Cartilaginous fish such as sharks are considered fierce and invincible predators. In fact, they occupy various ecological niches and are also endangered due to human activities. A new paper in the journal Science has estimated the global extinction rate of sharks and rays and found an explanation for their plight.

Fish are a large group of primary aquatic vertebrates with a highly variable composition. Besides ray-finned fish, to which the vast majority belong, there are also older fish, including cartilaginous fish, which live in the seas. There are not many representatives of this class, only about 1,200 species of sharks, rays and chimeras (full-bodied) are victims of humans (especially their food), and vice versa.

In a new article published by a leading scientific journal Science, An assessment of the dynamics of the number of cartilaginous animals over the last 50 years is given. Their catch increased rapidly since the 1970s and reached its maximum in the 1980s. However, despite the increased efforts of fishermen, the amount of fish caught later decreased. The authors note that the self-reproductive potential of sharks and rays may be weakened. However, it has not yet been applied to the World Oceans.

The calculations cover a variety of natural habitats from the 1970s to the present. They differ in geographical location, water depth and ecosystem diversity. This is how biologists were able to map “bright spots” of cartilaginous biodiversity (where RLI changed little and fish did generally well) and “dark spots” where “diversity of sharks, sharks, and rays was dramatically halved.” a century).

The authors took into account that such fish represent different ecomorphotypes: they differ in structure, size and lifestyle. Scientists have found out which ecological groups of cartilaginous animals are more affected and for what reasons. Including contribution to the problems of different regions of the world and individual countries.

In addition to losing an average of half their populations, rays and sharks are estimated to have lost 19 percent of their RLI globally. This trend initially affected rivers, estuaries and other coastal water areas, then spread to the open ocean and its depths.

The loss of ecomorphotypes, called “ecological erosion” and describing the lost functions of fish in communities, was 22 percent. According to the authors, the real culprits are countries with weak economies, low fishing productivity and overpopulation in coastal areas.