You will find a fisherman in Forbidden Jungle. He will ask you to catch 200 pounds of fish for him. This will begin a mini-game in which you lie down on the dock and dangle your net in the water to catch fish. There is a total of 220 pounds of fish, so be careful not to miss many. The yellow fish are worth 5 pounds each, while the greens are only 1 pound.
Be careful not to catch any eels. If you catch even one, you will have to restart the mission.
Completing this gives you access to the fisherman's boat in Sandover Village, allowing you to travel to Misty Island.
With Hand Over Fish, you just need to slide your finger across the touchscreen to move the net, instead of .
Credit to Asher1985 for the Vita info.