Northwest Fisheries Science Center

Scientists trail killer whales at sea for insight into winter habitat, food

Contributed by Michael Milstein

NOAA Fisheries scientists aboard a research ship are following Southern Resident Killer Whales south along the West Coast, collecting remains of their prey, fecal samples, acoustic recordings and other data to better understand the endangered whales’ winter range and important winter food sources.

The three pods of Southern Residents typically spend much of the spring and summer in Puget Sound and other parts of the Salish Sea northwest of Seattle. But in winter they usually leave the interior waters, likely in search of food, with two pods – K and L – often venturing hundreds of miles south along the West Coast as far as Northern California.

The specific areas they frequent, the prey they rely on and what drives their movements in winter has remained largely a mystery, though.

“We’re really getting a lot of good data about what they’re doing during a period of the year we want to know more about,” research scientist Brad Hanson said from the NOAA Fisheries research vessel Bell. M Shimada. “Ideally we want to understand how they’re making the decisions they do.”

On Feb. 11 Hanson and other researchers from NOAA Fisheries’ Northwest Fisheries Science Center left Newport, Ore., aboard the Shimada. They first caught up with the J pod of Southern Residents in the northern Strait of Georgia, guided by a tracking tag on a male whale known as J27 that reports the whale’s position via satellite.

The researchers use a smaller work boat to follow whales close enough to collect leftover bits and pieces of the whales’ prey and fecal samples for clues as to what the whales are eating. They also carry a specialized dart projector to collect tiny samples of the whales’ blubber for research on the whales’ genetics, the type of prey they have been foraging on for the past two months and possible exposure to environmental contaminants.

Updates on the whales’ movements and research efforts are posted regularly on the NWFSC website. NOAA Fisheries needs information about the habitat and prey the whales rely on in winter to inform decisions on their protection and possible designation of critical habitat for the whales.

In the Strait of Georgia, which separates Vancouver Island from the British Columbia mainland, researchers on Feb. 13 collected the first sample of scales from a fish the whales consumed outside of Puget Sound in February. Scales can reveal the species and age of fish the whales are eating, providing new insight into the kinds of prey they rely on during the winter. If the fish is a Chinook salmon, the whales’ preferred prey, the river system the fish originated from can be determined.

Two days later the researchers got a look at the newest Southern Resident, a calf known as J51. They also discovered that the tag on J27 had detached, as it is designed to do after several weeks. On Feb. 17 they located the K and L pods near the entrance of the Strait of Juan de Fuca and attached a new satellite tag on a male whale known as L84. The ship began following the two pods, which sometimes travel together in winter.

“This will be an opportunity to see how closely they stick together as they move,” Hanson said.

About 40 whales including the K and most of the L pod continued south as far as the mouth of the Columbia River, where they spent much of the day Feb. 19 swimming in a small patch of ocean about four miles off Cape Disappointment. The whales stayed within a small area but apparently were not feeding because researchers listening from the ship did not hear the vocalizations or clicks that normally accompany hunting and feeding, Hanson said.

Then early on Feb. 20 the whales suddenly turned south along the Oregon Coast. In previous years once they headed south from the Columbia they usually continued all the way to Northern California.

A key question is what drives the whales’ winter travels. Researchers are collecting oceanographic data on temperatures and other environmental conditions for clues about what factors the whales may be responding to. Social interaction and pursuit of prey both play a role, Hanson said, and “at this time of year prey is probably more the driving force because it’s more dispersed.”

“Somehow they’re taking stock of what’s going on around them and making decisions about where to go and when,” Hanson said while trying to catch up to the southbound whales. “Understanding how they assess their environment is one of our main goals.”

Following the whales at sea provides details scientists could never get from tracking tags alone, Hanson noted. For instance, it might have been easy to assume the whales were feeding off the Columbia unless researchers had been there to recognize that they actually were not.

“There’s a real value to being able to conduct these observational studies off the NOAA research vessel Bell M. Shimada to interpret their behavior up close,” Hanson said. “It makes a big difference to be here with them.”

This research was conducted under a federal permit.