Exotic Marine Fish - evidence of rising sea temperatures around Wales?

Graham Oliver

Atlantic Tripletail (Lobotes surinamensis) caught near Peterstone, east of Cardiff. Original fish preserved in spirit.

Preparing a model of Atlantic Tripletail in a laboratory at Amgueddfa Cymru.

The finished model of Atlantic Tripletail.

In the past few years fishermen and members of the public have been reporting unusual catches and strandings of marine fish from around our shores — fish that would normally live in much warmer, tropical waters. Is this further evidence of rising sea temperatures around the shores of Wales?

These specimens are brought to National Museum Cardiff for identification, where they are incorporated into the national collections. In order to display their natural colours, painted casts are made and exhibited alongside the actual fish preserved in fluid.

The first UK sightings of tropical Tripletail

In 2006, an Atlantic Tripletail (Lobotes surinamensis) was caught in a fisherman's net in the Bristol Channel, near Peterstone, east of Cardiff. As the fisherman did not recognize the 60cm specimen, he brought it to the Museum for identification.

Tripletails are normally found in tropical and subtropical waters, and this individual is the first record from UK waters.

We know that these fish like muddy estuaries, which may be part of the reason it was in the Bristol Channel. They are semi-migratory, often associating themselves with floating debris, and it is possible it travelled here via the warm waters of the Gulf Stream.

Jacks, Swordfish and Leatherbacks

Another exotic catch was of a juvenile Jack, caught off the entrance to Milford Haven in August 2007. It is difficult to identify juvenile Jacks and the specimen needed to be X-rayed to confirm that it was the first Welsh record of an Almaco Jack (Seriola rivoliana).

This species is usually found in the warm waters of the Caribbean, but between July and September 2007 six were found along the south and west coasts of Britain, doubling the number of records since the first in 1984.

Then in 2008 a 2.2metre-long Swordfish (Xiphias gladius) was found dead on a beach near Barry in south Wales. Although this was not a new record, this oceanic species is seldom caught in Welsh waters.

These records of warm-water fish appear to be further evidence of rising sea temperatures. The findings coincide with increasing numbers of turtles, especially Leatherbacks, in the Irish Sea. However, the occurrence of exotic marine species is not new, and the Gulf Stream has frequently brought warmer water animals to our shores.

Most recently, two species of shipworm (Bankia gouldi and Uperotus lieberkindii) have been found in timbers washed up on the Lleyn Peninsula in north Wales. These are both warm-temperate and tropical species, and have not been recorded before from the UK.

The establishment of such exotic species around the British coastline, or at least an increase in their frequency, would reflect real changes in their geographical range.

The recording of marine species is vital to our recognition of such events, and the role of fishermen and the public cannot be underestimated — indeed we welcome this participation, and look forward to the arrival of the next mystery creature at the enquiry desk.

Juvenile specimen of an Almaco Jack (Seriola rivoliana) caught at Milford Haven.

X-ray image of the juvenile Almaco Jack, used to help confirm its identification.

The Swordfish (Xiphias gladius) found dead on Barry beach. Note the damage to the side of the fish, probably caused after death.

Boarfish (Capros aper) found off the coast of Wales. Although not a rare fish, it is rarely seen as it tends to live in deeper waters.

Comments (2)

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Amgueddfa Cymru
25 July 2017, 12:17
Dear Francisco,

Thank you for your message that we received via the website. We have forwarded this on to Graham, who will email you directly about your request.

Thanks again,

Digital Team
Franciscio J Garcia De Leon
25 July 2017, 01:31

Dear Graham Oliver
I am Francisco Garcia De Leon, researcher at CIBNOR (www.cibnor.mx) in Mexico and I am currently studying the populations of Seriola rivoliana, and I saw your article of exotic species found in Wales. I would like to know if the specimens were fixed and kept in alcohol. If so, could you send me a fin clip? I am studying the genetics of populations of this species through the use of SNPs markers and it would be interesting to know which populations are the ones that are initiating the migration towards the north in these moments of climatic change.

Thanks for your support