sea lion
A pair of California sea lions nuzzles on a dock on Pier 39, in San Francisco, California, Nov.6 2005. DON EMMERT/AFP/Getty Images

A wildlife welfare group reported Sunday at least 13 California sea lions were found dead along Washington's shoreline since September this year.

Seal Sitters Marine Mammal Stranding Network, an organization that responds to reports of stranded or dead sea lions, stated that six of the sea lions died of gunshot wounds, four in West Seattle and two in Kitsap County. The other seven are suspected to have died from "acute trauma" caused by human interactions around Kitsap County and the Puget Sound.

Last week, one animal washed up on the shore in West Seattle in a decapitated condition. Necropsy couldn’t be conducted due to the decomposition.

The shooting deaths of several of the sea lions are being investigated by The National Oceanic and Atmospheric Administration Fisheries Office of Law Enforcement.

In the United States, marine animals are protected under the Marine Mammal Protection Act, which prohibits harassment, hunting, capturing, or killing of the animals. Violation of the act could result in fines of up to $28,520 and/or one year in prison.

“We are concerned about a number of recent reports of marine mammal deaths caused by gunshots in the greater Seattle area. All marine mammals are protected by the Marine Mammal Protection Act and OLE investigates all reported unlawful takes of sea lions,” Greg Busch, assistant director of the NOAA Fisheries Office of Law Enforcement, said, Lex 18 reported.

Reports of sea lion deaths peak mostly during the fishing season.

“Animals searching for food to survive and fishermen searching out fish for consumption or livelihood are on an annual, never-ending collision course,” the welfare group said in a statement.

Speaking to BuzzFeed News about the shooting, Michael Milstein, a spokesperson for NOAA Fisheries said, "The reality is we do see this happen from time to time. Historically, there's been animosity toward sea lions because in some sense they compete with us for resources — for fish."

National Geographic reported at least 700 California sea lions were found dead with gunshot and stab wounds between 1998 and 2017 and charges were filed only for a handful of the killings and all of them were against fishermen.

A recent NOAA study stated that despite the killings, the population of the California sea lions has increased from fewer than 90,000 animals in 1975 to an estimated 281,450 in 2008. Milstein said the nearness of several shootings to dense areas of West Seattle was particularly troubling.

"If there's a lot of people around, on the one hand, that presents the risk of somebody getting hurt. At the same time, we are hopeful that people will see or hear something that will help us in these cases, and we really need people to be our eyes and ears out there,” he said.

NOAA Fisheries also put out suggestions on how to prevent marine mammals from interfering in fishing which includes making loud noises, using rubber bullets and water-soluble paintball guns.