"If a fish is found in the belly of a bird, it may be eaten, even though the ṭāfiyah (fish which is found dead floating on the surface of the water) is not eaten. If it is found in the stomach of a bird, it may be eaten, and according to Imām al-Shāfiʿī (رحمه الله), it may not be eaten because it is like excrement. The excrement of birds is impure according to him. We say that it only becomes excrement when it undergoes change. With regard to small fish which are cooked without removing their insides, our companions (of the madhhab) say that it will not be permissible to eat because its excrement is impure. According to us, the rest of its parts are permissible to eat."
[al-Bināyah, Kitāb al-Dhabāʾiḥ, al-Samak idhā māta bi-āfah, Vol. 11, pg. 615, Dār al-Kutub al-ʿIlmiyyah]
"I say: In Miʿrāj al-Dirāyah, it is written: If a fish is found in the stomach of a bird, it may be eaten. According to al-Shāfiʿī (رحمه الله), it may not be eaten because it is like excrement and the excrement of a bird according to him is impure. We say that it will only be considered to be excrement when it undergoes change. With regard to small fish which are cooked without removing their insides, his companions (i.e. those of al-Shāfiʿī (رحمه الله)) say that it is not permissible to eat because its excrement is impure. According to the rest of the Imāms, it is permissible."
[Radd al-Muḥtār, Kitāb al-Dhabāʾiḥ, Vol. 6, pg. 309, H.M. Saʿīd]
"Small fish are all makrūh taḥrīmī; this is the most correct view."
[Jawāhir al-Akhlāṭī, Kitāb al-Dhabāʾiḥ, pgs. 229 & 287, manuscript]
"Regarding this, this humble servant experienced difficulty for a considerable period of time: why has the excrement of fish been determined to be ḥarām? Satisfaction was found in the conclusion of karāhah taḥrīmiyyah from the text of Jawāhir al-Akhlāṭī.
The ʿillah (cause) for the impermissibility of small fish is that they are eaten without removing the filth. From this, the intent is determined."
[Aḥsan al-Fatāwā, Kitāb al-Ṣayd wa 'l-Dhabāʾiḥ, Vol. 7, pg. 389, H.M. Saʿīd]
Question: Is it permissible to eat the fish which has not had the filth removed and is dried with its stomach intact, or not?
Answer: After cutting opening the fish, washing it, and purifying it (i.e. removing the impurities), it will be permissible to eat.