There are more frequent collisions between whales and boats than previously thought, according to a new study that looked at the rising whale injuries off the coast of New England.
The study paid an exclusive focus on humpback whales in the southern Gulf of Maine and found that nearly 15 percent of them, which swim to the area every spring to feed, were found to have injuries or scars indicating at least one vessel strike.
Published in the journal Marine Mammal Science, the study noted that vessel strikes on whales have been largely underestimated as the figures are suppressed compared to the actual strike toll on the animals.
Regarding deaths, a report in the Journal of Marine Biology dating back to 2012 noted that of the 108 reported whale collisions that took place between 1978 and 2011 off Alaska, 25 resulted in the death of the animal.
Methodology of Study
In the latest study, researchers reviewed the injuries of 624 individual whales photographed for nine years from 2004 to 2013 in the coasts of Massachusetts, Maine, and New Hampshire. The 210,733 photos were categorized according to the type of injury caused by vessel strikes.
According to the findings, 14.7 percent or 92 of the 624 individual humpback whales in the study had injuries from at least one vessel strike, with the majority having four or fewer strike injuries.
Multiple injuries found in parts of a whale's body were hard to assess whether caused by one or more ship strikes. The researchers also spotted one injured whale calf getting injured in two separate events. Irrespective of the frequency of injury, researchers were unanimous in the belief that whale-boat collisions are hazardous and need to be checked.
One reason for the number of injured whales looking fewer was that the whales killed in ship strikes were not being added to the list of injured.
"Vessel strikes are a significant risk to both whales and to boaters," said lead author Alex Hill from Whale and Dolphin Conservation, a charity working for the protection of marine mammals in Plymouth, Massachusetts.
Hill called for long-term studies in determining the effectiveness of outreach programs as well as the management policies and actions necessary to evaluate the whale population.
The Whale and Dolphin Conservation said whales are unlikely to survive if they are struck by vessels in certain sensitive areas. Similarly, whale and boat collisions can also cause injury and death to people who get thrown off the vessel when it is struck by a whale. There have been collisions leading to the sinking of small vessels.
Impact Of Ship Strikes On Whale Populations
There had been studies to know the impact of ship strikes on whale populations. There are different opinions on the outcome.
A study in 2014 focusing on the eastern North Pacific blue whales proposed changes to shipping lanes to decrease the odds of whale-boat collisions. The study, published in PLOS ONE, held the view that reducing ship strikes go a long way in safeguarding the blue whales.
However, another study published in the same year, this time in Marine Mammal Science, said that reducing collisions would not significantly affect the blue whale population.
Slow Whales Becoming Vulnerable To Strikes
Studies say vessel strikes happen because whales are slow swimmers and they spend more time at the surface and areas of high shipping traffic.
Among the whales, humpbacks are more vulnerable as they are oblivious of the risk of incoming ships because they are busy feeding or mating.
Humpback Whales Are Endangered
The new study also pointed out the fact that humpback whales are listed endangered under the U.S. Endangered Species Act. Still, there are no regulations in place to reduce the collision risk by restraining vessels in their vicinity.
Meanwhile, Dave Wiley of the Stellwagen Bank National Marine Sanctuary said the study is useful in framing regulations for federal managers. He said it is "troublesome" to see strike rates are going up.
On the other hand, Scott Kraus of the New England Aquarium expressed skepticism, saying that the number of ship strikes could be exaggerated because the researchers' method of interpreting scars on humpback whales could lead to error. He did, however concur that the study results are valid.
“There are a lot of whales getting hit by small vessels, and there may very well need to be some management actions around high-density whale areas,” he said.