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Diversity of Pacific Trout

Status
Completed
Start Date
June, 2016

Understanding the history of Pacific trout (Oncorhynchus spp.) is important for understanding their persistence and evolutionary diversification within dynamic environments. The collection of work highlighted here provides a status update on the subspecies’ native range in North America and their introduced range in South America.

Distribution of cutthroat trout subspecies (Oncorhynchus clarkii ssp.) in western North America (Penaluna et al. 2016).

Distribution of cutthroat trout subspecies (Oncorhynchus clarkii ssp.) in western North America (Penaluna et al. 2016).

Pacific trout of the genus Oncorhynchus are greatly valued for ecological, socioeconomic, and cultural reasons, and have been the subject of substantial research and conservation efforts. Although Pacific trout share many notable life-history characteristics with Pacific salmon and salmonids, they also have distinctive traits. They are: 

  • Optionally anadromous—some forms of O. mykiss and O. clarkii (rainbow and cutthroat trout) may or may not spawn in freshwater and migrate to spend part of their adult life in the ocean. 
  • Iteroparous—repeat spawners. 
  • Spring spawners—months of spawning can vary widely depending on local conditions. 
  • Capable of living up to 10 years or more.

Pacific trout are found in western North America, mostly in streams and river systems that drain into the Pacific Ocean. Some populations, however, exist in closed interior basins. Others occupy streams that drain into the Gulf of Mexico east of the Continental Divide. Substantial declines in abundance and contractions in distribution across species and subspecies, by at least two-thirds of historical levels, have led to elevated protection in all or some portions of their ranges. Two cutthroat trout subspecies, Alvord cutthroat (Oncorhynchus clarkii alvordensis) and yellowfin cutthroat (O. clarkii macdonaldi), are considered extinct.

Human influences leading to declines in Pacific trout began with Euro-American colonization of North America (Penaluna et al. 2016). The decline of Pacific trout over recent decades and, in some cases, the past century reflects the challenges of balancing societal values with natural resources and wild places under a changing climate. Overfishing and land-use activities such as timber harvest, agriculture and ranching, and mining have led to habitat degradation. Dams that impede migration, nonnative species, and climate change are other significant threats.

Map of current and historical ranges of Pacific trout species in western North America from Alaska to northern Mexico showing coastal rainbow trout range from western Alaska to coastal southern California mostly in coastal drainages.

Pacific trout(Oncorhynchus species and Oncorhynchus mykiss subspecies) of western North America (Penaluna et al. 2016).

Pacific trout have evolved characteristics that will be key to their future persistence. These characteristics include genetic, phenotypic, and life-history diversity, as well as the ability to migrate long distances through highly variable stream conditions. Strong relationships among science and land and resource management, along with public support for flexible management approaches, are needed elements for restoring the diversity of Pacific trout and minimizing their vulnerability.

Map of current and historic ranges of cutthroat trout subspecies in western North America from Alaska to northern Mexico showing coastal cutthroat trout range from the Kenai Peninsula of Alaska through coastal drainages of Oregon and Washington to the north coast of California.

Cutthroat trout subspecies (Oncorhynchus clarkii ssp.) of western North America (Penaluna et al. 2016).

Key Personnel

Project Contact

  • Person
    Brooke Penaluna

    Brooke Penaluna

    Research Fisheries Biologist
    https://research.fs.usda.gov/about/people/brooke.penaluna

Collaborators

  • Ivan Arismendi, Oregon State University

  •  Phaedra Budy, U.S. Geological Survey

  • Andrew Whitely, University of Montana

  • Brad Shepard (retired), Shepard and Associates

Publications

External Publications

  • Arismendi, I.; Penaluna, B.E.; Gomez-Uchida, D.; Di Prinzio, C.; Rodriguez-Olarte, D.; Carvajal-Vallejos, F.M.; Mojica, J.I.; Mazzoni, R.; Cussac, V.; Maldonado, M.; Pellegrini Caramaschi, E.; Zeballos, A.J.; Villalba, A.; Van Damme, P.A.; Córdova, L.; Iglesias-Rios, R.; Cañas-Rojas, D.; Cañas-Merino, M.; Benavente, J.N.; Núñez-Flores, M.; Musleh, S.S.; Savaria, P. 2019. Trout and Char of South America. Chapter 9. In: Kershner, J.L.; Williams, J.E.; Gresswell, R.E.; Lobon-Cervia, J., eds. Trout and char of the world. Bethesda, MD: American Fisheries Society. 777 p.

  • Budy, P.; Rogers, K.B.; Kanno, Y.; Penaluna, B.E.; Hitt, N.P.; Thiede, G.P.; Dunham, J.; Mellison, C.; Somer, W.L.; DeRoito, J. 2019. Distribution and status of trout and char in North America. Chapter 7. In: Kershner, J.L.; Williams, J.E.; Gresswell, R.E.; Lobon-Cervia, J., eds. Trout and char of the world. Bethesda, MD: American Fisheries Society. 777 p.

  • Shepard, B.B.; Arismendi, I.; David, B.; Caudron, A.; Dedual, M.; Draper, M.; Hogan, Z.; Impson, D.; Penaluna, B.E.; Vermillion, D.; Young, K.A. 2019. Global perspectives on the management of trout and char. Chapter 15. In: Kershner, J.L.; Williams, J.E.; Gresswell, R.E.; Lobon-Cervia, J., eds. Trout and char of the world. Bethesda, MD: American Fisheries Society. 777 p.

  • Whitely, A.R.; Penaluna, B.E.; Taylor, E.B.; Weiss, S.; Abadia-Cardoso, A.; Gomez-Uchida, D.; Koizumi, I.; Trotter, P. 2019. Trout and char: genetics, taxonomy, and systematics. Chapter 5. In: Kershner, J.L.; Williams, J.E.; Gresswell, R.E.; Lobon-Cervia, J., eds. Trout and char of the world. Bethesda, MD: American Fisheries Society. 777 p.

Last updated December 3, 2025
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