The accusations come from creel fishermen in the north-east of Scotland, who are losing thousands of creels and miles of plastic rope every year in an ongoing ‘turf’ war over lucrative fishing grounds.
Ian Mathieson, who fishes for crab and lobster out of Stonehaven, has personally lost more than 2,000 creels and nearly 100 miles of rope over his 15 years in business.
In a recent incident, believed to be the biggest single loss reported to the Scottish Government, he lost 600 lobster pots and 15 miles of rope - containing an estimated 20 tonnes of plastic.
Police have launched an investigation into the case.
That is around an extra six tonnes of plastic pollution entering local seas annually, where it poses a significant danger to marine life.
And that's just the tip of the iceberg, with incidents being reported all around the country.
Mr Mathieson says the situation is nothing new, but is getting worse, with more gear conflict episodes than ever before.
He claims Marine Scotland is “not fit for purpose” and is failing to effectively manage fishing fleets.
In an angry letter to environment secretary Roseanna Cunningham, he calls for tougher action on “the biggest rogues”, including suspending licences of offenders and forcing them to “recover all the plastic they’ve cut and dumped on the seabed”.
He said he believed, with good management, conflict between fishing fleets would be ended, the marine environment would benefit and Scotland’s seas could be fished sustainably for generations to come.
Pregnant whale killed
His letter comes in the same week a pregnant minke whale and her calf died after becoming tangled in a fishing net in Orkney.
Sustainable fisheries campaigners have echoed the fishermen's calls.
Phil Taylor, head of policy and operations at Open Seas, said: “Damage and loss of one fisherman’s gear because of another’s action is a sad reflection of poor oversight and management of our seas by the Scottish Government.
“Ministers and Marine Scotland are taking a light touch approach to looking after our public seas, and this is sadly resulting in a ‘race to the bottom’ situation like this, where no one wins.
“Gear conflict can take many forms, whether it’s vandalism of someone’s property, littering or intimidation and has been around for a long time. Yet it could be easily solved if we properly planned out how to use our seas.
“Management zones, indicating which type of fishing can occur where, would resolve conflict between different users, and a comprehensive system of vessel tracking would show when one vessel has caused damage to another’s equipment.”
A Scottish Government spokesman said: “As this is an ongoing police investigation, we are unable to comment on the specifics of the individual case. However, we are absolutely clear illegal activity cannot be tolerated and would advise any concerns are reported to Police Scotland.
"Progress has been made to tackle gear conflict, including restricting unlicensed fishermen, technology trials for gear marking, and inshore fisheries pilots testing the impact of separating different methods of fishing within specified areas. We are also allocating £1.5 million for new tracking equipment across the inshore fleet over the next two years to help improve evidence gathering.
“The majority of Scottish fishers work well together, with a small minority of static and mobile fishers involved in gear conflict. We encourage them to work together to resolve difficulties locally where possible, support local voluntary codes of conduct, and are working in partnership with the industry to develop lasting solutions.
“As outlined in the Programme For Government, we are working with the sector and coastal communities to develop proposals to tackle the issue of fishing litter and lost gear.”
The United Nations estimates 640,000 tonnes of fishing nets are dumped in oceans around the globe every year.
Known as ghost gear, the nets kill and injure more than 100,000 whales, dolphins, seals and turtles annually.
It can take as long as 600 years for these nets and synthetic ropes to break down in the water, gradually fragmenting into ever smaller pieces – eventually becoming microplastics, which can cause further harm when eaten by fish and birds.