by Tracie Hornung, Communications Director, The Whale Museum
The mortality rate of orcas in the Southern Resident Community has exceeded the birth rate for the last few years, according to researchers at the Center for Whale Research in Friday Harbor. The population is 83, down from 98 in 1995. Eight of the orcas have died this year, with only three births occurring. And, says Ken Balcomb of the Center, over the next several years we can expect an even greater population reduction.
By studying which whales have died and which remain, itts not difficult for researchers to make population projections. For example, because of reduced numbers of reproductive females, half of the 15 maternal lineages in L pod and two or three lineages within K pod are threatened with extinction.
"Even if L pod loses no more members," Balcomb says, "theyyre due for a crash--and thatts even if all the reproducing females had babies now."
High levels of toxins in the animals and severely reduced salmon runs are probably the culprits, he says.
He notes that the research of Peter Ross, Ph.D., of the Institute for Ocean Sciences in Sidney, British Columbia, shows that some adult males in J pod carry enormous levels of polychlorinated-biphenyls (PCBs). The conclusion of the study Ross participated in states, "Results suggest that contaminant levels may be high enough in some of the marine mammals inhabiting this coastal region of Canada to affect reproduction, immune function and endocrine function and that the killer whale population may be at particular risk." (In April, Canada listed the Southern Resident orcas as threatened.)
Marine animals get contaminated primarily from eating contaminated prey. Although the resident orcas prefer salmon, they will eat rockfish or bottomfish, species that carry even higher levels of PCBs than salmon. As salmon populations decline (to the point that some stocks are now listed as threatened), Balcomb says the orcas are probably shifting to other, more toxic fish. Thus, the whales are now most likely accumulating even higher levels of toxins--even though the highly stable, long-lasting PCBs were banned in the United States more than 20 years ago. He adds that the the decline in the orca population will probably continue for at least another two decades.
Balcomb says it may help to list the orcas under the U.S. Endangered Species Act, but only if governments also address the larger issues of pollution and habitat degradation.
"We need politicians to take some risks," he says. He favors the removal of salmon-obstructing dams, an immediate end to watershed-damaging logging, increased funding for salmon restoration, and environmental monitoring and cleanup.
(For more information on threats facing the orcas see Issues.)