Long time ago, I've read something about the speed motion of the tuna : it seems to depend of the Reverse Karman Vortex Street. The RKVS produces something like a jet-stream, but it needs a quick oscillation of the tuna fin (something like 5 to 10Hz, and that's impossible to do it with a fin by a human).
I've found a sort of abstract from the MIT web site :
http://web.mit.edu/ahtechet/www/CMI/CMIpt1by2.pdf
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