The Qur’an gives us general guidelines. It does not give us specifics. We tale the specifics from hadith. For example, does the Qur’an tell us that eating dogs is haram? It doesn’t but all Muslims agree that it is haram.
Here’s one hadith that states this:
In a hadith from Imam Baqir (A.S.), Muhammad ibn Muslim asks:
"We are given fish that do not bear an extra layer on them (scales)". The Imam replied: "Eat all fish that have scales and do not eat those that do not."
The only seafoods that are permissible are:
Fish with scales