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National Marine Mammal Laboratory (NMML)

Cetacean Assessment and Ecology Program

Cook Inlet Beluga Habitat Analysis

Figure showing Cook Inlet beluga habitat and sightings (see caption)
Figure 1.  Cook Inlet beluga habitat (black) predicted by the Resource Selection Function model with beluga sightings shown in gray. The right side of this figure shows a magnification of the boxed area.

More than half of Alaska’s residents live in the area immediately surrounding Cook Inlet, a semiconfined body of water which is home to a small, isolated population of beluga whales. With less than 300 animals remaining, the Cook Inlet beluga population is susceptible to local physical, ecological, and anthropogenic stressors. Current plans to further develop portions of Cook Inlet make identifying habitat requirements particularly timely for this beluga population.

Geographic information systems (GIS) and various statistical techniques are powerful tools that have helped elucidate the relationship between several environmental parameters and the summer distribution of beluga whales. Classification and regression tree (CART) and resource selection function (RSF) models were used to determine the ecological importance of bathymetry as well as the distance from river inlets (categorized as low, medium, or high according to rate of river flow) and proximity to mudflats.

The CART model provided insight on the underlying structure of the data while the RSF model allowed environmental variables to be assessed individually based on the level of significance. The importance of the rate of river flow varied slightly between the models, but in general belugas preferred to be near higher flow rivers and proximate to mudflats. Using GIS to map the results from the RSF model resulted in a spatial depiction of available beluga habitat (Fig. 1 above).

In addition to the environmental factors already being examined, proposals are underway to examine biological factors (such as prey availability) as well as anthropogenic factors that may be influencing the distribution of belugas in Cook Inlet. In the future, we hope to increase the predictive power of habitat models by accounting for activities such as fishing, oil and gas activity, military action, and transportation. Overall, the current and future work involved in determining beluga habitat provides an example of how the interdisciplinary integration of GIS and statistical modeling can reveal important aspects of the habitat requirements of this depleted stock of whales.

By Kim Goetz

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