From seafood, only fish is made Halaal for us. Rasulullah (Sallallaahu
Alayhi Wasallam) said, 'Two carions are made Halaal for us; Fish and locust.
' (Mishkaat vol.2 pg.361). Fish is classified as a Vertebra. Crabs and
lobsters are not vertebras but they belong to the Crustaece group, hence,
not permissible.