Hood Canal risk of fish kill rising

BREMERTON — The oxygen concentration in Hood Canal was at record-high levels at the beginning of the year but has been dropping rapidly since May, increasing the risk of fish kills this fall.

A researcher said December's cold weather may have raised the oxygen levels and that summer heat is likely responsible for their fall.

Jan Newton, an oceanographer with the Hood Canal Dissolved Oxygen Program, said a number of factors are involved. At the moment, the average oxygen concentration remains in a healthy range, but the recent decline has been steep.

"Some [factors] are related to ocean conditions, and some are local conditions. What is interesting now is the drawdown in the 2009 data," she said. "They have a sharper slope than any other lines on the graph."

The Kitsap Sun newspaper reports that studies show sunny weather causes the growth of plankton, which use oxygen as they die and decay.

When oxygen levels become low, the risk of a sudden fish kill increases under certain wind conditions.

In most years, the lowest average oxygen concentration is measured in early September, and then it gradually increases through the winter.

The Hood Canal Dissolved Oxygen Program is wrapping up three years of study. Its report is due early next year.

Funding for the research will run out next year.

The Hood Canal Coordinating Council is considering steps to nurse the waterway back to health.