What is the ruling on the blood of fish?
Chapter on Praying with Impurity and Other Matters
Al-Mughni
Book of Prayer
Primary text
The apparent ruling concerning the blood of fish is that it is pure. This is because their permissibility (eating them) is not conditional upon the shedding of blood (as with land animals); if it were impure, permissibility would depend on draining it during slaughter. Furthermore, when left alone, fish blood transforms into water.
Supporting text
Abu Thawr ruled that fish blood is impure because it is flowing blood, thus falling under the general prohibition: {Or spilled blood} (Quran 6:145).