AN ALIEN species has been discovered in the Haven waterway, possibly the first instance of its kind making a home in Wales.

The species, known as Eusarsiella zostericola, is a marine ostracod, a tiny sea creature related to crabs, shrimps and lobsters generally around 1mm in length which originates from North America.

The creature resembles a shrimp encased between two hard plates of chitin, which acts as a shell.

It is not known how the crustacean came to find a home in the Haven, but its introduction was probably accidental.

Jonathan Monk, the Port of Milford Haven’s environmental manager said: “Like many things in the marine environment, especially tiny things in mud, sometimes things may have been there for a while, it’s just a case of seeing them!

“The waterway is one of the best studied bits of the sea in the whole of the UK - however it is still not uncommon to come across a new marine species.”

Mr Monk said the port authority takes hygiene measures to prevent the spread of invasive species, including making sure boats adhere to the International Ballast Water Convention.

Under this law, vessels must treat their ballast water to prevent transport of non-natives.

He added that the species is not likely to be harmful: “The port is not concerned that this species will cause problems in the ecosystem of the Haven.

“However, we remain vigilant for non-native species and are committed to minimise the risk of spreading where we can, and encourage users of the Waterway to do likewise.”

Eusarsiella zostericola is believed to have been introduced into the UK in the mid-20th Century from the Atlantic coast of the USA with populations in the Blackwater estuary in Essex, Medway estuary in Kent, as well as the Thames estuary and the Solent.