Southern resident killer whales have not been getting enough to eat since 2018

A new University of British Columbia study has found that the southern resident killer whale population isn't getting enough food.

The animals have been in an energy deficit for six of the last 40 years. In the most recent years of the study were three. About 17 percent of the daily required energy for an average adult killer whale is the difference in energy.

There's a sense of urgency to this kind of research with the low population of southern residents. The west coast of Canada is home to both killer whales and Chinook salmon. It is possible that studying what is happening to the population will lead to solutions.

As of October 2021, the southern resident population numbered 73 individuals, compared to 300 for the northern population. The growth of the southern resident population may be hampered by a lack of food according to studies.

The researchers looked at how the abundance, age and size of the killer whales in the Salish Sea and at the west coast of Vancouver Island changed over time.

The study used estimates of the abundance and size of chinook salmon to show that they have likely resulted in energy deficits for killer whales. The co-author says that the years where southern residents were in an energy deficit were also years where other studies reported lower population growth and higher mortality rates for the killer whales.

There are correlations between the survival rate and fertility of southern residents. Climate change, susceptibility to disease, and other factors could be to blame for the decline in the abundance of chinook salmon.

When the abundance of their primary prey declines, the animals can switch to other salmon species, as shown by the model.

The commercial fishing of chinook salmon in Canada was reduced in the late 1990s due to declining abundance. Since the mid-1980s, the abundance of Steller sea lions has increased so much that they consume more fish than all the BC commercial fishing.

The dire situation for southern resident killer whales may lead to a reduction in the catch of larger chinook salmon, which are predictors of whether the southern residents fall short energy-wise. Fishing techniques that increase the survival of larger fish could be promoted.

There are other factors that could be affecting the availability of prey for the southern residents. The area could be used for future research. The model could be used to determine if the northern residents have an energy deficit.

It's not known where southern residents are during the winter. There was a study published.

More information: Fanny Couture et al, Requirements and availability of prey for northeastern pacific southern resident killer whales, PLOS ONE (2022). DOI: 10.1371/journal.pone.0270523 Journal information: PLoS ONE