Because they must migrate up to the headwaters of rivers to spawn, salmon were badly affected when man developed the rivers for navigation and industry, then polluted them and, for hydroelectric schemes, sometimes blocked them. The final disaster was the Greenland fishery that started in the early 1960s. This has now been controlled, but the Atlantic salmon is unlikely to recover its former numbers. Moreover, some of the unique stocks that each river system originally had have been exterminated and others adulterated, so that the Atlantic salmon's original genetic diversity has been irretrievably destroyed. The author, who works on fishes at the British Museum, Natural History, is Chairman of IUCN's SSC Fish Group.