Ever-increasing levels of predation by Steller sea lions, and to some degree California sea lions, on white sturgeon appears to be a trend that is continuing upward in the waters below the lower Columbia River's Bonneville Dam.

Through January, sea lions have been observed taking more than 300 white sturgeon below the dam, said Robert Stansell of the U.S. Army Corps of Engineers, which operates the dam. Stansell heads up research at the dam aimed at evaluating the impact that preying pinnipeds (sea lions and seals) have on salmon and steelhead that are headed upstream past Bonneville to spawn. The migrating fish include numerous stocks that are protected under the Endangered Species Act.

Researchers began observations from the top of the dam Jan. 8 five days per week and are seeing a few steelhead and a lot of sturgeon being snatched by the pinnipeds.

"We're ahead of the curve," Stansell said of an observed sturgeon death toll that is already nearly halfway to last year's record total, 758. Last year's total was tallied during observations from Jan. 13 into early May. California sea lions were seen taking 37 of the sturgeon with Steller sea lions taking the rest, mostly by the end of March.

The sturgeon taken last year were estimated to be from 2 to 7 feet long but most, 79.4 percent were fish 4 feet long or shorter, according to the study's final 2009 report.

"We've got February and March to go," Stansell said. Much of the feeding frenzy shifts to spring chinook salmon when the numbers of spawning fish begin to swell in later March and April. The Steller and California sea lions typically have left the area below Bonneville by the end of May.

The Steller sea lions have in recent year begun to congregate below the dam, which is at the head of the lower river's primary sturgeon spawning grounds. Bonneville Dam is located about 146 river miles upstream from the mouth of the river and the Pacific Ocean.

The Corps research began in 2002 to, primarily, chart the eating behaviors of California sea lions. In the first year of the study, no Steller sea lions were seen at the dam. But the number has grown over time with 17 Stellers in 2008 setting a record that was broken last year with the appearance of 26 Steller sea lions at the dam.

Already 16 Stellers have settled in below the dam this year. Observers have also seen five different California sea lions visiting the dam so far this year, but no more than two on any given day. The number of California sea lions visiting the dam grows as spring chinook run builds each year.

The high count since 2002 was 104 individual California sea lions in 2003, but the tally settled in the 70-80 range from 2005-2008 before falling to 54 last year. The 2009 season marked the first prolonged effort to trap and remove California sea lions from below the dam. Four were trapped and relocated to aquariums and 10 were trapped and euthanized.

The removals by the states of Oregon and Washington have been federally approved as a means of controlling impacts on listed salmon and steelhead stocks. In 2008 11 sea lions were effectively removed from the area. The authority was granted under Section 120 of the Marine Mammal Protection Act, which allows the removal of individually identifiable pinnipeds that are having a significant impact on listed salmon.

The white sturgeon are not ESA listed, but are also not in the greatest shape. Surveys indicate white sturgeon are declining in number, prompting state fishery managers in Washington and Oregon to consider reducing this year's harvest by 20 percent to 50 percent. The Oregon and Washington fish and wildlife commissions both take up the topic at week's end.

"We're a little concerned" about the impact that sea lions may be having on the overall status of the lower Columbia white sturgeon population, Rick Hargrave of the Oregon Department of Fish and Wildlife said.

The state agencies last month started hazing the sea lions from boats in hope of reducing the predation activities.

Lethal removal of Steller sea lions is not an option, since they are protected under both the ESA and the MMPA. The eastern population of Steller sea lions, of which the Columbia River pinnipeds are a part, are listed as threatened under the ESA.

But a recovery plan completed in 2008 for both the eastern and endangered western populations says that perhaps ESA protections may no longer be necessary for the eastern group, which has been growing at a rate of about 3 percent in recent years.

"The primary action in the plan is to initiate a status review for the eastern DPS and consider removing it from the federal List of Endangered Wildlife and Plants," according to the recovery plan completed by NOAA Fisheries Service's Alaska Region.

"We expect to initiate a review under Section 4 of the Endangered Species Act of the status of the eastern distinct population segment of Steller sea lions in the very near future," Lisa Rotterman, Steller sea lion coordinator for the Alaska Region, said this week. Such a review is called a "5-year review."

"We will begin this process with the publication of a Federal Register notice notifying the public of the initiation of the 5-year review and requesting relevant, new information on the listed species, and threats to that species," she said.

The states meanwhile took an early opportunity to test their trapping skills. In May of last year a California sea lion was seen hitching a ride on a tug boat through Bonneville Dam's navigation lock and has spent the summer, fall and early winter above the dam.

"C697 was subsequently observed on many days after that either in the near dam forebay near the Bradford Island fishway exit, the Bridge of the Gods, Stevenson, and even up at The Dalles Dam spillway area. As of the date of this report, the last reported sighting upstream of Bonneville was on October 19," according to the 2009 final report.

State officials did manage to trap the marine mammal recently and transport him down to the river mouth.