Size and Distribution of Parr Produced from Natural‐ and Hatchery‐Origin Steelhead Spawning Naturally in a Small Pacific Northwest Coastal Stream

Journal Article · 25 June 2022 · Transactions of the American Fisheries Society

DOI: https://doi.org/10.1002/tafs.10366 · OSTI ID:1876097

Kennedy, Benjamen M.  ^[1]; Smith, Matt J. ^[1]; Holmes, John S. A. ^[1]; Root, Roger P. ^[1]; Smith, Christian T.  ^[1]; Peterson, Douglas P.  ^[1]

---

1. U.S. Fish and Wildlife Service Abernathy Fish Technology Center 1440 Abernathy Creek Road, Longview Washington 98632 USA

Abstract Recent studies suggest that steelhead Oncorhynchus mykiss produced from local hatchery‐origin (HOR) adults have lower lifetime fitness than their natural‐origin (NOR) counterparts. To increase our understanding of this pattern, we compared age‐1 parr size and distribution produced by a local integrated population of HOR and NOR adults spawning naturally across a range of environmental conditions. Across 8 years, we used genetic parentage assignments and field measurements of parr in conjunction with creek temperature and flow data to find small, nonbiologically significant differences in size between parr of different parent origins. This suggests that parr produced by HOR adults are acquiring enough resources to grow at a rate similar to that of parr produced by NOR adults. In contrast to origin, we found strong positive associations between mean size of parr and annual mean water temperature and summer flow. Additionally, the distribution of parr was similar and HOR‐produced parr were not skewed relative to the location of the hatchery. Parr occupying the full extent of accessible and suitable habitat might be a positive outcome for hatchery programs seeking to supplement an existing population or replace an extirpated population. However, these results also imply that HOR fish could be competing with NOR fish for food and space, which might be less desirable if the goal of the hatchery program is harvest and not supplementation. Our results highlight the importance of clearly articulated goals for the hatchery program, as the observed pattern could be deemed a benefit or a risk depending on the hatchery's purpose. Lastly, projections for higher water temperatures and reduced summer flows, when considered in the context of the correlations we observed for size of parr, imply that coastal steelhead populations could start experiencing negative climate impacts with respect to steelhead parr growth metrics during the summer in the next few decades.

• Sponsoring Organization: USDOE
• OSTI ID: 1876097
• Journal Information: Transactions of the American Fisheries Society, Journal Name: Transactions of the American Fisheries Society Journal Issue: 4 Vol. 151; ISSN 0002-8487
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United States
• Language: English