When large cruise ships get too close to harbor seals, the animals become distressed, according to a new federal study.
The National Oceanic and Atmospheric Administration released a report Monday on seal behavior in Disenchantment Bay, a Southeast fjord that cruise ships frequent for a view of the Hubbard Glacier.
The study, which was a cooperative effort involving NOAA, the cruise industry and the Yakutat Tlingits, found that when the large ships got closer than 1,600 feet, seals were more likely to jump off the ice floes they haul out on.
The closer the ships got, the more likely the seals were to dive into the water, according to the Anchorage Daily News. When a ship was about 300 feet away, a seal was 25 times more likely to jump into the water than when the ship was 1,600 feet way, the study found.
The researchers said one concern is that if seals are routinely disturbed, it will drain their energy reserves, possibly resulting in lower reproduction or reduced survival.
"It really confirms what has been known for some time: that as ships get closer to seals, the seals will get off the ice floes," said John Hansen, president of the North West CruiseShip Association. He said as a result the association has operating practices in place to minimize disturbance of the animals.
However, that's not always possible because of weather, navigational and other reasons, including not being able to see the seals, said John Jansen, the study's lead author.
During the study, biologists documented many times when the ships got within 300 feet of seals, he said.
The study also found that the more time ships spend in Disenchantment Bay, the closer the seals come to one another. Such huddling behavior is common among animals that feel threatened, said Jansen.
The research, which began in 2002, also compared harbor seal numbers in Disenchantment Bay with those of Icy Bay, a nearby glacial fjord with similar natural characteristics. The only major difference between the two bays is that cruise ships do not visit Icy Bay, Jansen said.
Icy and Disenchantment Bays started out with roughly the same number of seals in May, between 1,000 and 1,500, Jansen said. The study found that seal populations in Icy Bay increased from May to August, while in Disenchantment Bay, they peaked in June and then declined slightly. Icy Bay ended the summer with 5,400 seals while Disenchantment Bay had only 1,800.
Whether the seals are leaving Disenchantment Bay and heading to Icy Bay is unknown because scientists have yet to track the movements of individual seals with radio transmitters. Hopefully that will be the next phase of the research, Jansen said.
With the increase in cruise ships in Disenchantment Bay since the 1970s, the Tlingits have become concerned about whether ships are disturbing the seals, especially during pupping season in May and June.
"We feel strongly that they do affect the seals during those months," said tribal member Bert Adams Sr., a charter captain and former president of Yakutat's tribal council.
"The local people are saying that the seals are moving from Disenchantment Bay to Icy Bay because there is less disturbance there," Adams said.