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Cetacean Assessment & Ecology Program

Decline of Beluga Whales in Cook Inlet

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Figure 4. Time series of abundance estimates for the Cook Inlet beluga population, 1994-2006. Dotted trend line shows an annual rate of decline of 5.6%.

On 29 March 2006, NMFS formally initiated a status review of the Cook Inlet (Alaska) beluga whale population to incorporate new scientific findings available since the publication of the last scientific review in 2000. This current status review, published in December 2006, is now available as an AFSC Processed Report.

Findings of this review indicate a 92% probability that the Cook Inlet beluga population is failing to increase at a rate of at least 2% per year as a healthy cetacean population would. Furthermore, there is a 60% probability that the population is declining and will continue to decline.

In January 2007, the abundance estimate from the 2006 aerial survey was completed. The result was an estimated 302 whales (CV 16% and a 95% confidence interval between 222 and 410). Although this estimate is larger than the estimate of 278 for 2005, it is still below the average of 370 for the years 1999-2004. A trend line fit to the estimates for 1999 to 2006 yielded an average rate of decline of 4.1% per year (SE = 0.0165) which is significantly different from a constant population level at the 5% level.

Prior to 1999 a subsistence harvest averaging 70 beluga per year between 1994 and 1998 was thought to be the cause of the observed decline of this population. Since 1999 the population has failed to increase and may have continued to decline. Including abundance estimates from the time series before 1999 produced an annual rate of decline of 5.6% for 1994 to 2006 (Fig. 4).

These findings will be reviewed by the NMFS Alaska Regional Office to assess whether there should be a proposal to list the population as threatened or endangered under the Endangered Species Act.

By Kim Shelden and Rod Hobbs

Satellite Telemetry Describes First Migratory Movement of South Pacific Humpback Whales to Their Feeding Grounds

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Figure 5. Track of a humpback whale monitored with satellite telemetry from the Cook Islands to the Antarctic.

In August, NMML scientists Alex Zerbini and Phil Clapham were involved in setting up a satellite tagging project for humpback whales in the Cook Islands (South Pacific). The work was conducted in collaboration with Nan Hauser (Cook Islands Whale Research), the South Pacific Whale Research Consortium, and the Greenland Institute of Natural Resources. NMML provided three Argos-monitored satellite tags and methodological expertise; the tags were deployed by Hauser and her field team, which included Ygor Geyer from Zerbini’s Brazilian research group.

Two tags were attached to humpback whales (both mature females); one functioned for only a few days, while the other worked for 2 weeks while the whale remained in the vicinity of the southern Cook Islands. However, the latter tag suddenly came to life again in late December (after over 3 months’ silence) and has continued to report positions every 3 days (Fig. 5) The whale has moved more than 3,000 km south of the Cook Islands and is currently continuing to migrate south into Antarctic waters.

This represents the first documented migratory movement of any humpback whale in the South Pacific and the first connection of any kind between the Cook Islands and a high-latitude feeding ground. As such, it contributes important information regarding population structure and migratory destinations.

By Alex Zerbini and Phil Clapham

Field Work

Members of the Cetacean Assessment and Ecology Program traveled to Carmel, California, in December to begin the census of the eastern Pacific stock of gray whales at Granite Canyon. During the week, the survey site was set up and contract observers were trained. The contract observers will conduct the bulk of the survey with participants from NMML returning for double counts and other calibration activities in January.

By Paul Wade


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