Fishing requires two things: a body of water and the fishing rod tool. The former can be found naturally in the game or created with the bottomless pot, while the later is obtained from Gillian after doing some quests for her.
Fishing is done via a mini-game that requires players to rapidly press the "A" button continuously while the fish is quiet, and hold down the "A" button while the fish is trying to free itself.
All the catches can be displayed in bodies of water with their preferred water type, with a maximum of 50 fish displayed per island.
After the Builder obtains the fishing rod from Gillian, the toughie and elder npc villagers will fish in any body of water, and they will put their catches in nearby chests. This includes the named toughie npc villagers like Digby or Gillian too.
Catching all 40 different species unlocks the Marine Monument recipe.
Each fish has four values that determine where it can spawn: water type, size, island, and specific location.
Fish only live in the four water types: fresh water, muddy water, seawater and hot water. They cannot live in the other liquid types (poison, lava and plasma).
The size refers to the size of the shadows that appear when fishing. There are four possible sizes: small, medium, large and gigantic.
The island refers to the general location it can be fished in.
Some species can only be fished in very specific locations or under specific situations, like the Angelfish being only catchable in the underground lake in Khrumbul-Dun's mines. Some species spawns are determined by the map tile you're fishing on. Map tiles cover an area of 32x32 blocks, and depending on the block type, the minimap will display a kind of tile or another.
Additionally, each species comes in three sizes: standard, big (★) and whopping great (★★). This secondary size value is independent of the fish's species shadow size that determines spawns, and is mostly for decoration purposes. However, some food recipes like the Smoked salmon can be made in better quality by using big or whopping great ingredients. Another detail to notice is that while any size will count for unlocking the Marine monument, only the standard size for each species counts towards filling the Builderpedia in.
The following list does not provide every location for each species, but their most common or even unique location in some cases.
Image
Name
Water type
Size
Islands
Details
Angelfish
Fresh water
Small
Khrumbul-Dun
Fish in the underground lake.
Anglerfish
Sea water
Medium
Furrowfield Moonbrooke
FF Fish in deep sea water, from any non-rocky tile. MB Fish in shallow sea water, from any rocky tile.
Arowana
Hot water
Large
Isle of Awakening
Fish in hot water.
Bass
Muddy water
Medium
Isle of Awakening
Fish in muddy water.
Blowfish
Sea water
Medium
Moonbrooke
Fish in deep sea water, in the northernmost part of the island. Fish in shallow sea water, from any non-rocky tile.
Blue Betta
Fresh water Hot water
Small
Isle of Awakening Khrumbul-Dun Moonbrooke
IoA Fish in hot water. KD Fish in fresh water, not in the underground lake. MB Fish around the Shrine of Rendarak.
Blue Queen
Sea water
Medium
Khrumbul-Dun
Fish in shallow sea water. Fish in deep sea water, from any rocky tile.
Blue Tang
Sea water Hot water
Medium
Furrowfield Moonbrooke
Fish in shallow sea water, from any non-rocky tile.
Carp
Fresh water
Medium
Furrowfield Moonbrooke
FF Fish in fresh water. MB Fish in fresh water, but not in the frozen river.
Clownfish
Sea water Hot water
Small
Isle of Awakening Furrowfield Angler's Isle
Fish in shallow sea water, from any non-rocky tile.
Coelacanth
Fresh water
Gigantic
Moonbrooke
Fish around the Shrine of Rendarak.
Colourful Carp
water
Large
Furrowfield Khrumbul-Dun Moonbrooke
FF Fish in fresh water. KD Fish in the underground lake. MB Fish in fresh water, but not in Rendarak nor the frozen river.
Flounder
Sea water
Medium
Furrowfield Khrumbul-Dun
Fish in deep sea water, from any non-rocky tile.
Goldfish
Fresh water
Small
Isle of Awakening Moonbrooke
IoA Fish in fresh water. MB Fish in fresh water, but not in Rendarak nor the frozen river.
Halibut
Sea water
Medium
Moonbrooke Gurgling Lagoon
MB Fish in shallow sea water, from any non-rocky tile. GL Fish in shallow sea water or deep sea water.
Humphead Wrasse
Sea water
Large
Furrowfield Khrumbul-Dun
FF Fish in shallow sea water, from any rocky tile. KD Fish in shallow sea water, from any non-rocky tile.
Jellyfish
Sea water
Medium
Khrumbul-Dun Moonbrooke
KD Fish in deep sea water, from ay non-rocky tile. MB Fish in shallow sea water or deep sea water.
King Salmon
Fresh water Sea water
Large
Moonbrooke
Fish in the frozen river, under the large bridge in the east.
Lake Trout
Fresh water
Small
Moonbrooke
Fish in fresh water, but not in Rendarak.
Lemontail
Fresh water Muddy water
Small
Isle of Awakening Furrowfield Khrumbul-Dun
IoA, FF Fish in muddy water. KD Fish in fresh water, but not in the underground lake.
Mackerel
Sea water
Medium
Isle of Awakening Furrowfield Khrumbul-Dun Angler's Isle
IoA Fish in shallow sea water, from any non-rocky tile. FF Fish in shallow sea water, from any non-rocky tile. KD Fish in shallow sea water. AI Fish in shallow sea water, from any non-rocky tile.
Manta Ray
Sea water
Gigantic
Moonbrooke
Fish in deep sea water, in the northernmost part of the island.
Marlin
Sea water
Gigantic
Khrumbul-Dun Moonbrooke
Fish in deep sea water, from any non-rocky tile.
Moonfish
Sea water
Large
Furrowfield Khrumbul-Dun
Fish in deep sea water, from any non-rocky tile.
Nautilus
Sea water
Large
Gurgling Lagoon
Fish in shallow sea water.
Neon Tetra
Fresh water
Small
Isle of Awakening Khrumbul-Dun
IoA Fish in hot water. KD Fish in fresh water, but not in the underground lake.
Pink Queen
Sea water
Small
Furrowfield Khrumbul-Dun
FF Fish around the old Deitree's island. FF Fish in deep sea water, from any non-rocky tile. KD Fish in shallow sea water, from and non-rocky tile.
Piranha
Muddy water
Small
Isle of Awakening Moonbrooke
Fish in muddy water.
Rainbow Trout
Sea water
Medium
Isle of Awakening Khrumbul-Dun Moonbrooke
IoA Fish in fresh water. KD Fish in the underground lake. MB Fish in the frozen river.
Red Betta
Fresh water Hot water
Medium
Isle of Awakening Khrumbul-Dun Moonbrooke
IoA Fish in hot water. KD Fish in fresh water, but not in the underground lake. MB Fish around the Shrine of Rendarak.
Red Snapper
Sea water
Medium
Furrowfield Moonbrooke Gurgling Lagoon
FF Fish around the old Deitree's island. MB Fish in shallow or deep sea water. GL Fish in shallow sea water.
Rockfish
Sea water
Medium
Isle of Awakening Furrowfield Khrumbul-Dun Angler's Isle
IoA Fish in shallow sea water, from any rocky tile. FF Fish in shallow or deep sea water, from any rocky tile. KD Fish in shallow or deep sea water, from any rocky tile. AI Fish in shallow sea water, from any rocky tile.
Salmon
Sea water
Medium
Furrowfield Moonbrooke
FF Fish around the old Deitree's island. MB Fish in fresh water, including the frozen river. MB Fish in shallow or deep sea water, from any non-rocky tile.
Seahorse
Sea water
Small
Furrowfield Khrumbul-Dun
Fish in shallow of deep sea water, from any rocky tile.
Squid
Sea water
Medium
Furrowfield Khrumbul-Dun Moonbrooke
FF Fish in shallow or deep sea water, from any non-rocky tile. KD Fish in shallow or deep sea water, from any rocky tile. MB Fish in shallow sea water, from any rocky tile.
Striped Beakfish
Sea water
Medium
Isle of Awakening Furrowfield Khrumbul-Dun Angler's Isle
IoA Fish in shallow sea water, from any rocky tile. FF Fish in deep sea water, from any rocky tile. KD Fish in shallow or deep sea water, from any rocky tile. AI Fish in shallow sea water, from any rocky tile.
Stripy Salmon
Fresh water
Small
Moonbrooke
Fish around the Shrine of Rendarak.
Sunfish
Sea water
Gigantic
Isle of Awakening Furrowfield Moonbrooke Angler's Isle
IoA Fish in shallow or deep sea water, from any non-rocky tile. FF Fish in shallow sea water, from any non-rocky tile. MB Fish in shallow or deep sea water, from any rocky tile. AI Fish in shallow sea water, from any non-rocky tile.