News Release
| Release Number: | 05-079 |
| Dated: | 5/31/2005 |
| Contact: | Diana J. Fredlund, 503-808-4510 |
PORTLAND, Ore. — The U.S. Army Corps of Engineers began installing barriers at Bonneville Lock and Dam today designed to keep sea lions from entering the fishways while allowing fish to pass.
The barriers, which consist of metal racks or gates are being installed into the four adult fishway entrances at Bonneville’s Second Powerhouse. Each barrier is 12-feet wide and 18-feet long; connected end-to-end the two pieces form a 36-foot high barrier in front of the fishway entrances. The gap between the bars is 15 and ¾ inches, too small for sea lions to squeeze through.
“The idea is to exclude the sea lions while not impeding passage for the fish migrating upriver,” said Michael Crump, the Corps structural engineer who designed the devices. “Once the barriers are in place we will monitor the movement of the fish to make sure it doesn’t hinder them.”
The Corps wanted to install the barriers before the sea lions left for mating season, so staff could verify their success at keeping the pinnipeds out of the fishways, said John Kranda, the Corps’ project manager. Even more important, the barriers will be tested throughout the summer fish migration, without sea lions present, to make sure there are no serious problems with fish passage. The test will include periods with the gates in and out to see if fish pass and behave differently under these two conditions. With the sea lions present this could have trapped one of the predators inside the ladder. The University of Idaho will radiotag about 400 salmon to see if fish behavior changes with the entrances installed and when they are removed.
“It was important to get as much information as we can so we can be ready to deploy next spring when the sea lions return,” Kranda said. A decision will be made to provide additional barriers for the dam’s First Powerhouse entrances following the test program and if any design modifications are needed.
For many years sea lions have been swimming nearly 140 miles up the Columbia River to Bonneville Lock and Dam, to await the annual spring migration of salmon, steelhead and other anadromous fish. Generally arriving in mid-to late-February, the predominantly male sea lions eat to gain weight and energy in preparation for the spring mating season in Southern California in late May and June.
Last year, 2004, was the first time any sea lion had entered the fishways, either in search of fish or just exploring. Biologists are concerned their presence in the fishways may delay fish passage, as well as damage sensitive monitoring equipment.