Anglers in Suffolk are being urged to contact police over illegal fishing following increased reports along the River Gipping in recent weeks.
Sergeant Brian Calver, from Suffolk police's rural crime team, said fish poaching is not just restricted to rural areas but is also prevalent in towns that have a watercourse.
Sgt Calver said the force has most recently received reports along the stretch of the Gipping between Needham Market and Claydon but illegal fishing also takes place in Ipswich.
He said: "In essence, an awful lot of the Gipping is managed by clubs, they lease the angling rights.
"We've recently received reports of illegal fishing, we get it quite a bit in Ipswich. We often get reports near the Yarmouth Road bridge heading up towards Sproughton.
"You talking things like fixed lines, illegal nets, people putting out nets right across the river, and these are people who are generally taking the fish for food.
"The club waters have got their rules in place, you can legally take wild fish from a river in certain circumstances, but these people are taking all they can get for food."
There are wider implications to illegal fishing, Sgt Calver added.
For example, a specimen carp may be worth in excess of £10,000 and the cost of replacing such fish can have a huge impact on businesses and clubs if stolen.
"We've had quite a few reports recently on the stretch between Needham Market and Claydon, that sort of area, not just netting, but people have been seen to take pike from there," Sgt Calver added.
"The bottom line is they haven't got permission to be there. They're not club members, we know from research done from the Environment Agency, that these people we suspect haven't got valid rod licences either.
"A lot people might think, 'well it's only a couple of fish' but it has quite an impact on the ecological balance and membership for those clubs.
"If large fish are taken out of those rivers, it becomes less attractive for people to want to join that club so they then lose out on membership."
Sgt Calver urged anyone with information about illegal fishing to report it to police on 101, quoting Operation Traverse or to the Environment Agency on 0800 807060.
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