Eel

The Eel is an fish that can be found in the river. It appears from June to September. It will appear from 4PM to 9AM. When selling it to Re-Tail, the player will earn 2,000 Bells.

Location
The Eel is found in the river.

The Museum
The Eel can be donated to the museum. Upon doing so, the following text is given by Blathers:

"Eels are born in the ocean but swim upstream through rivers when they become adults. They do, however, eventually swim back to the ocean when it is time to lay eggs. Their blood can be toxic, which is why you've never heard of eel sashimi. It's just to dangerous. Cooked eel, however, is edible and has no poisonous effects to speak of, making it a popular dish. For a long time, the egg-laying locations and habits of eels were largely a mystery. However, they are gradually being revealed through research, making eels a very hot topic of study."

Quote
Upon catching the fish, the player will say the following:

"I caught an eel! Things just got REAL!"