The fin whale is decomposing at popular Cefn Sidan sands in CarmarthenshirevideoHeadline ,,Sea monster washes up on Welsh beach

New footage shows the sheer scale of a huge whale that is decomposing on a Welsh beach. The endangered 70ft sea creature is one of the biggest animals in the world and shocked beachgoers who discovered it at Cefn Sidan sands in Pembrey, Carmarthenshire, when they made the unusual discovery.

The “very large” fin whale is believed to be a female but had been dead for some time when it was discovered meaning it was already in a “bad state of decomposition”, according to the Marine Environmental Monitoring (MEM).

The UK Cetacean Strandings Investigation Programme (CSIP) has now advised the local council to leave the whale to naturally decompose, but it’s impossible to say how long this could take given the sheer size of the sea creature.

The blue whale The blue whale is the only whale larger than the fin whale(Image: John Myers)

Its head alone was over 16ft (5m) in length and around 8ft (2.5m) wide. Stay informed on Carms news by signing up to our newsletter here.

Researchers have explained that such strandings are becoming increasingly common in the UK which could in part be to do with the ban on whaling which was introduced in 1984.

Rob Deaville, CSIP Project Manager at the Zoological Society of London explained: “Unfortunately, the fin whale’s remains are too decomposed for us to conduct a full investigation, so we’ll never know exactly what caused this particular individual to pass away.

Fin whaleFin whales are nicknamed “razorbacks”(Image: John Myers)

“What we can say though is that although small in number, fin whale strandings are increasing around the UK. It’s possible that this may at least in part be associated with the ban on whaling signed by much of the world in 1984, that has led to increases in some whale populations.

“So paradoxically, although a sad event, this may be a sign of good news for the species as a whole”.

The whale is only the fifth fin whale to ever become stranded on a Welsh beach according to CSIP.

The whaleThe surprising discovery was made on Cefn Sidan Sands(Image: John Myers)

Matthew Westfield, CSIP Strandings Coordinator for Wales said: “Since CSIP first started investigating strandings back in 1990, the project has only ever recorded four other fin whales stranded on the Welsh coast – so this one found on Cefn Sidan was quite unusual.

“Given its size and the isolated location, we’ve advised the council to leave it on the beach where it can decompose naturally over time. It’s impossible to know how long this will take, and it may be that high tides end up carrying it away before it’s fully decomposed.”