Something strange is stirring in the seas around Britain. Last week fishermen in the West Country hauled up an enormous catch of anchovies, a fish usually seen in the warmer waters of the Bay of Biscay at this time of year (Report, Oct 31).

An angler using a rod and line in the Bristol Channel recently caught an almaco jack, a fish normally found in the Caribbean or off Florida. And grey trigger fish from the Mediterranean were caught off the West Coast of Scotland only a fortnight ago.

Bizarre as these catches are, they only add to a growing list of other exotic creatures found off the coast of Britain in recent years. Tuna, red mullet, angel fish, pilchard, squid, John Dory, sea horses, leatherback turtles and other warm-water sea life are becoming more familiar visitors off our shores.

The warmer waters of the North Atlantic are encouraging this mass migration, but this is more than just a blip in sea temperature. In the North Sea, our usual cold-water fish such as cod and whiting have been moving northward or deeper as the sea has warmed over the past 25 years. And on the other side of the Atlantic, a similar shift in fish has been happening over the past 40 years off the northeast coast of the US. It all suggests that the seas are being warmed by a profound climate change, driving fish populations further northwards.