Just doing some elementary sums, 30mph is equivalent to more than 13 metres per second...so if, for arguments sake, the sturgeon was 3m long (I'm sure they get bigger but this would by no means be small) and he happened to pass over it exactly in line with the way the fish was laying it'd only be underneath the boat for one fifth of a second....either this guy has a very widescreen display or he's got bionic eyes. Or pehaps he's a bulsh*tter.
I know which category I'm inclined to place him in.