Southern Residents Depend on Healthy Chinook Populations
Approximately 80 percent of the Southern Resident orca diet is Chinook salmon, with the average adult requiring roughly 200-385 pounds daily to remain healthy. Orcas can travel up to 160 kilometres during a 24-hour period in search of Chinook.
However, some salmon stocks—including Chinook—have been declining to the point where the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) recommends a number of salmon stocks be listed under the Species at Risk Act. A few local Chinook populations, for example, are at only 5-10 percent of their historical numbers. Simply put, there isn’t enough salmon to feed Southern Residents and starvation is hindering their ability to carry pregnancies to term, keep calves alive, and survive as adults.
Salmon stocks need more than conservation measures to protect them; fisheries management actions must support rebuilding stocks
How bad is the Chinook situation?
Fisheries and Oceans Canada (DFO) was able to generate an assessment on only 15 of the 35 conservation units for Southern B.C. Chinook in 2016, and 11 of these were in the “red zone” of the federal government’s Wild Salmon Policy. We’ve also seen consistently low returns of early-timed (spring and early summer) Fraser Chinook salmon, which are key runs in the diet of Southern Residents, returning to the Fraser River during the last several years.
It’s time for the federal government to use fisheries management actions to help promote stock rebuilding; they must go beyond conservation measures in order to increase Chinook availability for orcas before the population dwindles below the alarmingly-low 76 whales that remain in the three pods—J, K and L.
The connection between Chinook and pregnancies
A direct link between the abundance of Chinook salmon and viable pregnancies has been proven. A study released in 2017 by the University of Washington Center for Conservation Biology, NOAA’s Northwest fisheries Science Center, and the Center for Whale Research shows that up to 69 percent of pregnancies failed between 2008 and 2014 due to stress brought on by low abundance of Chinook salmon.
A lack of orcas’ preferred prey is resulting in poor nutrition and that is having a significant impact on their growth and reproduction abilities, with Southern Resident killer whales last reproducing seven viable calves in 2015. Of those calves, five remain alive; however, the most recent mortality was of J-52, also known as Sonic, who died from starvation in September 2017.