Fish : mainly a note on ocean varieties

 Ocean fish.

Pelagic fish live near the surface, and have more oil in their muscles. 

• : Herring, mackerel, anchovies, and sardines ... are broadly in this group, though the names may contain mixed species in industry. For omega3, mackerel is the riches, followed by herring. Good luck getting fish that actually match, in cans labeled as such ... in Malaysia. 
• : Scombridae includes mackerel, tuna, and bonito.
• : Pomfret are pelagic - and are considered "butterfish" on account of their culinary quality; whereas escolar are conventionally deemed false butterfish, on account of their indigestible waxy esters. 

Demersal fish live near the floor, and have less oil - thus "whitefish", "flatfish", and other cartilaginous fish, have their oil concentrated in the liver. 

• : Cod / Gadidae is a major family of whitefish, which are in colder waters an apex predator : haddock, pollock, whiting, etc. 
• : Sciaenidae / croakers / drums make a noise. 
• : Snappers (sleeker, faster) and groupers (pudgier, slower) are short-distance prey-swallowers.

There are too many fish called "bass".

Tilapia, perch, bass, trout, and carp are common freshwater fish.