The fish will be grazing on plankton when a supertrawler looms up in the dark. First, the thud of the propellers will be audible, then the engines, then the sonar rays, before the vast trawling nets close in. For some fish, capture in the mesh means an excruciating death: mackerel, for example, drown as they stop swimming when confined.
It may be eight hours before the catch is hauled aboard, when at least a third of it will be tossed back into the water. Only prime specimens are wanted, not the "by-catch" of juveniles, less marketable fish, and even porpoises, swept up by the nets that rake in all that lies in their path. The porpoises' lungs may be punctured before they are cast adrift, ensuring that they sink.
For years, the unpalatable details of the industry that delivers fish to supermarket shelves have been a well-kept secret, along with the scientific data that shows that some fish are being fished to near-extinction. But not any longer.