After decades of indiscriminate killing, resident pods of orcas are now protected and a popular tourist attraction on B.C.'s south coast. (CBC)

The oldest resident orca on B.C.'s south coast is believed to have died.

The matriarch of K pod, known as K7 and more affectionately as Lummi, hasn't been seen since Christmas.

"She wasn't seen with the rest of K pod on June 3, the first day that Ks were documented in inland waters," said Erin Heydenreich, a senior staff member at the Center for Whale Research in Friday Harbor, on the San Juan islands in Washington state.

Lummi was easy to spot because of the two notches on her dorsal fin and her distinctive markings. Orca experts believe the cetacean matriarch was born about 98 years ago.

"It is sad when one of the most recognizable whales dies, but it's also inevitable. She is old," said Heydenreich, who said if K7 isn't seen for a full year, she will officially be declared dead.

K7's age was notable for two reasons: female orcas generally live only 50 years in the wild, but the grandmother whale is believed to have survived for nearly a century during one of the most dangerous periods for orcas.

For much of the 20th century, orcas were regarded as killers, and often shot like pests by fishermen and fisheries officers, bombed by planes for target practice, or killed in clumsy attempts to capture them for display.

"They were a sort of enemy of the fishermen for quite a long time," said Heydenreich.

Population in decline

Official protection of orcas in B.C. waters started in the early 1970s, but they have since faced the hazards of pollution and declining salmon stocks.

Scientists divide West Coast orcas, also known as killer whales, into four separate populations.

The southern and northern resident orca populations return every summer to the islands along the B.C. coast to hunt salmon in larger pods using complex vocalizations.

A third group of transient orcas roam more freely over a much wider overlapping range in smaller pods, and generally hunt marine mammals silently.

Not much is known about a recently documented fourth population living farther offshore that is believed to feed mainly on fish, but also hunts marine mammals and sea birds.

The southern resident population is the most familiar to British Columbians and is frequently seen off Vancouver Island.

There are approximately 80 left in the southern resident population, and they support a whale-watching industry estimated to be worth more than $100 million per year, more than the entire B.C. commercial salmon fishery, according to the Western Canada Wilderness Committee.

The southern resident population has dropped as much as 20 per cent in the past 12 years, and recent studies have indicted the population could be extinct in as little as 30 years if the downward trend continues.