Please read the Law Of God Part One article for a better understanding on Mosaic Laws.
Leviticus 11:9-12 Ceremonial law
“These you may eat of all that are in the water: whatever in the water has fins and scales, whether in the seas or in the rivers—that you may eat. But all in the seas or in the rivers that do not have fins and scales, all that move in the water or any living thing which is in the water, they are an abomination to you. They shall be an abomination to you; you shall not eat their flesh, but you shall regard their carcasses as an abomination. Whatever in the water does not have fins or scales that shall be an abomination to you.”
Ceremonial law again which is no longer binding to Christians.
Scavengers by nature could place toxins into the human body and shellfish can cause allergic reactions. Shellfish and fish without scales or fins are filter feeders of the sea eating dead matter and waste, God gave his people a way of clean living which would in-turn bring out their devotion to the Father for his caring nature.
The creator is in control and food was a part of the intelligent plan for mankind. Clean animals have a split hoof and chew the cud, or eat plants. Herbivores generally are healthier for mankind to eat having an advanced digestive system where food is purified before any toxins are absorbed into the body.
When we mess with food we create our own diseases so who is more intelligent God or mankind?
Mad-cow disease came about by feeding parts of other cattle.
Injecting chemicals into food to make them last longer is also not what God designed for us to eat.