Sustaining local fisheries key to orcas’ survival

Southern resident whales depend upon Chinook stocks, says Lance Barrett-Lennard.

Tuesday marked World Fisheries Day, which highlights the importance of sustainable fisheries for the long-term conservation of our oceans and marine wildlife.

It also serves as a stark reminder of the dire state of many fisheries around the world. According to the United Nations, nearly onethird of fish stocks are being overfished and another 60 per cent are being fully fished. Additionally, loss or degradation of marine habitats, pollution and global warming are contributing to the decline of many fish stocks.

Unfortunately, B.C. is no exception to this trend. Declines in the availability of Chinook salmon are having a dramatic impact on B.C.’s most iconic marine animals — the southern resident killer whale population.

This unique group of orca whales is listed as an endangered species by Canada and the U.S. Its population has declined by more than 20 per cent over the past 25 years, and today there are only 76 southern resident whales remaining.

The declining population is due to a confluence of factors, such as underwater noise, boat disturbance and pollution. However, most researchers agree limited prey availability is the most serious and immediate threat. Southern resident killer whales feed almost exclusively on Chinook, which constitute approximately 80 per cent of their diet.

Chinook salmon stocks fluctuate year to year. While part of this variation is natural, it is also being driven by man-made factors, such as climate change, degradation of Chinook spawning habitats in rivers, and fishing. In years with low Chinook stocks, the mortality rate of southern resident orcas rises. A recent international study suggested a 30 per cent increase in Chinook would be needed to recover this orca population.

To better understand the link, the Coastal Ocean Research Institute at Ocean Wise, along with research partners at NOAA in the U.S., have been utilizing drones to study southern resident killer whales since 2015. We analyze the aerial images from drones using a technique called photogrammetry, which generates precise measurements of the length, width, shape and pregnancy status of individual whales. The study indicates the whales are in poor condition, most likely due to nutritional stress. Other research supports this finding. So, what is the solution?

There is no silver bullet, and the path forward will require a multi-pronged approach involving the not-for-profit, public, and private sectors. Collaboration will be essential to securing the necessary resources and broad commitment for meaningful change.

Take, for example, the Enhancing Cetacean Habitat and Observation (ECHO) Program, which aims to better understand and manage the impact of shipping activities on at-risk whales and cetaceans in the region. This program is led by Vancouver Fraser Port Authority and enjoys the support of Ocean Wise, along with dozens of other partners from the scientific and environmental communities, government, as well as industry.

The port authority also recently conducted a study in which vessels travelling in the Haro Strait — a key feeding area for whales — reduced their speed to better understand how underwater noise may interfere with the echolocation sounds used by whales to find Chinook.

The Government of Canada has also taken steps to address the situation, recently announcing its intention to implement regulations that will require all vessels to remain at least 200 metres from southern resident whales, twice the current limit.

Other conservation options will also require collaboration across sectors. For instance, we know southern residents tend to hunt for Chinook in consistent locations. Implementing fishing restrictions in these areas, especially during years with low salmon stocks, will help improve prey availability. As part of a longerterm strategy, stream restoration will be critical for improving the Chinook population and ensuring southern resident killer whales can survive and thrive in local waters.

In keeping with the goals of World Fisheries Day, I encourage everyone to reflect on what is happening beneath the waters’ surface. Having orcas reside in our backyard is a privilege and responsibility. Industry and government should be applauded for steps taken to address the situation, but more needs to be done so we do not lose these B.C. treasures forever.