An increase in trout poaching has prompted a warning that hidden cameras will catch poachers in the act.

Eastern region Fish & Game officers said incidents of trout poaching were on the rise but hidden cameras were helping catch those responsible.

Fish & Game officer Anthony van Dorp said a "string of incidents" were currently being investigated but he couldn't give details for "operational reasons".

"What I can say is we've captured some excellent images and are now working with police to identify the offenders and we want to enlist the public to help stamp out the potential threat to the local economy."

He said Rotorua's world-renowned trout fisheries were always more sensitive during spawning season, which was now well underway.

Mr van Dorp said taking spawning trout could have a serious impact on future trout numbers.

"Poachers also trample on spawning beds and destroy eggs already laid in the stream, which can seriously impact on future trout stocks from wild spawning," he said.

"Our message to poachers is that you might think you've got away with it but you never know when that knock on the door is going to come."

Mr van Dorp said an illegally poached trout wasn't worth the repercussions when prosecuted.

"It could be the most horrendously expensive trout of your life."

Poachers face fines of up to $10,000 and a year in prison if caught.

Mr van Dorp said Fish & Game officers were startled to pull a large trout out of their Lake Tarawera fish trap to discover what they first thought was a fishing fly stuck in its back.

On a closer examination they found a 90mm length of metal sticking out - which turned out to be the broken-off point of a poacher's spear.

"The poor fish had managed to escape with the barb still sticking into his flesh - the wound was quite fresh," Mr van Dorp said.

"Yet another ugly example of poachers at work."

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