Warmer rivers may hurt fish

Study finds higher temps in lower peninsula spawning waterways

Posted: Monday, February 06, 2006

A study released Monday found water temperatures in the Ninilchik River, Deep Creek, Stariski Creek and Anchor River are rising, a trend that could pose problems for migrating salmon, decrease salmon egg and fry survival and make salmon at all life stages more vulnerable to disease.

The Homer Soil and Water Conservation District and Cook Inlet Keeper, partners in the Lower Kenai Peninsula Watershed Project, conducted the study, compared it to previously gathered temperature data and found that four streams have exceeded the Alaska Department of Environmental Conservation’s standards for salmon protection for six years in a row. According to the study’s report, the warming trend could seriously jeopardize the productivity of the streams.

The ADEC has been charged with protecting water quality and has created a set of standards to indicate the quality markers that must be met in order to maintain healthy streams. To meet the ADEC temperature standard for streams, water temperatures must not exceed 55 degrees Fahrenheit.

In 2005, all four streams exceeded the temperature standard for more than 80 days. Temperatures exceeding 55 degrees decrease salmon egg and fry survival rates.

“The warmer the water, the less oxygen there is and the harder it is for them to breath,” said Sue Mauger, a stream ecologist with Cook Inlet Keeper.

When water temperatures climb, oxygen levels decline, suffocating eggs and fry, and increasing their vulnerability to disease.

In some cases, the study measured temperatures exceeding 68 degrees. Temperatures exceeding 68 are particularly dangerous since they affect salmon at all stages of life, Mauger said.

Beyond 68 degrees, adult salmon also become more vulnerable to disease and their ability to swim up stream is inhibited.

The trend could alter when the fish migrate upstream to spawn. Temperatures and stream discharge affect when the fish move upstream, Mauger said. But predicting exactly how fish migrations will be affected is difficult to gauge.

“It’s hard to know how quickly the fish will learn and adapt,” Mauger said.

The streams studied provide spawning habitat for chinook, coho and pink salmon, as well as steelhead and rainbow trout, and Dolly Varden char.

Also alarming is the study’s finding that the elevated temperatures are occurring earlier and more consistently than in previous years.

It is unlikely that the problem is limited to the four streams studied, according to Shirley Schollenberg, Homer Soil and Water Conservation District manager.

“Rising stream temperatures appear to be a peninsulawide problem,” Schollenberg said. “By most accounts, weather conditions across the state are rapidly changing. We need state agencies to take the initiative and institute a statewide temperature monitoring.”

In 2004 Mauger and her monitoring team set up 10 instruments for the Kenai Watershed Forum to record temperatures across the peninsula and found similar trends in streams from Kasilof north to Captain Cook State Recreation Area past Nikiski to Cooper Landing.

Although climate change is a likely factor in the warming trend being observed, land use activities, such as road building, logging and gravel mining also may be contributing to the temperature changes, Mauger said.

Land use activities can lead to warmer streams when they remove vegetation and, consequently, shade from stream banks. When roads are built near streams rainwater falling on sun-warmed pavement carries heat from the road into nearby streams.

More research is needed to identify all of the sources contributing excess heat to the streams and to determine how much of the heat each source is responsible for, Mauger said.

Although research is an important first step, Mauger said more needs to be done.

“These waters are out of compliance ... (and) we have seen for many years these exceedances,” Mauger said.

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