Answer
According to the three Madhaahib, viz. Shaaf’ee, Maaliki and Hanbaliy, Crab
and prawns are permissible, irrespective of them being fish or not. However,
according to the Hanafi Madhab, crab and prawn are not permissible as they
are not fish.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai