Graduation Date

Fall 2023

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Darren Ward

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Andre Buchheister

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Mark Henderson

Third Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Fisheries

Abstract

Substantial investment in habitat restoration efforts have been made to promote coho salmon (Oncorhynchus kisutch) recovery, yet sampling efforts to document the response of coho salmon populations to wetland restoration are limited. I investigated two cohorts of juvenile coho salmon growth, movement, and survival within the Humboldt Bay drainage in California. My study sites included restoration features and other sample areas in upland creek habitat and in lowland estuarine wetlands that were located in the four largest watersheds within the Humboldt Bay drainage. The objectives of this study were to: (1) determine if coho salmon are using restored, off-channel habitats and characterize seasonal patterns of occupancy, (2) estimate growth rates of juvenile coho salmon residing in restoration sites and to compare these estimates to growth rates of their stream-rearing counterparts, and (3) estimate survival of juvenile coho salmon that utilize estuary sites as long-term habitat before outmigrating and compare these estimates to survival of their stream-rearing counterparts. I conducted monthly sampling events at each site from October through May of the 2020 and 2021 water years and included 10,671 marked individuals in my analyses. To compare growth differences across sites and years, I constructed a Bayesian mixed effects model. I constructed two multi-state mark recapture models to evaluate survival and movement between freshwater and estuarine rearing fish in two watersheds, and a Cormack Jolly Seber model to evaluate survival in an estuary of a third watershed. Juvenile coho salmon residing in off-channel habitat experienced the same or higher growth rates than mainstem rearing fish, often moving into restored habitat at smaller sizes than stream-rearing fish. Sites that experienced the highest growth were two estuarine restoration features. The two creeks analyzed with multi-state models showed similarities in movement patterns (e.g., one pulse of movement to the estuaries in early winter, and another in late spring), but the magnitude of movement was different between cohorts and watersheds. Stream-rearing estimates of survival were similar to estuary survival for one watershed and higher than estuary survival for the other watershed. Estuary estimates of apparent survival are potentially lower than true survival due to antenna array placement in the estuaries surveyed. Based on growth and survival of fish in estuary restoration areas, it is likely that these habitats are increasing productivity of the juvenile coho salmon populations in Humboldt Bay. Enhancing estuary habitat is important for coho salmon conservation because it contributes to survival of displaced fish that would otherwise likely perish, directly increasing productivity of the population. The findings of this research indicate a greater need for consideration of habitat diversity for coho salmon restoration.

Citation Style

Transactions of the American Fisheries Society

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