The ban on commercial fishing is among legal measures aimed at conserving fish during their breeding and egg-laying season, department chief Adisorn Promthep said.
Anyone caught fishing on a commercial scale during that period faces a fine of up to Bt50,000 or five times the value of the fish taken.
Ten provinces whose climatic and geographical conditions differ from those in the rest of the country will be able to set their own terms for the fishing ban. They are Phang Nga, Nakhon Nayok, Lampang, Lamphun, Nakhon Ratchasima, Nong Bua Lamphu, Khon Kaen, Udon Ratchathani, Narathiwat and Phatthalung.