The U.S. Environmental Protection Agency (EPA) released water temperature guidance on Tuesday to protect Pacific Northwest salmon and trout. The guidance, according to EPA officials, is intended to assist the states of Idaho, Oregon, and Washington and Pacific Northwest tribes to develop temperature water quality standards that will meet the requirements of the Clean Water Act and the Endangered Species Act.

Federal scientists believe elevated water temperature, caused in part by development and population growth, is a factor in the decline of threatened and endangered pacific salmon and bull trout. Warm water can kill cold water fish directly, but is more likely to stunt fish growth, increase disease and provide advantages to warm water species.

According to the National Oceanic and Atmospheric Administration (NOAA) Fisheries, elevated water temperature is the most widespread water quality problem in the Pacific Northwest and have identified some 1,500 rivers and streams in Idaho, Oregon, and Washington as "temperature impaired."

High water temperature, combined with low water levels, was a major cause of last year's massive fish kill that killed more 30,000 adult fall chinook in the lower Klamath River.

States and tribes that meet the EPA's guidance on water temperature are likely to satisfy requirements for both the Endangered Species Act and the Essential Fish Habitat rules, according to NOAA Fisheries Regional Administrator Bob Lohn.

The Clean Water Act requires states and authorized tribes to adopt water quality standards and requires the EPA to approve or disapprove the standards. The Endangered Species Act requires EPA to consult with NOAA Fisheries and the U.S. Fish and Wildlife Service to ensure state standards do not jeopardize the continued existence of salmon and trout listed on the Endangered Species Act.

"We strongly encourage states and tribes in the Pacific Northwest to adopt the recommendations in EPA's guidance to protect and aid in the recovery of the Bull Trout and other threatened and endangered salmonids," said USFWS Regional Director David Allen.

State and tribal water temperature standards that differ from EPA's guidance may also be acceptable as long as EPA determines they meet Clean Water Act requirements and they don't jeopardize the fish in accordance with the Endangered Species Act.

"We think the guidance will help set the stage for the states to revise their water quality standards to protect threatened and endangered fish," said Dave Peeler of the Washington Department of Ecology.