312. Bloodspots in Eggs
46:1 Blood that is found in eggs is forbidden and may render the entire egg forbidden. When cooking with eggs, we are therefore required to check them first. (Regarding modern, commercially-produced eggs, see Igros Moshe Yoreh Deah 1:36)
46:2 Fish blood is permitted but one may not collect it in a vessel. If one does so, it is prohibited because people will mistake it for other blood. Fish blood is only permitted when recognizable as such, for example if it has scales in it.