A fisherman has described his astonishment after finding a 14-stone swordfish tangled in his lobster gear - in the River Forth near Alloa, 20 miles from the sea.

Brian Hynd, 48, said he had set lobster pots in the river off Alloa in Clackmannanshire "as an experiment" after hearing that lobsters had been caught as far up river as nearby Kincardine.

He set out with his nephew aboard their boat the Telstar, moored in Alloa Harbour, about noon on Sunday to see what they had got.

Mr Hynd said: "There were no lobsters, which wasn't much of a surprise, but thrashing about caught in the ropes was this enormous swordfish. We got the shock of our lives.

"It was still alive and thrashing about in the brackish water. We hauled it in and gutted it and I think we'll barbecue it.

"I've been fishing the river off Alloa man and boy since I was ten years old and I've never seen anything like it. I've seen plenty of porpoises  and even leatherback turtles, but never a swordfish so far up the river. It must be something to do with the seas getting warmer."  

Mr Hynd believes the  fish is a Razorbill Swordfish, although it may be a Marlin Swordfish. It was over nine feet long, and weighed over 200 pounds, and was 20 miles inland from the Forth Bridge when it got stuck in Mr Hynd's ropes.  

Dr Krishen Rana, senior lecturer at the Institute of Aquaculture at Stirling University, who studied photographs of the monster fish, said he was "surprised" that a swordfish had been found in the River Forth.

He said: "Finding a swordfish on the River Forth would be very unlikely, although it's not an impossibility. There was a porpoise that had strayed up all the way to River Allan just a couple of years ago, which shows unusual creatures can be found far inland,  but a Razorbill Swordfish would be very rare around these parts."  

Dr Rana added: "It certainly appears to be a genuine swordfish, and is quite different to what would normally be found in the River Forth.  

"It would be unusual to find a swordfish in Scotland, but they are sometimes found off the coast of Britain, as well as just off Norway and Sweden.   

"The Forth water is very tidal, so there's a good chance it could have washed in, due to the saline water in that region."  

Swordfish are generally found in warm and temperate oceans worldwide, although they do move to cooler waters during the summer months.