Fishing rod
From Nookipedia, the Animal Crossing wiki
Fishing Rods are used to catch fish. Catching fish is essential to the game if you want to complete the Museum. Silver and Golden Fishing Rods lure fish from farther away distances. It is said that it can catch better as well.
Obtaining
In Animal Crossing
Regular
Purchase from Tom Nook's Store for 500 Bells.
Gold
Catch all the fish.
In Wild World
Regular
Purchase from Tom Nook's Store for 500 Bells.
Gold
Catch every fish, then the next time you play, Tortimer will give you the Golden Rod.
In City Folk
Regular
Purchase from Tom Nook's Store for 500 Bells.
Silver
Purchase from Tom Nook's Store for 500 Bells, rarely sold. This rod attracts a decent amount of fish.
Gold
Catch every fish, then talk to Mayor Tortimer. This rod attracts lots of fish.