An annual census on the southern resident killer whale population in B.C. waters has been released – and it's causing concern among experts.

The population of the endangered orcas has dropped from 83 in 2016 to now 75. The Centre for Whale Research says it’s a 30 year low and experts say the primary issue is a lack of food.

Southern resident killer whales dine on chinook and chum salmon, which have also seen a decline in population.

“The southern resident killer whale population peaked in the late 80s and early 1990s,” said Dan Kukat, former president of the Pacific Whale Watch Association. “At the same time that the chinook salmon populations also peaked, it was throughout the early 90’s as well. So there’s a very strong correlation.”

Since last spring, more than 750,000 chinook salmon have been dumped into Sooke waters. It was part of a project by Fisheries and Oceans Canada to bolster the whales population by providing them more abundant food sources.

“Fundamentally one of the most important aspects to their survival is, are there enough fish in the ocean to sustain this population?” said Dr. Anna Hall, a marine mammal zoologist.

Other factors that could affect the whales numbers are collisions with ships and contaminants in the water, according to Hall.

Kukat, who also owns SpringTide Whale Watching, said he'd like to see the federal government reopen fish hatcheries to further bolster food sources for the orcas. Some anglers on southern Vancouver Island have called for similar measures.

Correction: An earlier version of this story reported that conservation groups were asking the federal government to reopen fish hatcheries. In fact, Dan Kukat, the owner of a whale-watching business and former president of the Pacific Whale Watch Association, called for the reopening of hatcheries.