Wildlife watchers on the B.C. coast were saddened when news came that J-32, also known as “Rhapsody,” a female member of the southern resident killer whale population, was found dead offshore from Vancouver Island in the Strait of Georgia. It was not only a setback to this endangered population of whales; it was also a blow to recovery efforts. Rhapsody was pregnant at the time of her death, and her loss triggers concerns about the future viability of this population, which now sits at just 77 individuals.
Mother Nature can be unpredictable, and it’s possible that this tragedy was simply part of what happens in our ocean. On the other hand, humans may well have played an inadvertent role in reducing the quality of killer whale habitat or food supply.
Reduced food availability, noise and disturbance, and high levels of chemical pollutants represent the primary risks to the health of these cetaceans. A draft Killer Whale Action Plan is being finalized by the Canadian government after years of painstaking consultations and input. The stakes could not be higher. The southern resident killer whale populations plies the urban waters of the Salish Sea, sharing the transboundary watershed with more than seven million people: that’s 100,000 people for each killer whale.
“Killer whales are long-lived animals at the top of the food chain; they are inherently vulnerable to human impacts,” said Dr. Peter Ross, director of the Vancouver Aquarium’s Ocean Pollution Research Program. Canada’s only marine mammal toxicologist, Dr. Ross’s past work has demonstrated that these killer whales are among the world’s most PCB-contaminated marine mammals in the world, surpassing the threatened St Lawrence beluga whales by two to four times.
“At these levels of PCBs, I would expect that these killer whales would be at increased risk for infections and reproductive impairment,” said Dr. Ross.
The good news is that despite lingering PCBs in their bodies, things have improved considerably for this major chemical concern in the oceans. “We have estimated that the levels of PCBs are down three- to four-fold in killer whales since regulations were implemented in the 1970s,” said Dr. Ross. That’s good news for other sea life as well, as these killer whales are providing a snapshot of the state of the coastal food web.
Southern resident killer whales are primarily salmon eaters, and their mortality spikes during years in which Chinook salmon are scarce. Efforts to determine which runs of Chinook are most important to them so that their food supply can be protected and enhanced have so far been unsuccessful. However, a new research method, tested by Vancouver Aquarium Cetacean Research program director Dr. Lance Barrett-Lennard and NOAA colleagues John Durban and Holly Fearnbach in the summer of 2014, shows considerable promise.
“Instead of working after the fact by linking killer whale deaths to salmon availability, we are using photographs taken with a small unmanned hexacopter to assess the body condition — fatness or thinness — of the whales,” said Dr. Barrett-Lennard. “This provides a very sensitive measure of the immediate impact of fluctuations in the salmon supply on the whales and provides a glimmer of hope that we may be able to take appropriate actions to help Rhapsody’s family survive and recover.”
A full necropsy is now underway to determine the cause of the whale’s death.
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