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Project Description

The small, isolated stock of beluga whales in Cook Inlet is listed as depleted under the MMPA, and NMFS is currently reviewing its status for possible listing as endangered under the ESA. The lower end of the OSP range for this population is thought to be 780, yet the latest abundance estimate, 375, is less than half of this number. Monitoring of this population should be continued through: 1) annual aerial surveys and abundance estimates; 2) documentation of the proportion of calves relative to juveniles and adult whales; 3) identification of critical habitat including prey distribution and calving grounds; 4) risk assessments and population viability analysis; and 5) support of research on comparative beluga populations in the Bering, Chukchi, and Beaufort Seas.

Issues & Justification

Between 1994 and 1998, annual estimates of the abundance of the Cook Inlet beluga stock declined by almost 50% from 653 to 347, respectively (Hobbs et al. 2000), and the whale distribution has shrunk over the past several decades (Rugh et al. 2000). During this same period, 1994-98, available data show that the unregulated harvest by Native subsistence hunters was significant, averaging 70 whales per year (Mahoney and Shelden 2000). Through a series of voluntary and legal actions in 1999, the harvest was reduced to two or fewer whales per year. With this significant reduction in mortality, NMFS anticipated that the population would soon begin to recover at a rate between 2% and 6% per year. However, this growth has not yet been apparent; instead, abundance estimates have not changed appreciably and remain near 300. In fact, it appears that there is a 2-3% annual rate of decline since 1999. In November 2006 NMML published a status review and extinction risk assessment of the CIB (Hobbs et al., 2006). Based on the findings the AKR proposed listing the CIB as endangered under the ESA in April 2007. In June 2007 special funds were provided by HQ to increase funding for existing projects and initiate several new projects including funding aerial survey work through 2009, completing habitat analyzes, completing a tooth ageing project and initiating a comparison study between Bristol Bay belugas and CIB. Although each of these studies was intended as a complete project it is still necessary to provide travel expenses for NMML employees to oversee and participate in these projects.

As part of the effort to complete the decision whether or not to list the Cook Inlet Beluga as endangered under the ESA, the NMML has been requested to provide a completed abundance estimate from the June 2008 survey by September 1, 2008. In the past the analysis of video and observer data has taken 5 to 7 months. To complete the estimate in a little more than 2 months will require increased hours for the existing analysis crew, additional video analysts and workstations and upgrades to the video analysis software. The funding will cover the increased hours for existing personnel and the additional temporary personnel, the cost of analysis computers, software upgrades and software support prior to and during the analysis period.

Goals

  • Estimate the abundance of Cook Inlet beluga whales by September 1, 2008.
  • Monitor trends in growth of this population.
  • Assess risk and analyze population viability.
  • Document habitat features pertinent to belugas.
  • Research comparative populations in the Bering, Chukchi, and Beaufort Seas.

Methods

An aerial survey is flown each June to record locations of beluga groups, count whales, and document whales by using paired video cameras. Group size is estimated from aerial video data and observer counts. These are summed by survey and averaged to estimate abundance. Abundance estimates are corrected for missed groups and for availability and perception biases.

Trends in growth, population viability and extinction risk are estimated using population dynamics models and Bayesian analysis of the time series of abundance estimates. Calving rates are monitored by estimating fraction of mature animals in the population and the number of calves produced each year. Aerial video and photo data collected during the annual abundance survey and dedicated surveys in other months is analyzed to estimate these parameters.

Seasonal distribution data, diet data, and telemetry data will be combined in a multilayer spatiotemporal GIS habitat model. Distribution data is derived from aerial survey sightings and locations of tagged whales. Diet data from stomach contents and fatty acid and stable isotope analyses will be compared to seasonal distribution of available prey to estimate carrying capacity of available prey base. Telemetry data will be used to determine movements and dive behavior. Critical habitat such as feeding, calving and rearing grounds, and movement corridors will be mapped and compared to known risks such as oil or toxic spills, sewage outfalls, and loss of habitat due to development or siltation.

Distribution and habitat studies on comparative populations in other areas of Alaska and in Chukotka, Russia are undertaken in collaboration with other research groups, including tagging, diet, and genetic studies.

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