The demonstrators walked through the town to the district office protesting a dredging contract commissioned to a contractor by Seatran Ferry Co to clear the channel at the ferry port.
The firm, which operates a ferry service between Don Sak and Samui and Phangan islands, removed mud from the seabed and dumped it on the Don Sak habour. This angered fishermen who largely rely on catches in the area.
Prakob Chansaeng, the Don Sak mayor, said the mud dump could affect the livelihood of fishermen relying on the catch along the coast, and could also discourage tourism in the district as Irrawaddy dolphins were found off the district coast.
Deputy provincial governor Wongsiri Promchana and Maj Gen Theenachat Chinda-ngern, who is in charge of army affairs in Surat Thani, called a meeting with the demonstrators and the firm's representative.
Wut Sittisurat, the Seatran Ferry representative, admitted the dredging had caused a problem, and pledged to work toward a solution acceptable to the fishermen.
The meeting decided to temporarily halt the dredging project pending an investigation into the damage claimed by the protesters, Manager Online reported.