Environment officers patrolling Lincolnshire's riverbanks have been given stab vests and batons for their own protection.
They say it is a deterrent against possible attacks from anglers as the officers enforce fishing rights.
Gangmasters are being urged to educate migrant workers about fishing rights to make sure they do not break the law.
Roger Ferguson, from the Environment Agency, said about the kit: "It gives me some protection."
The law states that anyone fishing on a river or a stream can take home only two fish they have caught per day.
The rest have to be thrown back.
Environment officers are concerned that eastern Europeans coming into this country may not be aware of the law, so workshops are being held to get the message across.
Mr Ferguson said he had encountered problems with irate anglers of all nationalities.
"I have been on the wrong end of somebody kicking off with a filleting knife. At the end of the day any person that we check is an unknown risk.
"We have to uphold the law whether people think it's right or wrong."