Life is full of wonderful mysteries. And, society is full of inexpert experts trying to offer explanations to reporters. So, bucking the experts, we think the reason 60,000 Pacific or "White" Sturgeon are swimming around in a ball-like mass, forty feet below the surface, just downstream of Bonneville Dam, is to have fun. A bit of Acipenser erotica, perhaps.
When sonar surveys spotted a vast pile of rubble in the Columbia River below Bonneville Dam a few months ago, officials suddenly worried that part of the dam structure was eroding into the river...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.
On videos recorded by the underwater camera, the fish appear to be lounging, many on top of one another, some even upside down, at depths of 40 to 50 feet. Biologists considered whether the fish may be putting up an organized defense against sea lions showing up in increasing numbers to gobble salmon and sturgeon below the dam.
They discovered the sturgeon ball just as sea lions started to show up, but they also point out that sturgeon have been known to gather — though in lower numbers — in other places where there are no sea lions.
"The correlation [with sea lions] would probably be pretty weak," Schwartz said. "They all seemed to be just hanging out together."
Other equally plausible explanations:
Protesting the dam.
Seeking thermal optima.
Looking for more food now that humans have screwed up the marine ecosystem.
Frightened by the sight of truck nutz on nearby bridges
Via::The Seattle Times, Huge "sturgeon ball" in Columbia a mystery Image credit::IBID