Science Matters: Orca survival depends on protecting chinook salmon

  • Jul. 6, 2017 12:30 a.m.

Two of British Columbia’s most iconic species, chinook salmon and southern resident killer whales, are in trouble. The whale depends on the salmon for survival. Is it time to manage chinook fisheries with killer whales in mind?

In marine ecosystems, cause and effect is a challenge. It’s almost impossible to claim with certainty that depletion of one species is caused by abundance or lack of another. The general rule is that big things eat smaller things, so any given species will eat dozens of others, even their smaller kin. The southern resident killer whales, also known as orcas, are an exception. Despite their immense intelligence, or perhaps because of it, their diet consists almost entirely of chinook salmon, with only traces of other salmon, and virtually no other fish species.

Every killer whale population has its own unique culture, which includes language, social behaviours and dietary preferences. A large male weighs nearly as much as two Ford 150 pickup trucks. Sustaining this mass of warm-blooded flesh in a cold ocean requires using echolocation to find and capture fish in blackness. Understanding the patterns of their chinook prey is a highly specialized activity passed on through generations of learned behaviour.

After each capture, an orca normally shares the fish with the pod. That’s remarkable considering the whale could practically swallow the prey whole. If the 78 southern resident killer whales are to survive, this cultural feeding ritual needs to occur about 1,400 times a day. That’s become difficult, as chinook salmon populations that migrate through waters where the southern resident killer whale feed are severely depleted, and the fish are smaller on average than they once were.

Fisheries and Oceans Canada’s assessments show most chinook populations in southern B.C. are well below historical levels and continue to decline. In November 2018, the Committee on the Status of Endangered Wildlife in Canada will determine the status of several populations, and will likely declare many endangered.

Fishing is not the only threat chinook face, but it has a major impact. Fishing tends to target salmon as they return to spawn — after they’ve survived, against all odds, through 99 per cent of their expected lives. Those that spawn hold the genetic blueprint to help their offspring withstand current environmental conditions. With far fewer chinook making it to spawning grounds, each survivor is a critical contributor to the next generation. Estimates show commercial and sport fisheries in British Columbia took more than half a million chinook in 2016. For some chinook populations, people harvest well over half the returning fish.

Noise from shipping also hinders the whales’ ability to communicate with each other, find prey and avoid danger — by up to 97 per cent in the noisiest areas. Commercial shipping has increased dramatically in recent years. One large ship transits the Salish Sea, on average, every hour of every day of every year.

Federal whale biologists have identified a priority recovery strategy: refuges where orcas can feed without competition from fisheries and that are quiet enough that echolocation is not masked and social behaviours aren’t disrupted. These areas are currently being identified and could be established within killer whale critical habitat areas. Many other issues, including pollution, must also be addressed.

Rebuilding chinook populations is critical to rebuilding whale populations, yet there are no recovery plans to increase chinook populations to upper benchmarks, as required by Canada’s Wild Salmon Policy. More than 300,000 recreational fishing licences are issued annually in B.C., which creates a formidable competitor to killer whales. Like whales, humans have also learned over generations about the behaviour of their prey.

The federal government is undertaking a scientific review to prioritize killer whale recovery actions. Part of this process involves public consultation. Anyone concerned about orcas should contribute.

Understanding the importance of chinook to killer whales makes it difficult to justify catching them without considering the whales’ needs. The complexity of marine ecosystems makes it easy for individuals to point fingers to the myriad other threats such as climate change and habitat destruction. But we must recognize that, collectively, our habits have become destructive to the environment and other species.

The fate of two of British Columbia’s most iconic animals and the ecosystems and economies that depend on them rests in our hands.

David Suzuki is a scientist, broadcaster, author and co-founder of the David Suzuki Foundation.

Just Posted

Christmas season in Red Deer begins with Festival of Trees

The kickoff to the Christmas season in Red Deer is upon us.… Continue reading

Judge allows Mr. Big evidence in murder trial

Two men accused of triple-murder admitted their involvement to undercover police

Red Deer agency supporting for LGBTQ2S+ youth

New report on LGBTQ2S+ youth from the Office of the Child and Youth Advocate

Four people arrested after gas and dash

Four people were arrested after an alleged gas and dash in two… Continue reading

VIDEO: Replay Red Deer: Nov. 19

Watch news highlights from the week of Nov. 13

Red Deer Christmas Bureau to help 1,300 children this year

Demand is high, but Red Deer always provides

CP Holiday train to stop in Ponoka for another year

The popular train will feature entertainment from Colin James and Emma-Lee

Kittens rescued after allegedly being tossed from vehicle

Couple finds abandoned kittens new home through Facebook

VIDEO: ‘Party bus’ goes up in flames in Vancouver

Fire crews responded to the late night blaze

Chicken crosses B.C. road, stops traffic

Rooster makes early morning commuters wait in Maple Ridge

Red Deerian honours her brother who died in a motorcycle collision

Houaida Haddad is encouraging Red Deer residents to donate blood

Red Deer County firefighters to be recognized for Waterton help

RCMP brass will give formal recognition Monday

Ron James tries to lighten humanity’s load through humour

The comedian returns to Red Deer for shows Dec. 1 and 2

Most Read


Five-day delivery plus unlimited digital access for $185 for 260 issues (must live in delivery area to qualify) Unlimited Digital Access 99 cents for the first four weeks and then only $15 per month Five-day delivery plus unlimited digital access for $15 a month