News Release
| Release Number: | 05-055 |
| Dated: | 4/25/2005 |
| Contact: | Diana J. Fredlund, 503-808-4510 |
PORTLAND, Ore. — Whether it’s the racket sea lions don’t like, or that more fish are swimming upriver, hungry pinnipeds have not been entering the fishways as they did in past weeks.
The sea lions have not been seen in the Bonneville Dam fishways since Friday.
Since 2002 sea lions have been gathering below Bonneville dam in growing numbers, but this is the first year they have made their way up both the Washington and Oregon fishways as far as the viewing windows.
To discourage sea lion incursions, engineers and biologists have been using escalating harassment techniques agreed upon by the U.S. Army Corps of Engineers, National Marine Fisheries Service and Oregon and Washington departments of fish and wildlife, aimed at keeping the pinnipeds out of the fishways. These techniques are consistent with the Marine Mammal Protection Act.
The next step in that harassment began Friday when hydrophones were installed underwater that emit a high frequency sound sea lions do not like but fish cannot hear (humans only hear a clicking sound). “The hydrophones act a lot like a fence,” said Robert Stansell, a biologist with Bonneville Lock and Dam. “The sound gets louder when the sea lions approach the junction pool. The closer they get, the louder the sound becomes; they should swim away before it gets too loud for them, thus preventing them from passing that area. ”
A long-term solution is being developed: a barrier that allows fish to pass but stops sea lions from entering the fishway. These gates will be normally installed when the first sea lion is seen in the tailrace, usually late February or early March, and removed after the last sea lion leaves.
The Corps hopes to design, construct and place the barrier before the sea lions depart for Southern California. A schedule should be finalized by early next week.
There are other last resort measures the Corps can take to discourage sea lion incursions if the hydrophones don’t keep them out, like rubber arrows and rubber bullets, but Stansell is hopeful the increased numbers of fish in the river may make it unnecessary. The daily fish count has been increasing every day since April 17 when 210 salmon were counted, to more than 3,600 passing through on April 24.
“We can’t say for sure if it is the hydrophones or the fact that hunting is easier now that more fish are in the river, but we’re just happy they seem to have decided the fishways are just too much trouble.” - 30 -