Rainbow trout

The Rainbow Trout (ニジマス, Nijimasu) is a common fish that appears at different times of the year. From March to June, it can be found between 4 AM to 9 AM and 4 PM to 9 PM, but can be found again in fall from September to November, between 4 AM to 9 PM. It sells for 800 Bells.

In
When a Rainbow Trout is donated, Blathers will say this:

In
When a Rainbow Trout is donated, Blathers will say this:

After donation, the Rainbow Trout can be found in the second tank of the aquarium.

In
When a Rainbow Trout is donated, Blathers will say this:

Once donated, the Rainbow Trout can be found in the middle-left tank in the aquarium.

In
An information board in the aquarium will display this description of the Rainbow Trout upon donation:

Real-world information
The rainbow fish or Oncorhynchus mykiss is a member of the salmon family native to tributaries of the Pacific Ocean in Asia and North America. Rainbow trout vary in color - lake varieties light and silvery while river variants are vibrant and colorful. It is a type of sport fish, which means a fish that has been introtuced to countries simply to be caught for the purpose of sport. Popular bait used for rainbow-trout fishing is salmon eggs, which causes confusion because they are related. Introducing this fish to parts of South America has caused problems for native fish, by either being eaten, outsported or catching disease, which has given them the label of pest by fisheries. Rainbow trout have a varied diet, mainly eating insects but can eat smaller fish starting from when they are born.