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Third Season Of Sea Lion Trapping Ends; NOAA to Evaluate Effectiveness of Program by Staff Columbia Basin Bulletin, June 4, 2010

A third season of trapping sea lions below the lower Columbia River's Bonneville Dam has come to a close, leaving state and federal officials and others to ponder the success thus far of the effort to reduce predation on salmon and steelhead spawners.

The federal authorization provided to the states of Idaho, Oregon and Washington for the controversial undertaking requires that, after receipt of the annual reports from the states covering the first three years of authorized activity, the effectiveness of the removal programs actions and any lethal take be evaluated.

NOAA Fisheries, which processed the states request for legal take authority, will this fall reconvene the task force, originally assembled three years ago, to help evaluate the states' reports and other information.

The federal agency will then consider the reports, task force recommendations, and the issues set out in section 120 of the Marine Mammal Protection Act, and may modify the authorization and conditions for the coming year(s), or revoke the authorization for lethal take.

The authorization is valid until June 30, 2012, at which time it may be extended for an additional period of five years. But it can be modified or revoked by NOAA Fisheries at any time with 72 hours notice, according to the March 18, 2008 authorization letter from the federal agency to the states.

The states in December 2006 submitted their application for authorization under Section 120 to remove California sea lions that are known, as a result of research observations, to prey on salmon as the fish search for a passage route -- fish ladders -- at the dam. Among the salmon and steelhead stocks are fish protected under the Endangered Species Act.

During the application consideration process a "pinniped fishery-interaction task force" was established, as required by the MMPA, to review the application. All but one member of the task force concluded that California sea lions are having a significant negative impact on the recovery of Columbia Basin threatened and endangered salmonids. The dissenting member maintained that the level of pinniped predation at Bonneville Dam is not significant when considered in the context of other sources of mortality, such as hydropower operations and harvest.

In 2008, 11 California sea lions were effectively removed from below the dam, and in 2009, 14 were removed. An additional animal deemed eligible for removal was trapped in 2009 near Astoria, Ore., and euthanized.

Six of the animals captured in floating box traps in 2008 -- all of which were determined to be in good health -- were relocated to SeaWorld facilities in Orlando, Fla., and San Antonio, Texas. Another died while under anesthesia for a health examination.

However, the states suspended relocation efforts in 2008 after six other pinnipeds -- two Steller and four California sea lions -- died of stress and heat prostration in cage traps. An investigation by NOAA-Fisheries found that the cage doors fell shut behind the animals while the traps were unattended, but did not determine why the doors closed. The MMPA authorization does not allow removal of Steller sea lions, which are also protected under the ESA.

In 2009, the states resumed trapping efforts and removed 15 California sea lions that met the criteria outlined by NOAA Fisheries. Four of those sea lions were relocated to zoos and aquariums - two to the Shedd Aquarium in Chicago and two to the Gladys Porter Zoo in Brownsville, Texas. The other 11 animals were found unacceptable for transfer to zoological facilities due to health reasons and were euthanized.

This year 12 California sea lions were lethally removed from below the dam during what was a boom or bust trapping season.

The season started during the week of March 1 with one marine mammal captured and euthanized. The following week, seven California sea lions were trapped. Five of the pinnipeds were euthanized. Two of the captured animals were not on the removal list. One was branded and outfitted with an acoustic tag so its movements could be charted and the other was branded. Both were released.

Single animals were trapped and euthanized during the weeks of March 29 and April 5. Then the traps were empty for a month before three animals were captured during the week of May 3. Two were released and one was euthanized. Another trapping drought ensued before last week's captures.

Seven California sea lions were trapped during the last week in May. Five were branded, so they can be more easily identified by observers atop the dam, and released. Two were on the list for removal and were euthanized.

Preliminary date compiled by U.S. Army Corps of Engineers researchers indicates that as many as 82 different California sea lions and at least 53 Steller sea lions visited the dam since observations began March 1. That's up from last year's total of 54 but well below the peak of 104 in 2003.

The California sea lions seen this year include 38 that are on the list for removal.

Researchers note that, unlike previous years in the study that began in 2002, two-thirds of the animals seen this year are "new," meaning they are first-time visitors or have visited the dam before but have not previously been identified. Typically only about one-third of each year's visitors are new.

Many of the sea lion visitors seem to be taking a look around and then leaving, according to Robert Stansell, who heads the Corps' research at the dam. The newcomers average length of stay at the dam is much lower than that of old-timers, for the most part.

The researchers estimate that through May 27 the "expanded" take of salmon -- which includes observed weekday take plus an estimation of weekend predation -- was 5,392 chinook salmon. That's the highest total ever, bettering expanded take of just under 4,500 in both 2008 and 2009. But this year's take is likely to represent only about 2.1 percent of the upriver spring chinook salmon run, which would be the lowest since 2004 because of the large size of the salmon run. It is on track to become the second largest upriver spring chinook return during the course of the study.

While most trapping operations at Bonneville Dam ended for the year last week, trapping of California sea lions in the Columbia River will continue in Astoria and, on a limited basis, at Bonneville Dam.

Both Stansell, and the Oregon Department of Fish and Wildlife's Robin Brown, who leads the trapping effort, say more animals than usual have lingered, at the dam and at Astoria, late into the season.

"It's been odd year," Brown said. As many as a dozen California sea lions could still be seen at the dam last week and six or so were spotted there early this week, as were 100 or more at Astoria. Typically the marine mammals, all males, would be headed south by now, bound for breeding grounds off the coast of Southern California and in Mexico.

The time lapses between successful trapping efforts is something experienced last year as well, Brown said. It may be that the remaining animals are leery of the traps.

"The ones we got early are the ones that are familiar with the traps" -- sea lions that have longer histories at the dam, Brown said. He called the trapping effort thus far successful, though not quite as successful as the states would like it to be.

"We hoped this year we would really put a dent in the listed animals that need to go," Brown said of animals that have repeat visits to the dam and are known to be the largest consumers of salmon.

"It's still a little too early to tell," Brown said, whether the removal program can accomplish its goal reducing sea lion predation to 1 percent or less of the annual upriver spring chinook return to Bonneville.

The influx of new sea lion visitors this year could be mirroring events of a decade ago, according to researchers. Sea lions historically did not swim the 146 river miles inland to the dam in great numbers.

But their population at the dam swelled rapidly during the first few years of this century at the same time annual spring salmon returns jumped from the tens of thousands that prevailed in the 1990s to the hundreds of thousands over the past decade. The prevailing theory is that the sea lions, which forage north between breeding seasons, hopped on that gravy train toward Bonneville and found good hunting. And many of them remembered, and returned year after year.

After a relative slump over the past five years in salmon returns (an average of almost 135,000 as compared to a 2000-2004 average of 285,000), this year's run is expected total 315,000. That would be the biggest return since 2001 and 2002 and the third largest on a record dating back to 1938.

The three states are authorized to use lethal removal only on individual sea lions that are highly identifiable (natural markings or man-made ones like branding), and that continue to eat salmon, after deterrence methods are unsuccessful. Authorization is for as many as 85 nuisance animals annually, but NOAA Fisheries estimated at the beginning of process that the actual number will be closer to 30 a year.