Whale strikes by boats undercounted, study says
Actual numbers could be 15% higher because of deaths
A new study suggests that nearly 15% of the protected humpback whales that come to feed every spring in the southern Gulf of Maine have been struck by boats and other vessels — putting both boaters and the sea mammals at risk.
Researchers believe their findings, which appear in the most recent issue of Marine Mammal
Science, are likely underestimated because the study does not account for whales that actually are killed in ship strikes.
The analysis is based on injuries to 624 individual whales photographed between 2004 and 2013 in a body of water just off the coasts of Massachusetts, New Hampshire and Maine.
Multiple reviewers evaluated 210,733 photos for five categories of injuries consistent with a vessel strike.
Of the 624 individual whales reviewed, 92, or 14.7%, had injuries attributed to at least one vessel strike. A total of 149 injuries were documented, according to the study.
Most of the whales had four or fewer vessel strike injuries. Seven whales had at least three vesselstrike injuries, and two whales had at least four injuries.
In most cases, researchers could not determine whether multiple injuries in different parts of the whale’s body were caused by one or more strike.
But at least one whale calf appeared to have injuries from two separate events, based on fresh marks in different body regions within weeks of when the calf was photographed with initial healing wounds.
Whatever the actual total or frequency of injury, researchers and activists agree that whaleboat collisions can be catastrophic.
The Whale and Dolphin Conservation (WDC), a charity dedicated to protecting the animals, maintains that people can be injured or killed from being thrown when the small vessel is struck by a whale. Some collisions have caused small vessels to sink.
If whales are struck in certain areas by a large vessel, they are unlikely to survive, according to the WDC.
Other studies have determined that vessel strikes probably occur because whales, in general, are slow swimmers, spend considerable time at the surface of the water, and stay in areas that tend to overlap with heavy shipping traffic.
Certain types of whales, such as humpbacks, are either unable or unlikely to detect oncoming ships. They may be engaged in activities such as feeding and mating and are either oblivious to, or may not respond to approaching ships.
Researchers for the Gulf of Maine study point out that, while humpback whales are listed as endangered under the U.S. Endangered Species Act, there currently are no regulations or guidelines in place to reduce the likelihood of collisions with vessels in their vicinity — except those actively engaged in whale watching.
They hope that their research, and other long-term studies, can help regulators develop new guidelines on boat traffic, and better assess the health of the humpback whale population.
If whales are struck in certain areas by a large vessel, they are unlikely to survive, the Whale and Dolphin Conservation says.