by Tracie Hornung
 
Orcas, also known as killer whales, are dying at an unprecedented rate in the Pacific Northwest. Whale researchers fear that toxins, such as PCBs released more than 20 years ago, are the primary culprits.
    The whales under study are those of Washington and British Columbia, Canada, called the southern and northern resident communities. Traveling in family groups called pods, the orcas-especially those in the southern community-have arguably become the most popular whales in the world.
    A study of the southern residents, precipitated by the capture of live orcas for aquariums, began in 1976 by the Center for Whale Research on San Juan Island. (As a result of that and other studies, live capture operations were stopped in the United States and Canada.) Since then the organization has studied the orcas extensively. Although for several years it appeared that the southern resident

population was rebounding from the captures (to a high in 1995 of 98 whales), the population has dwindled in recent years. In fact, in 1999 the southern residents lost nine members-more than in any year since the study began-and only two calves born then have survived.
    The increasing orca mortality rates have so alarmed researchers in Canada that last spring they convinced their federal government to list the southern resident orcas as threatened, and all other orcas in Canadian waters as vulnerable. Most whale researchers in the Pacific Northwest, including those at the Center for Whale Research, Richard Osborne of The Whale Museum in Friday Harbor, Wash., and Dr. Peter Ross of the Institute of Ocean Sciences in British Columbia, suspect that the

orcas' biggest threat lies in reason PCB levels. Ross, a marine mammal toxicologist, and several other Canadian researchers have been studying tissue samples taken with small pneumatic darts from live whales. Their studies have resulted in some frightening discoveries, including the fact that Pacific Northwest orcas are now among the most toxic cetaceans in the worldÐwith up to 500 times the amount of PCBs as humans. The orcas are even more contaminated than the endangered beluga whales in Canada's St. Lawrence River estuary, which drains the highly industrialized Great Lakes.
    The researchers also learned that while PCB concentrations increase in orca males as they age, levels drop off in females as they calveÐ when they pass the poisons to their

offspring through their milk. Over time, the toxins can weaken whales' immune systems (making them more susceptible to viruses), impair reproduction and cause neurological problems.
    Highly stable and nonflammable, PCBs were used for decades in plastics and as an insulator in electrical devices. The pollutants leaked into streams and oceans, and eventually into the atmosphere as vapor. Although they were banned in the United States and Canada more than 20 years ago, PCBs are found around the globe and their stability ensures that they will remain for several decades. Some nations still manufacture them.
    Osborne, of The Whale Museum, is currently working with other researchers to persuade the U.S. Government to add the southern resident orcas to the Endangered Species List.
    For more information go to The Whale Museum's Web site at www.whale-museum.org