Useless fishes .)

• 17 Pound Catfish(can be held in off-hand, lol)
• 19 Pound Catfish (can be held in off-hand, lol)
• 22 Pound Catfish (can be held in off-hand, lol)
• 26 Pound Catfish (can be held in off-hand, lol)
• 32 Pound Catfish (can be held in off-hand, lol)
• 19 Pound Lobster
• 40 Pound Grouper
• 47 Pound Grouper
• 53 Pound Grouper
• 59 Pound Grouper
• 68 Pound Grouper
• 9 Pound Lobster
• 7 Pound Lobster
• 12 Pound Lobster
• 70 Pound Mightfish (can be held in off-hand, lol)
• 19 Pound Lobster
• 15 Pound Lobster
• 21 Pound Lobster
• 22 Pound Lobster
• 85 Pound Mightfish (can be held in off-hand, lol)
• 18 Pound Salmon (can be held in off-hand, lol)
• 15 Pound Salmon (can be held in off-hand, lol)
• 22 Pound Salmon (can be held in off-hand, lol)

Items obtainable only by fishing

• Steelscale Crushfish (one-hand Mace) thx Ryvinn!
• The 1 Ring  (+1 str/agi/sta/int/spi)
• Message in a bottle
• Rumsey Rum Light (+5sta/15min + drunk)
• Rumsey Rum Dark (+10sta/15min + drunk)
• Rumsey Rum Black Label (15sta/15min + drunk)
• Waterlogged Crate
• Iron Bound Trunk
• Sealed Crate
• Watertight Trunk
• Ironbound Locked Chest
• Heavy Crate
• Tightly Sealed Trunk
• Small Chest
• Reinforced Locked Chest
• Sturdy Locked Chest
• Mithril Bound Trunk
• Dented Crate

Fishes worth of something.

Those with yellow background are really worth of something. Those marked with emphasize are used in cooking of food boosting (buffing) your stats, see Cooking overview - table with valuable food for details.