Killer whale Research > Alaska Killer whale count

ALASKA KILLER WHALE RESEARCH

A Consortium study of the potential impact of killer whale predation on declining Steller sea lion populations suggests that killer whales may have contributed to the decline, and may be preventing population recovery. Unfortunately, the analysis is compromised by a lack of data on killer whale numbers in western Alaska. In order to draw a more accurate conclusion, estimates of killer whale numbers are needed, along with data on the proportion of killer whales feeding on marine mammals. Both of these issues are being addressed in a three component study.

killer whales at sunset photo by J.K.Ford

First, a survey of mariners was conducted in the Gulf of Alaska and Aleutian Islands in the summer (July/August) and again in the winter (January/February) to help identify areas of killer whale concentrations for researchers to direct their field studies.

The second study component has concentrated on field observations between Kodiak and Dutch Harbor, where trained investigators observe, photograph, and acoustically record killer whales for identification. Biopsy samples also are collected for genetic and dietary analysis to determine the proportion of killer whales feeding on marine mammals.

Lastly, we are comparing predation rates in southeastern Alaska to those in areas of depleted sea lion populations in western Alaska. Using tested techniques and experienced observers, the proportion of Steller sea lions consumed by marine mammal eating killer whales is being estimated. We are also recording killer whale calls in southeastern Alaska to determine their structure and composition at the time of kill. This procedure will provide data for use in concurrent studies in the Gulf of Alaska and Aleutian Islands that seek to use vocalizations as indicators of predation.

The killer whale studies are being undertaken by Craig Matkin, Jan Straley, Lance Barrett-Lennard, Volker Deecke and colleagues. Estimates of population numbers and diet composition derived from our studies will be used to refine our predation model, and, ultimately, to assess the impact of killer whale predation on Steller sea lions.

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