NOAA Fisheries News Releases
NEWS RELEASE
March 27, 2006
Sheela McLean
(907) 586-7032
NOAA Scientists Study Harbor Seals and Cruise Ships
Scientists from the U.S. National Oceanic and Atmospheric Administration (NOAA), working with the Alaska cruise ship industry and members of the Yakutat Tlingit Tribe, are documenting interactions between harbor seals and approaching cruise ships in Disenchantment Bay, near Yakutat.
Since 2002, NOAA biologists have been mapping and counting seals by aerial survey, and observing seal behavior from cruise ships in Disenchantment Bay, a glacial fjord that is a popular destination for cruise ships. The initial report from this study showed that when cruise ships approached closer than 500 meters (about 1600 feet) seals left the ice floes on which they were resting with increasing frequency: Seals were 25 times more likely to enter the water if the ship was 100 meters away than if it was 500 meters away. Seals were also more likely to abandon ice floes if the ship came at them head-on rather than at an angle.
In the new findings released in their final report, the NOAA scientists describe the interactions between cruise ships and harbor seals during weekly peaks and lulls in ship traffic. A stated goal of the study was to produce reliable information about how seals interact with their environment, including cruise ships, so that representatives from the cruise industry, the local Tlingit Tribe, and NOAA could work together to promote healthy populations of harbor seals. The Yakutat Tlingit Tribe relies on the seals for subsistence and some believe there has been a population decline as cruise ship traffic has increased.
A cruise ship gets a close-up view of Hubbard Glacier in Disenchantment Bay
“We had outstanding support from many organizations and agencies,” said principal researcher, John Jansen of NOAA’s Alaska Fisheries Science Center. “In particular, the local traditional knowledge provided by the Tribe, and the cruise industry’s cooperation in allowing scientists to observe seals from ships, greatly improved the study design.”
“The research provides a better understanding of the distances and time-scales over which large vessels interact with and impact seals” Jansen said. “We hope that this study and our continued monitoring of the seals will ensure the long-term health of the population for the benefit of both visitors and Alaska Native subsistence users.”
Harbor seals, Phoca vitulina, haul out year-round on floating ice in tidewater glacial fjords which are popular destinations for tourism. Glacial ice may function uniquely as both a refuge from land and marine predators and a reliable platform for resting and rearing pups.
The cooperative study examined potential effects of cruise ships on the behavior, abundance and distribution of harbor seals from early pupping to the molting season —approximately early May to mid-August. Researchers assessed the seals’ responses to ships on three scales: 1) fine scale, involving direct observations of seal behavior in relation to vessel approach distance and angle; 2) medium scale, consisting of weekly aerial surveys of seal distribution and abundance in the bay; and 3) large scale, where monthly aerial photographs of seal distribution and abundance were taken at Disenchantment Bay and Icy Bay, a nearby glacial fjord not visited by cruise ships.
An adult harbor seal hauled out on ice near a tidewater glacier
The new findings, relating to the medium and large scale studies, indicated that there were no short-term changes in the general location of hauled out seals in relation to the presence or absence of cruise ships or in relation to the location of visiting ships. Nor did seals appear to leave or avoid the bay as a short-term response to the arrival or continued presence of ships. Seals were, however, more densely concentrated as cruise ships spent more time in the bay. One concern is that if seals are being disturbed into the water regularly by approaching ships, or spend more time in the water to find a suitable haul-out area when ships are present, it may disrupt their energy budget, causing them to require more food and have reduced survival or reproductive rates. Scientists also discovered that the total number of seals increased dramatically from May to August at cruise-ship-free Icy Bay, in contrast to Disenchantment Bay which showed a modest peak in June (at mid-pupping) followed by a slight decline.
“We don’t yet have any information about the actual movement of seals so we don’t know if seals are migrating away from an area visited by cruise ships, either during the summer or over longer periods of months to years. These are certainly important questions for the future” said Jansen. “Some of these types of questions are more difficult to answer because they require longer-term monitoring.”
Once considered abundant throughout their range, counts of harbor seals over the last 30 years have declined in some areas of Alaska, including the Kodiak Archipelago and Prince William Sound. Of recent concern is the approximately 50% decline in harbor seals since 1992 at Glacier Bay National Park where numbers of watercraft, including cruise ships, have increased steadily over the same period.
NOAA’s final report, entitled “Disturbance of harbor seals by cruise ships in Disenchantment Bay, Alaska: an investigation at three spatial and temporal scales”, can be found online at http://www.afsc.noaa.gov/Publications/ProcRpt/PR%202006-02.pdf.
According to this final report, the multi-agency, multi-organization effort, led by NOAA’s National Marine Mammal Laboratory, had support not only from the Yakutat Tlingit Tribe and the NorthWest CruiseShip Association, but also from NOAA’s National Weather Service, Cruise Line Agencies of Alaska, the U.S. Forest Service, the U.S. National Park Service, the U.S. Fish and Wildlife Service, Alaska’s Department of Fish and Game, and the City and Borough of Yakutat.
NOAA’s National Marine Fisheries Service (NOAA Fisheries) is dedicated to protecting and preserving our nation’s living marine resources through scientific research, management, enforcement, and the conservation of marine mammals and other protected marine species and their habitat. To learn more about NOAA Fisheries in Alaska, please visit our websites at www.fakr.noaa.gov and at www.afsc.noaa.gov.