All the crew were arrested on people smuggling charges, even though they claimed to have alerted the Italian coastguard that there was a boat in distress, 24 miles off the Italian island of Lampedusa.
Members of the crew are known to have been active in rescuing thousands of migrants in distress, as well as retrieving human remains caught in their nets for a dignified burial on land.
The Tunisian Fishermen Association of Zarzis has supported the fishers and sent a letter to the Italian embassy in Tunis.
Italy has been at the forefront of a dispute with the rest of the European Union about accepting migrants rescued from the Mediterranean Sea while making crossings in overcrowded and unseaworthy boats.
Two Tunisian fishers were previously put on trial after they guided 44 migrants into Italian waters were acquitted of all criminal charges.
