Hey guys,
I know this thread is years old, but it seems to be the one, where we have the most information on dispatching fish, so I will add a bit more to it.
Personally, I brain, bleed and gut fish. From educating myself here on DB and looking at what the fish fanatical Japanese do, it seemed to be a smart way of doing things.
I often spear in Thailand and like so many other places, they don't bleed nor gut there. But I suspect the reason is partly that intestines can be and sometimes are used for fish soups but a bigger part of the explanation is that fish is sold whole by weight.
Lately, I have seen a few anglers say they don't gut because it leaves the fish open to bacteria infections.
Some even don't brain, but just put their whole fish in a cold slurry which I find less than humane.
Anyways, here comes the piece of information I wanted to add to the discussion. Last year, I was on a photo assignment in Japan and one night I was chatting to a local marine biologist in a sushi restaurant. He was from Kinki University which is one of two that are famous for the research into fish farming and his specialty was parasites in fish.
I tell him about how I bleed and gut pretty fast after braining and he says, that is indeed a very good practice. He said that studies have shown that parasites in a fish's gut will migrate into the flesh of the fish in hopes of surviving longer, once their host is dead. He said, this is the reason, sashimi fish are gutted fast.
Being given a more scientific reason to continue what I was already doing felt good