To bleed them, all you need to do is cut the artery that runs along the bottom of the area between their gills. You'll know you cut through the artery if there is a lot of blood loss or blood on the knife. If there's no blood, then try again a little higher. After you've cut through the artery, place them in ice.
It turns out that most of the blood in the main arteries is emptied out after three minutes if the fish is left to bleed out into water. Almost the same amount of residual blood is found in the fish whether it is left to bleed out for 3 or 30 minutes.
Kill, bleed, and gut a fish as quickly as possible after landing. A single, heavy blow to the head stuns or kills the fish, making the fish easier to handle. It also prevents the bruised flesh that occurs when fish flop around after being landed. Slitting the throat or cutting the gills also kills the fish quickly.
Yes, fish feel pain
A significant body of scientific evidence suggests that yes, fish can feel pain. Their complex nervous systems, as well as how they behave when injured, challenge long-held beliefs that fish can be treated without any real regard for their welfare.
“Fish do feel pain. It's likely different from what humans feel, but it is still a kind of pain.” At the anatomical level, fish have neurons known as nociceptors, which detect potential harm, such as high temperatures, intense pressure, and caustic chemicals.
The process of bleeding out the fish is simple. I reach a finger in behind the gill plate and pull out the gills. You can also use a scissors or knife to cut where the bottom of the gills meet at the throat. Not only will your fillets be nearly blood-free, you will also be rewarded with a cleaner workspace.
Because bleeding your fish helps get all the blood out – which produces tastier fillets. It's amazing how much better a well-bled fish tastes over a fillet that hasn't been bled properly. Plus, it's a humane way to kill fish quickly.
The blow should be aimed just above the eyes to impact on the brain. The effectiveness of the stun should be checked and another blow applied if the fish is not unconscious. Spiking involves driving a sharp spike (such as an ice pick or a sharpened screwdriver) into the brain of the fish.
Ike jime is a traditional Japanese slaughter technique that involves instantaneously euthanizing a fish by inserting a spike into its brain cavity. The fish is then thoroughly bled and undergoes spinal cord destruction (shinkei jime) before getting iced down.
The best treatment is to spike it. This can be done by looking for the spot behind the flathead's eyes where the 'armour' of the fish's head meets the soft flesh near the backbone. Insert a sharpened screwdriver or tent peg in here at a 45 degree angle towards the head. Make sure you get it smack bang in the middle.
Fish don't audibly scream when they're impaled on hooks or grimace when the hooks are ripped from their mouths, but their behavior offers evidence of their suffering—if we're willing to look.
While mammals and birds possess the prerequisite neural architecture for phenomenal consciousness, it is concluded that fish lack these essential characteristics and hence do not feel pain.
Summary: Fish do not feel pain the way humans do, according to a team of neurobiologists, behavioral ecologists and fishery scientists. The researchers conclude that fish do not have the neuro-physiological capacity for a conscious awareness of pain. Fish do not feel pain the way humans do.