[6] Sea Lions Digest 4 Percent Of Upriver Run

As the spring chinook run in the Columbia River has tapered off, so has predation by marine mammals on the hatchery and wild salmon that have been trickling upriver since late March. But not before they took a pretty big bite out of this year's return--about 4 percent according to preliminary numbers in a report issued by the corps of Engineers at the end of May.

Sea lions have pretty much moved south down the West Coast towards breeding grounds, but not before some have bulked up significantly. One sea lion, C 265, who has been in the neighborhood for the past five years, was trapped near Astoria and weighed in at 559 pounds. After being radio-tagged and tracked--the pinniped was down near Newport, Oregon in late March, but spent most of his time in April and May feeding on salmon at Bonneville--he was trapped once again at Astoria May 21 and tipped the scales at 1,043 pounds That's a gain of 484 pound in two-and-a-half months.

The Corp's report said that the increased harassment program didn't have any substantial impact on reducing predation, "but it continues to be effective short term when working specific locations."

The hazing program began on Feb. 28 and worked on reducing the numbers of Steller sea lions and their take of sturgeon. The report also said hazing kept the California sea lions further away from the dam and from surfacing as much.

Sea lions first showed up at Bonneville Dam last December, about a month earlier than the year before, and harbor seals appeared in January. More than 50 sea lions were sighted near the dam at the end of April--with about 80 different individuals over the course of the season--about half of them had been observed feeding there in previous years.

By June 11, more than 75,000 adult spring chinook run had been counted passing the dam. By May 24, observers had seen nearly 3,600 salmon and steelhead taken by predators, along with 361 sturgeon, 55 of them longer than 5 feet, and 119 lamprey.

Rep. Doc Hastings, R-Wash., and Rep. Brian Baird, D-Wash., proposed a bill earlier this year that would allow lethal removal of the most aggressive sea lions, who are protected under the Marine Mammal Act. NOAA Fisheries has accepted applications from both Oregon and Washington for permission to use lethal means to reduce the predation on ESA-listed salmon and steelhead at Bonneville, but the agency could take more than a year before it reaches a decision.

Hundreds of miles upriver at Lower Granite Dam, NOAA Fisheries' Jerry Harmon told NW Fishletter that about 30 percent of the spring chinook were showing up with seal bites this year, "a little higher than normal." -B. R.

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