No apparent shortage of prey for southern resident killer whales in Canadian waters during summer
University of British Columbia
A popular belief that there are fewer Chinook salmon during the summer in Canadian waters for southern resident killer whales, compared to an abundance of fish for northern resident killer whales, has been debunked by a study led by scientists at the University of British Columbia.
In a paper published today in the Canadian Journal of Fisheries and Aquatic Sciences, researchers report that the numbers of Chinook salmon in the Salish Sea in summertime are four to six times more abundant for southern resident killer whales than northern resident killer whales.
“People have been talking about a prey shortage as if it’s a fact, but this is the first study to quantify and compare the amount of their preferred prey, Chinook salmon, available to southern and northern resident killer whales,” said lead author Dr. Mei Sato (she/her), a research associate at the Institute for the Oceans and Fisheries at UBC at the time of the study, and now an assistant scientist at Woods Hole Oceanographic Institution.
https://www.eurekalert.org/news-releases/931090
Here's a link to the actual study:
https://cdnsciencepub.com/doi/full/10.1139/cjfas-2020-0445
On TV tonight, one of the people from UBC who did the study speculates the Southern Residents have stopped coming in summer because the matriarch (100 year old "Granny"
who guided them to the Salish Sea every year died in 2016. He says a change of leadership may have changed the feeding patterns of the 3 southern populations.