14-foot fish spotted in river, giving hope to vanished giant's return (Hudson, Sturgeon)

[jpak]

https://www.nationalgeographic.com/environment/2019/03/14-foot-atlantic-sturgeon-fish-hudson-river-endangered-species/

COLD SPRING, NEW YORK One day last June, two researchers were towing a special sonar system up and down the Hudson River near Hyde Park, New York, the site of President Franklin Delano Roosevelt’s home, when they saw something pleasantly shocking.

They were helping state biologists assess whether the spawning or foraging of a fabled and endangered bottom-feeding denizen, the Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), was being disrupted when commercial vessels dropped anchor in a spot designated as a waiting area to manage ship traffic.

The anchorage, established in 1999, happened to be located in a stretch of the Hudson that is one of the most important spawning grounds in its range along the coast from Florida through Canada’s maritime provinces. More anchorages were planned elsewhere in the Hudson.

Unlike a simple depth sounder, this “side-scan” sonar sweeps high-frequency beams of sound out at angles, producing a detailed three-dimensional portrait of the river bed and any decent-size fish—and often precise enough to reveal the sturgeon’s distinctive profile, as low-slung as a Formula One car.

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[democratisphere]

1. Hope the sturgeon makes a strong comeback.