Sweetfish

The Sweetfish is a fish found in the river between 4am to 9pm during the months of July through to the first half of September, but is most common between July to August. It sells for 900 Bells in Tom Nook's store.

Further Information
The sweetfish or Ayu is an amphidromous fish, the only species in the genus Plecoglossus and in family Plecoglossidae. It is a relative of the smelts and is placed in the order Osmeriformes. Native to the Palearctic ecozone, it occurs in rivers, lakes, and coastal waters of western Hokkaidō in Japan southward to the Korean Peninsula, China, and Taiwan. The name "sweetfish" is due to the sweetness of its flesh. In reference to its typical one-year life span, it is also known as nen-gyo ("year-fish"). The ayu is Gunma Prefecture's prefectural fish.