A lower white sturgeon harvest will be allowed on the lower Columbia River because recreational fisheries this year hauled in more of the big fish than Oregon-Washington guidelines allow, according to state fishery officials.

The reduction is needed to bring the overall harvest back in line with limits established in a three-year agreement between the states.

Officials are also concerned by a potentially declining lower Columbia sturgeon population estimates.

"Possible explanations include declining natural production and increased predation by sea lions," said Brad James, fish biologist for the Washington Department of Fish and Wildlife.

Fishery managers from Washington and Oregon will consider those issues next year when they meet to work out the next three-year harvest agreement.

James said that tagging data indicates a gradual decline in some segments of the Columbia River sturgeon population in recent years.

An effort was begun last week to harass Steller sea lions that have swum the 140 miles upriver to Bonneville. The hazing is intended to discourage predation in a 5.5-mile stretch of river below the dam, the sturgeon's primary spawning area and an area where the older, larger fish tend to congregate even outside the spawning season, James said. The states each provide a boat crew two days per week for the hazing.

"They've encountered them both on oversize sturgeon and in the area" and have had some success in shooing the pinnipeds downstream, James said. Official fear that the loss of the broodstock may lower population productivity and as a result reduce recruitment into the midsize range that are made available for harvest. The loss of juvenile sturgeon likewise could impact future abundance of legal-size fish.

The presence of Stellers and of California sea lions in the river has grown in recent years. Historically few of the marine mammals were sighted as far upriver as Bonneville.

The abundance of 42- to 60-inch sturgeon declined from an estimated 136,900 in 2005 to 121,500 in 2006. Numbers of 42- to 48-inch white sturgeon declined from an estimated 36,900 annually for the 1996-2000 period to 94,000 in 2001-2006. Numbers of fish between 48 and 60 inches long increased from 25,000 annually in 1996-2000 to 33,200 in 2001-2006.

Fishery management is aimed at assuring sustainable levels of legal-size fish.

White sturgeon populations above Bonneville Dam are less productive than their downriver mates, cut off from the access to the marine environment and more affected by development of the river's federal hydro system. Functionally separate populations exist in the reservoirs above Bonneville, The Dalles and John Day dams.

The 2008 sport fishery for Columbia River white sturgeon from Bonneville Dam to the river mouth will have catch limits that are 3,500 fish fewer than in 2007.

The largest adjustment is in the area from Buoy 10 at the mouth of the Columbia River to the Wauna powerlines 40 miles upstream, where anglers will be limited to 13,143 legal-size sturgeon. This year's catch was estimated at 19,131 fish -- 2,857 above the annual harvest guideline for that area.

For waters above the Wauna powerlines to Bonneville Dam, fishery managers set a harvest level for 2008 of 13,900 white sturgeon, compared to this year's catch of 14,750.

"By keeping this year's fishery below the Wauna powerlines open through the Fourth of July, we knew the catch would likely exceed the quota," James said. "We let anglers know this would require a reduction in the guideline for 2008, and they generally agreed with that approach."

The 13,900-fish harvest guideline above the Wauna powerlines is still higher than in 2006, when the actual catch fell short of the 12,800-fish guideline.

"That shortfall was credited to the guidelines for both this year and next year, and translates into additional days of being allowed to retain a sturgeon," James said.

Catch guidelines for areas above Bonneville Dam to McNary Dam are likely to remain the same as this year, James said. As in previous years, anglers in all areas will be limited to one legal-sized white sturgeon per day and five per year. Anglers must release all green sturgeon, a separate species listed for protection under the federal Endangered Species Act.

Fishing seasons established for the 2008 white sturgeon sport fishery on the Columbia River and adjacent tributaries are as follows:

-- Buoy 10 to the Wauna powerlines: Fishing for retention of white sturgeon is open seven days per week from Jan. 1 to April 30 and from May 10 to June 24. From Jan. 1 to April 30, retained sturgeon must be a minimum of 42 inches and a maximum of 60 inches. From May 10 to June 24, retained sturgeon must be a minimum of 45 inches and a maximum of 60 inches. Catch-and-release fishing is allowed May 1 to May 9 and June 25 to Dec. 31.

-- Wauna powerlines to Bonneville Dam: Fishing for retention of white sturgeon is open four days per week (Thursday through Sunday) Jan. 1 through July 31 and Oct. 1 through Dec. 31. Retained sturgeon must be a minimum of 42 inches and a maximum of 60 inches. Catch-and-release fishing is allowed Aug. 1 through Sept. 30 and on days when retention is prohibited. All fishing for sturgeon will be closed from May through July in a sturgeon spawning sanctuary downriver from Bonneville Dam 5.5 miles to Navigation Marker 85.

--Above Bonneville Dam: Fishing for retention of white sturgeon opens seven days per week Jan. 1 until individual catch guidelines are met in the Bonneville, The Dalles and John Day pools. In the Bonneville Pool, retained sturgeon must be a minimum of 42 inches and a maximum of 60 inches. In The Dalles and John Day pools, retained sturgeon must be a minimum of 48 inches and a maximum of 60 inches. Catch-and-release fishing is allowed after the guidelines are met in all three areas above Bonneville Dam. All fishing will be closed from May through July in two spawning sanctuaries located below John Day Dam downstream 2.4 miles and from McNary Dam downstream 1.5 miles.

Those fishing periods will be reassessed in June, based on available catch data, James said. Any changes will be posted on the WDFW website (http://wdfw.wa.gov/) and distributed to the news media.