Killer whales, which were proposed for threatened status last year, have instead been listed as endangered by the National Marine Fisheries Service. Either listing indicates a risk of extinction and requires that actions by federal agencies not harm the population of the species. The Fisheries Service expects that efforts to increase local salmon stocks will benefit the 89 remaining whales, whose number is up from 79 in 2001 but still lower than the 97 counted in the 1990's. The whales' small population makes them more vulnerable to disease, oil spills, toxic chemicals and declining salmon upon which to feed. Known officially as southern resident killer whales, and often called orcas, they communicate by emitting high-frequency sonar, which is increasingly disrupted by vessel traffic. The whales visit Puget Sound every summer. They can live up to 90 years. L. D. Kirshenbaum (NYT)