Fishing is possible while you are already employed by another job in the job centre. To do the job, you do not need to go to the job centre.
1. Go to a YouTool shop (marked on the map simply as “Tool Store”) and purchase some fishing rods (multiple are recommended as they sometimes break)
2. Go to the beach and stand in water which is roughly knee height and use a rod from your inventory
3. After a while a fish will be caught and you must complete the quick time event bar to reel it in successfully
4. When you’ve caught as many fish as you want to, take them to Pearl’s Restaurant at the end of the pier (marked as a P on the map), there is a back door to the restaurant where Pearl will buy them from you 3 at a time