The fishermen, including many women, shouted slogans against the Centre and Sri Lankan governments and sought immediate release of their colleagues, S Armstrong, Pamban Nesakarankan Trust President said.
The 18 fishermen along with their three boats were arrested by the Sri Lankan naval personnel off Katchathivu on December 29 and later lodged in a prison in Jaffna.
The fishermen also decided to observe a relay fast from January 9 if the arrested fishermen were not released by then.