NWFSC researchers returned from 21 days aboard the NOAA ship Bell M. Shimada, tracking endangered Southern Resident killer whales (SRKWs) off the coasts of Washington and Oregon. Good weather and ocean conditions allowed researchers exceptional access to the whales, including a newly documented calf, during their winter foraging period.
The winter survey addressed a high research priority to fill a major gap in our understanding of SRKWs life history—where these whales go during the winter, what they do, and what they eat.
Satellite tags reveal coastal distribution
Led by Dr. Brad Hanson, manager of the Marine Mammal and Seabird Ecology Program, scientists tagged two whales this winter to obtain information about the whales’ winter migration and the extent of their range.
The tagged adult whale J27 and the rest of J pod were monitored for about six weeks as the animals spent their time in the Salish Sea, the inland waters shared by Washington state and Canada. On December 31, scientists observed a new calf (J50) off the north side of San Juan Island, followed by another calf (J51) on February 15.
While aboard the NOAA research vessel, scientists tagged L84. This allowed the survey crew to follow L pod as well as K pod (which are known to sometimes travel together), as the animals travelled along the continental shelf up and down the Washington coast as far south as central Oregon.
On February 25, the survey team spotted a new calf (L121) with other whales in the L pod about 15 miles west of Westport, WA, documenting the third baby born to this endangered species in recent months and the first time a baby was spotted on the outer coast. The population now totals 80, still dangerously low.
While the satellite tag data pinpointed where the whales went, the observations at sea provided a richer data set that put the movement data in context, which will be critical to helping scientists interpret why SRKWs use (or don’t use) certain areas.
For example, this winter K and L pod spent a significant amount of time travelling between Westport, WA and the mouth of the Columbia River, but observations did not show that the whales spent much time foraging in this seemingly popular area. Neither did the whales travel all the way down to northern California this year, an area where they have been known to forage in the past.
“We have had the unique opportunity to spend up to 24 hours a day with [the whales] over the course of several days, which is unprecedented in its own right, but all the more significant on the outer coast where we know so little about where they spend so much of their time,” said Dr. Hanson.
Prey and fecal samples, acoustics may provide more clues about killer whales
During the research cruise, the team was able to study the wide-ranging movements and behavior of K and L pods, which are known to travel together. Scientists observed limited foraging during their three weeks at sea, which could likely point to food being scarce this time of year.
In addition to behavioral observations, the survey team collected acoustic recordings and several prey and fecal samples. Lab analysis of prey samples, such as fish scales, will address the question of what species these whales eat during the winter and, in the case of Chinook salmon, what specific runs are most important to the SRKW winter diet. Fecal samples will also be analyzed for measurements of stress and nutrition.
The cruise was well timed to observe how the whales utilize their habitat during the winter, and also allowed for the collection of related ecosystem data such as seabird counts, oceanographic information, and zooplankton collections.
Understanding the ocean’s productivity along the continental shelf can provide key information about the winter foraging habitat necessary to sustain marine wildlife, including widely-dispersed prey that endangered killer whales depend on to survive this time of year.
Tissue biopsies used to measure contaminant levels and identify family structure
Tissue biopsies were taken from the killer whales to yield information on the level of contaminants and their genetic stock structure (i.e., family relationships). Contaminant levels help assess the health of the whales as well as make inferences about their diet. Skin samples can be used to genotype the whales, which can be used in ongoing studies of family relationships. Further analyses of the stable isotopes in the skin can yield information on their winter diet.
The success of the satellite tagging project and interdisciplinary winter survey are due in no small part to our collaborators from Cascadia Research, Biowaves, and the Department of Fisheries and Oceans-Canada, as well as the logistical support provided by our colleagues at NOAA’s Office of Marine and Aviation Operations and the crew of the NOAA ship Bell M. Shimada.