Is only roe from sturgeon considered as caviar?
It's even more specific than that: traditionally, only eggs from the sturgeon of the Caspian or Black Seas are considered caviar.

Other fish eggs that are eaten in the same manner as caviar are: sturgeon eggs from elsewhere, paddlefish eggs, salmon eggs, trout eggs, carp eggs, or lumpfish or whitefish eggs.  Of these, only the carp is adaptable to warm climates; all of the others are cold-water fish.

So, if you want fish eggs that you can use as "caviar" that you raise &amp; eat fresh in the hot areas of Pakistan, you'd be limited to carp eggs. That said ... Pakistan has high mountains and cold areas as well, presumably you could raise salmon or trout in mountain streams/lakes for their eggs, which are enjoyed by more people than carp eggs.