As fish does not require ritual slaughter it is halal in raw and uncooked form. Caution should be exercised in buying cooked fish as many non Muslim recipes nclude beer in the batter.also some fast food non Muslim outlets profess to fry their fish in vegetable oils but add beef dripping to the oil. A famous outlet also fries their fish dish in vegetable oil separate from its Harlaam meat products. However cross contamination occurs when the oil is filtered daily

As-salamu'alaykom,

The Qur'an says its harum (dead meat) but most scholars refer to the hadiths on this issue and from that they extrapolate that its halol.
If one disregards the hadiths completely like a section of Muslims the called "Quranites" one would conclude fish is harrum.

...and Allah and his Messenger (sallah hu alayhe wassalam) knows better.

I belive it maybe it's best to buy from Halal store through i belive it is halal because it's not meat like chicken or beef...those meats are not halal unless they are cooked and slaughtered in the way Allah(SWT) has told us to.