In religion and mythology
In His first avatara, Lord Vishnu took the form of a matsya (fish). Matsya is generally respresented with the upper torso of a man and the lower of a fish.
Many tribal and fishing communities use fish as totems. For example, the Mals of Midnapur and Manbhum (Hinduised tribe of Central India and W.Bengal) have penkal mach and sal mach as their totem.
In many parts of our country, fish as a food finds place in many religious cermonies / rituals including weddings and sraddha .
In several temples tanks fishes are protected, fed (usually with puffed rice) and venerated. For example, at the Kuleepini threetham in the Koodalma nikyam temple ( Irinjalakuda in Thrissur District of Kerala), Meenootal – feeding of fishes – is an important ritual.