The weapon of choice in my Inflatable is ...a big pair of Scissors.
Simply because one quick snip and I have decapitated a fresh caught mackerel before it has time to squirm its way all over the floor of the boat. Fish and scissors are then thrown in a plastic bucket. They also cut nice strips off the dead mackerel for bait.
Probably more chance of putting a fish hook through a tube than cut it with a bait knife or scissors. Also watch some fish.. A large spur dog put a nice 6" long scar in my PVC tube with the spike in its dorsel fin. I was kind to it though..and let it go again without the scissor treatment as its a protected species in our waters
I wont post a photo of snipping the head of a mackerel..but it is instant and humane.. better than letting them twitch to death in a bucket or bash their skulls in hitting them on a thwart or using a priest.