OrcaThere’s been a baby boom in the local orca population. Last year five orcas joined the pods that frequent Puget Sound and the waters around the San Juan and Gulf islands. And two more killer whales have been born so far in 2010.

That brings the current number of southern resident killer whales to 89, and an official count of 87 for 2009 (orca calves aren’t officially tallied until they’ve passed the one-year mark). We keep a tally of the orca pods for our Cascadia Scorecard, in which we monitor the populations of five key species—local orcas, Chinook salmon, sage-grouse, wolves, and caribou—as a way to take the pulse of Northwest wildlife.

The National Oceanic and Atmospheric Administration, the US agency responsible for orca recovery, announced this month that it’s doing a 5-year status review, which is essentially a routine checkup on the orca population to see how they’re faring since they were declared federally endangered in 2005.

So what explains the orca baby boom? Is there something in the water? In fact, there is. Or rather, was.

  • About two years ago favorable, non el Nino ocean conditions gave a boost to Chinook salmon—the orcas’ favorite food—driving populations up for Puget Sound, northern British Columbia and southeast Alaska, though the numbers were down or average for some other important runs. But it seems to have been enough to help the resident killer whales.

    “Their populations go up and down according to the fish,” said Howard Garrett, director of the nonprofit Orca Network.

    Another factor in their favor was an increase in the number of male orcas that have reached sexual maturity, Garrett said.

    Looking at this short-term population trend, “we can be cautiously optimistic,” he said. But there’s still plenty of reason for concern.

    King salmon_Flickr_Soggydan Dan BennettSalmon stocks struggling

    In 2001, the southern resident orcas were deemed endangered by the Canadian government. In 2005, the US government caught up with the Canadians and made the same designation.

    The prime threats to their survival are toxic chemicals that harm their immune system and reproduction, oil spills, noise disturbance from boats, and—perhaps most importantly—a shortage of Chinook salmon.

    West Coast salmon runs have experienced record lows in recent years, including Sacramento River Chinook, whose spawning grounds are within the southern extent of the orcas’ range. A recent study on orca prey determined that Chinook salmon from BC’s Fraser River comprised 80 percent or more of the orcas’ summer diet—a salmon run that had poor returns in recent years and that’s expected to be poor this year as well. (Be advised, however, that a recent article in the Tacoma News Tribune over emphasized the importance of the Fraser River fish, which made up the bulk of their diet from June to September, but not necessarily the rest of the year.)

    Orca experts note that declining Columbia River salmon runs are a hugely significant threat to the killer whales, a concern they raised in a letter critical of salmon recovery plans for that river system.

    Yet the most aggressive action taken so far by NOAA to protect the orcas has focused on new rules to reduce boat noise and traffic.

    In their letter, the experts caution that “(t)he recovery of Southern Resident Killer Whales depends on abundant food, which will be difficult, if not impossible, to provide without restoring productivity from the Columbia Basin.”

    The road to recovery?

    Orca pop 2010NOAA scientists report that there were more than 200 orcas in the local population until about the mid- to late-1800s when they increasingly were hunted by Euro-American. The hunting continued into the 1900s, eventually morphing in the 1960s and ’70s into hunts for live orcas that were sent to aquariums and marine parks. By 1976, the year of the last Puget Sound capture before the practice was outlawed, the southern resident population had sunk to 70 orcas.

    Slowly, the number of local orcas has been increasing overall, though there have been significant dips lasting a few years.

    The population will be eligible for delisting under the US Endangered Species Act when two criteria are met:

    1. The number of southern residents grows on average 2.3 percent for a 28 year period. (This is based on past population trends and by looking at other groups of orcas.)
    2. The population is comprised of a sustainable number of reproductive females and males and that each of the three pods have strong numbers. (This is spelled out in detail under the “Delisting Criteria” portion of the recovery plan.)

    The recovery plan gives an example of what that would look like. If the population were to grow 2.3 percent on average beginning in 2001 with an initial population of 81 animals, recovery could be reached by 2029 with 155 orcas.

    The population isn’t yet on track to meet that goal. So far, the average annual change since ’01 is 0.6 percent, not counting this year’s increase.

    The public has until July 6, 2010 to provide any new data regarding the local killer whales to NOAA to help the agency assess the health of the local population.

    Population data was assembled using family lineage information provided by the Center for Whale Research, with assistance from dedicated whale-watchers Richard Philpot and Lisa Moorby of Pender Island, the Orca Network and NOAA. 

    Orca photo courtesy of Flickr user Michael Feist under a Creative Commons license.

    King Salmon photo courtesy of Flickr user Soggydan Dan Bennett under a Creative Commons license.