Answer
Clams ? we do not know what is Clams
Crab ? no
Tuna ? yes
Dolphins ? no
Lobsters ? no
Oysters ? no
Octopus ? no
Shellfish ? no
Shrimp ? no
Snails ? no
Snakes ? no
According to the three Madhaahib, viz. Shaaf?ee, Maaliki and Hanbaliy, Crab is permissible, irrespective of it being a fish or not. However, according to the Hanafi Madhab, crab is not permissible as it is not a fish.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai