Question

Respected sir/madam,
Actually it is a common doubt,
Why do fishes always die , opening their mouth?

Answer 1

Fish need to open and close their mouths in order to pass water through their gills and if they stopped doing that it will suffocate to death.
Fish wide open their mouths due to bad weather conditions and poor oxygen content. When they die they may be at the surface reaching for oxygen but perhaps with the strain their hearts gave in.