Springtime Brings a Rumble to the Hudson River

Something has been making an inexplicable low, percussive rumble in the Hudson River each spring, and for years nobody could explain it. Researchers now can: it's 800-pound (Acipenser oxyrinchus) sturgeon, spawning.

A paper in Endangered Species Research marks the first scientific verification of the sound. Researchers believe the likely mechanism is male thrashing during egg fertilization, with swim bladder resonance amplifying the result.

Each spring, these giants leave the ocean and swim up the Hudson to spawn. The team captured the sound using passive acoustic monitoring, placing underwater microphones in the river for extended periods. The technique is common in marine and terrestrial research but has been used far less in freshwater systems.

That methodological gap matters. The discovery gives the New York State Department of Environmental Conservation a new tool to monitor Atlantic sturgeon behavior. Monitoring matters because overfishing in the 19th and 20th centuries devastated their populations, and nearly 30 years of protection hasn't translated into a meaningful comeback. Lake sturgeon, a separate species, are already known to make similar sounds during spawning; these are the first such recordings for the Atlantic variety.

Whether the sound is intentional communication or simply the acoustic byproduct of large fish doing what large fish do remains an open question.

Read the full story at Popular Science, June 3, 2026

Hot Take: The Hudson River producing mysterious thunder that turns out to be ancient armored fish conducting their reproductive affairs at scale is, taxonomically speaking, a more satisfying explanation than anything else that river has been blamed for.