I was recently pondering why exactly do the Jewish and Islamic peoples ban pork? Was thinking that it was probably tied to public health rather than someone just hell bent on preventing people from enjoying pork and shellfish.
This may have been written elsewhere, but it isn't just a prohibition on shell fish and pork. The prohibition is on creatures that live in water that don't have scales, and land animals that don't have a cloven hoof. Hence eels, sharks and shellfish, bivalves and molluscs are all banned, as well as horses, dogs, cats and reptiles.
hi! not discouraging other responses, particularly re shellfish, but you can get started in this section of the FAQ