Grantee Research Project Results

The Importance of Thermal Refugia as Critical Habitat for Threatened Juvenile Salmonids

EPA Grant Number: FP917091
Title: The Importance of Thermal Refugia as Critical Habitat for Threatened Juvenile Salmonids
Investigators: Brewitt, Kimberly Sarah
Institution: University of California - Santa Cruz
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Ecosystem Services: Aquatic Systems Ecology

Objective:

Water temperatures have critical impacts on fish physiology, distribution, and behavior. Elevated river water temperatures, caused by changes in land and water use, decrease the amount of usable freshwater habitat available to declining salmon populations along the Pacific coast of the United States. At the limits of their thermal tolerance, salmonids may behaviorally thermoregulate by moving to localized patches of colder water, or thermal refugia. As water temperatures continue to rise, it will be important to understand the implications for salmonid growth and survival. This research project will focus on defining the mechanisms driving salmonid use of thermal refugia on the Klamath River in northern California and on developing a bioenergetics model that can be used to inform future fisheries and water management decisions.

Synopsis:

Recent increases in river water temperatures caused by climate change and altered land-use practices threaten the health of salmon populations world-wide. This fellow’s research will focus on quantifying how fluctuations in temperature and prey availability drive variations in the amount of usable freshwater salmonid habitat during periods of high summer water temperatures, and on developing a bioenergetics model that can be used to inform future fisheries and water management decisions.

Approach:

The first stage of research will entail collecting field data to map the thermal environment surrounding coolwater refugia, to radio tag juvenile salmonids for spatiotemporal distribution data, and to collect water samples to quantify daily prey availability. Correlating these data will allow me to determine how spatiotemporal temperature dynamics and food availability drive salmonid behavior. A thorough understanding of thermal refugia use by salmonids will be essential for the preservation of salmon populations in coming decades as climate change may lead to substantial changes in water temperatures and river flow regimes, further decreasing available freshwater habitat.

Expected Results:

This research will provide a better understanding of the specific mechanisms driving salmonid use of thermal refugia. The results of the field research will be integrated into a bioenergetics model, which will quantify the amount of thermally prohibitive versus usable habitat for different food and temperature scenarios. This will allow fisheries and land managers to gain a better understanding of the conditions under which thermal refugia become critical habitat, and the importance of variations in temperature and prey availability in influencing the superiority of a given habitat. Many tributaries on the West Coast have heavily logged watersheds, which can significantly impact water quality and temperature. Determining the relative importance of thermal refugia to salmonid survival will therefore help inform logging and other land-use practices in the region. These findings will be important for decisions concerning designations of critical habitat in rivers with high summer water temperatures, as the model will be applicable to similar systems.

Potential to Further Environmental/Human Health Protection:

This research will examine how elevated river water temperatures influence the growth and survival of juvenile salmonid populations. It will use field data on temperature dynamics, spatiotemporal fish distribution, and prey availability data to construct a bioenergetics model to examine the patchy nature of usable habitat for salmonids in rivers with high summer water temperatures. With an understanding of the importance of coolwater tributary inputs, this research will be an important tool for fisheries and land managers in determining watershed land-use practices.

Supplemental Keywords:

climate change, critical habitat, salmonid, steelhead, water temperature, refugia, thermoregulate,

Progress and Final Reports:

2011

2012

Final