Southern Resident Killer Whale
Southern Resident killer whale numbers were cut by more than a third by the live-capture industry in the 1960s and 1970s, but once live capture was banned numbers rebounded by the mid-1990s. However, for unknown reasons the population declined by 17 percent from 1996 to 2001 and little recovery of the population has occurred since.
Killer whales are found in every ocean around the world, but the species is segmented into many small populations, at least two of which are likely separate species, that differ significantly genetically, and in appearance, behavior, social structure, feeding strategies and vocalizations. In the North Pacific, there are three different ‘ecotypes’ of killer whales. The “Resident” killer whales are fish eaters found along the coasts. “Bigg’s” or “Transient” killer whales are marine mammal hunters and are also found all along the North American coast. The little known “Offshore” killer whales, which feed on schooling fishes and possibly sharks, are found mostly along the continental slope. In the eastern North Pacific there are three populations of resident killer whales: Alaska Residents, Northern Residents, and Southern Residents. Southern Residents, which comprise the smallest population, are found mostly off British Columbia, Washington and Oregon.
The Southern Resident killer whale population may have numbered more than 200 animals prior to the 20th century. However, with modern impacts on their prey base, opportunistic shooting prior to the 1960s, and the capture or killing of nearly 50 whales for marine parks and display in the 1960s and 1970s, the first complete count found just 70 whales remaining in 1974. With the cessation of capture and shootings, the population slowly increased to a peak of 96-98 whales in the mid-1990s. However, in just five years from 1996 to 2001 the population declined to 81 whales, which led to its listing as endangered under the Endangered Species Act (ESA) in 2005.
Although it had appeared that Southern Resident killer whale numbers had stabilized after 2001 and may have increased somewhat, declines since 2004, early deaths, and no births for two years created new concerns for the population. Somewhat encouragingly, over the winters of 2014-2015 and 2015-2016, ten births occurred in the population, of which eight have survived through April 2016. Nonetheless, there were just 80 whales in the population in mid-2015, which was no better than the low in 2001 that led to its designation as endangered. By the end of 2015 the total had grown to 84. While the increase in births was very positive, almost all of the new whales for which gender has been determined were males. Because of several recent deaths in J Pod, the population size declined to just 76 individuals by December 2017. A population viability analysis published in 2017 suggests that the population is stable, but that new or increased impacts would cause further decline. A robust population recovery will likely require an increase in the abundance and availability of Chinook salmon, and a reduction in noise and contaminants.
The skewed sex ratio in calves could have been an anomaly or perhaps an indication that pollutants are affecting the reproductive process in these killer whales. Either way, it will likely have a negative impact on the recovery of the population. The positive outlook created by all the births did not last, however, as six known whales and three neonates (unnamed babies) died in late 2016. By the end of year, the population was back down to 78 individuals. Among the whales lost was J2. At an estimated age of 105, she was the oldest southern resident killer whale. As part of photogrammetric studies of southern and northern resident killer whales, John Durban and Holly Fernbach of the National Marine Fisheries Service had noted that she looked thin in the early fall of 2016. The effect of the loss of a matriarch is not known, but research has suggested that post-menopausal female killer whales make important contributions to their pods. They often appear to lead the pod, presumably using their accumulated knowledge of the environment to find food. They also appear to support individuals in other ways, as sons who lose their mothers are three times more likely to die.
Scientists are uncertain about how many Southern Resident killer whales can be supported by the environment. Although the environment’s carrying capacity may have exceeded 200 whales before the 20th century, it may not be able to support that many Southern Resident killer whales now. Like the other fish-eating killer whale populations in the North Pacific, the Southern Residents are dietary specialists on fish, and particularly Chinook salmon. Recent scientific findings suggest that the reproductive and mortality rates of resident killer whales are related to the abundance of Chinook salmon, which has declined significantly from before the era of intense commercial fishing and widespread habitat destruction. Modeling studies suggest the modern carrying capacity is roughly 90 whales.
What the Commission Is Doing
The Marine Mammal Commission has long been concerned about the fate of Southern Resident killer whales. The Commission has consulted with and assessed each of the steps taken by the National Marine Fisheries Service (NMFS) to promote the recovery of the population, and has provided recommendations to NMFS for improvements to their efforts. Some of the Commission’s recommendations have been to:
- Make monitoring of population status a high priority recovery action;
- Make monitoring and evaluation of the effectiveness of recovery actions a high priority;
- Recognize natural sound characteristics as an essential feature of the critical habitat of Southern resident killer whales;
- Implement a precautionary approach with regard to management of contaminants to prevent them from entering the Puget Sound environment;
- Undertake an of winter habitat use by Southern Resident killer whales;
- Develop regulatory provisions to establish vessel stand-by zones around Southern Resident killer whales beyond the 200-yard approach limit (e.g., beyond 400-600 yards) and limit the number of vessels that can be present between that boundary and the 200-yard approach limit at any one time;
- Adopt a regulatory speed limit of either seven knots or, at a minimum, a “slow safe speed” requirement within 400 yards of killer whales;
- Develop a monitoring plan to assess compliance with and effectiveness of vessel-approach regulations; and
- Include implementation of a “no-go” zone off the west coast of San Juan Island.
Commission Reports and Publications
For more information on the Southern Resident Killer Whale, see the Commission’s 2010-2011 annual report (pages 95 – 99).
|Letter Date||Letter Description|
|August 30, 2018|
|March 31, 2017|
|August 13, 2013|
|February 4, 2013|
|January 15, 2010|
|March 2, 2007|
|August 14, 2006|
|March 22, 2005|
The lack of clear recovery since 2001 may reflect a lower carrying capacity, but many researchers are concerned that human activities and impacts, in addition to those that contributed to the decline in carrying capacity, are preventing the population from growing further. Declines in some stocks of Chinook salmon could be limiting growth and reproduction, and contributing to a higher mortality rate of Southern Resident killer whale. Southern Residents spend much of their lives in inland waters near numerous sources of pollutants that accumulate in the fish they consume. Some researchers have argued that calf and juvenile deaths, delayed breeding, and now a skewer sex-ration in calves, may be related to the effects of persistent organic pollutants (POPs) that have accumulated in the fatty tissues of the whales. Southern Resident killer whales have been shown to have high tissue levels of DDT, PCBs and flame retardants, all of which are associated with lowered disease resistance and/or decreased reproduction in marine mammals. Recent research that looked at hormone levels in feces found that, between 2008 and 2014, over 2/3 of detectable pregnancies were unsuccessful. The authors of the study concluded that limited availability of Chinook salmon was the primary cause, while the release of POPs as the mother metabolizes her fat may have been a contributing factor.
The Salish Sea is busy with boat traffic traveling to and from Vancouver, Seattle and Tacoma, and many smaller ports. That traffic could increase substantially in the future with the construction of a new oil pipeline in British Columbia, which will result in a roughly seven-time increase in the number of oil tankers passing through key habitat in the San Juan Islands. In April 2017, two Northwest Indian tribes, the Tulalip and Suquamish, sued the U.S. Coast Guard, alleging that they failed to consult with NMFS regarding its traffic-separation scheme for the Strait of Juan de Fuca, and its potential impact on the Southern Resident killer whale population.
In addition, the whales are often shadowed by numerous whale-watching vessels, which affect the whales’ behavior and activities. The impacts of the presence of those vessels and noise they generate have been documented by researchers and NMFS has developed vessel regulations designed to reduce those impacts. These impacts can interact detrimentally. For example, when prey is very scarce, animals will mobilize their fat reserves for energy, which can release large concentrations of POPs into their blood streams and cause a serious toxic response. Related to this phenomenon is the release of a lifetime accumulation of POPs in the milk of first-time mothers, which may explain the very low survival rate of first calves. Even when calves do survive the POPs they get a young, formative age may have serious consequences for their growth and development.
A recent review (Matkin et al. 2017) found evidence of poor body condition in Southern Resident killer whales that was associated with mortality in all age classes. The evidence included photographs and stranding data that enabled correlation of body condition, growth rate, reproductive status/success and mortality. The review concluded that “food availability, contaminant burden and noise and vessel stress would all appear to be acting in concert causing the decline in this population.”
Current Conservation Efforts
NMFS is undertaking a suite of management and research activities designed to enhance the recovery of the population. Those activities include:
- Implementation of vessel regulations and guidelines
- Support of salmon restoration efforts
- Oil spill response preparation
- Studies to improve understanding of the impacts of anthropogenic sound
- Public outreach and education
- Studying year-round movements and diets
- Conducting stranding investigations and health assessments
- Monitoring the population trend
Following ESA-listing of the population, NMFS designated critical habitat in the inland waters of Washington in 2006. In response to a petition received in 2014, NMFS is now revising the critical habitat designation, taking into consideration the coastal areas of the West Coast that are used by Southern Resident killer whale and important habitat features such as prey availability and anthropogenic sound.
Additionally, in response to a petition, NMFS agreed to include the captive female Southern Resident killer whale known as “Lolita” in the population’s endangered species designation. Lolita, who was captured in 1970, currently resides at the Miami Seaquarium. Of the members of the Southern Resident killer whale population that were captured during the 1960s and 1970s, she is the only one still alive.
In 2015, NMFS identified eight of the marine species or populations most at risk of extinction, including the Southern Resident killer whale. NMFS will be dedicating itself and focusing its resources on saving these “Species in the Spotlight” from extinction. In February 2010, NMFS released its five-year action plan for stabilizing the Southern Resident killer whale population. Major initiatives include protecting the whales from harmful vessel impacts, recovery of critical salmon stocks, and protecting critical habitat in offshore water.
In December 2016, NMFS published the initiation of a new five-year ESA review of Southern Resident killer whales. The review identifies new research and conservation efforts that have been undertaken since the implementation of the 2008 Recovery Plan and the 2015 report on research activities, and how they contribute to improved understanding of the population and its recovery. The review concludes that “the overall status of the population is not consistent with a healthy, recovered population”, and that “Southern Resident killer whales remain in danger of extinction.”
In November 2016, three organizations petitioned NMFS to establish a protection zone for the southern resident killer whale population, intended to reduce disturbance of killer whales by vessel traffic and vessel noise. The proposed zone is along the southwest shore of San Juan Island in Puget Sound, Washington, a key feeding area. The petitioners requested that access to the proposed zone by certain vessels be prohibited during the months of April through September, when SRKWs typically make use of the area for feeding. In January 2017, NMFS asked for information and comments on: (1) the need for a protection zone, (2) its geographic scope, (3) alternative management options to regulate vessel traffic, (4) effects of vessels on killer whales and their habitat, (5) potential economic impacts, and (6) any additional information that NMFS should consider. NMFS is analyzing the comments they received and later in 2017 it will publish its response to the petition which may include new management regulations. The Commission submitted its comments and recommendations regarding the proposed protective zone in March 2017. Its letter included the recommendation that NMFS (1) designate a time-limited SRKW protection zone (e.g. six years) with boundaries that encompass the largest size considered in the petition, (2) prohibit vessel access to the protection zone with certain exceptions, and (3) undertake monitoring studies focused on assessing a) the sources and levels of noise within the protection zone, b) changes in foraging activity and behavior of SRKWs in response to protection zone measures, and c) the overall health, reproduction, and abundance of individuals in the Southern Resident killer whale population.
Selected Peer-Reviewed Publications
Population growth is limited by nutritional impacts on pregnancy success in endangered Southern Resident killer whales (Orcinus orca). Samuel K. Wasser et al. 2017. PLoS ONE 12(6): e0179824. https://doi.org/10.1371/journal.pone.0179824
Effects of age, sex and reproductive status on persistent organic pollutant concentrations in “Southern Resident” killer whales. Margaret M. Krahn et al. 2009. Marine Pollution Bulletin 58(2009):1522-1529
Review of Recent Research on Southern Resident Killer Whales (SRKW) to Detect Evidence of Poor Body Condition in the Population. Matkin, CO, MJ Moore, and FMD Gulland. 2017. Independent Science Panel Report to the SeaDoc Society. 3 pp. +Appendices. DOI 10.1575/1912/8803