The Legend of Zelda: Phantom Hourglass/Sidequests

Fishing
After you speak to the Wayfarer on Bannan island and get the mermaid to visit him, you get the fishing rod. Now, as you travel around the seas, you may see fish shadows. If you approach these shadows, you can select the fishing option from the menu and begin fishing.

How to play
The view will switch to Link on the ship's prow and he will cast the line. The fish will leave a noticeable wake as it heads towards the bait. When the screen flashes "PULL!", slide the stylus down to hook the fish. A bar indicating the stress on the line is on the right side of the screen. Hold the stylus at the very bottom of the screen to make the slider on the gauge go up. When the slider is sufficiently high enough, frantically draw small circles on the touchscreen to reel in the fish. If the slider gets close to the bottom of the gauge, hold the stylus at the bottom of the screen to relieve some stress. Rinse and repeat to bring in the fish.

On a side note, the position of the stylus at the bottom of the screen does matter. If the fish is pulling to the right, hold your stylus at the bottom left, and vice versa for a fish pulling to the left. This will make the stress in the line drop faster.

Sometimes a hooked fish will jump. If this happens, there will be a warning tone and the screen will flash "LET GO!". At this time, you should take the stylus off of the touchscreen until the fish is done jumping. If you don't do this, the line will snap and the fish will get away.

Types of fish
Initially, there are three types of fish to bring in: skippyjack, toona, and loovar. The skippyjack is the smallest, and the loovar is the largest. Larger fish, generally, are harder to bring in. When you get one of each fish, talk to the wayfarer to get the Big Catch Lure. This lure allows you to hunt the Rusty Swordfish, which is much bigger and tougher to catch than anything you've seen before. Talk to the wayfarer again after catching one to get a ship part and hear about the final type of fish, the Neptoona. Catching the Neptoona nets you a Heart Container from the wayfarer.

Neptoonas and Rusty Swordfish have a different fish shadow on the chart, with a definite swordfish-shaped shadow.

Occasionally, you'll find a stowfish attached to one of the larger fish you pull up. Showing this to the wayfarer will get you a ship part.