Killer Appetites in Western Alaska

Craig Matkin (North Gulf Oceanic Society) and Dr. Lance Barrett-Lennard
(UBC and Vancouver Aquarium Marine Science Centre) are leading a three-year
study of killer whales in western Alaska. The goals are to:

 
  1. Estimate the abundance and distribution of killer whales

  2. Distinguish the proportion of whales that are fish eaters (residents) and marine mammal eaters (transients)

  3. Describe the diet and foraging behavior of transient killer whales.
The ultimate goal is to determine the impact of killer whale predation on Steller sea lion populations.
The center of attention lies between Kodiak Island and Unimak Island-a distance of approximately 800 miles. To maximize encounters with killer whales, researchers are using chartered fishing boats to search for killer whales, focusing on areas where mariners have reported seeing them in the past.


Dr. Lance Barrett-Lennard with hydrophone
They also use hydrophones (underwater microphones) to locate killer whales when they are too far away to be seen. Individual killer whales can be distinguished based on unique natural markings. Thus, the first priority during an encounter is to take identification photographs to keep track of previously sighted individuals and trace movement patterns.
When a new group of killer whales is encountered, Matkin and Barrett-Lennard take minute skin samples with ultra-lightweight biopsy darts. They later extract and analyze DNA from the samples to determine whether the whales are transients, residents, or members of previously unstudied populations. They also observe the whales for as long as possible to document hunting and feeding behaviors.

Killer whale with ultra-lightweight biopsy dart
The first field season—2002—was a resounding success. Three boats put in over 150 days total scouring the eastern and western ends of the study area. In 75 encounters with killer whales, over 500 rolls of film and 34 skin biopsies were taken. Data analysis has begun, and a number of findings are emerging.
  1. Killer whales are relatively common in the areas surveyed, and are particularly abundant in the ocean passes between the Gulf of Alaska and Bering Sea.

  2. Populations in the study area belong to resident and transient populations that are genetically similar to those found in British Columbia and southeast Alaska. However, individuals seem to spend their lives in their respective areas.

  3. The diet of transient killer whales near the western end of the Alaska Peninsula includes gray whales, fur seals, and Steller sea lions.
  


Craig Matkin taking photo ID's of a pod of killer whales.

The plan for 2003 is to use the same basic research methods, but to expand both the territory covered and the duration of the field season. Stay tuned for more.

7 April 2003

 

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