Fisherman:
"All they had was a knife and cutting the cartoid artery with a sharp knife rendered the animal unconscious before it was aware of it as it bled to death. That was the most humane method at that time."
Animals dont become unconscious as soon as their throat is cut. It takes a while for them to die and they are in distress the whole time. A blow to the head to instantly kill it first would be more humane.
The 'captive bolt' method used in non-religious meat processing plants these days does not stun the animal- it kills it outright, and then the throat is cut.