What makes fish smell?

We know that sea water contains3% of salt in itself however the fish only holds about 1% of salt in its body. When a fish is killed the bacteria and enzymes in its body starts the process of natural decomposition and starts converting trimethylamine oxide(TMAO) into trimethylamine (TMA) which is responsible for the pungent smell.moreover, the 1% salt in the fish body increases the process of decay.more the quantity of TMAO of fish surface more the smelly it will be.that is the reason of a COD fish being more smelly than a catfish.

TMAO----->>TMA (PRODUCES SMELL)