Industrial fishing is driving a great many marine species towards extinction, sharks and rays in particular. The findings are contained in a new study.
A third of cartilaginous fish (Chondrichthyes), a class that also includes sharks, rays and chimaeras, risk extinction due to overfishing. This is what a team of researchers led by Nicholas K. Dulvy discovered, publishing a report on 6 September in the journal Current Biology titled "Overfishing is driving a third of sharks and rays towards global extinction".
The researchers identified 1,199 species of Chondrichthyes in total, also known as cartilaginous fish, and found that 391 of them (32.6 per cent) are to be considered threatened, with 180 species (15 per cent) classified as Vulnerable (VU) on the scale of the International Union for Conservation of Nature (Iucn), the largest database of information on the conservation status of animal and plant species across the globe. 121 (10.1 per cent) are considered Endangered (EN) and 90 (7.5 per cent) are Critically Endangered (CR).
In particular, the researchers found that rays are more threatened than previously thought, with 36 per cent of species at risk. For sharks this figure stands at 31.2 per cent and for chimaeras at 7.7 per cent.
These assessments are even more alarming when compared with the findings of the 2014 survey, the year of the first census. Seven years ago, 181 species were threatened with extinction (24 per cent of a total of 1,041). In less than a decade, therefore, the number has more than doubled.
The vast majority of species — 99.6 per cent — are threatened by overfishing, known in English as overfishing. Sharks and rays (as well as a great many other marine species that do not belong to the class Chondrichthyes) are not necessarily hunted as a food source, but are victims of bycatch — that is, accidental capture: they become entangled in fishing nets intended for other animals.
Overfishing is the primary threat to all 391 at-risk species and the sole threat to two thirds of the total, 67.3 per cent. Three species, moreover, are classified as "Critically Endangered" (CR), but are feared to be already extinct, as they have not been sighted for decades. If that were the case, they would be the first marine species to have been driven extinct by fishing.
Dulvy himself, at the end of January of this year, had conducted a study, subsequently published in the journal Nature, demonstrating that the global population of rays and sharks had declined by 70 per cent between 1970 and 2018, precisely as a result of industrial fishing.
The remaining species, by contrast, are threatened by other factors, all nonetheless linked to human activity and the exploitation of natural resources. Specifically, the researchers cite habitat loss and degradation (31.2 per cent), climate change (10.2 per cent) and pollution (6.9 per cent).
It is essential to act now to prevent the extinction of further species and to protect the food security and ecosystem functions provided by these iconic predators.
Nicholas K. Dulvy
For this reason, the report underlines the importance of limiting fishing, actively protecting marine protected areas and developing new strategies that can reduce or limit the mortality of these creatures.
These species have inhabited the seas for 420 million years and have dominated the ecosystems in which they live ever since. They have survived at least five mass extinctions and now risk failing to survive the sixth as a result of our food system.