The maritime industry is becoming increasingly environmentally cautious as seen by the drive of decarbonization, sulfur cap 2020 and the emergence of green shipping. However, the damage to the marine environment is often overlooked. Aquatic animals are getting killed by industrial ships and not many people are aware of this.
A vessel collision or strike is defined as any impact between any part of a watercraft (most commonly bow or propeller) and a live marine animal. Even though collisions happen “once in a blue moon”, captains and senior officers have to be aware of this issue and try to the best of their abilities to avoid hitting sea creatures.
Ships hitting sea creatures are not talked about enough
Collision incidents with smaller species are scarce, likely as a result of reporting biases. On the other hand, collisions between large vessels and marine animals may not be reported because vessel crew are not aware of the collision. Even if carcasses floated, they might be consumed by scavengers or were too decomposed to reach shore.
There is no global encouragement nor database for smaller species such as sea turtles unlike that of the ship strike database for cetaceans (aquatic mammals) established by the International Whaling Commission (IWC). The lack of accurate data makes it even more challenging to assess the frequency and consequences of collisions with smaller species than it is for large whales. As such, the number of vessel collisions are often undercounted.
Most scientific publications have focused on collisions between vessels and larger sea creatures such as North Atlantic Right whales, fin whales, blue whales, humpback whales, sperm whales and Florida manatees. However, there is increasing evidence that more marine species are at risk of collision, especially within coastal areas frequented by smaller vessels.
Research done by Nelson Mandela University in South Africa by Plön found that at least 75 marine species are affected, including smaller whales, dolphins, porpoises, dugongs, manatees, whale sharks, sharks, seals, sea otters, sea turtles, penguins, and fish.
Ships are unable to avoid animals
In a summary of vessel classes involved in collisions with marine animals compiled by Plön, there are a broad range of vessel types, from canoes to even aircraft and navy vessels. Vessels that travel at a higher speed pose a greater risk to animals as it results in a stronger impact which increases the risk of blunt force trauma.
Larger ships are unlikely to see sea creatures due to their size and speed. In some cases, coastal wildlife such as sea turtles resting near the surface may appear as a mat of algae in the water. Upon hitting them, the captain may not even notice as it may feel as though the ship travelled through seaweed.
Even if the crew is aware of an animal’s location, the ability to avoid it will depend on detection distance, vessel speed and largely on the vessel maneuverability. Small vessels may be able to move out of the way, even when an animal is close and the vessel is going at high speed, due to better agility.
In contrast, large vessels need a greater response time to divert course with a greater turning angle and greater distance to avoid an animal. Larger vessels also have deeper drafts and thus, a larger strike zone. As such, larger vessels possess a major risk to marine animals.
Animals are unable to avoid ships
Animals such as whales, turtles and otters slowly swimming, resting and lodging just below the surface of the water face a high risk of collision because they are in the path of a vessel’s hull and propeller.
Some species such as sea turtles are often unable to avoid ships because they move slowly in the water. In the case of whales, the average speed is a little more than 20 mph (32.2 km/h) over a sustained period.
In extremely short bursts, some whale species can travel more than 30 mph (48.3 km/h). Whereas the average speed of ships such as bulk carriers, container ships, oil and chemical tankers, RORO vessels and cruise ships range from 13 to 25 knots (24 km/h – 46km/h). Since the speed of whales are relatively faster, why do they not swim out of the way of approaching vessels?
One theory is that sea creatures may not see vessels as a threat. For example, they may be accustomed to the sounds vessels make, just like an individual living in a city. Essentially, it is similar to a hit-and-run accident but happening to coastal wildlife.
A study of tagged blue whales near shipping lanes off the coast of southern California by McKenna et al., found that whales do not avoid areas of heavy ship traffic. They also found that blue whales at the surface were limited in their ability to avoid collisions with fast ships because they responded to approaching ships with a slow descent and no lateral movement away from the ship.
According to Plön, there are animal-related factors that prevent them from avoiding ships such as the time spent on the surface, the type of behavior and hearing capabilities.
Behaviors such as resting, nursing, foraging and socializing are highly distracting and will prevent them from detecting incoming ships.
Younger animals are particularly at risk, because they are more playful and less experienced and might be left alone while a parent forages for food.
Marine animals such as whales live in a world of sound and are known for their exceptional hearing abilities with a 12-octave hearing range as compared to eight in humans. With that said, why are whales unable to hear incoming ships?
Large ships such as cargo ships and tankers create something called a “bow null effect” blocking the engine noise by the bow which masks out engine noise located at the rear of the ship. This phenomenon might explain why marine animals are not disturbed by the vessels noise and why those that spend a lot of time at the water surface are prone to vessel strike.
Shipping is the center pillar of the world’s trade, with 80 percent of the trade volume transported by sea. It is inevitable for ships to pass through clusters where marine animals are located in. While shipping is of upmost importance to our world today, marine life is equally important too. There are precautions that can be taken such as having slow zones, better technologies that warn captains of potential strikes, better mapping, and warning system for whales.
Photo credit: iStock/gvictoria
