From Nookipedia, the Animal Crossing wiki
Animal Crossing (GCN) and Animal Forest e+
Summer Fishing Tourney
In Animal Crossing during June, Chip the beaver will host a fishing tournament every Sunday where players can win furniture for record-breaking fish. Chip will give players a prize for every fish they give him that beats the previous record for the day. Fish caught before the tourney can be given to Chip for prizes. If players have the record at the end of the day, they will receive an additional gift in the mail. Players can talk to Tortimer at any time during the tourney to receive the Angler Trophy.
Fall Fishing Tourney
The Fishing Tourney reappears in November. It is same from the one in June.
Animal Crossing: Wild World
Although the tournament starts at 12 P.M., players can use any previously caught fish in it. Players can take the fish to Tortimer who is outside of the Town Hall. If it is the biggest fish caught that day, players get the prize of a random item. A villager may later submit a larger fish, however, so players have to keep trying. If at 6 P.M., players still have the largest fish caught, they win the Fish Trophy, which is mailed to them. If players do not have a fishing rod at the beginning, they can talk to Tortimer for a free one.
Animal Crossing: City Folk
In Animal Crossing: City Folk, there are two types of tourney, with different fish available in each. Chip returns to the front of the Town Hall with his tent full of coolers, and is standing eagerly for contestants to bring in fish to be measured, after which he eats the player's submission. Winning the tourneys will get players a Gold or Silver Trophy, dependent on which tourney they entered, that arrives by post the next morning. Additionally, players receive a piece of common furniture from Chip every time they beat a previous record.
During the tournaments held on the second Saturday of the month, any fish is accepted. The prize is the Gold Trophy.
During the tournaments held on the third Saturday of the month, only specific fish will be accepted in the competition. For each of those tourneys, the specific fish is chosen at random from a potential three each month. The prize is the Silver Trophy.
Animal Crossing: New Leaf
In New Leaf, the Fishing Tourney is slightly different compared to the last games. The heights of the fish are automatically recorded as part of the new updates in the game. But as it was in Animal Crossing: Let's go to the City/City Folk, there are certain months where Chip will accept any fish, while some months he will ask the player to catch one type of fish.
Fish can be submitted to Chip from 9 A.M. to 6 P.M. Upon submitting the fish to Chip, he will give the player a piece of furniture, wallpaper or flooring. He will give out ordinary furniture, wallpaper or flooring if the player submits a record breaking fish at or below the average size of the fish. However, if the size is above average, he will give the player a furniture, wallpaper or flooring from the Fish set at random. The items given from the Fish set are split into two groups; one group in which can only be obtained during months where Chip will accept any fish, while the other group is for when Chip will only accept a certain kind of fish by what he tells the players to catch.
One Type of Fish
Any Type of Fish
There will be a plinth inside Chip's tent. When the winners are announced inside the tent, the winners will stand on the first, second and third stands on the plinth. During the winners are announcements, they will let off party poppers and Chip will give each person an award (i.e. a trophy) according to his or her position. The awards ceremony must take place before 9 P.M. or else it will be canceled, and trophies will be mailed.