Catastrophic consequences of ship collisions on marine life – oceanbites

This blog is a guest post written by Sachithra Lakshani. She is a final-year student at the Ocean University of Sri Lanka, pursuing a B.Sc. (Hons) in Fisheries and Marine Sciences. Her academic journey is centered on Marine Ecology and Biodiversity, where she is determined to uncover the ocean’s enigmatic mysteries. Currently, her research interests span the broad intersection of fish pathology and microbiology as she immerses herself in the study of fish diseases within the ornamental industry, aiming to contribute to our understanding of these ailments and promote the well-being of aquatic creatures. Beyond the academic realm, you’ll often find her exploring nature, devouring books, and enjoying music.

If you’re a graduate student with an interest in marine science communication, feel free to reach out to us to write your own guest post!

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Reference: Schoeman, R. P., Patterson-Abrolat, C., & Plön, S. (2020). A Global Review of Vessel Collisions with Marine Animals. Frontiers in Marine Science, 8, 714013. doi: https://doi.org/10.3389/fmars.2020.00292

Addressing Ship Collisions

Collisions between marine animals and large vessels can occur in shipping lanes, posing a threat to nearly 80 marine species, including whales. Unfortunately, no effective measures have been implemented to minimize this damage as of yet. The number of reported ship collisions has increased to unprecedented proportions in recent years due to multiple reasons, including the increasing size of vessels and more maritime traffic. The large number of marine animals, including more than 20,000 whales, that suffer fatal injuries every year as a result of these events is significant. Reporting bias leads to limited collision reports involving smaller marine species, making it difficult to predict the exact number of accidents in a given year. Collisions with smaller species are likely underreported compared to larger ones, as vessel crews may not be aware of the incidents. Moreover, fatal collisions with cetaceans, whale sharks, and sea turtles often go unnoticed since their carcasses sink quickly. This lack of comprehensive data hinders precise estimations of the frequency of such accidents. Not only are marine animals affected, but human passengers can also face serious injuries or even die as a result of these incidents. 

Animals at Risk

Larger marine animals such as whales and sharks are among the species most commonly injured in these collisions. According to a report by the National Academy of Sciences, these fatal collisions can even threaten endangered marine species, which is bad news for the survival of those animals. Many scientists are focused on understanding why the populations of whales and sharks appears to be decreasing overall, and shipping collisions may be partially to blame. For example, the whale shark is one of the marine species most commonly involved in collisions. However, because their carcasses sink so quickly, it is difficult to determine the number of whale sharks that have been affected by such incidents over the past few decades, making management strategies difficult to implement.

Thousands of marine animals are killed over this issue of ship collisions worldwide, but the reported numbers represent only the tip of the ice-berg. In most cases, large vessel collisions are not reported because passengers or vessel crews may not be aware of the collision. Therefore, most of the data are collected from small vessel collisions, and so current numbers are likely underreporting.

Exploring the Root Causes

Ship collisions may be due to vessel-related or animal-related factors. Among the various types of vessels, smaller vessels are more prone to collisions and resulting serious damages due to their high speed, which can lead to losing control and reduced maneuverability. Sailors who operate these vessels have motivation to avoid such damages, as they can affect both marine animals and the humans aboard their ships. In contrast, larger vessels may collide with marine animals due to their size and difficulty in detecting these creatures. Smaller vessels do have an overall advantage in terms of avoiding collisions however, as they have better visibility for seeing marine animals, as well as the ability to change course or reduce speed to avoid collisions. 

Regarding animal related factors, many large marine animals, including whales, are vulnerable to collision with ships due to their long distance migratory patterns, which often align with shipping routes. Also, whales, sea turtles, and dolphins must frequently come to the ocean’s surface to breathe. Sea turtles in particular are also vulnerable to collide with ships during their breeding and nesting seasons when they make their way to land. 

Consequences for Marine Life

One of the key issues marine animals face after a collision is altered locomotion, which has long term consequences. Serious locomotion issues could arise due to injuries to fins, tails, and turtle shells. Altered locomotion means that animals may not be able to move as fast or maneuver as efficiently, and so these individuals are more likely to be eaten by predators. Wounds and broken bones also increase the energy consumption of animals, and as a result a huge amount of energy is required for body maintenance while a minimum amount of energy is available for other purposes, including growth, reproduction and other metabolic activities. Lack of energy reduces the ability of marine animals to find food and avoid being eaten. Due to the typically long life span and low reproductive rate of large marine animals, a high degree of mortality from shipping collisions directly affects the stability of populations. 

Challenges in Preventing Collisions

It is difficult to answer why marine animals do not simply move away from approaching vessels.  Scientists believe that during their resting, foraging, migrating, and other socializing periods, animals concentrate their attention to these behaviors and neglect the risk of potential environmental threats. Furthermore, marine animals often cannot detect the sounds of shipping vessels when they reach the surface of the ocean because of acoustic shadows – or areas where sound does not effectively travel due to waves or wind currents. These shadows tend to occur in front of ships, so animals may not detect the vessels until it is too late. All of these factors make it challenging for marine animals to hear approaching ships.

Areas with high vessel and marine animal density have a higher potential for ship collisions. To prevent collisions, sailors should remain alert while traveling through high-risk areas. To reduce the risk of ship collisions on marine animals, sailors can enhance their visibility with polarized sunglasses, preventing glare from the water’s surface. Additionally, following speed guidelines and maintaining proper control when navigating through high-risk areas is crucial to minimize collisions. Further valuable recommendations for vessel operators include adhering to guidelines, maintaining a safe distance from marine animals, and utilizing technology like radar and thermal imaging to detect and avoid collisions. Hiring marine mammal observers can also help reduce ship collision risks, offering a potential career option in marine conservation. On an individual level, supporting conservation efforts and spreading awareness about the issue are essential actions. By backing organizations that protect marine animals and habitats and educating others about responsible practices, individuals contribute significantly to safeguarding marine life. Making informed choices, such as opting for whale watching tours with responsible operators who follow guidelines, reinforces the collective effort to protect marine animals from ship collisions. 

Cover Photo: A yearling Right Whale injured from entanglement in commercial fishing gear. By the Georgia Wildlife Resources Division CC BY-NC-SA 2.0

I am a PhD candidate at Wake Forest University, and I received a B.S. in Biology from Cornell University. My research focuses on the terrestrial locomotion of fishes. I am particularly interested in how different fishes move differently on land, and how one fish may move differently in different environments. While I tend to study small amphibious fishes, I’ve had a lifelong fascination with all ocean animals, and sharks in particular. When not doing science, I enjoy running, attempting to bake and cook, and reading.