Observers Aboard Cruise Ships Logged Over 1,600 Humpback Encounters in Glacier Bay

On July 12, 2001, a cruise ship more than 850 feet long, carrying nearly 3000 passengers and crew, headed out of Glacier Bay National Park and Preserve in clear weather and calm seas. Just after 2:30 pm, near Bartlett Cove, the captain slowed the ship so Park Service interpretive rangers could step onto a ranger boat, then sped up again. Reports say that as it accelerated, humpback whales were sighted about 700 yards (640 m) off its left side, heading in the direction of the ship’s path. Neither the ship nor the whales changed course, and at the last sighting the whales were so close they were hidden beneath the bow. Some passengers reported a loud thud, while others heard or felt nothing. No whale was seen resurfacing, the incident went unreported to the Park Service, and the ship sailed on.

Four days later a dead humpback was found bloated and floating near where the encounter had happened. A necropsy several days later found a fractured skull and vertebrae and concluded that the whale, which was pregnant, had likely died of massive blunt trauma to the right side of its head.

A humpback whale discovered near the entrance of Glacier Bay in 2001. Necropsy reports indicated that it died of blunt trauma consistent with a collision with a large vessel. NPS Photo.

More ships, more whales

Accidental encounters between ships and whales have increased over the past few decades, the authors write, as whale populations recover from the large-scale commercial whaling of the 1950s and 1960s and as ships grow in number and size. In Glacier Bay they have likely increased for the same reasons: cruise ships entered the park on 55 occasions in 1970 and 224 in 2009, and monitoring in 1985 recorded 41 individual humpbacks using the waters of Glacier Bay and Icy Strait, a number that had passed 150 by 2009.

An endangered humpback whale surfaces in Glacier Bay National Park and Preserve with a cruise ship in the background. Park managers must consider how daily and seasonal cruise ship traffic might affect the whales. NPS Photo.

A hard trade-off

The authors call these encounters a perplexing issue for park management, reflecting trade-offs between protecting resources and visitor experience. They have talked with hundreds of cruise passengers (no formal survey was done) and heard two themes: seeing a humpback is among the most thrilling parts of a trip, and the closer the encounter, the more thrilling it is. For many passengers a whale sighting may be a once-in-a-lifetime event, which the authors say brings a keener appreciation of conservation and natural history, consistent with the Park Service mandate.

Yet the same encounters could harm whales. The noise from a ship’s propulsion may be loud enough to degrade the whales’ acoustic habitat and mask vital communication, and the closer a ship comes, the louder the noise. If a ship comes too close, a lethal collision may follow, reducing the number of whales using the bay, both in the year it happens and later.

Putting observers on board

The Glacier Bay Science Advisory Board made it a top research priority for the Park Service to place observers on ships to record how often and how close they come to humpbacks and other marine life. From July 2006, observers spent the day aboard ships while they were in the park, standing on the bow with rangefinder binoculars and handheld GPS units. They went out with the park’s interpretive rangers and recorded encounters near Bartlett Cove. After 2007 it was clear that many encounters happened before or after observers boarded or left, especially at the mouth of the bay and in Icy Strait. So from 2008, with funding from the National Fish and Wildlife Foundation and the Pacific Life Foundation and in cooperation with the University of Washington and the University of Alaska Southeast, observers began boarding ships in Skagway and Juneau and leaving at the next port, Ketchikan or Sitka, before flying back to Juneau to repeat.

An observer stationed near the bow of a cruise ship with laser rangefinder binoculars. NPS Photo.

By the end of the 2009 season observers had been aboard 23 different cruise ships on 380 entries into the park, 49% of all entries since the project began, logging over 2,700 hours and over 1,600 unique encounters with whales.

What they found

Encounters are frequent, and many are close. Counting encounters up to 3,281 ft (1 km), about 20% occurred within 985 ft (300 m) of the bow, and only about 3% within 328 ft (100 m). By any measure, the authors say, those are near misses: an adult whale swimming toward the ship’s path at a typical 7.2 ft/sec (2.2 m/sec) from 165 ft (50 m) away has about 6 seconds to avoid a ship moving at 16 knots (about 26 ft/sec or 8 m/sec).

The chance of an encounter also varies a great deal by place and month. It is always high in the lower bay, especially in the June-August peak season, compared with the middle bay and the West Arm, and high rates also occur in Icy Strait, undoubtedly with the same whales. The authors read this as support for the park’s rules for peak and shoulder seasons and for seasonal speed limits in the lower bay, and say the state of Alaska should consider similar steps in Icy Strait.

Is it illegal to hit a whale?

Since whales spend much of their time underwater and out of view, people often ask, and the authors’ answer is some form of “it depends.” As they paraphrase the federal rule (50 CFR § 224.103), it is unlawful to approach a humpback within 100 yards (91.4 m) or to disrupt its normal behavior or prior activity, unless the ship’s maneuverability is restricted; otherwise ships must operate at a slow, safe speed when near a humpback. A safe speed lets a ship take proper and effective action to avoid a collision and varies with visibility, maneuverability and sea conditions. The harder question is what happens when a ship cannot see what it may hit, such as a whale that spends 10-20 minutes underwater before resurfacing near the ship.

What remains open

Encounters are inevitable as long as ships and whales use the confined waters of Icy Strait and Glacier Bay. What remains to be determined is whether they harm the whales that use the area and how likely another lethal collision is. Whether the level of cruise ships and visitation justifies the impact on humpbacks will remain a significant management question. The authors say passengers will keep enjoying the encounters, the team will keep recording and analyzing their effects, and managers will have to weigh visitor levels against encounter rates when they decide on quotas for cruise ships.

Sources

• Scott M. Gende, Karin Harris, Julie Nielsen and A. Noble Hendrix (the source gives no affiliations), Using Observers to Record Encounters Between Cruise Ships and Humpback Whales, National Park Service article; the cruise ship’s name, three maps and the figure references to a missing figure are left out; rewritten in hubnx's own words.