The Bureau of Land Management will decline recreational dredging permits for a two-mile stretch of the South Yuba River this year, citing concerns about stirring up mercury particles before a long-anticipated water test.

During controlled studies, the Bureau of Land Management will investigate whether dredging releases methyl mercury to the sediment's surface where fish and aquatic insects could then ingest the toxin.

"What we don't want happening is other people dredging at the same time and skewing results," said Jeff Horn, outdoor recreation planner for BLM.

Gold mining activity 150 years ago turned the South Yuba River into a mercury hot spot, but up until now, few studies have been conducted in the watershed, Horn said.

The closure is not expected to impact many recreational gold seekers, since only two discretionary special use permits were issued last year. Mining claims will remain intact, Horn said.

The affected area is located about a mile and a half above Purdon Crossing at Overlook Point and spans to the Forest Service boundary. The few hardy souls who choose to search for gold in the remote area are required to haul dredging equipment in by foot for miles using a wheelbarrow on narrow dirt paths, Horn said.

"It's a long, arduous process," he said.

Recreational dredging is closed from now until August, Horn said. Check BLM's website for more information or contact the Folsom field office at (916) 985-4474.