Like someone else mentioned before, fishing is basically out of the question. Right now the job market for Noer is pretty dismall since, you know, the island is about to be overun with monsters and no one can stop it. The slaves are only really good for throwing their lives away at this point. Either learn how to fight (and likely get mauled and/or raped to death), or pick up a pickaxe and start mining (where you'll likely get mauled and/or raped to death), or just sell your body (where you'll just be raped to near death). Remember that people from sybaris are discriminated against. Asaide from the Saint's church (which is a scummy religious org) no one is really out to help these people. They're not giving them charity and handouts and they're certainly not giving them any real chances to just live a decent life, let alone a chance to escape from the island. So it doesnt really matter what skills they had before if no one is willing to hire them, and slavery just insures they're stuck on the doomed island.They can easily train all the excess slaves to fish if that is actually a real concern. Food is a concern only for people from sybaris and i dislike how all the people from sybaris just lost all their skills and became vagrants without knowledge from their past lives conveniently for the author.