Prospects good for chub recovery.

Byline: SCOTT MABEN The Register-Guard

SPRINGFIELD - The Oregon chub is one step closer to shedding its designation as an endangered species thanks to a healthy population that biologists stumbled upon last fall in the lower McKenzie River.

Close to 1,000 of the minnows are thought to live in side channels and backwater areas of Big Island, a braided stretch of river just north of the Thurston area, recent surveys show. That's enough to be considered a genetically viable population, fisheries biologists said.

"Not only did we get another population that probably will work toward our goal of downlisting the species from endangered to threatened, but this also extended the species into another basin, which will reduce the risk of extinction," said Paul Scheerer, a state biologist who heads up Oregon chub recovery for the state Department of Fish & Wildlife.

The presence of chub also indicates healthy habitat for other native species, including spring chinook salmon, which is listed as threatened in the McKenzie.

The federal government listed Oregon chub as an endangered species in 1993, and it was thought to have vanished in the McKenzie basin as early as 1899. But biologists conducting a routine fish survey in the 108-acre Big Island area last November were amazed to find that the fish somehow survived undetected for decades.

During a more intensive survey this spring, biologists estimated that 940 adult Oregon chub inhabit the island's slow-water hideaways. This exceeds the 500-adult minimum for a genetically viable population.

For the fish to be downlisted to threatened, the state must find 10 populations of 500 or more adults that are stable or increasing in abundance for at least five years. The 10 populations must be distributed throughout the Willamette Valley with at least three each in the Middle Fork Willamette drainage, the Santiam drainage and the mid-Willamette drainage, which includes the McKenzie.

If 20 stable populations are found, the chub will be removed from the list altogether. So far, nine populations meet the criteria. The chub survives in the North Fork of the Willamette between Jasper and Oakridge, the main stem between Eugene and Jefferson and the Santiam River, where populations have struggled since the 1996 floods.

Loss of habitat for flood control, agricultural practices and development has hammered Oregon chub populations. The fish also succumbs to predation by non-native fish such as largemouth bass, bluegill and crappies.

"This seems to be the biggest obstacle toward recovery of this species," Scheerer said.

Some chub populations in the Santiam declined after floods washed in bass and bluegill. No predatory fish were found in the Big Island area, and the McKenzie's cold water is considered a barrier to those invasive species.

"Oregon chub were found to be most abundant in the isolated beaver ponds on the island and were found only in association with other native fish species," Scheerer said.

The state also sampled for Oregon chub upstream and downstream from Big Island, including in Cedar Creek and an oxbow near Weyerhaeuser's linerboard plant, but found none.

State biologists happened upon a small population in May while surveying for cutthroat trout in three manmade ponds feeding into the Mohawk River near Marcola. One of the ponds contains about 120 chub. The other two, which have bass and bluegill, have none.

Scheerer said the state may be able to help the chub develop a viable population there by removing the non-native fish and connecting the three ponds.

The state will monitor Big Island's chub population annually for five years. The island and adjacent lands are owned by the McKenzie River Trust, a Eugene-based land conservancy that protected the area with a conservation easement.

CAPTION(S):

THOMAS BOYD / The Register-Guard A biologist holds an Oregon chub found in the McKenzie River system.