I want to know oyster is halal or haram in addition with crab and prawn.
Answer
(Fatwa: 609/104/B=1434)
According to Hanafis it is haram to eat oyster and crab. Among the sea animals only fish is halal as per Hanafi Fiqh while rest of the sea animals are haram. However, according to all Ahl Sunnah, doctors and the famous zoologist Allama Damiri (رحمة الله) are of the opinion that prawn is among the specimen of fish. Hadhrat Thanavi (رحمة الله) has also written the same in Imdadul Fatawa. Some people also have the view that prawn is an insect hence they forbid to eat it. But we do not accept their view. If one does not eat it as precautionary measure then it is also allowable. You should see Fatawa Rahimia if you want to know more details about it.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband