A video, shared with Sky News, shows thousands of dead prawns covering the seafloor on Scotland's west coast, as well as five different species of shark and the critically endangered mature flapper skate.

Campaigners say the film exposes a hidden problem of discarding at sea that causes harm to marine life.

"The impact on marine life is very concerning," Lauren Smith from Shark and Skate Scotland told Sky News.

"Flapper skate are a critically endangered species and to see these animals being caught and killed by bottom trawling is both heartbreaking and alarming," she said.

The historical range of flapper skate has been severely reduced in recent decades. Charities say this is due to overfishing and that Scotland's inshore waters are now a vital stronghold for the species.

Prawns are commonly 'tailed' on the boat and throwing away prawn heads is permitted on the west coast, but discarding bycatch fish such as cod is illegal. Under the 2019 'Landing Obligation', most fish must be landed and declared at port.

Although accidental bycatch is not a crime, the law requires all skates and rays to be "released immediately" when they are more likely to survive.

'Sickening to see the waste and disregard for life in our sea'

The video was filmed by local marine ecologist Peter Hume of Sea Kintyre after he was tipped off about suspicious fishing activity by Shark and Skate Scotland.

"All around the pier there were mountains of discarded skate and langoustines," he told Sky News.

"It was sickening to see the waste and apparent disregard for the life in our sea and the wasteful result of a fishery that is undermining other fishing opportunities for the local community."

Mr Hume says the skate in his video appear to have been thrown overboard after suffocating, which he says indicates the discarding is illegal.

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Large volumes of fish and other marine life are routinely caught in bottom-trawl nets used to sweep the seabed. Charities say unintended bycatch is a particular problem in the prawn trawl fishery due to the small mesh size of the nets. They say discarding often happens at sea so videos like Peter's is rare.

"The environmental impact of bottom-trawling is usually hidden from public view," explains Nick Underdown, Head of Campaigns at Open Seas, a Scottish marine sustainability charity.

"Bottom trawling is a largely indiscriminate method of fishing, but most people have no idea that their scampi and chips are caught using this method and at such an environmental cost. For too long, poorly regulated prawn trawling has been wreaking havoc on fish stocks and the health of our seas."

Open Seas is calling for better mandatory vessels tracking for bottom trawlers to stop poor practice.

It has urged the Scottish government to incentivise more sustainable alternatives to trawling.

Peter Hume says he has reported the incident in his video to Marine Scotland and Police Scotland.