My question is regarding seafood. Are we permissible to eat sharks, octopus and similar fish that eat other sea creatures? Another doubt is, under what conditions are we allowed to eat horses or donkeys?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is lawful to eat Sharks, octopus and other sea animals for the general meaning of the verse in which Allaah Says (what means): {Lawful to you is game from the sea and its food as provision for you and the travelers.}[Quran 5:96]. Also for the general meaning of the saying of Allaah (which means): {It is He who created for you all of that which is on earth.}[Quran 2:29].

In addition to these verses, the Prophet said about the sea: "Its water  purifies and its dead are lawful to eat.” [Abu Daawood and An-Nasaa'i]

It is also lawful to eat horsemeat. Asmaa' said: "We slaughtered a horse during the life time of the Prophet while we were in Madeenah and we ate its meat." [Al-Bukhari and Muslim] Besides, Jaabir said: "The Prophet forbade us from eating the meat of domestic donkeys and allowed us eating horse meat."

As regards the meat of domestic donkeys, it is forbidden to eat it for the above Hadeeth and for the Hadeeth reported by Al-Bukhari that 'Ali Ibn Abu Taalib said that the Prophet forbade temporary marriage on the day of the battle of Khaybar and he forbade us eating the meat of donkeys.

However, it is lawful to eat the meat of wild donkeys as in principle they are lawful to eat because there is no evidence that they are forbidden to eat, and for the meaning of the Hadeeth narrated by 'Ali that they are lawful to eat, and for the Hadeeth that As-Sa'b Ibn Juthama gifted a wild ass to the Prophet .

Allaah Knows best.