Something fishy happened here

Photo courtesy Kyle Horvath/Cramer Fish Sciences

Last week’s write-up about the discovery of a green sturgeon in the Stanislaus River got a lot of clicks. I suspect that’s because it’s so unusual these days to hear “good news” about Central Valley fisheries.

One thing you might have missed in the guts of that story was how biologists were able to definitively identify the fish.

The Cramer Fish Sciences technician who first spotted the 4- to 6-foot long sturgeon returned to the Stan to dive and look for it again. And he got some great pictures.

Photo courtesy Kyle Horvath/Cramer Fish Sciences

It sure looked like a green sturgeon. But experts needed DNA to rule out the possibility of a more common white sturgeon.

So the technician returned to the same place yet again and this time couldn’t find the fish. But he took a water sample. And within days or weeks at most (this all transpired in early October), the results of DNA testing confirmed that a green sturgeon had been in the area.

What I didn’t know was that taking a water sample in the mere vicinity of a fish would be enough for positive identification. But of course, fish urinate and shed skin cells and who knows what else. All of that becomes mobilized in the water and can register a DNA hit.

One expert with the National Marine Fisheries Service told me that the DNA testing can be effective as far as 500 meters (1,640 feet, or nearly one-third of a mile) from the fish.

A Smithsonian article provides more insight,¬†concluding that the science — still in its infancy — could be useful in setting fishing quotes or assessing impacts of various projects on endangered species.

For a rare fish, there’s nowhere to hide these days.

At any rate, they cracked the case. And we now know that green sturgeon — one of them, at least — have returned to the Stanislaus River.

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