Police have been swotting up on the habits of salmon as part of efforts to crack down on fish poaching in Glens of Antrim rivers.
Officers have met with salmon experts to discover where the fish are most vulnerable to poachers.
The PSNI in the Moyle area of Antrim have been working with the Glens and Margy angling clubs and bailiffs to tackle the issue of salmon poaching in the region.
Sergeant David Armour, from Ballycastle and Cushendall Neighbourhood Policing Team, said: "Over the last year we have been responding to concerns of salmon poaching from rivers. We increased our patrols of the river banks and poaching equipment was recovered.
"We will continue to work with angling clubs and the water bailiff for the area to enhance our knowledge. Earlier this year, officers from the Neighbourhood Policing Team visited a local salmon station to learn about when and where the fish are at their most vulnerable to the poacher; this helps us target our operations.
"We are determined to prevent salmon poaching from happening and will continue to target known poaching hot spots," he said.
Salmon poaching is a big problem on the rivers which run through the Glens of Antrim.
A court in Ballymena recently heard how water bailiffs used "nightsight" and camouflage to swoop on poachers who were dressed in black and wearing balaclavas at the Glenarm River.
An enforcement officer said up to 10 nets were found in the river in a year and that salmon stocks are declining.
The officer said there is a market for salmon because it has "probably doubled in price".
The County Court Appeals Court in Ballymena was told a man from Glenarm was found with a fish in his pocket when bailiffs swooped last October.
The man, 59-year-old Arthur Gibson of Feystown Road, was appealing the level of fines he had to pay for illegal fishing.
He had the appeal rejected and ended up paying another £200 in court costs, bringing the total for fines and costs to £2,125.