I'm not sure whether logically you can have such a thing as a footprint in water... but if you can, then the footprints of human fishermen now cover much more of the world's oceans than half a century ago.
In a WWF-commissioned report out this week, the spread is documented graphically.
The authors, based at the University of British Columbia in Canada, use the concept of "primary production required" (PPR) to illustrate the spread.
The spread is shown even more graphically in an animation produced along with the report, which shows nations sending ever bigger boats across the high seas to find fish in areas ever more remote from land.
Today there is barely an area untouched by fishing.
Regulation of fishing on the high seas has historically been done with the lightest of light touches.
Environmental groups are of course urging the commission to go further. And a policy paper this week from the Pew Environment Group shows that in one sense, regulating bottom fishing should be very easy.
But as WWF's animation shows, exploitation of the oceans' riches is now a global phenomenon, and has become so with incredible speed.
Read the full article, Fishing's Global Footprint, on the BBC website.