Question 647: Salaam. Are prawns and shrimp same or different? Which one is halal? I want to know the rules on eating Sea Creatures and made sure if Shrimp and Prawns are Halal?
Answer 647: It is not permissible to eat from marine animals anything except fish that has scale; shrimp is considered from that category [of permissible sea animals]. But other than fish that does not have scale is forbidden.
No marine animal is halal, except fish that has scales, amongst which are prawns. As for other animals, other than fish, like carp as well as other kinds of fish that have no scales, it is not permissible to consume. 
When it comes to the general guidelines about halal and haram animal, there are many criteria and standards stated in the narrations of the Infallible Imams (a.s.); for instance, certain rules and guidelines have been explained for terrestrial animals, birds and aquatic animals. The criterion mentioned for halal aquatic animals is that they should have scales. It has reported that Muhammad bin Muslim asked Imam Baqir (a.s.): “They bring us fish without scales (what should we do)?”
Imam Baqir (a.s.) replied: “Eat the fish that has scales and do not eat the fish that does not have scales?” Scales are the small, thin horny or bony plates protecting the skin of fish and reptiles, typically overlapping one another.
It should be noted that the fish should be from the category of scaly fish and there is no objection, if the fish have lost their scales due certain environmental factors or the way the fish live as stated in the narrations.
As for shrimps, we have special narrations according to which “eating shrimps is allowed and that shrimps are a kind fish.”
As for the philosophy of the permissibility of eating shrimps, there are different probabilities which are enumerated as under:
- Shrimps are from the category of scaly fish though we do not see the scales with naked eyes.
- Shrimps have had scales in the beginning but they have lost their scales over time.
- Despite the fact that, essentially shrimp don’t have scales, from the legal perspective it is set within the category of fish that have scales. In other words, for reasons we are not aware of, it has been considered as an exception and consequently halal, although it does not have scales.
In addition, we have a hadith that states the impermissibility of crab: “Eating jerī (type of fish), turtle and crab is haram.” It is clear that crabs are not from the category of scaly fish.
Note: The terms shrimp and prawn are common names, not scientific names. They are vernacular or colloquial terms which lack the formal definition of scientific terms. It seems the both are amongst fish that have scales. If so, there would be no problem to eat them.
For further information on this matter, please read the following answers:
Index: Halal and Haram Meat / The impermissibility of eating rabbit meat, answer 418.
Index: Ruling on foods and drinks containing alcohol / Vanilla Extract, answer 578.
Index: Cheese and Walnuts / Eating cheese in the morning is Makruh, answer 593.
 Tawzih al-Masael of Maraja, Vol. 2, Pgs. 590-591, issue 2615; Imam Khomeini, Tahrir al-Wasilah, vol. 2, pg. 137, book of foods and drinks, issue 2; Ibid (translation), Vol. 3, Pg. 274, issue 2; al-Mukhtasar al-Nafi’, pg. 251; Sharayi’ al-Islam, pg. 169; Tawzih al-Masael (annotated by Imam Khomeini), Vol. 2, Pg. 593, special issue according to Ayatollah Makarem, issue 2255; Majma al-Masael, Ayatollah Golpayegani, Vol. 3, Pg. 64.
 . Wasail al-Shi’ah, vol.16, pg. 397, and 398, hadith 1, chapt.8.
 . Ibid, hadith 3 & 7.
 . Ibid, chap.10 (Haram Foodstuffs), pg. 405.
 . Wasail al-Shi’ah, pg. 408, hadith 5 & 12 (Haram foodstuffs).
 . Footnote of Wasa’il al-Shia, pg. 408.
 . Wasa’il al-Shia, vol. 24, pg. 146, book of foods and drinks, chapter 16, hadith 1.