Sea food is a delicacy that many of us enjoy. In some places, it’s an important part of the daily diet, and in other places its loved so much that its consumed in every meal of the day, including breakfast. For example, in Basra Southern Iraq, it is well known that they eat fish in the morning as well as other main meals. At the same time, the Shia Islamic law relating to Sea food and what can be consumed differs extensively to other Muslim jurisprudential schools, such as Hanbali and Hanafi. Whilst the latter believe many of the sea creatures are halal to eat, the majority of the scholars from the school of Ahlulbayt state that what can be consumed from the sea is limited.
The following is the opinion of what is common amongst Shia scholars, almash-hoor, such as that of Ayatollah Sistani (ha). The Fish that is halal to eat must have scales as well as be caught alive out of water. In addition, shrimp and prawn are halal too. All other sea creatures are not permissible to consume. So, for example, Crab, Oyster, squid, lobster, swordfish, Calamari and octopus are all haram and not allowed. Hence for the fish to be halal it must have scales. The scales could have existed at some stage during the life of the fish, which is fine. As long as the fish has some scales it is halal to consume. The eggs of the fish that have scales are halal too. Conversely the eggs of haram fish (ie those without scales) is haram. Examples of fish that have scales include cod, Salmon, Herring, Bass, Sardines, whitefish and Kingfish. Tuna is also halal, except for Dogtooth Tuna which is also known as Peg Tooth Tuna as well as Scaleless Tuna. You can find a link under the video with names of some of the fish that have scales.
What is very important to note however, is the need to establish and ascertain whether fish has scales before eating it. This is the case if we’re buying fish, or being served fish in the restaurant or part of flight meal for example. Just because a Muslim is serving it or it’s a halal restaurant does not suffice, since we have to be certain that the fish we are eating has no scales. This is done by asking which kind of fish it is and looking it up there and then to find out if it’s a scale fish. Having doubt about this, or just accepting it via a possibility is not good enough.
So, for example, during a flight when you are given an option to have fish, you must be sure it’s a scale fish, otherwise you shouldn’t eat it. You must ask the name of the fish and then find out if it has scales. Maybe it’s a good idea to have on your phone a list of commonly used scale fish so that you can check it during the flight in case you don’t have access to the internet. Also, note that oil extracted from fish without scales, or other sea animals such as sharks etc., are haram to consume as well. Without going into detail, the basis for the prohibition of Scaleless fish as well as other marine creatures, except shrimp and prawn, is the existence of many narrations from the Ahlulbayt (a) that point to this.
For example in Al-Kafi vol.6, Imam Al-Baqir (a) is narrated to have said: "Eat any fish that has scales, and do not eat what does not have scales." If you have any questions on this regard, please contact me on the ask the sheikh section on islamiced.org