[REVISION HISTORY]

Southern right whale mortality in Chubut, Argentina

Updated 14 times since CLSTR started tracking revisions of this situation.

What changed

2026-10-20 22:35 UTC → 2026-10-22 01:22 UTC · added ~~removed~~

In early September 2026, the first aerial census of the season along the Península Valdés coastline in Chubut, Argentina, recorded 1,375 Southern right whales, including 409 calves. This was a notable decrease from the 2,110 whales recorded in 2025, though researchers from the Marine Mammal Laboratory (LAMAMA) noted such fluctuations are natural and remain within expected values. By late September, investigations intensified into an unusually high mortality rate among Southern Right Whale calves in the region, specifically near Puerto Madryn and Península Valdés. Since June, dozens of carcasses have been discovered, leading experts to fear that the current season could surpass the record of 113 deaths documented in 2012. By mid-October, the investigation shifted focus as the mortality pattern became more atypical. While previous calf deaths were linked to the bacterium ‘Erysipelothrix rhusiopathiae’, which is associated with septicemia and multi-organ failure, recent carcasses of juveniles and large adults do not show the skin lesions typically associated with this pathogen. Following the discovery of seven whales dead within a single week in mid-October, researchers have proposed two distinct causes for the mortality. While calves are linked to the aforementioned bacterium, the deaths of adults and juveniles—who appeared to be in good nutritional condition—are being investigated under the hypothesis of red tide poisoning from natural biotoxins. ~~The Whale Conservation Institute (ICB)~~ By late October, reports indicated a record loss of more than 340 calves in the Nuevo and ~~CONICET are monitoring~~ San José gulfs, representing over 70 percent of the ~~situation~~ calves counted this season. Greenpeace Argentina has expressed concern regarding human and industrial pressures, highlighting threats such as ~~local organizations call~~ seismic exploration for hydrocarbons, increased ~~resources~~ maritime traffic, and ~~transparency.~~ the risk of offshore oil spills.

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