Interesting little story about Tuna stock levels over at the BBC. What caught my attention was this little bit…

Total extinction for a fish species is relatively uncommon, given their mobility. But once numbers have fallen, ecological factors can take over that mean the stock is highly unlikely ever to rebuild.
It appears to have happened on the Grand Banks near Newfoundland, where cod fishing was banned in 1992.
There are still cod there; but their numbers do not appear to be increasing. Boris Worm from Dalhousie University in nearby Nova Scotia believes the ecosystem has moved into a new, probably stable, state.

“Other species have increased in abundance, species that usually were preyed upon by cod,” he says.
“Things like herring or capelin or sand lance, for example, are now thought to prey heavily on the larvae and eggs of cod; so the prey now is the predator, and that may diminish the ability of cod to recover.”

Could the bluefin tuna become ecologically trapped at a vanishingly low population level?