From Nookipedia, the Animal Crossing wiki
The Pike (パイク, Paiku) is an uncommon fish that appears from fall to early winter, from 4 AM to 9 PM. It is found in rivers and sells for 1,800 Bells. It appears in Animal Crossing: City Folk and Animal Crossing: New Leaf.
Donating to the Museum
In City Folk
Blathers will comment on the player's donation as follows:
"Hootie hoo... Why, you've managed to catch quite a massive fish, haven't you? Commendable! The pike, a relative of the salmon, can grow to...a whopping 52 inches (130 centimeters) or more in length! If I met one of these during a dip in the water, I do believe I'd launch into thrashing panic mode!"
It can be found in the middle-right tank in the Aquarium exhibit.
In New Leaf
"Pike are only found in cold water, so they cannot live in warmer parts of the world. They can grow over three feet (90 cm) long and as such are a very popular fish with anglers. Pike have a slightly protruding jaw and large mouths with sharp teeth, making them powerful predators. They use these teeth for tearing apart not only other fish but also birds and other aquatic creatures."
Once players have caught a particular fish or bug, they can find information about it in the bug or fish menus. Once the Pike has been caught, the following information can be found in the fish menu:
The Esox Lucius, or Northern Pike, is one of the two living species of the Esox family. The other one being the Muskellunge or Musky. They can live up to 30 years of age. A pike's diet consists mainly on small shoal fish, insects, amphibians, and small mammals (such as moles and mice), and even small or young birds can be a target. They have also been known to be cannibalistic, sometimes feeding on smaller pike. Pike can be found in North America and Europe.