July 27, 2018 — Thousands of dead fish washed up in the Mystic River in Everett and Somerville this week, blanketing the muddy shorelines and emanating a stench that customers and employees at a nearby Costco store said could be whiffed from the parking lot.

But city and state officials, as well as local environmentalists, said Thursday that while the sight was alarming, the fish had died due to natural causes.

Patrick Herron, executive director of the Mystic River Watershed Association, said the Department of Environmental Protection and state Division of Fisheries and Wildlife were investigating what he called a “die-off” that left tens of thousands of menhaden — or, as they’re more commonly known, “pogies” — in the area.

Herron said the likely explanation is that the fish were driven into the shallow, warmer waters by a predator. Once in that area of the river, the fish depleted the oxygen supply and ultimately perished, he said.

Read the full story at the Boston Globe