Fish is often mixed with salt to prevent it from spoilage for a long time, and varieties of fish are made in this form including: sardines, fseekh, herring, and salah. All of these are pure, and are permissible to eat them as long as there is no harm in them because it is forbidden to harm oneself.
Ad-Dardiri – one of the Sheikhs of the Malikis – may Allah be pleased with him, says: what I believe as part of religion is that, the fseekh is pure because it is not salted or cracked until after its death. The blood is not judged to be impure until after it has been spilled. As for the fish after it has been killed, if remnants of blood is found in it, then it has the same ruling like the remnant blood in the veins of the animal that is slaughtered in Sharia way. So there is no doubt that the moisture coming out of it after that is pure. This is the view of the Hanafis, Hambalis and some Maliki scholars.