Thermal refugia use by adult salmonids in the Klamath basin

Joshua Strange
School of Aquatic and Fishery Sciences

Project Description
Altered thermal regimes are a growing problem in rivers throughout the Pacific Northwest. The Klamath River of southern Oregon and northern California is no exception and has experienced increasing problems with high water temperatures, which has been spotlighted by recent fish kills of juvenile and adult salmonids. Thermal refugia clearly plays an important role in mitigating thermally related stress and mortality in the Klamath River, but the details are still not well understood, especially with regards to adult salmonids.

This project will build upon previous studies and will investigate patterns and implications of thermal refugia use by adult salmonids on the Klamath River. I will accomplish this by 1) employing temperature sensitive radio tags to track the movements and internal body temperatures of adult spring chinook during upstream migration; 2) monitoring and compiling temperature and flow data for the Klamath River during the study period; 3) monitoring adult salmonid use of the largest coldest thermal refuge on the Klamath River at the mouth of Blue Creek. The results of this study will be interpreted in light of previous studies on the Klamath River and elsewhere in the literature.

 

Objectives

  • Determine the residence times and patterns of use of thermal refugia by adult spring chinook in the Klamath River Basin during upstream migration.
  • Determine the bioenergetic benefits of thermal refugia use for adult spring chinook.
  • Determine the bioenergetic costs of exposure to high water temperatures for adult spring chinook in the Klamath River, and the primary sub-lethal effects associated with the exposure.
  • Determine the degree of utilization of the mouth of Blue Creek as a thermal refugia by adult salmonids.

Significance
The results of this study will increase the understanding of thermal refugia use by adult salmonids in the Klamath Basin, in particular spring chinook salmon. Given the run timing of spring chinook and the stressful thermal regime of the Klamath River, it is vital to adequately understand the relationship between thermal refugia and stock health. This is especially true for the precarious remaining wild populations (~1,000 adults), found primarily in the Salmon River.

The restoration of spring chinook throughout the Klamath Basin in goal shared by the Basin's Tribal Nations, governmental agencies, and NGOs alike. If this goal is to be achieved, the potential broodstock represented by the few remaining wild populations must be protected, and a greater understanding of thermal refugia and sub-lethal effects of temperature stress is critical to protecting those populations. Restoration of spring chinook throughout the Klamath Basin is a subject of paramount relevance given the current opportunity presented by the expiration of PacifiCorp's license for the five mainstem dams that comprise the Klamath Hydroelectric Project. While the outcome of the relicensing process is unclear, it is clear that a robust understanding of thermal refugia will be necessary in order to successfully restore spring chinook to the upper Basin due to the nature of its hydrology and the increased length of migration.