Small marine animals increasingly impacted by shipping collisions – report

At least 75 species of marine animals are affected by maritime vessel collisions – a figure much higher and more diverse than previously anticipated.

A recent study, A Global Review of Vessel Collisions with Marine Animals, compiled in South Africa by Nelson Mandela University School of Environmental Sciences, the Endangered Wildlife Trust and the African Observatory Network, raised the alarm that shipping collisions did not just affect large whales.

Researchers found that at least 75 marine species, including smaller whales, dolphins, porpoises, dugongs, manatees, sharks, seals, sea otters, sea turtles, penguins and fish were at risk of being hit by maritime vessels.

The discovery was as a result of a lack of reporting smaller animals being killed by smaller vessels. Before the study, the focus was on North Atlantic right whales, fin whales, blue whales, humpback whales, sperm whales and Florida manatees.

Commercial and recreational shipping voyages have increased significantly, especially between 1950 and 1980, which saw a sharp increase in whale deaths due to ship strikes. But it took 25 years before vessel strikes were prioritised by the International Whaling Commission Conservation Committee (IWC-CC). This resulted in the Ship Strike Working Group being established, in an effort to monitor and help reduce the number of ship strikes.

According to the report, among the first known collisions was in 1877, when a ship struck a small whale. In 1908, a sperm whale was the first whale to be identified as a ship strike casualty.

We now know that a host of other marine species are routinely struck and killed by vessels.

In the 1980s, just over 10% of all sea turtles in the New York State Marine Mammal and Sea Turtle Standing Program were found to have propeller wounds.

Crews are often not even aware that smaller marine species are being hit by ships, and the fact that the carcasses of cetaceans (whales, dolphins and porpoises), sea turtles and whale sharks tend to sink to the ocean floor quickly does not help the lack of reporting these incidents, the report revealed.

But even if their carcasses floated to the surface, lurking predators and decomposition would swiftly get rid of the evidence.

The report hypothesised that perhaps the public is less concerned about smaller marine species being hit by ships than if a large whale or dolphin is struck and killed. It is further revealed that no global database exists to record ships colliding with smaller marine species – only with cetaceans.

It was explained in the report that when a vessel collides with an animal, causing sharp or blunt force trauma, injury can be immediately lethal, or result in the slow deterioration and eventual death of injured creatures.

Whales and manatees with gashes from rotating ship propellers or abrasions from the ship’s bow, hull, skeg or rudder were found to experience reduced welfare due to pain and stress. But larger marine species could still survive a blow from a ship.

A similar injury “could easily decapitate a fish or penguin”, the report lamented.

People are also at risk when a vessel strikes an animal, especially smaller ships.

When reviewing the possible long-term effects of marine animals being injured or killed by ships, it was found that not enough is known to conclude that population decreases could directly be attributed to vessel-related deaths.

The report explained that factors such as high mortality or low fertility rates could contribute to decreases in population growth.

Larger species have been observed for longer, and more is known about specific species whose population growth rates are adversely affected by shipping strikes. These species include the North Atlantic right whale, Hauraki Gulf Bryde’s whale, the North Pacific blue whale, North Pacific humpback whales, North Pacific fin whales and Canary Island sperm whales.

The way in which smaller species are being affected by vessel strikes is slowly starting to be understood, most notably for Perth’s Little penguins and Florida’s sea turtles.

“However, for most smaller species, this impact still needs to be assessed,” the report said.

In finding possible solutions for humans and sea creatures to coexist, the need to identify high-risk areas was emphasised, in the hopes that shipping lanes and routes could work around identified areas of high marine animal density.

Rerouting ships travelling through known areas of high animal concentrations, while maintaining safe navigation, even seasonally, could save hundreds of species’ lives.

But this is not always feasible, and the compliance of rerouted ships would have to be monitored. This also applies to large commercial vessels, which still does not account for small vessel collisions.

More accurate information is needed on small vessels, as larger vessels have GPS positions and known shipping routes. Smaller vessels are more difficult to monitor, and are capable of high speeds, which significantly increases the likelihood of colliding with a marine animal.

The fact that marine animals do not make way for ships approaching them seems baffling, but the report explained that certain behaviour, such as resting, nursing, foraging or socialising could distract animals from sensing an incoming vessel.

Reducing the speed of ships could therefore be a viable solution. When vessels travelled at 10 knots, the probability of lethal injuries decreased by 50%. While surveying humpback whales, it was found that slower speeds meant they were three times more likely to be spotted. This would also work for vessels that cannot be rerouted.

Another factor discussed was the fact that animals may not be able to hear vessels because of noise disturbances.

Cetaceans depend on sound for communication, navigation and to find food, the International Fund for Animal Welfare (IFAW) explained.

According to the IFAW, blue whales could once hear each other across the entire ocean. Their ability to communicate has decreased by more than 90%, and in some areas noise levels have more than doubled every 10 years between 1960 and 2000 alone.

Under the sea, marine animals mostly hear the continuous drone of ships, blasts from airguns in search of oil and gas, naval mine and torpedo explosions, active sonar during military activities, fishing boat sonars used to locate schools of fish, and pile-driving during construction work.

But despite the United Nations recognising underwater noise as a major marine pollutant, not much has been done to improve the design of ships, which are reportedly only getting bigger and faster, and therefore noisier.

Should ships travel slower and install propeller guards, this could help protect animals by reducing sharp force injuries.

Propeller guards still resulted in injuries, but it was found that smaller ships with propeller guards travelling at idle speeds reduced injuries to loggerhead sea turtles by 30%.

But until more accurate databases are established for smaller species threatened by shipping collisions, species-specific necropsy protocols are established and high-risk areas are identified, smaller marine animals will continue to be injured or killed by vessels, the report concluded.

These actions “would be a valuable step towards the mitigation of collisions with species other than large whales”.

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