![]() ![]() The flesh is edible and is consumed in some countries, but is tough and unattractive compared to other fish. The market is "bogus" since dried manta gills have never been used historically in Chinese medicine, and there is no evidence that the gills have any medicinal value. Demand for their dried gill rakers, cartilaginous structures protecting the gills, has been growing in traditional Chinese medicine practices. Manta rays use their gills to filter plankton from the sea. Manta populations suffer when they are caught as bycatch by fishermen fishing for other species, but fisheries which target manta rays are even more harmful. They have one of the highest brain-to-body mass ratios of all fish. Manta rays are largest rays in the world, with wingspans reaching 7 metres. All species in the family are either endangered or critically endangered Sawfish are a family of rays which have a long rostrum resembling a saw. Most particularly, the continuing decline of threatened rays and sharks is the consequence of unregulated fishing, as illustrated by a recent international survey which listed only 38 species of skates and rays still subsisting in the highly impacted Mediterranean Sea. As with sharks, rays are increasingly becoming vulnerable because of commercial and recreational fishing pressures, the impact of non-ray fisheries on the seabed and ray prey species, and other habitat alterations such as damage and loss from coastal development and marine pollution. They cannot recover as rapidly as many faster growing fish can if their populations are depleted. ![]() They are K-strategists which grow slowly, mature late sexually and produce few offspring. Like sharks, rays are relatively long living and thrive in stable populations. There are four orders of rays: stingrays, skates, electric rays and sawfishes. ![]() In 2010 a global IUCN study of vertebrates found that of 1,044 cartilaginous (ray and shark) species examined, 345 or 33% were threatened with extinction. Because rays and sharks are closely related, they are often studied together. Cartilaginous fishes have skeletons made of cartilage while bony fishes have skeletons made of bone. Modern fish are either cartilaginous or bony. Together rays and sharks make up the class of modern cartilaginous fishes. Threatened species are also referred to as a red-listed species, as they are listed in the IUCN Red List of Threatened Species. The terms can be used somewhat interchangeably, as all vulnerable species are threatened, all endangered species are vulnerable and threatened, and all critically endangered species are endangered, vulnerable and threatened. The term threatened strictly refers to these three categories (critically endangered, endangered and vulnerable), while vulnerable is used to refer to the least at risk of these categories. The International Union for Conservation of Nature ( IUCN) ranks threatened species in three categories: Vulnerable species Endangered species Critically endangered species Threatened rays are those vulnerable to endangerment ( extinction) in the near future. This is a recent trend and has caused a population loss of up to 86% in the last six to eight years. The market for shark and ray products is first and foremost a luxury one: The gill plates, in the case of manta rays, are used in China for a tonic soup that has become fashionable because of perceived medicinal properties, even though it is not in the traditional Chinese pharmacopoeia. ![]()
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