Gemma Fraser: Plenty of fish in the sea

OYSTERS and swordfish are delicacies that would make any seafood lover drool. But while such banquets are regularly served fresh from the sea in sun-kissed harbour-side restaurants on the Spanish riviera and Greek islands, it would take a giant leap of imagination to picture a similar scene in Leith or Cramond.

However, the idea may not be as far-fetched as it seems. A growing band of warm water and even tropical sea life has been popping up in the waves of the Firth of Forth in recent years, including swordfish and sunfish.

With the water temperature in the estuary set to rise in the coming years as a result of global warming, it seems that this might just be for starters.

Marine experts are predicting a sharp rise in the number of fish usually found in the Mediterranean turning up in the Forth, as the gap between temperatures narrows.

Native Scottish oysters – which until recently were thought to be extinct – are expected to make a comeback, while the brightly-coloured trigger fish and the pizza-topping favourite anchovy are also likely to take up residence here.

The latest unusual species to wash up in the Forth, found this week by a passerby in North Queensferry, was a Ray's bream. The piranha lookalike caused alarm at the time and was taken to Deep Sea World to be identified. The breed is usually found in the Med but is now appearing more regularly off British shores.

Michael Morris, from Deep Sea World, says: "In the last few weeks a number of Ray's bream have been spotted in the Firth of Forth and there has also been another specimen washed up at Torness.

"We've had reports of many more washing up along the north-east coast of England and other parts of Scotland.

"They're fascinating looking fish and have been compared in appearance to piranhas because of their rows of razor-sharp teeth. However, they pose no threat whatsoever."

Although the effects of climate change are thought to be responsible for much of the changes to the estuary's sea life, marine experts are unsure of the exact reasons for the return of the Ray's bream to our waters.

They have been turning up periodically for hundreds of years, with one of the last major "invasions" in the 1960s, but this time they are still here after three consecutive years when they would usually stop returning after one or two.

Mr Morris adds: "They're actually found from the Mediterranean up to Scandinavia, although they do not usually travel close to shore. No-one is entirely sure why but they do appear to migrate in small shoals in response to changes in sea temperature. It may be that they come inshore while following large shoals of smaller fish or other prey."

Currently, the most common species found in the Forth are cod, plaice, skate, eel and pollack, but in a decade or two the make-up could be vastly different, with permanent additions such as the Ray's bream, trigger fish and native oyster.

Chris Rowe, aquarist at Deep Sea World, says: "It tends to be bog-standard British species like sea bass, mackerel and bream that you find in the Forth, but some rarer fish like the Ray's bream are cropping up a bit more.

"If the temperature were three or four degrees higher it would attract quite a few more species and a lot more bream. However, rising temperatures will mean that cold-water species like cod and haddock will move north."

Dr Clive Fox, fisheries biologist at the Scottish Association for Marine Science, explains that cleaner waters are also leading to the return of fish species previously thought to be extinct.

He says: "Most estuaries are becoming cleaner as controls on pollution have tightened up. That's led to a bit of a return in salmon in some cases. There are also a few records of native oysters possibly being found in the Forth. They used to be common in the 1800s. They were largely taken out by over-fishing and the effects of pollution.

"The long-term trend for continued warming is likely to lead to a change in the composition of fish.

"It's not suddenly going to become tropical, but in the summer we might get influxes of anchovy and trigger fish."

Douglas Herdson, independent fisheries biologist, adds: "Another fish which is spreading is the trigger fish and late last summer this species was found on the west coast of Scotland.

"I would expect over the next few years to see a spreading of this fish, from northern Spain, in the North Sea. I would also expect to see the gilt-head sea bream spread into the North Sea."

While the discovery of the Ray's bream caused a flurry of excitement, it seems likely that in 20 years' time, no-one will even bat an eyelid when they spot one as they walk along the Forth's shores.