Shark
Sharks, alongside rays and chimaeras, are known as chondrichthyan fishes (class Chondrichthyes). Sharks and rays together are termed elasmobranchs (subclass Elasmobranchii).
Conservation status
There are over 1,290 ‘described species’ of chondrichthyan living in our oceans for over 400 million years, but which are now threatened by a number of factors including fishing. The IUCN established a Shark Specialist Group (SSG) in 1991 as a response to the ‘severe’ impact of fishing on sharks (also rays and chimaeras). For example, the Whale Shark (Rhincodon typus and the largest living fish), which live in the Atlantic and Indo-Pacific, are listed as Endangered on the IUCN Red List – as global populations have declined by more than 50%. In 2024 the IUCN (SSG) published a report stating that ‘a third of sharks, rays, and chimaeras are threatened with extinction’. The 2,000-word report highlights that the global demand for Shark meat has doubled since 2005 and emphasises the threats posed by overfishing and bycatch.
Overview
The report goes on to describe how only 26% of species are targeted and that most are caught as bycatch (especially as a result of longline fishing). Sharks, rays and chimaeras play a vital part in marine ecosystems by, for example, cycling nutrients around the oceans. Some species act as carbon sinks or support ecosystems like mangroves that sequester carbon and several species are keystone or apex predators. Shark also provide food security for many coastal communities. The report does recognise the progress made in terms of conservation knowledge and policy and examples of sustainable fishing practices in Australia, Canada, and the USA.
Sharks are also on the Greenpeace Red List. In their review they talk about how the Shark population has plummeted leaving only 10% of the original population. They state: ‘More than one hundred million sharks are killed every year by commercial fisheries.’ and that ‘Shark-finning and fisheries in which sharks are caught as bycatch are the greatest threats to sharks’.
There are over 400 Shark species worldwide and over 40 of these live in or visit the seas around Britain. Species have interesting names and name sakes including Dagger Nose Sharks, Tiger Sharks, Catsharks, Zebra Sharks, Weasel Sharks, Night Sharks, Puffadder Shysharks, Great Hammerhead Sharks, Great White Sharks, Pelagic Thresher Sharks…. . Sharks have the best electrical sensitivity of any animal. They sense their prey through the electric fields they produce and can orient and maybe navigate via the electric fields produced by ocean currents within the Earth’s magnetic field. Most species live between 20 and 30 years. Whale Sharks live for over 100 years, and a recent study discovered a Greenland Shark about 272 years old (and thus the longest-lived vertebrate known).
https://www.iucnredlist.org/species/19488/2365291
https://www.iucnssg.org/iucnredlist.html
https://www.mcsuk.org/news/five-sharks-found-uk-waters/?gad_source=1