Rainbow fish caught in the tropical Thames

Looking like an extra from Finding Nemo, with yellow stripes, red fins and pearl-like dots, the rainbow wrasse has a distinctly tropical look.

Yet this was the amazing catch one Essex fisherman made off Southend Pier this weekend. The species is usually only found in the Mediterranean, and experts say it is simply another sign of the changing Thames.

Essex fishermen say they are regularly catching octopuses, squid, sardines, sea cucumbers, seahorses and even anchovies. It is believed the species are a result of the Thames Estuary warming up by about 3C. We have already seen rising numbers of seahorses and dolphins.

"This is definitely the first rainbow wrasse I've heard of, but there are a lot more semi-tropical fish coming up from the Mediterranean," said Chris Brown of the Sea Life centre in Weymouth. "We've seen everything from greater weaver fish, trigger fish, mantis shrimps and even loggerhead turtles. A lot of these species are beginning to breed around Britain as the water is getting so warm. These are the kind of things you would expect to see on holiday, but not here."

Ronan Roche, an Essex local government fisheries officer, said: "There are weird things being caught."