The man is accused of selling 14 catfish taken from the Kalamazoo River in Allegan County via the Craigslist website. The man's name wasn't released pending an arraignment in July.
The state Department of Natural Resources said it got a tip about the ad. Officers made contact with the man and purchased the catfish from him Tuesday.
The sale of the fish in this case is a misdemeanor punishable by up to 90 days behind bars and a fine between $250 and $1,000.