Investigators in Washington continue to investigate as 13 dead sea lions have reportedly washed ashore since September—six of which had gunshot wounds.

Seal Sitters Marine Mammal Stranding Network told The Seattle Times that the six shot California sea lions turned up in Puget Sound and Kitsap County. They said the other seven possibly died from “acute trauma” at the hands of humans, including one that was found decapitated Tuesday in a West Seattle cove.

A National Oceanic and Atmospheric Administration (NOAA) spokesman confirmed to the outlet that the agency has confirmed the deaths of five California sea lions, including four with gunshot wounds. In a statement issued to NBC News, NOAA said the sea lions are protected by the Marine Mammal Protection Act.

The Times noted that the sea lion population has exploded in the past several decades—going from 90,000 in 1975 to more than 250,000 in 2014—resulting in many conflicts between the sea mammal and fishermen, who often have to deal with them eating fish off their line.

Robin Lindsey of Seal Sitters told the newspaper that shootings involving sea lions are sometimes reported in the fall and spring, when the males migrate north from the Southern California Channel Islands to gather food. In a November 21 blog post, she wrote that more shootings have been reported this year.

Alarmingly, Lindsey claimed sea lion deaths are at their highest in December, January, and February.

KING reported that a local conservation organization, Sea Shepherd Seattle, is offering $5,500 for information that leads to an arrest or arrests in connection with the rash of sea lion-related deaths. NOAA continues to investigate the deaths.

[Featured image: Pixabay]