A few years ago, I weighed a 25 lb chinook just after bonking, but before and just after bleeding. I did the cut and gravity method. The fish lost 8 ounces. I'm curious if anyone knows what the blood volume of a similar size fish is? I'm sure it's more.

The thing is, most of the residual blood is not in the meat. It's in the internal organs (which hold more blood in the first place) and in the now-collapsed major blood vessels. Yeah, some of the blood will likely come out on the fillets when the fish is cleaned, but as long as it doesn't sit, it can be quickly washed off.

One drawback I would expect with the pump method would be texture changes. If your pump solution has less than 0.9% salt, it would impregnate the fillets with excess water and cause the meat to swell (like fingers in a bathtub). I would think, if done for very long, the fillets would become mushy. If the salt solution were too strong, the opposite should happen, at least in theory, making the meat more rubbery. Perhaps the pumping time is not long enough to allow this to happen? Of coarse, you could take IV fluid bags to the river, but...........

Years ago, I spent some time in a slaughter house. The cattle were stunned with a gun, then hoisted by there back legs and bled out from the jugular. Same thing works well with a fish. Not saying it's the best way, but it is easy and effective.