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To brain the big jacks I use my knifeto hit the brain by wiggling the knife back and forth with as much inward pressure as I can generate. The rocking motion from the wrist kinda drills through the softer skull material. The knife above and the several other knock off brands have what I consider to be the best tip and grip (plus a good locking sheath) for this.![]()
To execute this technique you need to have one hand as hard in the gills as you can grab and the tail locked up with your legs, scissor lock style. Worth pointing out that you need to draw your knife first if you keep it on the inside of your legs and go for the scissor lock immediately after its drawn. With the fishes head and tail immobilized you can get the knife precisely into position at the base of the skull well behind the eyes on the top of the AJ's head (dorsal) at a 45* angle. Complete dominating pressure from your legs and gill hand should keep the jack relatively submissive say 80% of the time. Do not stab violently into the skull, just get the knife into position and grind away with the point until you feel the fish kinda tremble and then relax, once it relaxes the deed is done. Its worth saying that if you line the fish up so that either its left or right side are facing you, you can see what you are doing better and have more leverage for the brain grind, but you expose yourself to the possibility of the fish headbutting the snot our of you. I had a mask broken, lip split, nose bloodied and reg pull from its mouth piece one very memorable dive because I failed to consider this.
I apologize to all my fellow shop operators for posting a pic of a knife from liesurepro but its the knife I use and have loved for many years now. I sell the tilos version (Stainless Steel) of it in my shop.
Blood in the water is way less of a shark issue than the thrashing of a wounded fish which travels in all directions at the speed of sound (in the water, so mach 4ish?). Blood has to diffuse into the water and drift across a shark's path which is only done at the direction and speed of the current and molecular diffusion..... which is pretty slow. Reef sharks primarily use there ability to detect vibrations and then sight to find wounded prey. Smell and the Ampulae of Lorenzini (sp?) are only useful at much closer ranges for the sharks we are talking about.