Rogue fishermen along the west coast of Scotland are using increasingly sophisticated techniques to avoid detection, Marine Scotland has said.
A group of fishermen in the Firth of Clyde have been using Facebook and other social media to stay one step ahead of fishery protection vessels.
The rise in illegal activity in the Firth of Clyde is thought to be down to increased demand for razor clams.
The clams can sell for £30 a kilo in places like Hong Kong.
The new market has encouraged the use of illegal methods to harvest the clams.
Small boats trail live electric cables into the sea, causing the clams to rise out of the seabed so they can be gathered by divers.
The fishermen use social media to share information about where the enforcement boats are, which makes their job increasingly difficult.
The impact on the marine environment is unknown but the Scottish government has announced a plan to test whether so-called electro-fishing might be a viable and sustainable option.
Aboard MPV Minna in the Firth of Clyde at sunrise, the first job of the day is a routine check on the Spes Bona, a trawler from Dunure in Ayrshire.
Robin and Donald Gibson are fishing for prawns. They haul in their nets as they wait for the Minna's high-speed inflatable to come alongside.
Once the boarding party have clambered up the ladder dangling down the side of the trawler, they check paperwork and net sizes. Everything is in full compliance.
This is the legal side of the fishing industry - highly regulated and carefully monitored.
But there are other operators who prefer to stay below the radar. Fishermen using small boats seeking to supply a new and lucrative market in the far east for razor clams.
Gathering them by hand is slow and laborious, so the rogue fishermen use electro-fishing.
It's dangerous work and it's illegal. Also, no-one knows what the impact will be on razor clam stocks.
The captain of the Minna, Stuart Gregor, says more than 20 boats are now operating out of west coast harbours and hundreds of tonnes of razor clams, sometimes known as spoots, are being shipped to the far east every week.
During the afternoon, the Minna moves closer to the shoreline. Culzean Bay is a popular location for the clam fishermen.
Up on the bridge, the crew spot a small boat. Its location is suspicious but it's in shallow waters so it's difficult to investigate what it's doing.
Stuart Gregor says a new controlled trial of electro-fishing should establish whether or not it is viable and sustainable.
That would mean he and his crew will no longer need to play cat and mouse with the clam fishermen.