Confrontations between rival navies are rare these days, but American seamen face another challenge: avoiding collisions with the largest animals that have ever existed.
Marine biologist Greg Silber is after new insights to prevent US vessels from striking whales. In 2009 he and his team used an artificial basin at the Naval Surface Warfare Center in West Bethesda, Maryland, to test the hydrodynamics of “ship strikes” — collisions between vessels and the massive yet highly vulnerable sea mammals.
Undertaken at a military facility and by a government organisation — Silber works for the National Oceanic and Atmospheric Administration, or NOAA — their resulting study had a purpose far beyond satisfying the researchers’ individual curiosity.
“What we did was build a whale model that was completely to scale,” Silber told Business Insider. “The same density, the same weight, the same size, relative to the size of the vessel model. And then we ran the ship model at the whale.” Researchers hoped that studying the dynamics of a simulated collision could help develops methods for avoiding ship strikes.
Granted, there were limits to what the study could achieve. Living whales are likely to move as a collision unfolds, and organic tissue don’t have the same properties as the plastic resin and fibreglass model the researchers used. But the simulations still gave a glimpse into what happens in the “near field,” Silber’s term for the few dozen yards that are closed before a ship and a whale collide.
For instance, researchers were able to figure out a “lethal” and “safe” zone for whales relative to a given naval vessel, based on the size and position of both (see chart at left).
“We know how vessels work. We know a little about how whales work. We don’t know anything about the actual interaction,” said Silber.
The oceans are vast — but not so vast that whale strikes are unavoidable. One line of the Old English epic Beowulf calls the ocean a “whale road,” and the animals can suffer the same violent fate as any creatures that share their habitat with human traffic.
Another Silber study collected nearly 300 incidents of confirmed or possible ship strikes in 27 years. Over two thirds were fatal for the whales involved.
In his research at the Naval Surface Warfare Center, Silber was surprised to find the model ship successfully recreated the suction effect of a working propeller — which is strong enough to suck in certain whales, a class of creatures that can weigh in excess of 100 tons.
“Even when the whale was at depth, let’s say [the equivalent of] 30 feet, 50 feet, maybe even 80 feet, it can be drawn towards the ship and then hit by the propeller,” said Silber. This “significant lateral drawing action,” which often occurred when the model whale was submerged rather than afloat, was perhaps Silber’s biggest finding, though it wasn’t always quite strong enough to draw all whales into a ship’s blades.
Ship strikes often occur head-on as well. The most extreme case may have been off the coast of Florida in 1991, when a Navy hydrofoil travelling at 45 miles an hour struck a whale, causing a fast landing that threw the crew forward.
A warped hull and broken steering arms on both sides of the vessel were only part of the $US1 million in damage.
The US Navy, which has nearly 300 vessels deployed around the world, has had an outsized role in reported ship strikes. Among the cases with “known vessel type” in Silber’s study, 23 involved the Navy, ahead of 20 container ships and 19 whale-watching ships.
But the Navy isn’t necessarily the most blameworthy party. Silber said the military branch reports cases “religiously,” even in cases where it can’t verify whether a strike actually took place. And since commercial ships are often larger in size than naval vessels, freighters and or massive container ships might not even notice they have struck a whale. Silber’s study notes that “a 10,000-ton Naval ship has a greater likelihood of recognising that a collision has occurred than does a 40,000-ton container ship.”
The Navy is also busier along seaboards than in the open ocean, where most ship strikes occur.
One whale species suffers from ship strikes most — and it’s also the Atlantic’s most critically endangered.
North Atlantic right whales as a species seem to be more prone to being hit by large vessels than other large whale species,” says Tony LaCasse, a representative of the New England Aquarium, which runs conservation programs targeting the species. “They are basically all black, and they often are feeding near the surface for long periods of times at a slow speed.”From the mid ’80s to the mid aughts, nearly 40 per cent of right whale deaths were attributed to ship strikes, a significant blow to a population thought to be smaller than 500 individuals. That vulnerability is what led Silber and his team to use the right whale, specifically, as their model.
In 2008, US agencies including NOAA implemented a speed limit of 10 knots for ships 65 feet or greater in length. The restriction applied to locations along the Atlantic seaboard at times of year when right whale populations were at their densest.
Silber’s study had called the casualty numbers are probably an under-counting, since “many other strikes likely go undetected or unreported.” He believes fatal ship strikes could number in the hundreds annually.
The world’s oceans are also set to get a little busier, with freight transport projected to grow four per cent every year this decade. If sea traffic increases as a result, whales will have additional deadly hazards to content with, on top of the ones already facing them.
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