A new electronic tagging system has discovered that fish can swim enormous distances around the North Sea by using undersea currents. These offshore currents, created by themovement of the tides, help fish to travel up to 10 times further than had been thought.
Standard tagging systems attach a plastic tag to a fish and then record where the fish is subsequently caught. On this basis, plaice might appear to move just 55 miles (88km) in 56 days.
But an electronic tag, developed by the Government's Centre for Environment, Fisheries and Aquaculture Science, in Lowestoft, discovered that during that period, the fish actually ranged up and down the east coast of Britain, covering a total distance of 900km.
This finding has important implications for attempts to set quotas to preserve fish stocks.
Julian Metcalfe, the scientist who led the research, said: "It does mean if you wanted to close areas from fishing, to protect the stocks, you would also have to close areas around it."
Cod and other species take advantage of the tidal drift, say the scientists, whose work is reported today in the science journal Nature: "When tidal stream are fast, individual fish can move up to 20km per day."
The idea of closing areas has been mooted as a method of managing cod stocks in the Atlantic, following a collapse in numbers through over-fishing.
The plaice move by swimming up into the tidal stream, which moves north or south, changing direction every six hours with the rise and fall of the tide around the British coast. By moving in and out of the stream, they can reach their spawning grounds in the North Sea and in the east of the Channel, and the feeding grounds in between, using less energy than if they were swimming in still water.Reuse content