I use a pump on every fish I bonk. It's called the heart. The heart of a fish has considerable automaticity, which means it's less regulated by the brain than ours, which in turn means it keeps beating for several minutes after you bonk the fish. I've seen catfish hearts beat for 30 minutes in a dead fish! If you immediately cut a gill arch after bonking a fish, the heart will pump out most of the blood, especially if you milk the back of the fish, letting gravity be your friend. You don't get every drop, but I don't think it really matters. Catching a quality fish, bleeding it how you choose, and getting it on ice asap matter more.

Interesting videos though.
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If every fisherman would pick up one piece of trash, we'd have cleaner rivers and more access.