TWO of Scotland's industrial rivers appear to be bouncing back to life with an array of unusual marine creatures.

The eelpout, sea mouse, and the colourful tub gurnard have joined cod and lemon sole in the Firth of Forth and the River Clyde, according to scientists from Scotland’s environment watchdog.

They said that despite the rivers’ long history of industrial use, they were much healthier than many people realise and contain an abundance of estuarine fish which are mobile, long-lived and found near the top of the food chain.

Myles O’Reilly, Senior Specialist Scientist at the Scottish Environment Protection Agency (Sepa), said: “The Forth Estuary with its extensive mudflats is relatively rich in fish species and acts as an important nursery ground for young marine fish.

“We undertook surveys of the fish that occur in the lower estuary close to the road and rail bridges and revealed 14 different species of fish. Trawling of the seabed between Port Edgar and Limekilns found the young stages of many commercial species such as whiting, cod, dab, plaice and lemon sole.

“We looked at the fish species that occur right in the centre of Glasgow close to the old suspension bridge at Carlton Place. Traps set overnight this spring highlighted the presence of shoals of perch and flounder, as well as sticklebacks.

“Migrating salmon smolts were also captured and there is evidence that elvers (young stage of eels) and lampreys also pass through the city centre on route to freshwaters.”

The work was carried out by Sepa to establish the health of our estuarine fish populations. All the fish were returned to the water.

Among the more colourful fish observed in the Forth Estuary was a young tub gurnard with blue-green pectoral fins and scientists also caught a sea mouse, a marine worm found in the North Atlantic, the North Sea, the Baltic Sea and the Mediterranean.

Mr O’Reilly added: “Traps set overnight for shore fish at Limekilns captured flounder and eelpout. Eelpout are unusual among Scottish fish in giving birth to live young.

“They are cool water species and thought to be potentially sensitive to global warming. We also use hand-operated seine nets in shallow bays to sample huge shoals of sprat, important food for seabirds, such as terns, nesting on nearby islands in the Firth of Forth.”

Sampling involves the use of a variety of fishing methods, including seabed and mid water trawls from Sepa’s survey vessel and special hand-operated nets.

In Glasgow, eight fish species were caught by trapping or using small seine nets at the mouth of the River Cart, where the water is slightly saltier. This included shoals of gobies and sprats along with flounder and salmon smolts as well as species typical of saltier estuarine waters such as eelpout.

Mr O’Reilly said: “It’s clear that the river (Clyde) supports populations of resident and migratory fish even in the middle of the city.

“This will come as no surprise to birdwatchers, as fish-eating birds such as cormorants, guillemots and mergansers are regularly seen feeding on the river.

“Flounder are a favourite prey and although these flatfish are usually thought of as sea fish, the young stages may venture far upstream into freshwaters.”