Killer whales, also called orcas, are among Puget Sound’s most distinctive and charismatic inhabitants. They occupy an important niche at the top of the food web and support a multi-million dollar whale-watching industry.
A unique population of orcas lives in and around the Salish Sea, which includes Puget Sound, the Strait of Juan de Fuca, and the Strait of Georgia. Called the Southern Resident Killer Whales, the community once numbered around 200 whales. In the past decade, the population totaled fewer than 90 individuals.
While other orca populations prey heavily on marine mammals, resident pods primarily eat fish, relying on Chinook salmon for a large part of their diet.
In the late-1990s, Southern Resident Killer Whales experienced a dramatic decline in population size. As a consequence, they were listed as Endangered under the Endangered Species Act in 2006.
Number of Southern Resident Killer Whales.
The Southern Resident Killer Whale population in Puget Sound is actually a large extended family, or clan, comprised of three pods: J, K, and L pods. Although they can be seen throughout the year in Puget Sound, they are most often seen during the summer, especially in Haro Strait west of San Juan Island, the Strait of Juan de Fuca, and in the Strait of Georgia near the Fraser River.
Threats to Southern Resident Killer Whales include contaminants, prey availability, vessels, and noise pollution. Additional human activities, such as underwater military activities, have been identified as a potential concern for killer whales, particularly on the outer coast. This issue has not been fully evaluated. Their small population size and social structure put them at risk for a catastrophic event, such as an oil spill, or a disease outbreak, that could impact the entire population.
Resident orcas were chosen as an indicator because they are top-level predators, spend a portion of the year in Puget Sound to feed and socialize, and are threatened by some of the pressures on the Sound, such as pollution and declining salmon and herring runs. Although a robust orca population is an important recovery goal both at the state and federal levels, there may be limits to how much the orca indicator can tell us about the overall health of Puget Sound. The Southern Resident Killer Whale population migrates in and out of the area, and thus is not entirely dependent on Puget Sound and its resources.
By 2020, achieve an end-of-year census of 95 individual Southern Resident Killer Whales, which would represent a 1% annual average growth rate from 2010 to 2020.
The 2020 target of reaching 95 whales has not been met, and in the short-term there has been no progress. In fact, we have lost ground.
Since 2010, the Southern Resident Killer Whale population has never been larger than 88 whales. Furthermore, as of July 1st 2013, the size of the population was 82 individuals, down by four whales relative to the 2010 baseline reference of 86 whales.
Although there has been no progress made since 2010, the population has been growing, albeit slowly at about 1% per year, over the longer term (1979 to 2010). This population growth trend is consistent with the 2020 target. However, trends could easily be reversed, as the Southern Resident Killer Whale population is very vulnerable to a variety of factors, making progress toward the 2020 target tenuous at best.
In the last decade, abundance of the Southern Resident Killer Whale population did not change significantly. Although there has been no progress in the short term, analysis of historic data shows modest growth, about 1% per year.
The census of the Southern Resident Killer Whale population, conducted annually by the Center for Whale Research, is an important method by which to assess the status and trends of this endangered population. The entire population is counted with a high degree of certainty using photo-identification techniques. Sighting networks throughout Puget Sound support the census.
Other populations of whales, such as Transients and Northern Resident Killer Whales, also frequent the Salish Sea, but their numbers are not reported here because the indicator and target focus only on Southern Resident Killer Whales.
The population size of Southern Resident Killer Whales changes temporarily throughout the year as whales are born and die. For example, by the end of 2011 there were 88 Southern Resident Killer Whales in total, with 26 in J pod, 20 in K pod and 42 in L pod (Figure 1). By August 2012, four whales had gone missing (J30, K40, L5, L12) and were presumed dead. A fifth missing whale (L112), drifted ashore dead in February 2012 on the outer coast of Washington. However, two new calves (J49, L119) were seen since in 2012.. Since the last census in June 2013, one male in L pod seems to have disappeared, potentially bringing the population total down from 82 to 81 individuals.
Thus, abundance did not change significantly in the last decade (Figure 1). However, although there has been no progress in the short term, analysis of historic data shows modest growth.
Since data became available in 1973, the Southern Resident Killer Whale population has by turns declined and grown. Despite year-to-year variability, total population size grew over the past four decades by about 1% per year: there were fewer than 70 whales in the early 1970s, and an annual average of 85 whales in the 2000s (Figure 1). Yet, compared to the Northern Resident Killer Whale population living in the Strait of Georgia, the Southern Resident Killer Whale population is smaller and has been growing more slowly overall.
At the pod level, the long-term population growth rate (from 1979 and 2010) is slightly lower for J and K pods combined (~2%) than for L pod (~1%). L pod is the largest of all pods. However, this pod has been in decline since the early 1990s.
The other two pods, J and K, are roughly the same size. Both J and K pods are growing, with J pod increasing more rapidly than K pod. This is likely due to the limited reproductive potential in K and L pods. Indeed, the sex ratio of K and L pods is skewed toward males. The lack of reproductive females, poor survival of calves, and factors associated with small population sizes such as inbreeding, along with human-caused threats, are a concern for the viability of this population.
J pod is also the pod that spends the most time in Puget Sound compared to the other two. The fact that Southern Resident Killer Whales only spend part of their lives in Puget Sound, and that the pod that spends the least time in Puget Sound has the steepest decline, suggests that the whales are impacted by conditions outside of Puget Sound.
Although the Southern Resident Killer Whale population’s long-term trend for population growth meets the growth rate target, the population growth rate does not meet the legal recovery criteria to delist the Southern Resident Killer Whales from the Endangered list (i.e., meeting an average growth rate of 2.3% per year for 28 years).
Restoration of this population of long-lived, slow-reproducing killer whales is a long-term effort that requires cooperation and coordination of West Coast communities from California to British Columbia. It will take many years to fill key data gaps and assess the effectiveness of ongoing recovery actions for the whales, salmon, and their habitat, and to observe significant increases in the Southern Resident population.
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