Illegal nets and unlicensed anglers were the target of a combined police and Environment Agency swoop on the River Welland in Spalding.
Joining officials on Thursday to quiz anglers on the banks was a fisheries enforcement officer, Rafal Sosnowski, who travelled from Poland.
His visit was arranged by the Angling Trust as part of its Building Bridges programme to integrate East Europeans into this country’s fishing community.
Lincolnshire Police rural crime sergeant Dave Robinson: “There’s been a lot of worry in the local community about fish being taken when they should not be. The local people believe it’s quite a big problem, but it’s not a problem that’s reported to us as a police force on a regular basis.
“Our wildlife crime officer seized some nets from the River Witham in Lincoln only last week.”
Sgt Robinson is urging South Holland residents who suspect illegal fishing is taking place to call Lincolnshire Police on 101 and quote Operation Traverse, which has been set up to tackle the problem.
Adrian Saunders, an Environment Agency fisheries specialist, said: “If nets are being used, we need to know where they are being set.”
The team spoke to half a dozen anglers in Spalding on Thursday – including members of the East European community – and all were licensed.