Southern Resident Killer Whales Face Many Challenges: Declining Salmon May be the Worst
Written by Stefania Gorgopa
Southern Resident Killer Whales (SRKW) are at risk and declining salmon are a large part of the problem. SRKW primarily eat Chinook Salmon. A large plentiful fish historically, Chinook were listed as threatened 20 years ago. Unfortunately, there has been no salmon stock improvement since their decline. Fisheries and Oceans Canada estimates that the entire SRKW population needs 723 Chinook Salmon each day.
There are many suspected reasons for the increased mortality and declining health of the SRKW. Inbreeding, disease, pollution, and vessel noise are contributing factors. However, their dependence on their preferred food source, Chinook salmon, means that SRKW are expected to become extinct within 100 years if the food supply is not improved.
Salmon are a key component in the food web, not just feeding SRKW but many other species, including humans. Chinook Salmon are part of important First Nations food, ceremonial, and social fisheries, as well as commercial and recreational fisheries. In response to low fish stocks, Fisheries and Oceans Canada are issuing closures and tighter restrictions on Chinook Salmon fishing for summer 2019. The fishing industry is bracing for the impact from the restrictions.
SRKW and humans are not the only ones competing for fish. Seals, sea lions, Alaskan and Northern Resident Killer Whales are all looking to feed on salmon. The marine mammal protections act enacted in 1972 banned the hunting of marine mammals, which has led to healthy and abundant seal and sea lion populations. Unfortunately, the increasing number of animals hunting salmon compounds the problem: there are not enough fish to go around. A proposed seal and sea lion cull is the subject of regionwide debate.
The demand for salmon intensifies as the supply decreases. 40% of Chinook runs are extinct and this is increasing the competition between whales, humans and other marine mammals. Annual marine surveys off the Pacific Coast have shown there is a change in the number and type of fish in these waters. The baseline availability of fish has changed quickly from the SRKW perspective, something people often forget.
There are several reasons for the decline of Chinook Salmon. Habitat destruction, pollution, predators and changes in the food web are a complicated network of causes. Lower water levels in rivers because of drought and higher water temperatures are deadly to young salmon. Without survivable conditions, young salmon cannot make their way from rivers to the ocean. If salmon are not reaching the ocean, they cannot feed on small plankton and grow up to feed larger marine mammals.
In 2013, a warm water mass called ‘The Blob’ killed much of the plankton in the oceans. Without the plankton that serves as a food supply for all larger marine life, fish, birds and mammals alike were affected by the large mortality event. The repercussions of the event are continuing to show up years later. Many juvenile salmon did not survive ‘The Blob’. Four years later their absence was obvious when four-year-old Chinook numbers were lower than expected in June 2017 surveys. The survey nets were filled with pyrosomes instead (tubular jelly animals, several feet in length). While there was a brief improvement in Chinook returns in 2013-2015, the blob effects have caused a downturn again. 2019 has a poor forecast for Chinook Salmon returns. The record lows of salmon returning to rivers to spawn sadly show that any improvement from the work to restore stocks since the 1990s has been counteracted.
For Killer Whales the food shortage goes beyond the numbers of fish available. The seasonal variety of fish, and body condition of salmon are important. When there are gaps in the calendar year where the preferred prey are missing, this has impacts on SRKW. Further, smaller fish make for less nutritious meals. The average weight of a four-year-old Chinook has decreased 20% from 1975 to 2005.
The marine survival study by Long Live the Kings and Pacific Salmon Foundation reveals the decline of salmon is the culmination of pollution, predators, habitat destruction and changes in food webs. These factors make it hard for the fish to make it to the open ocean, grow large and feed SRKW. To benefit Killer Whales, salmon need to grow big quickly. Small salmon are easy targets for most small predators. Large salmon are more difficult for predators like birds and seals to catch, but make a hearty meal for Killer Whales.
In 2014 Researchers began using drones to study Killer Whales from a unique perspective. What they discovered was that drone photography was a non-intrusive way to assess a whale’s health. The researchers found that some whales were showing symptoms of ‘peanut head’ where weight loss around the whales head results in a concave peanut shape distinct from a healthy whale.
Weight loss in Killer Whales is harmful because of the pollutants they accumulate in their tissues. Older whales may still have pollutants in their tissues from before many harmful toxins were banned. As the whales burned fat for energy they release the accumulated toxins into the blood stream. Researchers want to know more about why the whales are losing weight and what may be going on internally. Interestingly a conservation dog trained in detecting grizzly bear scat has been trained to work from the deck of a research boat. The dog can sniff out the kibble size fecal pellets left behind by whales. Researchers then collect the scat to be analyzed for diet composition and stress indicators.
The decline in SRKW health has been extremely evident in the last year. A SRKW in J-pod, identified as J50, was showing symptoms of peanut head, and continuing to lose weight. A rescue plan was formed for J50 to intervene and save her life. Unfortunately, she died before the plan could be implemented.
Around the same time all eyes were on Talequah, another southern resident. Her newborn calf died shortly after birth. What took the world by surprise was that she then carried her dead calf for over 1500 km. Her dedication to carry her dead calf for so long is a testament to the emotional intelligence of Killer Whales. J17, Talequah’s mother, is the latest whale to present with declining health. Unlike the SRKW, neighbouring whale populations are fat and robust, Transient Killer Whale populations and Northern Resident Killer Whales are both doing better than the SRKW. SRKW have the lowest birthrate of the three groups.
The causes of death in these whales are not universal. J50’s body was not recovered and even if it were, the combination of factors in her death would be difficult to untangle. It is unlikely a single disease or toxin is to blame for the populations decline in health, as it seems individual whales within the SRKW are hit harder than others. While there is not evidence of widespread starvation, there is clearly ongoing malnutrition.
The struggle the SRKW face is most evident in the changes in their behaviour. They don’t congregate as they used to. Now, they show up later in the season, and they are spread out and split up. Instead of socializing and resting, the whales are spending their time searching for food.
*This blog post summarizes the information presented in an article written by Lynda V. Mapes, published on April 28, 2019 in the Times Colonist, “Salmon’s decline adds to Salish Sea orcas’ struggle”.