A $5,500 reward has been offered for information leading to the arrest and conviction of the people responsible for shooting several sea lions that washed ashore near West Seattle.

Sea Shepherd Seattle, a marine conservation organization, and Captain Paul Watson announced a $5,000 reward Thursday. Project SeaWolf Coastal Protection, a marine mammal advocacy group, contributed $500.

Nearly a half dozen California sea lions have washed ashore in the last six weeks near West Seattle. Necropsies performed Thursday confirmed two of the sea lions found this week were killed by gunshot wounds, bringing the total killed to four, according to blubberblog.org.

There are several others still under investigation.

The National Oceanic and Atmospheric Administration (NOAA) confirmed they are investigating the deaths.

West Seattle Sea Lion killed
A sea lion found dead in West Seattle Wednesday was killed by gunshot wounds.

Randi Stone lives near Alki Beach. "I am kind of in a state right now where I am shocked that it is on the beach that I love. I've been here over 40 years, and this is what I am seeing,” Stone said. “It just underscores how we all have to take care of our environment."

Sea lions are protected by the Marine Mammal Act. The fine for killing a sea lion can be up to a year in prison and a $25,000 fine. Those that are illegally killed are often killed with no witnesses, so it's rare anyone is prosecuted for the crime.

Stone added, "I am heartbroken, just heartbroken, and I am fighting back the tears."

Also see | WATCH: Puget Sound sea lions ward off attacking orcas

The federal government calculates that more than 700 California sea lions have been killed in the last two decades. Sea lions are known to compete for fish and are often seen as a scourge on the fishing industry.

NOAA says it’s not uncommon to find sea lions shot in the winter in Puget Sound as they migrate north. In the winter, the males travel north while the females and pups stay off the coast of southern California. Nearly every California sea lion spotted in Puget Sound in the fall and winter are males.

The idea of hunting sea lions has gained new momentum in Washington as the Southern Resident orca population continues to decline. The orcas primarily eat salmon, and a joint Oregon state and NOAA study found in 2017 that marine mammals catch more salmon than commercial fishermen.

Also see | Marine mammals catching more salmon than fishermen harvest

As a call for a cull mounts, the Southern Resident Killer Whale Task Force appointed by Governor Inslee has not yet made such a recommendation.

If you have any information about crimes against marine mammals, call NOAA’s law enforcement hotline at 800-853-1964.