Photo by Stephen Wickenton/Shutterstock Sir David Attenborough turns 100 today. He has done more than anyone to show us the vast expanses and unimaginable depths of our oceans. From spider crabs living below two metres of Antarctic ice to the jelly-like snailfish existing in total darkness seven miles deep, advances in filming have taken us places that previous generations could not have dreamt of. And all from the comfort of our sofas. But the last century has also seen the plundering and poisoning of our oceans on an unprecedented scale. Attenborough is one of the last humans alive to have witnessed the transition from sail- and steam-powered trawlers to diesel engines and vast supertrawlers. This transformation from coastal gamble to global industry enabled fish to be harvested faster than they could reproduce.…