A decline in razor clam numbers along the Kalaloch Beach in Olympic National Park has prompted park officials to close the clamming season there for the rest of the season.

Park officials say this season’s harvest data, collected from October 2010 through February 2011, suggests the razor clam population has suffered a decline, possibly due to the presence of pathogen or from removal by storm surges.

Population level assessments for razor clam are conducted annually during the summer months by the park. During the harvest season, coastal ecologists obtain population estimates by monitoring diggers’ Catch Per Unit Levels, or CPUE.

Harvesters may retain 15 razor clams per dig date. Average CPUE has dropped dramatically -- from nearly seven per dig date to fewer than three -- since the beginning of the calendar year.

This season’s diminishing harvest is similar to the pattern observed in 2006-2007, according to Steve Fradkin, the park’s coastal ecologist. Following that season’s closure, subsequent stock assessments led to a decision to close the fishery for the following season in order for the stock to rebuild.

Historically, a significant percentage of the Kalaloch razor clam population has been infected with the shellfish disease nuclear inclusion X, or NIX. Though harmless to humans, high levels of NIX can be fatal to razor clams. In July 2010, the last period for which NIX data was available, approximately 95 percent of Kalaloch Beach razor clams were infected.

The emergency regulation change applies only to Kalaloch Beach. Razor clam harvest for all other coastal waters of the intertidal zone in Olympic National Park is always closed. No additional harvest dates will be announced during the 2010-2011 harvest season, which runs through April.