We ll continue to work with the researchers until we can put together some kind of proposal. Causes for the decline are still being studied, said Ken Balcomb, director of the Center for Whale Research in Friday Harbor. Baird pointed out that the whales in the southern resident community have three to five times higher levels of polychlorinated biphenyls, or PCBs, than the northern residents, which live in the less polluted areas of Northern British Columbia and Alaska. According to Balcomb, killer whales easily accumulate PCBs by eating salmon. That alone can create a health problem, he said, but the decline of salmon has forced whales to eat bottom fish, such as rockfish, that contain even higher levels of contaminants.
Females pass the PCBs on to their young through their milk.
Once in their body fat, the PCBs are not easily dislodged. The toxicity affects the immune system, which could allow natural diseases to kill the whales, Balcomb said. Also considered were natural problems, such as parasites. The capture of killer whales for marine parks in the 1960s in the United States and up through 1977 in Canada may still be having an impact on the population, Baird said. The capture focused on young males, he explained, which may have reduced the number of mature males now available to continue rebuilding the population.