But at least one issue gave the judge reason to pause -- whether the federal agency had given proper consideration to the impact sea lion removal would have on recreationists that enjoy viewing the large marine mammals.

"This is the point I'm most tentative about," Mosman said at the end of the hearing in Portland.

In its challenge of the NOAA decision, the Humane Society of the United States alleges the federal agency violated the Administrative Procedure Act, the Marine Mammal Protection Act and the National Environmental Policy Act.

A NEPA failing, the HSUS has said, is that "NMFS did not consider the effect of sea lion removal on aesthetic, wildlife-viewing, and other wildlife-dependent recreational interests in this National Landmark and National Scenic area." Nor did NOAA in its March 12 environmental assessment properly weigh the risk posed to Steller sea lions by the proposed shootings of California sea lions that also frequent the area below the dam, HSUS says.

In concluding remarks the judge said he was satisfied the Steller sea lion issue was "given a hard look by the agency."

NEPA requires an EA or a more exhaustive environmental impact statement to determine whether a proposed action will have a significant impact on the human environment. HSUS argues that the proposed sea lion removal deserved a more complete analysis.

Federal attorneys say that kayaking and wildlife viewing were considered in the EA and pointed out that the area where the pinnipeds congregate is off limits to the public. Federal briefs also note that there will undoubtedly still be sea lions below the dam and in the river even after the removal of up to 85 sea lions each year.

Mosman said Wednesday that on most of the points argued his initial thoughts favored the federal decision making. He said he planned to produce a written opinion "in the very near future" but needed time ponder those tentative inclinations. The review of the arguments, applicable case law and writing time would take about two weeks, he said.

A July 3 HSUS summary judgment motion asks the court to set aside NOAA's March decision granting five-year authorization to the states of Idaho, Oregon and Washington to lethally remove California sea lions, which prey on salmon, steelhead and other fishes below the dam and elsewhere in the lower river.

In making the decision, the agency determined that the situation satisfied the MMPA's requirement that only "individually identifiable pinnipeds which are having a significant negative impact on the decline or recovery of salmonid fishery stocks…" can be lethally removed. There are 13 Columbia River basin salmon and steelhead stocks listed under the Endangered Species Act

HSUS says that NOAA violated the MMPA by failing to properly define in its documents what level of salmon catch by the sea lions represents "a significant negative impact."

Mosman pointed out at several points in the debate that he is "not supposed to dive too deeply into the science." He cited recent precedent established in the U.S. Court of Appeals for the Ninth Circuit that says the science of the expert agency must be heeded.

The opinion in that case said the appellate court had been asked "to act as a panel of scientists," and that "in recent years, our environmental jurisprudence has, at times, shifted away from the appropriate standard of review and could be read to suggest that this court should play such a role."

"We defied well-established law concerning the deference we owe to agencies and their methodological choices," the en banc order said of an earlier decision by a three-member Ninth Circuit panel.

The Ninth Circuit "has some very pointed remarks about what the standard of review is," Mosman said. His task, he said, is to judge whether the decision is grounded in science and rational, and he cannot "pick" the science offered by HSUS over NOAA's unless the organization proves NOAA's choices are irrational.

The judge said Wednesday it is "within the authority and expertise of the agency to attempt to define" what is relatively ambiguous MMPA language regarding significance.

"It's not beautifully written, but I am unable to say it's contrary to the law," Mosman said of NOAA's criteria.

HSUS also argues that NOAA failed to consider other impacts to salmon, as required by the MMPA, and improperly left documents from the administrative record relating to previous ESA decisions allowing harvest and hydro system impacts on listed fish that are greater than sea lion impacts. HSUS attorneys said coming to "no significant impact" or no jeopardy conclusions in prior decisions while finding sea lion take significant is contrary to APA mandates.

Federal attorneys say that "NMFS appropriately considered the effects of the Columbia River power system and fishing on these species in the context of their MMPA decision process," and that NMFS's MMPA Section 120 finding does not "swerve from prior precedents" as HSUS contends.

HSUS attorney Rebecca Judd argued that the NOAA decision is irrational.

"They still haven't explained why 17 percent is not significant" while a sea lion take of 12.6 percent is significant, she said. Judd referred to the maximum allowable harvest of a salmon run. "I don't see any reasonable explanation in the record."

Mosman agreed with federal arguments, saying that the decisions are "made in very different settings" and answer to different statutory demands.

"I don't find the decision here to be arbitrary or capricious or irrational," Mosman said, again qualifying his conclusion as tentative.

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A stronger spring chinook salmon run and the larger contingent of predatory sea lions below the Columbia River's Bonneville Dam added up this spring to a jump in overall fish consumption over last year, according to a 2008 field report released this week by the U.S. Army Corps of Engineers.

The estimated sea lion "catch" of salmon and steelhead at the dam this year totals 4,927, the most ever recorded over the seven year history of the Corps research. The previous high was last year's 4,355 total.

The sea lions "impact" on the run was not, however, the greatest it has been. That "adjusted salmonid catch estimate" represented 3.2 percent of the 147,543 salmon passing the dam during the Jan. 1 to May 31 study period. Last year the toll was 4.7 percent on a smaller run, 88,474.

The adjusted estimate includes a tally of fish taken by sea lions actually observed by members of the research team from atop the dam. They recorded the prey species in as many instances as they could. The total was adjusted upward with estimates of the number of fish likely taken when observers were not present and with an apportioning of "unidentified salmonid" catch among the various predators -- California and Steller sea lions and harbor seals.

The research was launched in 2002 to evaluate a growing pinniped presence below the dam. In the several previous decades, few of the large marine mammals made the 146-mile trip from the Pacific Ocean. But, coincident with a rise in spring chinook salmon numbers, more and more sea lions have been seen at the dam during this decade.

The researchers have used surface observations to evaluate the seasonal presence, abundance, and predation activities of pinnipeds in the Bonneville Dam tailrace. The monitoring program is part of an ongoing effort to understand and appropriately manage pinniped predation on threatened and endangered salmonids, according to the 2008 report. A total of 13 Columbia basin salmon and steelhead stocks, including spring chinook and steelhead trout, are listed under the Endangered Species Act.

Observers were stationed at each of the three major tailrace areas of the dam -- two powerhouses and the spillway. In 2008, regular observations began on Jan. 11, Mondays through Fridays, and increased to seven days per week on Feb. 4. The regular observations -- from an hour before sunrise to an hour after sunset -- ended on May 31.

The report, "Evaluation of Pinniped Predation on Adult Salmonids and Other Fishes in the Bonneville Dam Tailrace," can be found online at: http://www.nwd-wc.usace.army.mil/tmt/documents/fish/

The report was produced by Sean Tackley, Robert Stansell and Karrie Gibbons.

Sea lions this spring nearly doubled their take of white sturgeon over last year's study record. A total of 606 sturgeon were observed taken as compared to 360 in 2007. The adjusted sturgeon take is estimated to be 1,139 this year.

The report says that Steller sea lions -- which are also a listed species -- again targeted white sturgeon, accounting for 97.7 percent of the observed catch this year. The Columbia River white sturgeon are not listed.

"Steller sea lions were known to be catching sturgeon in the vicinity of Bonneville Dam as early as November 2007, so observed and expanded catches represent minimum catch," the report says. The estimated total lengths of sturgeon caught in 2008 ranged from less than 2 feet long up to 7 feet long, , but 85.9 percent of the observed take were estimated to be 4 feet long or shorter.

California sea lions were the primary predator on salmonids, accounting for 96.2 percent of the 4,243 observed catches. That percentage was lower than what has been seen previously with Steller sea lions' increased interest in salmon and steelhead this year. Stellers took only 0.3 percent of the observed salmon take last year but were estimated to take 3.8 percent of the passing spawners in the spring of 2008.

Chinook salmon made up 93.2 percent of the observed sea lion adult salmonid catch in 2008. The expanded chinook catch estimate for the Bonneville Dam tailrace observation area was 4,115 or 2.3 percent of the chinook run at Bonneville Dam from Jan. 1 through June 15, according to the report.

Steelhead comprised about 6.8 percent of the observed adult salmonid catch during the same period. Steelhead, which are present in the Bonneville Dam tailrace throughout the winter and spring months, comprised the majority of salmonid catches prior to the onset of the spring chinook salmon run.

A total of 103 pinnipeds were observed below the dam during the research period this year. The number of California sea lions increased from 69 in 2007 to 84 in 2008 and the number of Stellers jumped from nine to 17. Two Pacific harbor seals were observed.

In the first year of the study only 30 individual California sea lions observed at the dam. The number spiked to 106 in 2003 and 101 in 204 in 2005, then dropped to 80 and 72 the next two years.

The sea lions' bite on listed salmon has caused concern among Columbia basin states, which expend much time and money to help improve the status of protected salmon. Idaho, Oregon and Washington late last year filed an application under the Marine Mammal Protection Act to lethally remove California sea lions.

The states' application was approved this spring by NOAA Fisheries Service. A lawsuit was immediately filed in an attempt to halt lethal removals. An agreement was reached, however, allowing the capture and transport of specific sea lions to zoos and/or aquariums, but no lethal removals. Six California sea lions were trapped and flown to SeaWorld facilities in Orlando, Fla., and San Antonio, Tex.

The states halted the trapping effort in early May after six sea lions were found dead in the traps, having apparently died of heat prostration. An investigation is under way in an attempt to determine how the sea lions became caged in the unmanned traps, which had been left open overnight.

The lawsuit meanwhile is ongoing. The Humane Society of the United States is asking the U.S. District Court to declare NOAA's decision of the lethal removal application illegal.

Again in 2008 the states, tribes and federal agencies tried non-lethal means to deter sea lion predation.

"As in previous years, hazing activity temporarily moved some sea lions out of tailrace areas, but the animals typically returned and resumed foraging shortly after hazers left the area. The high adult salmonid and sturgeon catch estimates seen in 2008 suggest that at best, hazing at the current level of intensity only blunts the ever-increasing predation trend," the report says.

Hazing from the dam itself involved a combination of acoustic, visual, and tactile non-lethal deterrents, including vessel chasing, above-water pyrotechnics (cracker shells, screamer shells or rockets), rubber bullets, rubber buckshot, and beanbags. Boat-based crews also used underwater percussive devices known as seal bombs.

"The Corps should continue to assist in the pursuit and evaluation of potential non-lethal deterrent technologies as part of a long-term strategy to reduce pinniped predation on adult salmonids, sturgeon, and lamprey in the Bonneville Dam tailrace," the report recommends.

"Acoustic deterrent devices (ADDs) were again installed at all main fishway entrances" as an attempt to scare off the pinnipeds, the report says. "As in previous years, pinnipeds were observed swimming and eating fish within 20 ft (6.1 m) to 50 ft (15.2 m) of some of the ADDs, with no obvious deterrent effect observed."

"The Corps should consider discontinuing the use of acoustic deterrent devices (ADDs), as this device has demonstrated little or no usefulness as a sea lion deterrent at fishway entrances," the report recommends.