At least two sea lions are known to have died, the Los Angeles Times reported. An adult female washed ashore mortally wounded Aug. 3 on Venice Beach while a pup was euthanized in 2009 after it was found on Dockweiler Beach with a bullet in its spine.
Marine Mammal Rescue has put up money for a $5,000 reward for information leading to the shooters. Peter Wallerstein, the organization's head, suspects fishermen are responsible.
"It is more common than not," he told KNBC-TV, Los Angeles. "Most of these actions take place miles off shore, so we're only seeing the ones that come to shore."
Bobby Shriver, a Santa Monica city councilman, said fishermen and the Fish and Game Department can use seal bombs and other legal means.
"If it was a fisherman and that person was trying to protect his or her livelihood, then there is a better way to do it," he said. "If it was just a mean person, than that person is going to get caught and go to jail. There is nothing to say about somebody who's just having sport on a defenseless creature by shooting them."