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Sharks need better protection to maintain functional diversity

A study led by the University of Zurich reveals a concerning gap in the conservation efforts for some of the ocean’s most endangered species: sharks, rays, and skates. 

These creatures, belonging to the elasmobranch group, are crucial for maintaining the ecological balance in marine environments. However, their survival is at risk due to inadequate protection.

Functional diversity 

The research was focused on the functional diversity of sharks, rays and other elasmobranchs. Functional diversity refers to the various ecological roles these creatures play in their ecosystems. 

This aspect of biodiversity, along with taxonomy (species variety) and phylogenetics (evolutionary history), forms a comprehensive understanding of biodiversity. 

How the research was conducted 

The researchers analyzed a global dataset containing the traits of more than 1,000 elasmobranch species to assess their functional diversity including richness, uniqueness, and specialization.

The analysis pinpointed several critically endangered species that are vital for maintaining the functional diversity of elasmobranchs. 

Critical insights 

“We identified the top endangered species crucial for maintaining the architecture of elasmobranch functional diversity, including the longfin mako shark, Ganges shark, daggernose shark, shortfin mako shark, and scalloped hammerhead shark,” explained Professor  Catalina Pimiento, who led the study.

These species contribute significantly to the intricate tapestry of ecological roles within marine environments.

Functional diversity hotspots 

Spatial analysis revealed that the richness of elasmobranch functional diversity is predominantly found along continental shelves and around oceanic islands. 

The experts identified 18 unique functional diversity hotspots, which only slightly overlap with those identified by other biodiversity facets. 

Study co-author Dr. John Griffin of Swansea University noted that many of these hotspots are under severe threat from industrial fishing.

Fishing pressure 

“Many of the hotspots vital for elasmobranch biodiversity converge with fishing pressure along the coast of China, others fall around oceanic islands and high seas,” said Dr. Griffin.

“In line with previous global analyses we found that hotspots of fishing pressure are mainly distributed along the coasts of China and Europe (both in the Atlantic and the Mediterranean),” wrote the researchers.

“Smaller fishing pressure hotspots occur on the coasts of the US and Canada and along the Atlantic coast of southern South America (southern Brazil, Uruguay, and Argentina), west Africa and in the Sea of Okhotsk in Russia.”

Lack of protection 

Alarmingly, the study revealed that the multiple facets of elasmobranch biodiversity remain inadequately protected within the global Marine Protected Area network, leaving these species vulnerable to various threats.

“Overall, our results highlight acute vulnerability of the world’s elasmobranchs’ functional diversity and reveal global priorities for elasmobranch functional biodiversity previously overlooked.”

The study is published in the journal Nature Communications.

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