The bottom left of the map has a store called fishing tackle. You can buy the fishing license for $2000.
Basic fishing bait is worth $7
Intermediate fishing bait is worth $10
Advanced fishing bait is worth $20
Mystery fishing bait is worth $30

At the very bottom of the map is the beach. To the left and right of the beach is your fishing spots. Go down the dock and click the water to fish. Once your rod starts bouncing click again. Click in the blue square to catch a fish.

Basic
Red bellied trout
Large blue crab
Silver-scaled fish

Intermediate
Squid
Ribbon fish
Carp

Advanced
Black sea bass
Iron bream
Tigerfish

Mystery
Yellowfish tuna

Basic
Blackfish
Deep sea bass
Anchovy
Dorado
Catfish
Dalmation molly
Spotted tigerfish

Intermediate
Jellyfish
Salmon
Redfish
Brown trout
Red velvetfish
Lobster
Blackfin tuna

Advanced
Clownfish
Cat shark
Swordfish
Wahoo
Grouper
Red salmon
Remora fish

Mystery
Asian arowana
Red Sturgeon
Tropical shark
Monster fish

I believe this is completely RNG. I tried at different spots on the dock and at different times. I didn't get any different fish. Just keep going and you should get all the fish. Anything I can do better let me know.