Influence of Early Life Stage Hatchery Enhancement Practices on Maternal Reproductive Investment in Coho Salmon (Oncorhynchus kisutch)

Fish hatchery enhancement programs are a central component of Canadian Pacific salmon management, supporting commercial, recreational, cultural, and conservation objectives. However, the consequences of captive rearing environments for the reproductive phenotype of returning adults remain poorly understood. In salmonids, maternal reproductive investment is predicted to be tied to early life-history conditions through developmental programming, creating the potential for mismatches between hatchery-origin reproductive phenotypes and the demands of natural environments. I quantified maternal reproductive traits in 171 mature female Coho Salmon (Oncorhynchus kisutch) from four hatchery treatment groups and a wild-origin control at the Nitinat River Hatchery on Vancouver Island, B.C. I evaluated body size, fecundity, ovary weight, egg weight, egg volume, and proximate egg composition across groups while controlling for maternal body size and sampling year. Hatchery rearing produced significant body size reductions in three of four treatment groups relative to wild-origin fish, and reproductive traits varied primarily as a function of body size, with hatchery life history explaining comparatively little additional variation once body size was accounted for. The principal exception to this trend was egg weight, which was significantly lower in the outplant treatment group relative to wild-origin fish after controlling for body size, likely reflecting early release timing, foraging challenges during lake rearing, and elevated maternal disease load rather than hatchery rearing. No significant differences in reproductive traits were detected between enriched and standard hatchery treatment groups. These findings indicate that the reproductive consequences of hatchery rearing are mediated primarily through body size, and that the nature and magnitude of effects depend on specific rearing conditions.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Biological Sciences

Grantor

Science

Year dc:date.issued

2026

Author dc:creator

• Olson, Erik

Advisor dc:contributor.advisor

• Rogers, Sean

Committee members dc:contributor.committeemember

• Syme, Douglas
• Post, John
• Ceballos Betancourt, Maria

Statement dc:rights

• Unless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

en

DOI

https://dx.doi.org/10.11575/PRISM/51501

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/125012