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Pacific Salmon Life History Research

Research to support hatchery reform and recovery of the Pacific salmon in the Pacific Northwest.

salmon red alevins

Pacific salmon have complex life cycles that begin with adults spawning in natal streams, rivers, or lakes. The age and seasonal timing of salmon life-cycle transitions are determined by their genetic makeup and influenced by conditions in nature or in the regional hatcheries that produce salmon.

  • Juvenile salmon stay in freshwater from a few months to several years. They then undergo smoltification, a physiological change that allows them to live in the ocean.
  • Salmon smolts migrate to sea and grow there until they become adults and initiate reproductive maturation.
  • Adults migrate from the ocean back to their natal, freshwater habitat where they spawn.
  • The rate at which salmon grow affects how fast they complete their life cycle, ranging from 1 to 4 years.
  • Salmon develop an odor memory for their natal habitat that helps them navigate home to spawn as adults.

Diagram of various Pacific salmon life history strategies. Photo: NOAA Fisheries


Our research in this area aims to:

  • Develop hatchery rearing practices to improve salmon smolts' survival while reducing their interactions with wild salmon.
  • Reduce early male maturation and straying (i.e., mis-migration during homing) of hatchery-produced salmon.
  • Understand the potential impacts of climate change on salmon's early life history transitions and survival.
  • Improve our understanding of how hatchery rearing affects aspects of salmon physiology and behavior (e.g., olfaction and homing) during later life-stages.


  • Salmon hatchery reform: Improving smolt quality.
  • Reducing early male maturation in hatchery salmon.
  • Evaluation of methods to reduce straying rates of barged juvenile salmon.
  • Evaluation of potential long-term epigenetic changes in salmonids in response to hatchery rearing.
  • Puget Sound Chinook salmon recovery.


  • Bonneville Power Administration¬†
  • Oregon Department of Fish and Wildlife
  • Washington Department of Fish and Wildlife
  • Idaho Department of Fish and Game
  • Shoshone-Bannock Tribes
  • Yakama Nation¬†
  • Nez Perce Tribe
  • Confederated Tribes of the Warm Springs Reservation¬†
  • Grant County Public Utility District
  • Douglas County Public Utility District
  • Chelan County Public Utility District


Adam Luckenbach, Environmental Physiology Program Manager

Last updated by Northwest Fisheries Science Center on February 21, 2023