One of the world's most threatened sharks has been spotted off the Pembrokeshire coast.
The Thresher Shark, which has been assessed as being vulnerable in the IUCN Red List of Threatened Species, has been seen twice during the National Whale and Dolphin Watch project that took place earlier this month. The first sighting was in St Brides Bay while the second was offshore, from Grassholm Island. Despite being occasional summer visitors to the British waters, they are not considered a common sight.
The Common Thresher's relatively low reproductive rate is one of the reasons why it is now classified as 'Endangered', however they are also highly susceptible to both targeted and by-catch fishing exploitation as their habitat occurs within largely unregulated and under reported gill net and longline fishing areas. The shark's high value - particularly for its meat, fins and liver - makes it vulnerable to rapid population depletion.
Because of its low reproduction rate, it is difficult for thresher shark populations to recover from exploitation and threats. However, some conservation efforts are underway. In 2017, all three thresher shark species became protected under the Convention on International Trade in Endangered Species (CITES), which is the international treaty which aims to protect threatened animals from the wildlife trade.
Threshers are the largest of this particular shark subspecies and can grow up to six meters in length, weighing up to 350kg. They also have the longest lifespan, living up to 50 years.
They have a distinct skin texture with small, overlapping scales, which are also known as dermal denticles, that are rough to the touch. Unlike most sharks, which have large mouths for hunting, Thresher sharks have small mouths set slightly below and backwards from the eyes. They have 24 to 29 rows of small, razor-sharp curved teeth and regenerate two sets of new teeth every 10 days during their younger years. They have no need of a large mouth as a result of their long, whip-like tails which are used for hunting purposes.
Common Threshers are highly migratory, living in tropical and temperate seas around the world, including the United Kingdom. They usually live in deep water, up to 650m depth, although they usually stay in close proximity to land, and are also nocturnal, due to their sensitivity to UV light. They have evolved to be endothermic due to spending most of their time in deep waters in the open sea. This means they can make their body temperatures warmer than the surrounding waters by body shivering and other internal mechanisms.
Other marine life spotted in Pembrokeshire's waters during the National Whale and Dolphin Watch included Risso's dolphins, bottlenose dolphins, common dolphins, grey seals and a fin whale.
Rare shark spotted in Pembrokeshire waters
One of the world's most threatened sharks has been spotted off the Pembrokeshire coast.
The Thresher Shark, which has been assessed as being vulnerable in the IUCN Red List of Threatened Species, has been seen twice during the National Whale and Dolphin Watch project that took place earlier this month. The first sighting was in St Brides Bay while the second was offshore, from Grassholm Island. Despite being occasional summer visitors to the British waters, they are not considered a common sight.
The Common Thresher's relatively low reproductive rate is one of the reasons why it is now classified as 'Endangered', however they are also highly susceptible to both targeted and by-catch fishing exploitation as their habitat occurs within largely unregulated and under reported gill net and longline fishing areas. The shark's high value - particularly for its meat, fins and liver - makes it vulnerable to rapid population depletion.