To avoid more whale deaths, ships must slow down
We live in a culture that is dependent on global trade and 90% of goods are transported by ships. As an increasingly important part of our economy, ships have become more efficient, and faster. But like many advances in human technology, whales pay a price. Ship strikes are only one of the many threats whales face, but for some endangered populations, they are, literally, a driving force to extinction.
With the story today of a blue whale struck dead by ship as it slept in the Indian Ocean, we should look at the many reasons why whales can not avoid ships. First of all, there is physics. The Lloyd Mirror Effect is an acoustic shadow in front of a large ship that results from the engines being at the stern and the sound blocked by the hull. As a result, a whale in the path of an approaching ship, is unlikely to hear it.
There is also biology. The drive to eat or mate may far outweigh the need to avoid a perceived threat, particularly if they have managed to avoid the threat before. Imagine a busy city has grown around your once quiet home. To get to your local store, you now have to cross a busy street. While stressful and irritating, you have grown accustomed to the noise. You are aware of the threat presented by the passing vehicles, but you need food, and must cross the road to get it. So far you have managed to get home safely. Then one day, a big truck is moving quickly, doesn’t see you, and…it’s too late.
And while there are multiple reasons whales get hit, there are very few solutions to reduce this threat. Studies of ship alarms have shown that whales react in a way that actually would increase the chances of getting struck. Thermal imaging relies on seeing the whale at the surface, not just below, in the path of a ship. Forward scanning sonar works best for object that are stationary, has limited range, and can not predict the whales’ behavior. That leaves two basic solutions- separate ships and whales and if you can’t, slow the ships down.
In some areas on the East Coast of the United States and Canada, Areas to Be Avoided have been implemented to reduce the risk of striking critically endangered North Atlantic right whales, of which fewer than 500 remain. These areas are marked on nautical charts and mariners route around them, reducing the chances of encountering important right whale habitat.
In the Bay of Fundy, and off the coast of Boston, shipping lanes have been moved out of important right whale habitat. And research has shown that if a whale is struck by a vessel traveling at 10kts or less, it has a more than 50% chance of surviving the strike. As a result, seasonal speed restrictions have been implemented along the busy ports of the East Coast of the US, requiring vessels of greater than 20m to reduce speeds to 10kts.
Far more animals are killed by vessel strikes than we know. Obvious external injuries, like the one depicted on the blue whale off Sri Lanka, is not typical. Sharp trauma, like a cut from a propeller, is obvious. But blunt force trauma is not. This occurs when the vessel’s hull strikes the animal and injuries are not externally visible. Without necropsying animals (internal exams), we will not fully understand the extent of this threat in Sri Lanka, or elsewhere.
Shipping is a part of our lives and we depend on it. But we also depend on whales to help keep the oceans thriving. Sharing the ocean comes at a cost. Whales have paid a price that is too high. It’s our turn to share that cost, through time and money, we need to slow ships down.Tagged in: blue whale, dolphin, endangered species, environment, green movement at 50, nature, Whale
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