A recreational fisher who sold crayfish to an undercover fishery officer has had his boat forfeited to the Crown.

Mark Webster, 58, was fined $2400 and his $25,000 boat was seized after he sold 143 crayfish to an undercover officer in Kaikoura and Christchurch.

Webster's sentencing in Christchurch District Court on Thursday is being held up by officials as an example of what can happen if recreational catches are sold rather than eaten.

The Christchurch man also forfeited 72 crayfish.

"It is illegal for recreational fishers to sell their catch. Recreationally caught fish are for your own personal consumption," Peter Hyde, the Canterbury Westland district compliance manager for the Ministry for Primary Industries says.

"This summer we will be actively targeting recreational fishers who choose to abuse the fishery regulations and limits."

The maximum penalty for selling a recreational catch is five years' imprisonment, and or a $250,000 fine.