Although the area is initially blocked off to the player, Pelican Town’s Sewers are a sprawling location with many useful resources and quests. Most importantly, it contains some interesting fish, most notably the Mutant Carp, one of only five different types of Legendary Fish in the entire game.
Here’s how to unlock the Sewers, the types of fish you can expect to find in the area, and more useful information you’ll need to traverse it.
The Sewers are located underneath Pelican Town and have two separate entrances: one is through a manhole cover labeled SEWER east of Emily and Haley’s house, and the other is through a locked grate at the southeast end of Cindersap forest.
To access either entrance, you’ll need the Rusty Key, which is unlocked after you have donated at least 60 different artifacts to the Museum. After obtaining the key, you’ll be able to use it to unlock the Sewers and traverse them as you please, although one area, the Mutant Bug Lair, will still be blocked off until you begin the Dark Talisman quest later on in the game.
In the Sewers’ murky green waters, you’ll be able to catch two different fish as well as Green Algae, White Algae, and Trash.
The first and most common fish found in the Sewers is the Carp, which can also be found in the mountain lake near the mine during Spring, Summer, and Fall, year-round in the Secret Woods northwest of Cindersap Forest, and later in the aforementioned Mutant Bug Lair.
The second and far rarer fish present in the Sewers’ waters is the Mutant Carp. It’s quite a difficult catch, but every time you cast your line out, you’ll have a 10% chance of hooking this strange-looking fish.
There are no special requirements needed to catch either the Carp or the Mutant Carp, though the Mutant Carp may take you a few tries to catch, as it is a Legendary Fish, and it moves very quickly and sporadically during the fishing minigame.
To make reeling in a Mutant Carp easier, it is a good idea to use either the Cork Bobber or the Trap Bobber with an Iridium Rod. The Cork Bobber will make the green fishing bar slightly larger, while the Trap Bobber causes the catching bar to move 33% slower, making it more difficult for the fish to escape once hooked.
The Carp has many specific uses.
First, one Carp is required for the Lake Fish Bundle at the Community Center.
Additionally, it can be used in four different recipes, most notably the Carp Surprise, which requires four Carps and can be prepared in your kitchen after upgrading your farmhouse. The other three recipes simply call for any type of fish; they are the Maki Roll, Quality Fertilizer, and Sashimi recipes.
Carp can also be placed in Emily and Haley’s Sewing Machine Spool with a piece of Cloth to create the Fishing Vest.
You can also place Carp in a Fish Pond, where they will reproduce daily and yield Yellow Carp Roe.
Finally, there are a few quests that call for Carp:
A villager can randomly request a Carp on the Help Wanted board in front of Pierre’s shop during Spring, Summer, or Fall. The reward for completing the quest is 90 gold and 150 friendship points with the corresponding villager.
Alternatively, during Spring, Summer, or Fall, either Willy or Demetrius can request between 1 and 5 Carp on the Help Wanted board. The reward is 30 gold per fish, and you get to keep the fish afterward.
It is not recommended to give Carp as a gift to any of Pelican Town’s villagers, as they all universally hate it.
The Mutant Carp is one of only five different Legendary Fish in the entire game, meaning you’ll only ever be able to catch it once per individual save file (or once per player in multiplayer).
Considering you’ll only ever be able to catch one of them, it isn’t recommended to use them for any recipes, though it technically can be used in the Maki Roll, Quality Fertilizer, and Sashimi recipes, which all call for one of any type of fish.
A regular quality Mutant Carp can be sold for a base price of 1,000 gold. The Silver Quality Mutant Carp sells for a base price of 1,250 gold, the Gold Quality sells for 1,500 gold, and the Iridium Quality sells for 2,000 gold.
Additionally, the Fisher and Angler Professions, unlocked at fishing levels 5 and 10 respectively, will also slightly boost its (and all other fish) sale price.
Finally, the Mutant Carp can also be put on display in a Fish Tank.