Raw Fish from Fishing
Aquaculture 2 adds dozens of fish: 
Atlantic Cod, 
Bluegill, 
Brown Trout, 
Catfish, 
Tuna, 
Piranha, and many more. When you catch a fish, it drops as a raw item. Most fish can be eaten raw but give poor hunger values and may cause hunger effects.
Cooking Fish
Place raw fish in a furnace, smoker, or campfire to cook them. Smokers cook fish faster than furnaces. Cooked fish restore more hunger and saturation than raw. You can also cook fish in a campfire for a quick meal while out fishing.
Seafood and Other Uses
Some fish can be crafted into other items — for example, certain fish are used in recipes for seafood dishes or as ingredients in mod-specific crafting. Check JEI/REI for recipes involving each fish. Some fish like Piranha or 
Jellyfish may have special uses or effects.
Tips
- Build a smoker near your fishing spot for fast cooking.
- Cook fish in bulk before adventures — they are a reliable food source.
- Some fish are better used as bait or in recipes than eaten.
- Keep a few raw fish for breeding or crafting if needed.