Abstract
Understanding interactions between large ships
and large whales is important to estimate risks posed to
whales by ships. The coastal waters of Alaska are a summer
feeding area for humpback whales (Megaptera novaeangliae)
as well as a prominent destination for large cruise
ships. Lethal collisions between cruise ships and humpback
whales have occurred throughout Alaska, including in
Glacier Bay National Park (GBNP). Although the National
Park Service (NPS) establishes quotas and operating
requirements for cruise ships within GBNP in part to
minimize ship–whale collisions, no study has quantified
ship–whale interactions in the park or in state waters where
ship traffic is unregulated. In 2008 and 2009, an observer
was placed on ships during 49 different cruises that
included entry into GBNP to record distance and bearing of
whales that surfaced within 1 km of the ship’s bow. A
relative coordinate system was developed in ArcGIS to
model the frequency of whale surface events using kernel
density. A total of 514 whale surface events were recorded.
Although ship–whale interactions were common within
GBNP, whales frequently surfaced in front of the bow in
waters immediately adjacent to the park (west Icy Strait)
where cruise ship traffic is not regulated by the NPS. When
ships transited at speeds 13 knots, whales frequently
surfaced closer to the ship’s midline and ship’s bow in
contrast to speeds slower than 13 knots. Our findings
confirm that ship speed is an effective mitigation measure
for protecting whales and should be applied to other areas
where ship–whale interactions are common.
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