From Nookipedia, the Animal Crossing wiki
The Arowana (アロワナ) is a golden fish that can be found in the river. Tied for second highest freshwater price with the Arapaima, this fish appears from 4 PM - 9 AM during the summer time. It sells for 10,000 Bells, beaten only by the Dorado and the Stringfish for freshwater price. It is very elusive, however, and is easy to pass over as a more common fish due to its shadow, which is about the same size as a Black Bass.
Donating to the Museum
In Animal Crossing
Blathers will say this upon donation:
"Another rare fish! You, old bean, are an angler for the ages! The bards will sing your praises! Thanks to generous individuals such as yourself, Player, the museum is growing by leaps and bounds. Your dragon fish has now found a home away from home. I promise, it will be very happy in its new digs!"
In Wild World
Blathers will accept the donation willingly. His words are as follows:
"I've never heard of a dish made with arowana... However, I find it hard to believe they're inedible. People eat ANYTHING. Still, they're probably more profitable to sell for viewing than for eating."
It appears in the middle tank in the aquarium.
In City Folk
"...It's said that arowana have retained the same appearance for nearly 100 million years! That's far longer than people or owls have been around... Hoo, the sights they must have seen... There's a bit of mystery about them, is there not? A fitting appearance for the king of tropical fish!"
It appears in the tank on the right in the aquarium.
In New Leaf
An information board in the aquarium will display this description of the Arowana:
"Arowanas are ancient fish that have remained basically unchanged for 100 million years. They are known for their large scales and the hair that sticks out from their lower lips. They have a remarkable jumping ability and can leap over a yard above the surface of the water. Males protect their babies by keeping them in their mouths and releasing them once they reach a certain size."
Arowanas, also known as aruanas or arawanas, are freshwater bony fish of the family Osteoglossidae, sometimes known as "bonytongues". The fish can obtain oxygen from air by sucking it into the swim bladder, which is lined with capillaries like lung tissue. In aquariums, Arowanas tend to merge in groups of five to eight; any fewer may show an excess of dominance and aggression.Osteoglossids are basal (primitive) fish from the lower Tertiary and are placed in the actinopterygiid order Osteoglossiformes. There are ten described living species: three from South America, one from Africa, four from Asia, and the remaining two from Australia. Osteoglossidae is the only exclusively freshwater fish family found on both sides of the Wallace Line. This may be explained by the fact that Asian arowanas (S. formosus) diverged from the Australian Scleropages, S. jardinii and S. leichardti, about 140 million years ago, making it likely that Asian arowanas were carried to Asia on the Indian subcontinent.
More information on this topic is available at Wikipedia.
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