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Beluga Whales in Cook Inlet

(Quarterly Report for Oct-Nov-Dec 2000)

by David J. Rugh

Kristin Laidre and Rod Hobbs of the National Marine Mammal Laboratory attach a satellite tag to a young beluga whale in Cook Inlet during the 2000 field season.

Beluga whales (Delphinapterus leucas) that inhabit Cook Inlet, Alaska, form a small, isolated stock that is geographically and genetically segregated from the other four stocks of belugas found in Alaskan waters.  The isolation of the Cook Inlet stock, combined with the belugas’ tendency towards site fidelity in summer, make these whales especially vulnerable to deleterious impacts from large or persistent harvests.  During the 1990s, results from summer aerial surveys conducted by the National Marine Fisheries Service (NMFS), indicated that both the distribution and abundance of the beluga stock in Cook Inlet was declining, while reported harvests by Native hunters had increased.  Resource managers, concerned about these trends, concluded that the Cook Inlet beluga situation was one of the most pressing conservation issues facing Alaska marine mammals during the past decade.


chart of summer Alaska beluga whale distribution

Summer distribution of beluga whale stocks in Alaska.

Genetic evidence indicates that beluga whales in Cook Inlet have not mixed with other beluga stocks for thousands of years.  The Alaska Peninsula forms a long barrier that geographically separates beluga whales in Cook Inlet from belugas in the Bering Sea.  Surveys for cetaceans conducted over the past three decades have reported no beluga sightings on the western end of the Alaska Peninsula and only a very few, scattered sightings along the northern portions of the Gulf of Alaska–from Kodiak to Yakutat Bay.  There is no evidence that any beluga groups consistently use any areas in the Gulf of Alaska other than in Cook Inlet.

Traditional Native knowledge and systematic aerial surveys dating as far back as the 1960s have shown that belugas have a strong fidelity to certain river mouths and bays in the northern part of Cook Inlet, especially in summer.  This distribution is apparently driven by the availability of anadromous fish, such as eulachon (Thaleichthys pacificus) and salmon (Oncorhynchus spp.)  The tenacity of these whales to specific areas year after year has made them relatively easy to hunt.  The rapid growth of Anchorage on the shores of Cook Inlet has resulted in an increase in Native populations from around Alaska, many of whom have sought to maintain hunting traditions.  Although the Alutiiq Eskimos and Dena’ina Athabascan Indians have hunted beluga whales in Cook Inlet for centuries, it is assumed the size of the historic take was relatively small. In the 1990s, however, the reported harvest –mostly by Eskimos– averaged 40-70 whales per year.  Furthermore, it has been estimated that one or two whales were struck but lost (fate unknown) for each whale successfully landed.  The high mortality rate in this small population led to acute management concerns.

Click here for aerial survey maps of beluga sightings in Cook Inlet, summer 2000 compared to sightings in 1974-75.  

Aerial Surveys

Each year since 1993, NMFS has conducted systematic aerial surveys of Cook Inlet for 2 weeks in June or July, a period when the weather is optimal and beluga groups are predictably concentrated near river mouths.  The surveys cover 10%- 30% of the inlet’s total surface area, including 100% of the coastal regions (approximately 1,400 km of shoreline) and up to 1,500 km of sawtooth transects across the open water areas.  Surveys are conducted in an Aero Commander aircraft,  flown at 240 m (800 ft) altitude, at approximately 170-185 km/hr (90-100 knots), the minimum safe flying speed. Surveys are conducted for a total of 40 hours, weather permitting. The aerial trackline is kept 1.4 km from shore so that there is a good view of any whales between the trackline and shore.  Two primary observers (and often a representative from a Native organization) search for whales on the shore side of the aircraft, where almost all the whales have been seen.  On the other side of the aircraft, one primary observer and a data recorder look for whales.  Although the observers focus their search laterally out to 1.4 km, whales are sometimes seen ahead of the aircraft as far away as 6 km.  A selective listening control device allows the data recorder to communicate with all of the crew or to aurally isolate observers; this allows for independent search efforts which can be used to check sighting rates.  Every hour or two, observers rotate positions to minimize strain from the intense search.

The aerial surveys of Cook Inlet have documented that most belugas consistently use shallow-water areas near river mouths along the northernmost portion of the inlet, especially between Beluga River and Anchorage and in Chickaloon Bay. Only during the first few surveys (1993-95) were beluga whales also found in the southern and central portions of the inlet.  Since then, all beluga sightings, other than a single or dead whale, have been in the northern reaches of the inlet.  Unlike sighting distributions recorded in the 1970s and 1980s, almost no whales were found more than a few kilometers offshore.  The stock’s  shrinking summer range was also noted by long-time local residents.  Fishermen, journalists, and Alaska Natives reported that while beluga sightings had been frequent near Homer (in the southern part of Cook Inlet) in past summers, few had been seen there in summer since the mid-1990s.

The beluga’s decline in distribution within Cook Inlet cannot be explained by an emigration of individuals from this population to other areas in the Gulf of Alaska.  In a review of all systematic survey effort for cetaceans (150,000 linear km) and respective sightings (23,000 cetaceans) in the Gulf of Alaska dating back to 1936,  only five beluga sightings occurred outside of Cook Inlet.  When all anecdotal reports are included, but with no record of search effort, a total of only 31 beluga sightings (including resightings) were reported outside of Cook Inlet.  Half of these sightings were reported in 1997-99; however, many sightings appear to be multiple reports for the same animal.  The network for collecting opportunistic sightings has increased dramatically in the past 2 years, so an increase in sighting reports is expected.

Abundance Estimates

The decline in distribution of beluga whales in Cook Inlet was paralleled by a decline in abundance.  Beluga counts by NMFS aerial observers were about 300 in 1994 and dropped below 200 in 1998.  Abundance estimates (corrected for whales missed by the observers) dropped from 653 in 1994 to 347 in 1998, a 14% per annum decline, or nearly a 50% decline during the survey period.  In the summer of 1998, the Native hunt for belugas ceased, and since then abundance estimates have stopped declining: 357 in 1999 and 435 in 2000.

Much of the scientific effort directed at the study of belugas  in Cook Inlet centers on calculating a reasonable estimate of how many whales are missed for each whale counted during aerial surveys.  After a group of whales is seen, the aircraft makes a series of straight-line passes, allowing two or more observers to independently count the whales at least four times each.  When both pairs of primary observers have completed four good counts each, the aircraft moves on in search of the next whale group, resulting in up to 16 counts of a single whale group.  In addition, the northern parts of Cook Inlet are surveyed at least three times annually; consequently, whale groups there each have a total of  nearly 50 counts in a survey season.

While observers count with the naked eye, a video camera records images of the whale groups for meticulous counts later in the laboratory. The video allows for precise documentation of time spent counting (to the tenth of a second) and for repeatable counts of whales at the surface. The videotapes are studied in the laboratory by several researchers independently.  The counts are then corrected for whales below the surface during the videotaping.  Corrected group sizes were calculated as the product of the counts made from the videotapes, a correction factor for whales not at the surface during the viewing period (based on average dive interval data from tagged whales), and a correction for whales missed due to video resolution.  Juvenile whales, which are dark gray and smaller than the white adults, are difficult to see and therefore particularly prone to being missed during counts.  By pairing two digital video cameras in the aircraft–one on a standard setting and the other zoomed to its maximum magnification–sample images are collected that can be studied to estimate the probability that juvenile whales are missed by the team studying standard video images.

Tagging Whales

Dive interval statistics are important in developing an accurate correction factor for whales missed during aerial counts.  Dive intervals are determined from data derived from VHF radio transmitters (“radio tags”) attached to the whales.  An inflatable boat was driven close to a whale, and when the animal surfaced to breathe, a tag on the end of a long pole was pushed onto the animal’s back.  Of eight successful attachments in 1994 and 1995, only five tags stayed attached for more than 1 hour (one stayed on for almost 7 hours); the others remained attached only a few minutes each.  From the dive interval data generated from the five tagged whales, it was estimated that belugas surface to breathe once every 24.5 sec.

Although tagged whales appeared to return to their normal behavior shortly after tagging events, there was concern that their surfacing behavior may have been subtly altered for several hours because of the harassment associated with the tagging process.  Consequently, a longer-lasting tag was needed.  In 1999 a tag was designed by Wildlife Computers in Redmond, Washington, to be pinned to the dorsal ridge of a whale, where there are no nerves.  The “satellite tag” has a  battery-driven VHF transmitter used to collect dive interval data (as on the suction cup tags), but unlike the suction cup tags, it also has a transmitter which relays signals through satellites to provide location data over weeks or months.  Although the capture process for attaching the new tag involved hoop nets and greater harassment, once attached, the new tags would send signals well beyond the duration of the harassment period.

After many unsuccessful attempts, a whale was encircled and tagged in May 1999, and two additional whales were captured and tagged in September 2000.  These three tagged whales provided location data for over 100 days each.  Their VHF tags gave 5 or more hours of dive interval data as well, and one of the whales tagged in September also had a suction cup Time-Depth Recorder (TDR) which provided dive behavior data every second for 55 hours.  The TDR stayed on the whale for 90 hours.  The two whales tagged in September 2000 have provided data on their winter distribution, answering one of the major remaining questions about the Cook Inlet stock.  Data derived from the tagged whales showed that the whales stayed in northern Cook Inlet throughout the tagging period (June to January) and that none went into the southern part of the inlet. (For an update on the whales tagged in September 2000 see the National Marine Mammal  Laboratory research report in this issue of the AFSC Quarterly Report.)


There has been considerable concern that the Cook Inlet environment may have been degraded by human development. Although the evident decline in abundance of belugas by approximately 60 whales per year from 1994 to 1998 can be explained by the known harvest during that period (approximately 40-70 whales per year), there is the potential that the habitat has changed under human influence to the point that the inlet can no longer support as many whales as it used to.

NMFS conducted a review of available reports and databases to document the degree of anthropogenic effects within the range of beluga habitats (to be published later this year in Marine Fisheries Review).  More in-depth studies are planned on the whales’ ecology through the use of geographic information systems (GIS) and collection of data on critical habitat issues.  In particular, more data are needed on seasonal fish runs in areas where beluga whales may feed.  Also, information is needed to profile the acoustic environment experienced by beluga whales.  Areas of high, moderate, and low use by belugas are being delineated and will be compared to relative impacts from anthropogenic sources such as petroleum development, ship traffic, fishery operations, septic waste, and other contaminants.  Comments from public hearings regarding habitat factors pertinent to the distribution and abundance of beluga whales in Cook Inlet are also taken into account.

Management of the Beluga Stock

NMFS research conducted on beluga whales in Cook Inlet indicated a distinct decline in the stock’s abundance.  The finding led to a  voluntary cessation of the hunt for beluga whales in Cook Inlet by Alaska Natives in the summer of 1998, followed by a special amendment to the Marine Mammal Protection Act (MMPA) in May 1999.  The amendment prohibited beluga hunting in Cook Inlet (at least until October 2000), except through cooperative agreements between NMFS and the respective Alaska Native organizations.  The amendment included regulations requiring reports to NMFS describing any hunting, along with submitting the lower left jaw of any killed whale.  Effective 31 May 2000, the Cook Inlet stock was listed as “depleted” under the MMPA.  Although there have been petitions to list the Cook Inlet stock as Endangered under the Endangered Species Act (ESA), NMFS reasoned in June 2000 that the cause of the decline is due to overhunting and can be managed under the MMPA.  Since  the hunting has stopped, the decline in whale abundance has also stopped.

Public Reviews

The research on Cook Inlet beluga whales has received intense public and scientific scrutiny, as well as considerable attention from the media. The Alaska Scientific Review Group (AKSRG), under the direction of the MMPA, is a formal review process tasked with critically examining marine mammal research conducted by NMFS in Alaska.  In anticipation of the importance of management decisions regarding Cook Inlet belugas,  NMFS initiated a formal status review in November 1998, beginning with sequential workshops held both by the Alaska Beluga Whale Committee (ABWC) and by the AKSRG.  Hunters, administrators, researchers, and other interested parties had an opportunity to hear presentations by biologists working on Cook Inlet beluga issues.  During the workshops, and later through the Federal Register process, NMFS solicited information and comments from the public from 19 November 1998 through 19 January 1999.  Comments were solicited in a second  public workshop held in Anchorage in March 1999.

Comments and reviews collected during the review process, especially from the Natives of Cook Inlet who are so intimately tied to the whales, have been helpful in directing research objectives and guiding management decisions.   NMFS is proposing an allowance for a closely-watched hunt of up to two whales per year for the foreseeable future.  The proposal is pending a final ruling by an Administrative Law Judge at the time of this writing.