Sea lions camped out below Bonneville Dam continue to show a persistent and adaptive nature, perhaps shifting more of their salmon eating to the dark hours to avoid daytime human harassment.

And a trap-and-haul effort appears to be, at least at the start, ineffective in reducing predation.

For the first time, the ongoing effort to discourage sea lion predation on salmon below the dam included the trapping pinnipeds earlier this month.

Five California sea lions and one Steller sea lion came to rest inside the trap April 4 and fish and wildlife officials decided to close the door.

The marine mammals were trucked down to the river mouth and released near Astoria, Ore.

The first of the trapped sea lions was spotted at the dam six days later, having swum the 140 miles upriver to again gorge on spawning salmon.

"They're virtually all back now," Robert Stansell of the U.S. Army Corps of Engineers this week.

The last of the relocated California sea lions showed up at the dam Tuesday, 13 days after his truck ride. The Steller had not been spotted as of Tuesday.

The sea lions' quick return to the dam was not surprising. In past years, some sea lions have been reported to make the upriver trip in just two days. Many of the sea lions are branded with identifying numbers for a variety of research purposes; others are identified by natural markings that distinguish them.

"The intent (of the trapping effort) is to trap them and mark the ones that aren't marked" and equip some of them with satellite tags so researchers can "prove and document" their behaviors, Stansell said.

State, federal and tribal officials are amidst an effort to test various non-lethal means of reducing predation of the upriver spring chinook run, which contains Snake River spring/summer and Upper Columbia spring chinook salmon stocks that are listed under the Endangered Species Act.

"It was a surprise they used the trap in the first year that it was in place" downstream from Bonneville's second powerhouse, Stansell said.

The trap, which Stansell described as looking like a "giant dog kennel sitting on a floating barge," was put into place late this winter. Researchers expected it would take a year or two before the pinnipeds became comfortable with the barge-trap's presence.

Since that first trapping effort, a few of the marine mammals have sidled in and out of the trap, but none of them have been trapped and hauled. Oregon Department of Fish and Wildlife officials conducted the trap and haul.

After the initial trapping, the Bonneville project crew recommended and implemented some improvements to the transfer cage and transport trailer. Specific safety issues were also discussed after the first trap and haul.

The sea lions presence below the dam has been a growing concern. Prior to 2000, few of the pinnipeds made the trip inland as far as Bonneville. But in recent years their number has grown. More than 100 individual sea lions were identified at the dam during the springs of 2003 and 2004 and about 80 were counted in each of the next two years.

The sea lions' considerable predation on migrating salmon, and on white sturgeon, has prompted federal, state and tribal fishery officials to mount a counterattack. Hazing from the dam and from boats below the dam is being carried out from dawn to dusk each day for the first time in an attempt to unsettle the foraging sea lions.

"Steller sea lion presence has been dramatically reduced, resulting in substantial declines in predation on white sturgeon near the dam," according to an April 13 report produced by Stansell and his research crew.

"Hazing has been less effective at reducing California sea lion numbers and predation, but observers and hazing personnel have reported changes in sea lion behaviors. These changes include increased travel between tailraces in response to hazing, less time spent at the surface during foraging, and less time spent close to dam structures.

"Chinook salmon, the primary prey item for California sea lions at Bonneville Dam, are only beginning to arrive, so it is uncertain what impact hazing might have on sea lion predation in the long-term as the run increases and more sea lions travel to Bonneville Dam," the report says.

Over the past three weeks the infamous "C404" has been dodging in and out of one of the dam's fish ladders, having been spotted in the Washington shore fish count window numerous times and in the tailrace area on most days.

C404 was the first California sea lion known to actually venture up the fish ladders, prompting the installation of $1 million worth of screening at the entrances to keep him and other pinnipeds out.

With main entrances now blocked to sea lions, this year C404 has been taking an alternate route, vaulting 4-foot-high floating orifice gates at Powerhouse 2 to enter the fishway.

C404 has also been a bit more nocturnal, appearing in the fishways before 5 a.m. and after 10 p.m.

"We have also been noting 2-5 California sea lions working Tanner Creek before 6:00h, so the hazing may have caused some of the animals to begin to forage at night," according to the report. "We will try and make some night observations in the near future."

Tanner Creek feeds the Bonneville Hatchery, about two miles downstream from the dam. Stansell theorizes that the cagy sea lions have taken note that the creek entrance is a funnel filled with spawning salmon, those bound for the hatchery and others that take a respite before resuming their journey upstream.

Stansell said researchers did attempt to monitor sea lion foraging at night during the 2003 and 2004 salmon migrations but saw no evidence that the pinnipeds were feeding after dark.

"Because of the (daytime) hazing we may be causing it," Stansell said of sea lion hunting behavior witnessed at night this year.

Meanwhile, the upriver spring chinook salmon run has begun to build in recent days, and so has sea lion predation. Observed salmon predation has increased from as few as 30 two weeks ago to over 100 on Monday, Stansell said.

"It's just exploding," he said. Researchers estimate that the pinnipeds consumed 3.4 percent of the upriver spring chinook run two years ago in the area immediately below the dam, and 2.8 percent last year.

That consumption has gained the attention of fishery managers. The states of Idaho, Oregon and Washington early this year submitted an application with the federal government for permission to lethally remove the most troublesome and voracious California sea lions, which are shielded by the Marine Mammal Protection Act. Receiving such permission, if it is indeed gained, can take several years. Gaining such permission can only come if all non-lethal means fail to reduce the predation.

Washington Congressmen Brian Baird and Doc Hastings last year and again March 29 introduced legislation in the House of Representatives intended to expedite that MMPA process.

In a Wednesday briefing on the legislation, Northwest Power and Conservation Council public affairs director Mark Walker told the Council that the new legislation would allow the Secretary of Commerce 90 days to decide whether lethal take is necessary, including a 30-day public comment period.

If the secretary decided lethal take is justified, he would then have 30 days to either approve or disapprove specific lethal take proposals after their submittal.

"The big problem here is that the bill waives NEPA," Walker said of the prolonged federal process for evaluating the environmental consequences of such actions. "That's a real hot button issue on capital hill," and likely more so with Democrats now holding a majority in both the House and Senate.

Marker noted that no companion bill had been introduced in the Senate.

"I got a negative response, to be honest with you," while querying Senate staffers about the prospects for a companion bill's introduction, Marker said.

The Council discussed whether or not to throw its support behind the bill, but opted to research the issue further and potentially address it during its May meeting in Walla Walla, Wash.

* From the CBB Members’ Archives:

--- (3/22/07) SEA LION HAZING CHANGING BEHAVIOR; LESS BIG STURGEON EATEN

http://www.cbbulletin.com/Archive/03232007/207311.aspx

--- (3/1/07) HAZING STARTS FOR FISH- GOBBLING SEA LIONS IN COLUMBIA RIVER

http://www.cbbulletin.com/Archive/03022007/204381.aspx

--- (2/2/07) PROCESS BEGINS TO CONSIDER LETHAL REMOVAL OF SEA LIONS

http://www.cbbulletin.com/Archive/02022007/201522.aspx

--- (6/23/07) PRELIMINARY DATA SHOWS SEA LION IMPACT ON 2006 SPRING FISH RUN

http://www.cbbulletin.com/Archive/06232006/172009.aspx