Does the Sharia permit the consumption of all sea animals?

The permissibility of consuming sea animals is widely discussed in the books of Islamic jurisprudence. Whilst scholars are divided with regards to what can be consumed, the Quran, in the following verses, suggests that eating sea animals is lawful without elaborating or making adistinction between different type of fish and other sea animals: 

“It is lawful for you to hunt and eat seafood, as a provision for you and for travellers. But hunting on land isforbidden to you while on pilgrimage...” (5:96)  

“And He is the One Who has subjected the sea, so from it you may eat tender seafood and extract ornaments to wear...” (16: 14) 

“The two bodies of water are not alike: one is fresh, palatable, and pleasant to drink and the other is salty and bitter. Yet from them both you eat tender seafood and extractornaments to wear…”(35:12) 

Most scholars opine for the permissibility of consuming all types of seafood based on the generality of the aforementioned verses and the juristicprinciples of aṣālat al-ḥill and aṣālat al-ibāḥa, according to which all things are permitted in the absence of any contrary evidence.  

It is important to note that there is a variety of opinions amongst scholars of different legal schools.[1] These differences stem from a range of conflicting and, at times, contradictory hadiths, on the one hand, and the discussions concerning what constitutes fishon the other. Some have also argued that other sea animals fall into the general category of al-khabāʾith which includes filthy and harmfulcreatures and are prohibited by the Quran (7:157) . The Quran, however, does not elaborate on what constitutes al-khabāʾith and there is no agreement upon it as different cultures and customs have different criteria to define theterm and what it entails.  

Nevertheless, according to the generality of the Quran and principles of aṣālat al-ḥill and aṣālat al-ibāḥa it may be concluded that all the sea animals are permitted to eat provided they are hunted as per sharia requirements. This includes fish with or without scales, non-fish like shrimp, lobsters, and mammals like whales. Although there are no requirements for slaughter, it has to be ascertained that they should not be caught dead, otherwise they fall into the prohibited category of mayta (5:3). Even if hunting or consumption of sea animals is permissible in the sharia, it is necessary to follow the rules of the land in which one reside in respect to wildlife conservation laws and others. If certain species are declared unlawful on the grounds of health, environment, or other factors, that would supersede the general permissibility of hunting, selling and consumption of these animals. Finally, one ought to be mindful of our impact on the environment. 

[1] Ḥanafīs: All kinds of fish (including turbot, carp, flipper and eel) are ḥalāl. Crab, mussel, oyster, lobster, crawfish and prawn are not permitted. Water animals such as walrus, sea pig etc. are also not permitted. 

Shāfiʿites and Ḥanbalites: All sea animals are ḥalāl with few exceptions.  

Mālikīs: All sea animals are ḥalāl except for eel.  

For the detailed discussion on these opinions, see al-Marghīnānī, al-Hidāya, v.4, pp. 353-354. 

Shiʿites: Only fish that has scale is halal. All other sea animals are prohibited except prawns. See al-Kulaynī, al-Kāfī, v. 6, p. 219; al-Ṭūsī, Tahdhīb al-aḥkām, v. 9, p. 13.