the shore along the lower edge of the intertidal zone. They create an extended, terraced, and ideal habitat for bivalves (Groesbeck, 2014; Deur, 2015). In the summer of 2022, the Swinomish Indian Tribal Community (SITC) constructed a new clam garden to resume their ancestral practice.

In a study that took place in June 2024, we conducted a physical oceanographic field campaign to assess the influence of flow on water properties in the clam garden. We deployed three acoustic Doppler current profilers (ADCP) in and around the clam garden to compare flow inside the clam garden, directly outside the clam garden, and at an adjacent, unwalled beach. We found that the residence time in the clam garden is double what it is at the unwalled control beach (average 23 minutes and 10 minutes, respectively), water slows down when it enters the clam garden, and bed friction velocity and vertical shear are reduced in the clam garden. We suspect that this combination increases larval recruitment of clams and contributes to increased availability of food and nutrients for clams in the clam garden, thus creating a more favorable habitat. In previous clam garden literature, increased biomass and density of clam populations have been found in clam gardens when compared to unwalled beaches, but the potential hydrodynamic influences on this pattern have not been quantified until now. The results from this study not only further our understanding of hydrodynamics in clam gardens but will also be used by the SITC to inform potential management and growing procedures for clams in their clam garden.

Type

Text

Keywords

Clam gardens, Hydrodynamics, Residence time, Shear, Nearshore physical oceanography

Publisher

Western Washington University

OCLC Number

1534626194

Subject – LCSH

Clam culture--Salish Sea (B.C. and Wash.); Clam populations--Salish Sea (B.C. and Wash.); Hydrodynamics; Physical oceanography--Salish Sea (B.C. and Wash.); Shear flow

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.

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Available for download on Friday, February 20, 2026

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