Three separate studies show noisy boat traffic makes it harder for killer whales, or orcas, to find food by using underwater sound waves, forcing them to swim harder and burn off more blubber, which is tainted with harmful chemicals.
"The presence of the whale watch fleet decreases sonar efficiency by 95-99 percent, while increasing food requirements; the resulting starvation forces the whales to draw down toxin-laden blubber, and they die," said Mark Anderson President of Orca Relief Citizens' Alliance (ORCA).
The studies were conducted by Seattle area researchers and funded by ORCA, formed five years ago to investigate the decline of the local killer whale population, which has shrunk 20 percent since 1995.
The whales' food supply, mainly salmon, appears to have declined in recent years and the fish that they do eat often contain polychlorinated biphenyls (PCBs) and other toxins.
University of Washington researchers reported noise from boat traffic may degrade the orcas' sonar efficiency by 95 percent to 99 percent. Another University of Washington study found a "strong statistical correlation between whale population decline and boat activity."
The third study, conducted by an ORCA official, concluded that adult whales were burning nearly 20 percent more energy than they did before whale watching became popular. Nearly 100 boats follow the local pods each day.
Ironically, whale watching has raised public awareness and support for local orcas, which spend eight months a year feeding in waters off the San Juan Islands between Washington state and British Columbia.
Last month U.S. marine officials agreed to rescue a sick adolescent orca near Seattle and return it to its home waters in Canada amid a public outcry that drowned out calls to let nature take its course.
Boats ferrying dozens of camera-toting tourists depart from Victoria, B.C., Seattle and other Washington state cities each day. Larger boats are expected to keep a safe distance, but many smaller private boats often creep within yards of the striking, black-and-white giants.