How can I stop fish from sticking to a stainless steel pan?
I used to have this fish sticking problem in my Aluminum wok.

The solution (accidentally discovered) was to put the fish in the wok only after the oil is hot enough.

Que: How do you decide whether the oil is hot enough?
Ans: Drop one Yellow Mustard Seed in the oil. If it cracks immediately then your oil is hot enough for the fish to be dropped in. If not, then you may like to wait for few more minutes and try the same with another mustard seed.

Yellow Mustard Seeds start cracking in very hot oil only as opposed to Cumin seeds which do turn brown in non-so-hot oil too.