Posted by Michael Milstein, The Oregonian May 15, 2008 19:37PM

When sonar surveys spotted a vast pile of rubble in the Columbia River below Bonneville Dam late last winter, officials suddenly worried part of the dam structure was eroding into the river.



U.S. Army Corps of EngineersThousands of
sturgeon - some 14 feet long - mass below
Bonneville Dam in this video frame from a
remotely operated submersible sent down
to investigate what was first thought to be
a pile of rubble. The "Mighty 86th Beavers"
on the screen refers to the Army dive team
operating the submersible, and the number
55.2 is the water depth in feet.

"Everybody said, 'Oh my gosh, we need to get divers out there right away,'" recalled Dennis Schwartz, a fisheries biologist with the U.S. Army Corps of Engineers, which oversees the dam.

What they found below the spillways in February was not a giant pile of rock at all, but a humongous pile of thousands upon thousands of sturgeon - some of them 14 feet long or longer - lounging together in frigid water at the bottom of the river.

"We call it the big sturgeon ball," Schwartz said.

Whole article...

Video of Sturgeon Ball

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It seems to me that these fish are reacting to some natural changes in the Earth and maybe we'd better figure it out. Remember the frogs in China before the earthquake???

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Nah. The article says that balling is a natural part of sturgeon behavior, they just haven't ever seen it happen with such large numbers of fish before. And just because someone hasn't seen it happen doesn't mean that it doesn't happen. How long have they been surveying the damn with sonar? For all we know, this might be something that happens once every 5, 10 years.. and nobody ever knew because there was no way to see to the bottom of the water before.

It's very interesting though.

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