A pod of orcas were photographed off the coast earlier this month. Research is showing southern resident killer whales may be causing the chinook salmon stocks to dwindle, one reader writes. Photo by Wayne Young

Orcas’ eating habits may lead to their own demise

Killer whales depending on dwindling chinook salmon stocks, reader writes

There has been much discussion of late concerning the shortage of large chinook salmon as a food source for southern resident killer whales. It now appears that the whales themselves may be responsible for the decreased size and age of chinook salmon.

A recent scientific paper published in the journal Fish and Fisheries found that chinook declines in age and size were most pronounced in northern populations, where resident killer whales were more numerous, but were common coastwide. While they stated that many factors come into play in determining age and size structures in any population, they could not find one which was more correlated than the resident killer whale impact.

The study involved 85 separate chinook stocks, both hatchery and wild, from Alaska to California totalling 1.5 million individual measurements. They found that hatcheries were not responsible for either smaller or younger chinook at maturity.

The authors noted that Chinook predation by marine mammals (ie. seals, sea lions and killer whales) increased three-fold since the mid 1970s. Resident killer whales in the northeast Pacific number greater than 2,300. Ninety per cent of their diet is chinook salmon age four to six years. Killer whales consumed 10,000 metric tonnes of chinook in 2015 which represents over two million adult fish.

The southern resident killer whales may be eating themselves out of a food source which could lead to their disappearance; but this may not be a bad thing if you are a chinook salmon.

Wayne Zaccarelli

Esquimalt

Just Posted

UPDATE: Woman hit by car in parking lot 93 years old

Driver of sedan backs into older adult walking through lot

Residents of tent cities unfairly labeled as criminals, says report

Some neighbours supportive of Regina Park camp

Delivery truck downs power lines in Sidney

A tractor trailer delivering eggs clipped a low-hanging wire on Second St.… Continue reading

Stolen West Shore vehicle found in ocean off Oak Bay

SUV was submerged 90 feet from shore at Cattle Point

Deadly mushroom spotted in Greater Victoria

Early return of death cap mushrooms prompts Island Health warning

Trudeau asks transport minister to tackle Greyhound’s western pullout

Prime Minister Justin Trudeau says he’s asked Transport Minister Marc Garneau to find solutions in Greyhound Canada’s absence.

Saanich Police investigate store robbery

Store video captures image of suspect

Greater Victoria Crime Stoppers wanted list for the week of July 17

Greater Victoria Crime Stoppers is seeking the public’s help in locating the… Continue reading

Restaurant Brands International to review policy over poaching employees

One of Canada’s largest fast-food company to review ‘no-poach’ franchise agreements

Calgary family’s vacation ends in tragedy on Texas highway

Three people died and four others were injured in the crash

Union construction cost competitive, B.C. Building Trades say

Non-union firms can bid on infrastructure, but employees have to join international unions

Trudeau to shuffle cabinet ahead of Liberals’ team for 2019

Trudeau could lighten the work loads of cabinet ministers who currently oversee more than one portfolio

Car calls 911 on possible impaired B.C. driver

A luxury car automatically calls Princeton police to scene of crash involving alcohol

BC Games marks 40 years in 2018

Cowichan Games a milestone for BC Games Society

Most Read