Here are the types of fish, what level you need to catch them and what tool you use to catch them. For caskets, the percentage is the likeliness of catching one.
1: Hake (Rod), Shrimp, Pirate Crew Casket (5%) (Net)
2: Anchovie ((Net)
4: Crab (Cage)
6: Tuna, Sardine (Nets)
8: Trout (Rod)
10: Crayfish (Cage)
12: Mousefish (Rod)
14: Pike (Rod)
20: Catfish (Rod)
22: Sole (Net)
24: Salmon (Fly Fishing)
28: Perch (Net)
32: Neptuniun Spinners (Net)
38: Lobster (Cage)
40: Pirate Captain Casket (5%), (Net)
46: Seal (Harpoon)
54: Dogfish (Rod)
62: Neptunian Jellyfish (Net)
68: Pirate Lord Casket (5%), (Net)
70: Swordfish (Harpoon)
80: Shark (Harpoon)
84: Frostwhale (Whalling, after Whalling Quest)
88: Southern Whale (Whalling, after Whalling Quest)
90: Great Whale (Whalling, after Whalling Quest)
98: Megawhale (Whalling, after Whaling Quest)
100: Super wealthy Pirate Casket (5%) (net)