Mystery Of The Day: Sturgeon Balls
by John Laumer, Philadelphia on 05.21.08
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
maybe they are adapting to the changes in their natural habitat?
that is very weird. . .
I speculate that it's adaptation as well, Jeff.
Nature is so cool.
I think fish generally do this when they are threatened in some way. I would say it's the Sea Lions mostly.
It is probably because they are stressed in some way. Maybe bad water chemistry, lack of food, too much food, other predators, perception of other predators, water temperature?
It is always interesting to watch fish in these 'bait balls'.
vsk
Apparently earth worms do the same thing. As part of his senior thesis at Carlton, my friend Chuk did an experiment with worms, cement, and various forms of earth (dirt, clay from nearby cliffs, etc). He'd put the worms at various depths and have various layers, including layers of quick-drying cement so he could time movement towards food etc.
In a few of his fishtanks full of sediment, he poured the concrete in a way that none of the worms escaped. In these cases, he found them in a tangled mass at the bottoms of the tanks. It was completely unexpected.
He also concluded an erotic last hurrah at a coming apocolypse. Chuk if you're reading this, feel free to correct any of this.
That must be quite a sight. I wonder what happened?
JJ
Adaptation is REACTIVE guys, it's not like fish can decide "Hey! lets come up with a new behavioral strategy to keep our numbers viable!"
Fish basically do two things. Eat and Spawn. It's most likely that they are either catching smelts coming off of the spillway or collecting Shad at the Terminus of their journey up the river.
I also read this on the Wikipedia link:
"In the late spring or early summer, they congregate in areas of rivers with a heavy current, gravel bottom, and a water temperature of 58 °F to 66 °F (14 °C to 19 °C)."
Sounds to me like this might be a romantic encounter.
Fish basically do two things. Eat and Spawn. It's most likely that they are either catching smelts coming off of the spillway or collecting Shad at the Terminus of their journey up the river.
I also read this on the Wikipedia link:
"In the late spring or early summer, they congregate in areas of rivers with a heavy current, gravel bottom, and a water temperature of 58 °F to 66 °F (14 °C to 19 °C)."
Sounds to me like this might be a romantic encounter.
I think WillyBe is probably on the right track.
I suspect that they are responding to a chemical message from upstream.
Of course, that leaves many unanswered questions. Is it a food signal, a sex signal or migration signal? Is it natural or manmade? Is it a new phenomenon or just a newly observed one? Will it threaten their existance (like a moth's instinct to fly towards a light)?
One problem is that chemical messengers (pheromones, etc.) may exist in such low concentrations that searching for and identifying them is made all the more difficult.
For more weird news about sturgeons, check out this youtube video: http://www.youtube.com/user/funkendub
Sturgeon are unable to pass through the fish ladders that WA state has provided for safe salmon passage past the dam... they have no where else to go. Its not really a laughing matter. Its the destruction of a species...
MAN I HEART NATURE RICHOUS