I've bled fish before - if I'm cleaning them within 6 hours - I don't bother.
With Tuna though - it is recommended.
You'll know when you hit the right spot - blood literally pumps out.
Only drawback - if in a fish box is the mess. The blood often congels - making clots that clog the drain. They are great for grossing out the crew - slurp one like an oyster
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