Sea lion pup
The creatures were shot due to 'an ongoing threat to the safety of the farm staff, fish and net pens'ROBYN BECK/Getty Images

As Californian wildlife lovers struggle mightily to save stranded sea lions along the Pacific coast, Canadians were shocked to learn that salmon farmers off Vancouver Island had slaughtered 15 of the animals.

The killings are nothing new at the open-pen salmon feedlots, though the public rarely learns about them. The 15 sea lions were shot by staff members of the salmon farming giant Cermaq for posing "an ongoing threat to the safety of the farm staff, fish and net pens." The company characterised the killings as a "marine mammal interaction."

Environmentalists complain that the killing field area is ecologically sensitive and that it is the farm operations — not the sea lions — who are intruding in the space by essentially placing fish factories in the midst of fish eaters.

Clayoquot Sound, where the animals were shot late in 2015, "is a UNESCO Biosphere Reserve. It's a recognition of just how special a place this is", Clayoquot Action's Bonny Glambeck told the Huffington Post. "Yet even here, wildlife is not safe from the Norwegian-owned industry."

The toll of the farms on marine mammals is astronomical. Since 1990, almost 6,000 harbour seals, 1,200 California sea lions and 363 endangered Steller sea lions have been killed by the British Columbia salmon farmers, according to statistics from the Canadian Department of Fisheries and Oceans.

The animals are not only shot but can become trapped and drown in the nets that surround the captive salmon. In 2013 at least 65 California sea lions and one harbour seal died after becoming entangled in nets in a six month period at three of the farms run by another Norwegian company, Grieg Seafoods.

As for shooting, salmon farmers have automatic authorisation to kill "problem" seals and sea lions, as long as they report the shootings. But there is no way to confirm the reports.

While the salmon farmers are eliminating sea lions, Californians are again struggling to save starving sea lions left stranded on beaches and further inland.

The numbers so far are high, but have not yet reached 2015's record of more than 3,000 animals stranding along the California coast by the end of the season. That is because experts believe many animals have already died of starvation, with many pups never making it off the beaches where they were born.

In early April a lethargic, apparently starving sea lion in critical condition was rescued on Salt Spring Island in British Columbia and is currently being cared for at the Vancouver Aquarium.