When Chinook salmon is off the menu, other prey will do for endangered orcas

When Chinook salmon is off the menu, other prey will do for endangered orcas

Source: mongabay

3/3/2021

A new study has found that endangered southern resident killer whales mainly consume endangered Chinook salmon, but will broaden their diet when this species isn’t available.
The researchers obtained data through prey and fecal waste collected from resident killer whales over a 13-year period.
Efforts to reinstate Chinook salmon populations through hatchery efforts can play an important role in supporting resident killer whale populations, although these programs need to be carefully managed to ensure that stocks are diverse, the study suggests.

For nearly 20 years, Robin Baird has been following killer whales, trying to figure out what they eat. At first, he would look to see what was in their mouths as the whales feasted on fish near the surface. But then he and his colleague, Brad Hanson, started looking for more subtle clues in their flukeprints — the orbs of placid water that appear on the surface when a killer whale dives into the sea, or flicks its tail underwater. In or around these flukeprints, you can find fish scales and fecal matter, which provide a treasure trove of information.

“If they’re catching things near the surface of the water, it’s much [easier] to be able to document than if they’re capturing things at depth,” Baird, a research biologist at Cascadia Research Collective, told Mongabay in an interview. “What the fecal samples do is they show … a higher proportion of things like lingcod and halibut and sole flounder [that] are caught deeper in the water column and less likely to be brought up to the surface.”