Places to fish
There's a pier, the beaches, the open sea, a river and a pond, and each has its own fish. The signpost in the plaza points the way.
The pier
The end of the pier is over deep water, which makes it the luckiest sea fishing on the island. The further out your bobber lands, the better.
The beaches and the sea
Crabs, flounders and shrimp live in the shallows off the beaches. Cast further out to reach the open sea. The biggest fish live in the deep.
The river
The river cuts across the island and has two bridges. Near the stall, where it runs into the sea, you can catch both river fish and sea fish.
The pond
The pond is a walk east of the plaza. It's still and deep, and luckier than it looks.
Hotspots
Gold twinkles on the water mark a hotspot. Fish bite faster there, but it runs dry after a few catches.
Not everything on the island is on the signpost. Try exploring after dark.