Fishing lets characters reel in fish from waters across Eth-Ur, which can then be cooked or sold.
Buy a Fishing Pole from Fishing Supplies or a fisherman in Faelindral, then equip it in your main weapon slot (you’ll need to unequip your shield first, since it’s two-handed). Pick up some Grubs for bait while you’re there — you can fish without bait, but you probably won’t catch much. Grubs can also be gathered with the Forage skill. Trainers can be found on the docks in Night Harbor, near the fish monger and fishing supplies vendor.