Graduation Date

Fall 2016

Document Type

Dissertation/Thesis

Program

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

Committee Chair Name

Darren Ward

Committee Chair Email

darren.ward@humboldt.edu

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Daniel Barton

Second Committee Member Email

daniel.barton@humboldt.edu

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Margaret Wilzbach

Third Committee Member Email

margaret.wilzbach@humboldt.edu

Third Committee Member Affiliation

HSU Faculty or Staff

Abstract

The Scott and Shasta rivers, Klamath River tributaries, experience spatial disparity in habitat quality in spring and summer as a result of historical and current land-use. Juvenile Coho Salmon (Oncorhynchus kisutch) born in the upper tributary reaches often rear in natal streams before migrating to sea. However, those born in the lower reaches often encounter unsuitable habitat and emigrate during their first spring to seek non-natal rearing habitats. It is assumed that these early outmigrants are population losses. This study evaluated first-summer survival, and contribution to the adult population, of non-natal rearing juveniles in the Klamath River Basin. In the spring of 2014 and 2015 juveniles were tagged using Passive Integrated Transponder (PIT) tags as they were leaving the lower Scott and Shasta Rivers. Movement and survival was subsequently tracked using recapture and detection efforts in potential mainstem summer rearing locations. Strontium microchemistry from otolith samples of returning adult Coho Salmon throughout the basin was analyzed to estimate the contribution of non-natal rearing juveniles to adult returns. Few tagged individuals were detected in non-natal rearing habitats, but those detected in these habitats had survival rates comparable to natal-rearing individuals. Otolith analysis indicated that the proportion of juvenile Coho Salmon rearing in non-natal habitats varied by spawning site. In total, 53% of the 116 adults sampled reared in a natal location as juveniles, while 47% reared in a non-natal location. These results suggest that non-natal rearing can contribute to adult returns and could be a significant population segment with increased restoration.

Citation Style

Transactions of the American Fisheries Society