Sharks are the largest fish on Earth. Whale sharks can reach up to 60 feet in length, which is
roughly equivalent to a four-story building. Their size makes great whites look like minnows.
But even giants can disappear. More than half the whale sharks have disappeared from the
ocean over the past several decades. Some populations have declined by more than 60%.
This decline is still a mystery to scientists. Overfishing and other known threats are not the only
explanation. Researchers can’t study the bodies of whale sharks that sink after they die.
A new clue has been discovered, and it is a significant one. A study published in the journal
Proceedings of the National Academy of Sciences found that whale shark deaths are most likely
due to cargo ships. The authors discovered that shipping traffic is a common cause of whale
shark deaths in areas with high populations of endangered fish. Ships are also known to strike
and kill these species.
As consumers, our lives connect us to this seemingly distant problem. More than into our
Robert Harcourt, an Australian marine ecologist who is not associated with the study, stated that
shipping is a major problem for giants in the sea. “We have an economy that relies on moving
things around the globe in a way that doesn’t consider the environmental impact.”
At least 75 marine species are endangered when ships strike them
A large tanker, painted in red, white, and blue, pulled into a port in southern Japan last fall, a
39-foot dead whale was draped limply across its bow.
Although tragic photos of whale strikes are uncommon, they are not rare. According to a recent
review, they affect at least 75 species of marine animals and could kill thousands each year.
Whale sharks and sea turtles are two of the most vulnerable species.
It is important to identify the most vulnerable animals in order to reduce collisions. This is where
this whale shark study comes into play. Large ships must report their location. The authors then
compared the points with the movements of hundreds of whale sharks that they had previously
tracked using satellite trackers. This is not an easy task: David Sims, marine ecologist at
Southampton, was a co-author of the study.
These fish are extremely vulnerable, according to the results. More than 90% of the ocean’s
surface that whale sharks use overlaps the routes of fishing vessels, tankers, and passenger
ships. Freya Womersley is a University of Southampton doctoral student and lead author of the
study. She says that whale sharks prefer to be near the coast where shipping is most busy.
It was also discovered that shark tracking devices often stopped working after the animals were
transported through busy shipping lanes. This could be due to the fact that the animals had
been killed by ships. Some trackers showed sharks swimming through dense shipping lanes
and sinking slowly to the seafloor — the “smoking gun” for a deadly ship strike, as Womersley
and Sims reported in The Conversation.
According to Womersley, sharks cruising in the Gulf of Mexico and the Arabian Gulf were most
at risk of being struck by ships. Vox reported that they spend a lot of time on the surface, where
they might be struck by a ship.
Although scientists aren’t able to determine the exact number of sharks that boats have killed,
they have this information about other marine giants such as the North Atlantic right whales.
The ships killed at most third-right whales that were killed in the past few years and injured
more. Only 360 are left today. Harcourt stated that right whales are known for being unable to
be run over by ships.
According to the review, other species of whales, mackerel Sharks, otters, and manatees are
also vulnerable. However, physical strikes are just one part of the problem.
Noisy ships disrupt animal’s senses
Most humans see the world with their eyes, while dogs and cats can smell it. However, whales
and dolphins depend on sound. They consider everything sound. It is how they map the
environment, find prey, and communicate with each other over hundreds of miles of ocean.
Shipping is a major obstacle to this strategy. The 32-fold increase of low frequencies of sound
along major shipping routes around the globe over the past 50 years has been due largely to
giant propellers. These frequencies are used by some whales to communicate. (Fish, including
whale sharks, don’t use sonar for communication so it is unlikely that this is a problem.
According to Daniel Costa, a University of California Santa Cruz marine ecologist, whale shark
research was not conducted in noisy areas. He said that whales have been louder than usual to
compensate for increased noise.
Researchers also found that noise can disrupt communication and interfere with behaviors like
hunting prey, sleeping, and mating. According to a review, more than 150 studies have shown
that noise can have significant effects on marine life.
These emissions contribute to climate change which is a threat to all marine life. Some animals
are more vulnerable to ship strikes due to warming. This is ironic. North Atlantic right whales, for
example, are moving north to Canadian waters as the ocean heats. They were not protected
from ship strikes until recently. Costa stated that “Climate Change keeps reshuffling it” making it
difficult for regulations to keep pace.
A safer sea
It is simple to make the oceans safer for giant marine animals. One option is to move ships
away from hot spots. For example, a 2015 study found that moving a shipping lane close to Sri
Lanka, 15 nautical miles away, could cut down the chance of blue whales being hit by ships by
95 percent. Advocates are now pushing for this.
It is possible to slow down ships even if they are moving at a slower speed. According to one
2006 study, the chance of a cargo ship killing a whale is less than half when it moves at about
10 knots (10 miles per hour) compared to almost 100 percent when it travels faster.
This “slow steaming”, also known as the “slow steaming”, is quieter and uses less fuel. Irfan
reports that a 10% speed drop can result in a 19% reduction in greenhouse gas emissions. The
fuel bill is also lower.
However, ships that slow down or take a different route have one major disadvantage: it takes
longer to deliver goods. This is one reason why studies such as these don’t always result in
shipping restrictions. This drawback makes other approaches appealing, such as designing
quieter vessels or adding wildlife repellents or propeller guards. However, the benefits of these
technologies have not been well established.
Womersley stated that shopping locally is not only an option to cut shipping costs, but it is
something we can do now and the return would be huge. Numerous marine giants are at top of the food chain and help stabilize the ocean ecosystems. They can also fertilize the oceans and
capture large amounts of carbon, which could fuel climate change.