The biggest enemy of the biggest fish in the sea is the big boats. A new study has identified key points of risk and proposed measures to reduce the mortality rate of whale sharks, whose world population has halved over the past 75 years.

Whale shark numbers have decreased across the planet in recent decades, but until now the reasons were unclear. Marine biologists from 50 international institutions publish this Monday in the journal PNAS New research results that point to collisions with large ships operating in major commercial shipping lanes. The impact of these accidents on mortality would have been underestimated and, according to scientists, could be the main reason for the decline in the population of this animal.

Since the whale shark (Rhinekodon Typus) spend a lot of time near the surface and congregate in coastal areas, leading experts to hypothesize that accidental accidents With larger ships they can become part of the mortality rate. To confirm an international team The movements of 350 samples are tracked and large ships around the world to identify risk areas and potential collisions.

Oceanologist Carlos Duarte says, “The conclusions drawn from this article are only for the great collaborative effort to collect all the data available around the world on the movement of these animals, in addition to the analysis of big data and simple statistical evaluation.” have been possible.” , one of the study’s lead authors, who is currently conducting research at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.

The team mapped the areas where shark numbers were highest (Hotspot) and those that match the world’s fleets of cargo ships, oil tankers, cruise ships and fishing vessels (the types of large ships capable of killing a whale shark in a single collision). The analysis showed that more than 90% of whale shark activities overlapped with that marine activity.

threatened giants

According to the International Union for Conservation of Nature (IUCN), the world population of these marine giants has declined by more than one. The world’s largest fish (they can be up to 20 meters in length) feed on small animals called zooplankton and, by regulating these microscopic organisms, play an important role in the health of the food chain and marine ecosystems.

The research results underscore the need for localized conservation measures to monitor collisions, regulate ship speed and reduce the risk of fatal collisions. “This is a significant contribution less than two months from the United Nations Conference on the Oceans [se celebrará en Lisboa entre el 27 de junio y el 1 de julio]which aims to unite the entire world to rebuild marine life, of which these giants of the ocean are an important component”, says Duterte.

The analysis of recorded incidents and monitoring of trade routes made it possible to identify the points of greatest risk of collision, which appeared especially in the areas adjacent to the bay. The study further showed that transmissions of whale sharks tagged by biologists were more often missed on the busiest shipping lanes; The team concluded that this disappearance was probably due to the whale sharks being killed and drowned in the ocean floor when they died.

security measures

So the results suggest that unscheduled or unrestricted conflicts explain the decline in population, which continues despite international trade and hunting ban laws passed in recent years. There are currently no international regulations to protect whale sharks from these types of accidents.

In this sense, the research team confirms that the existence of this species is at risk if immediate measures are not taken. They hope their findings can inform management and safety decisions. “We need to spend the time and energy developing strategies to protect this species from commercial shipping, before it is too late, so that the biggest fish on the planet can resist future threats such as changing ocean climates. could”, warned the university researcher. Southampton, Freya Vomersley, one of those responsible for the research.

The authors point out that at some point, mitigation measures are already underway for other large animals at risk (particularly whales) with real-time monitoring initiatives such as WhaleSafe or WhaleAlert. But they say additional measures are needed, such as isolating boats from samples and reducing boat speeds in some high-risk areas.