Fish Blood Circulatory System.

Like in humans the reason for the blood circulatory system is to move blood around the body to keep the different organs and functions working. The system which moves the blood around is made up of arteries and veins. Simply put Arteries move oxygenated blood while veins move deoxygenated blood. In human’s blood is moved around the body using the heart, deoxygenated blood travels through veins to the lungs where it gets oxygenated and leaves through the arteries. It is similar with fish however the deoxygenated blood travels through veins to the gills where it gets oxygenated and leaves through the arteries. The main Arteries in a fish are the Dorsal Artery and the Ventral Artery. The Dorsal Artery runs underneath the vertebrate from the tail of the fish through into its head. The Ventral Artery connects the heart to the gills which is found underneath the gills back through the gill latch. The Dorsal Vein runs a similar line to the Dorsal Artery.

Diagram showing the Dorsal Artery and Vein and also the Ventral Artery

How to Bleed a Fish

First kill the fish, whether this is with a donger or iki spike. The heart will beat for several minutes after the fish has died, so there is no worry about the blood not coming out. If you catch a fish like a Kahawai you will want to bleed it fairly quickly otherwise the meat will spoil or you might end up with that fishy taste. The best way to bleed a Kahawai or other fish is to cut up through the gill latch just past the gills (with a sharp knife) then up through until you reach where the spin and head met. This will cut through first the Ventral Artery, and then through the Dorsal Artery and Vein (found just under the vertebrate). Next pull the top of the head back towards the spin and blood should start to squirt out. You can also cut up from the bottom of the tail through to the vertebrate (this cuts through the lower Dorsal Vein and Artery). If you are on a boat do this over the side since it can get messy. It’s a good opportunity as well to gut the fish and clean out any excess blood using the sea water. To keep the meat in its best form you should then put the Kahawai on ice. Bleeding all fish is a good idea and the sooner you do it the better the result in terms of meat quality.

Diagram showing the cuts made to bleed a fish