Southern Resident Killer Whale Population Research Articles

The combined effects of predation, fishing, and ocean productivity on salmon species targeted by marine mammals in the northeast Pacific.

Along the northeast Pacific coast, the salmon-eating southern resident killer whale population (SRKW, Orcinus orca) have been at very low levels since the 1970s. Previous research have suggested that reduction in food availability, especially of Chinook salmon (Oncorhynchus tshawytscha), could be the main limiting factor for the SRKW population. Using the ecosystem modelling platform Ecopath with Ecosim (EwE), this study evaluated if the decline of the Pacific salmon populations between 1979 and 2020 may have been impacted by a combination of factors, including marine mammal predation, fishing activities, and climatic patterns. We found that the total mortality of most Chinook salmon populations has been relatively stable for all mature returning fish despite strong reduction in fishing mortality since the 1990s. This mortality pattern was mainly driven by pinnipeds, with increases in predation between 1979 and 2020 mortality ranging by factors of 1.8 to 8.5 across the different Chinook salmon population groups. The predation mortality on fall-run Chinook salmon smolts originating from the Salish Sea increased 4.6 times from 1979 to 2020, whereas the predation mortality on coho salmon (Oncorhynchus kisutch) smolts increased by a factor of 7.3. The model also revealed that the north Pacific gyre oscillation (NPGO) was the most important large-scale climatic index affecting the stock productivity of Chinook salmon populations from California to northern British Columbia. Overall, the model provided evidence that multiple factors may have affected Chinook salmon populations between 1979 and 2020, and suggested that predation mortality by marine mammals could be an important driver of salmon population declines during that time.

Destroying and Restoring Critical Habitats of Endangered Killer Whales.

Endangered species legislation in the United States and Canada aims to prevent extinction of species, in part by designating and protecting critical habitats essential to ensure survival and recovery. These strict laws prohibit adverse modification or destruction of critical habitat, respectively. Defining thresholds for such effects is challenging, especially for wholly aquatic taxa. Destruction of critical habitat (e.g., prey reduction and ocean noise) threatens the survival and recovery of the 75 members of the endangered southern resident killer whale population found in transboundary (Canada–United States) Pacific waters. The population's dynamics are now driven largely by the cumulative effects of prey limitation (e.g., the endangered Chinook salmon), anthropogenic noise and disturbance (e.g., reducing prey accessibility), and toxic contaminants, which are all forms of habitat degradation. It is difficult to define a single threshold beyond which habitat degradation becomes destruction, but multiple lines of evidence suggest that line may have been crossed already.

Stereotyped whistles in southern resident killer whales.

The endangered Southern Resident killer whales (Orcinus orca) of the northeast Pacific region use two main types of vocal signals to communicate: discrete calls and whistles. Despite being one of the most-studied cetacean populations in the world, whistles have not been as heavily analyzed due to their relatively low occurrence compared to discrete calls. The aim of the current study is to further investigate the whistle repertoire and characteristics of the Southern Resident killer whale population. Acoustic data were collected between 2006–2007 and 2015–2017 in the waters around San Juan Island, Washington State, USA from boats and from shore. A total of 228 whistles were extracted and analyzed with 53.5% of them found to be stereotyped. Three of the four stereotyped whistles identified by a previous study using recordings from 1979–1982 were still occurring, demonstrating that whistles are stable vocalizations for a period of more than 35 years. The presence of three new stereotyped whistles was also documented. These results demonstrate that whistles share the longevity and vocal tradition of discrete calls, and warrant further study as a key element of Southern Resident killer whale communication and cultural transmission.

How the Lummi Nation Revealed the Limits of Species and Habitats as Conservation Values in the Endangered Species Act: Healing as Indigenous Conservation

ABSTRACT In their recent efforts to protect the Southern Resident killer whale population in the Salish Sea and bring ‘Lolita’ home, the Lummi Nation exposed significant limitations to species and habitats as values in Western conservation models. Where Indigenous conservation falls outside this scope, it is often invisible to or actively suppressed by the settler state. The conservation practices of NOAA, in accordance with the federal policy of the ESA, have amounted to extractive colonial enterprises, treating the whales as educational, economic, and environmental possessions while degrading the relationship of the Lummi to the whales as relatives and attacking Lummi sovereignty.

Legal Options (and Obligations?) for Enhanced Canada–United States Cooperative Southern Resident Killer Whale Conservation

The critically endangered Southern Resident killer whale (SRKW) population is at a conservation crossroads. The SRKW’s range extends from California to southern Alaska, but the core habitat of the species is the inland Salish Sea. The principal threats to the population are the decline in Chinook salmon abundance, physical and acoustic disturbance, and environmental contamination. Effective management must respond to the cumulative impact of these threats. The SRKW population has been protected as an endangered species in Canadian and U.S. waters for more than a decade, and emergency conservation measures have been produced in both jurisdictions. Unfortunately, these conservation measures have failed to stabilize the population or advance cooperative ecosystem-based conservation. The United Nations Convention on the Law of the Sea (UNCLOS) legally obligates states to cooperate in marine mammal conservation and, with respect to cetaceans, specifically requires states to work through an appropriate institution for their conservation and management. This article examines ongoing efforts by Canada and the United States to stabilize and recover the SRKW population in view of UNCLOS and the objective of long-term stewardship. This assessment includes ad hoc cooperative mechanisms and possible developments under existing cooperative forums. Although the base legal obligations created by UNCLOS are likely met, the objective of institutionalized cooperative cetacean conservation and management in UNCLOS is not met; moreover, existing cooperative forums are insufficient to effect SRKW recovery. Canada and the United States continue to approve projects without properly assessing the cumulative transboundary impact on the SRKW population or quantifying their contribution to important ecosystem-based thresholds, which reveals the true extent of management dissonance in the Salish Sea. This analysis concludes that enhanced bi-lateral cooperation and long-term co-existence with the SRKW population requires the creation of a new institutional forum, analogous to the International Joint Commission, that coordinates SRKW recovery measures and assesses future projects in view of cumulative effects management.

A cumulative effects model for population trajectories of resident killer whales in the Northeast Pacific

Like numerous species at risk, the resident killer whale populations of the Northeast Pacific are vulnerable to the cumulative effects of anthropogenic threats. A Pathways of Effects conceptual model summarised the current understanding of each threat (prey availability, acoustic and physical disturbance, and contaminants), threat interactions, and potential impacts to fecundity and mortality. A Population Viability Analysis utilised the most recent available data to quantify impacts of threats on population parameters. The impacts of individual and cumulative threat scenarios on modelled Southern and Northern Resident Killer Whale populations were compared to the observed population demographics to define a model that best captured the real world dynamics. Of the individual and combined threat models tested, the cumulative model incorporating all threats predicted demographic rates closest to those observed for both populations. Recent low Chinook salmon abundance and its interactions with vessel disturbance and contamination strongly influenced modelled killer whale population dynamics. The cumulative effects population viability analysis model projected a mean increase in the modelled Northern Resident Killer Whale population to the carrying capacity within 25 years. In contrast, the mean modelled Southern Resident Killer Whale population trajectory was projected to decline under current conditions, with a 26% probability of population extinction, and in those projections, extinction was estimated to occur after 86 (± 11) years. Our results highlight the importance of considering the collective impact of multiple threats to imperilled species and the necessity of testing management and mitigation measures aimed at recovery using a holistic, validated model.

Effects of Vessel Distance and Sex on the Behavior of Endangered Killer Whales

Accurate knowledge of behavior is necessary to effectively manage the effects of human activities on wildlife, including vessel-based whale-watching. Yet, the wholly aquatic nature of cetaceans makes understanding their basic behavioral ecology quite challenging. An endangered population of killer whales faces several identified threats including prey availability and disturbance from vessels and sound. We used bio-logging tags that were temporally attached to individuals of the endangered Southern Resident killer whale population to more fully understand their subsurface behavior and to investigate vessel effects on behavior, including foraging behavior involving prey capture. We collected tag data over three field seasons in the waters surrounding the San Juan Islands, WA, United States, corresponding to the core summer area of the critical habitat of the population. Here, we used hidden Markov models to identify latent behavioral states that include characterization of different foraging states from sound and movement variables recorded by the multi-sensor tags. We tested a number of vessel variables (e.g., vessel counts, distance, and speed) on state transition probabilities, state occurrence and time spent within each behavioral state. Whales made fewer dives involving prey capture and spent less time in these dives when vessels had an average distance less than 400 yd (366 m). Additionally, we found both a sex and vessel distance effect on the state transition probabilities, suggesting that females and males respond differently to nearby vessels. Specifically, females were more likely to transition to a non-foraging state when vessels had an average distance less than 400 yd (366 m). A female’s decision to forego foraging states due to the close proximity of vessels could have cascading effects on the ability to meet energetic requirements to support reproductive efforts. This is particularly concerning in an endangered population that is in decline. Our findings, suggesting that female killer whales are at greater risk to close approaches by vessels, highlight the importance of understanding sex-specific responses to disturbance. These findings can inform future management decisions seeking to preserve foraging opportunities and enhance recovery efforts relevant to many cetacean species, including vulnerable and endangered populations.

How acoustics informs understanding of foraging behavior and effects of vessels and noise on killer whales

Foraging in toothed whales and dolphins is fundamentally tied to the use of sound. Resident-type killer whales (Orcinus orca) use echolocation to locate and capture fast-moving salmon and other fish prey. In addition to prey availability, disturbance from vessels and noise is a threat to the endangered Southern Resident killer whale population given considerable levels of commercial shipping, fishing, whale-watching and recreational vessel traffic in urban waterways that the whales use for feeding. In this study, we utilized suction cup-attached digital acoustic recording tags (DTAGs) to (1) describe whale acoustic and movement behavior during different phases of foraging that can be differentiated from other behaviors, (2) investigate vessel and noise effects on behavior and foraging outcomes in the endangered population, (3) compare foraging behavior between the endangered population that is struggling with population recovery and another population (Northern Resident killer whales) that is increasing in numbers, and (4) characterize diel patterns of foraging and other behaviors to describe their full activity budget and inform management of vessel traffic and noise during urban expansion along the Pacific Northwest coast of North America. This presentation will highlight results to date and implications for the conservation and management of marine protected species.

Male killer whales unexpectedly hunt more than females

It's hard to tell just how imperilled killer whales are. With several different forms – some of which may even be different species – it's unclear which are at serious risk and which are less vulnerable. But one group is definitely in jeopardy. ‘The southern resident killer whale population was listed as endangered in the United States in 2005’, says Jennifer Tennessen from the National Oceanic and Atmospheric Administration (NOAA), USA and the decline of Chinook salmon in the Pacific Northwest – which are consumed by the population of ∼75 whales – is believed to be one of the causes. While shipping also poses a risk to the animals, NOAA has been monitoring them for a decade and one of the scientists’ main goals was to estimate how much fish the charismatic whales capture. But, with the majority of pursuits occurring beneath the waves, Tennessen and her colleagues needed to develop a technique based on the animals’ manoeuvres that would allow them to identify when the mammals were successful.Heading into the Salish Sea, between Vancouver Island, British Columbia and Washington State, Tennessen and her colleagues – Marla Holt, Candice Emmons, Brad Hanson, Jeff Hogan and Deborah Giles – attached tags to 21 whales to record their sounds and underwater movements. Then the team followed the animals, noting where they surfaced and what they were up to, in addition to retrieving the remains of any meals. ‘Fieldwork is one of the most exciting yet simultaneously challenging aspects of the research’, says Tennessen, describing how she and her colleagues tracked the animals from small inflatable boats in all conditions.Safely back on shore, Tennessen and Holt began looking for patterns in the movement recordings that correlated with the tell-tale echolocation clicks produced by the whales when closing in on a fish. ‘Once a fish has been detected, the killer whale angles its body steeply downward, begins a descent to depths of about 50–300 m, and then remains underwater for about 7–10 min while pursuing the fish’, says Tennessen, adding that they abruptly roll on their sides and change direction frequently during a pursuit. Incorporating details of these signature manoeuvres into a computer program, Tennessen and Holt were able to identify successfully 126 occasions when the killer whales intercepted a tasty fish.However, when the team categorised all of the deep dives that they had recorded, they were surprised that some of the dives were unsuccessful and Tennessen explains that this was unexpected ‘because diving deep costs significant energy and it was thought that the payoff was a captured fish’. The team also compared the number of successful hunts, according to their movement signatures, with how often they observed the killer whales dining at the surface and discovered that some of the animals appear to consume their prey before reaching the surface; ‘underscoring…that surface observations alone can misrepresent the actual number of fish being captured’, says Tennessen. Most surprisingly, the team realised that the males were diving more than the females and that they were more successful. ‘[This] suggests that males may need to forage more in order to meet their greater metabolic needs’, she says.So male and female killer whales are not equal when it comes to hunting and now the team is eager to find out how the noise generated by shipping and other vessels affects the enigmatic mammals while searching for salmon beneath the waves.

Pre-oil spill baseline profiling for contaminants in Southern Resident killer whale fecal samples indicates possible exposure to vessel exhaust

The Southern Resident killer whale population (Orcinus orca) was listed as endangered in 2005 and shows little sign of recovery. Exposure to contaminants and risk of an oil spill are identified threats. Previous studies on contaminants have largely focused on legacy pollutants. Here we measure polycyclic aromatic hydrocarbons (PAHs) in whale fecal (scat) samples. PAHs are a diverse group of hazardous compounds (e.g., carcinogenic, mutagenic), and are a component of crude and refined oil as well as motor exhaust. The central finding from this study indicates low concentrations of the measured PAHs (<10 ppb, wet weight), as expected; however, PAHs were as high as 104 ppb prior to implementation of guidelines mandating increased distance between vessels and whales. While causality is unclear, the potential PAH exposure from vessels warrants continued monitoring. Historical precedent similarly emphasizes the importance of having pre-oil spill exposure data available as baseline to guide remediation goals.

Noise exposure from commercial shipping for the southern resident killer whale population

This study assesses vessel-noise exposure levels for Southern Resident Killer Whales (SRKW) in the Salish Sea. Kernel Density Estimation (KDE) was used to delineate SRKW summer core areas. Those areas were combined with the output of a regional cumulative noise model describing sound level variations generated by commercial vessels (1/3-octave-bands from 10 Hz to 63.1 kHz). Cumulative distribution functions were used to evaluate SRKW's noise exposure from 15 vessel categories over three zones located within the KDE. Median cumulative noise values were used to group categories based on the associated exposure levels. Ferries, Tugboats, Vehicle Carriers, Recreational Vessels, Containers, and Bulkers showed high levels of exposure (Leq−50th > 90 dB re 1 μPa) within SRKW core areas. Management actions aiming at reducing SRKW noise exposure during the summer should target the abovementioned categories and take into consideration the spatial distribution of their levels of exposure, their mechanical and their operational characteristics.

Evaluating anthropogenic threats to endangered killer whales to inform effective recovery plans

Understanding cumulative effects of multiple threats is key to guiding effective management to conserve endangered species. The critically endangered, Southern Resident killer whale population of the northeastern Pacific Ocean provides a data-rich case to explore anthropogenic threats on population viability. Primary threats include: limitation of preferred prey, Chinook salmon; anthropogenic noise and disturbance, which reduce foraging efficiency; and high levels of stored contaminants, including PCBs. We constructed a population viability analysis to explore possible demographic trajectories and the relative importance of anthropogenic stressors. The population is fragile, with no growth projected under current conditions, and decline expected if new or increased threats are imposed. Improvements in fecundity and calf survival are needed to reach a conservation objective of 2.3% annual population growth. Prey limitation is the most important factor affecting population growth. However, to meet recovery targets through prey management alone, Chinook abundance would have to be sustained near the highest levels since the 1970s. The most optimistic mitigation of noise and contaminants would make the difference between a declining and increasing population, but would be insufficient to reach recovery targets. Reducing acoustic disturbance by 50% combined with increasing Chinook by 15% would allow the population to reach 2.3% growth.

Population growth is limited by nutritional impacts on pregnancy success in endangered Southern Resident killer whales (Orcinus orca).

The Southern Resident killer whale population (Orcinus orca) was listed as endangered in 2005 and shows little sign of recovery. These fish eating whales feed primarily on endangered Chinook salmon. Population growth is constrained by low offspring production for the number of reproductive females in the population. Lack of prey, increased toxins and vessel disturbance have been listed as potential causes of the whale’s decline, but partitioning these pressures has been difficult. We validated and applied temporal measures of progesterone and testosterone metabolites to assess occurrence, stage and health of pregnancy from genotyped killer whale feces collected using detection dogs. Thyroid and glucocorticoid hormone metabolites were measured from these same samples to assess physiological stress. These methods enabled us to assess pregnancy occurrence and failure as well as how pregnancy success was temporally impacted by nutritional and other stressors, between 2008 and 2014. Up to 69% of all detectable pregnancies were unsuccessful; of these, up to 33% failed relatively late in gestation or immediately post-partum, when the cost is especially high. Low availability of Chinook salmon appears to be an important stressor among these fish-eating whales as well as a significant cause of late pregnancy failure, including unobserved perinatal loss. However, release of lipophilic toxicants during fat metabolism in the nutritionally deprived animals may also provide a contributor to these cumulative effects. Results point to the importance of promoting Chinook salmon recovery to enhance population growth of Southern Resident killer whales. The physiological measures used in this study can also be used to monitor the success of actions aimed at promoting adaptive management of this important apex predator to the Pacific Northwest.

Modulation in Persistent Organic Pollutant Concentration and Profile by Prey Availability and Reproductive Status in Southern Resident Killer Whale Scat Samples.

Persistent organic pollutants (POPs), specifically PCBs, PBDEs, and DDTs, in the marine environment are well documented, however accumulation and mobilization patterns at the top of the food-web are poorly understood. This study broadens the understanding of POPs in the endangered Southern Resident killer whale population by addressing modulation by prey availability and reproductive status, along with endocrine disrupting effects. A total of 140 killer whale scat samples collected from 54 unique whales across a 4 year sampling period (2010-2013) were analyzed for concentrations of POPs. Toxicant measures were linked to pod, age, and birth order in genotyped individuals, prey abundance using open-source test fishery data, and pregnancy status based on hormone indices from the same sample. Toxicant concentrations were highest and had the greatest potential for toxicity when prey abundance was the lowest. In addition, these toxicants were likely from endogenous lipid stores. Bioaccumulation of POPs increased with age, with the exception of presumed nulliparous females. The exceptional pattern may be explained by females experiencing unobserved neonatal loss. Transfer of POPs through mobilization of endogenous lipid stores during lactation was highest for first-borns with diminished transfer to subsequent calves. Contrary to expectation, POP concentrations did not demonstrate an associated disruption of thyroid hormone, although this association may have been masked by impacts of prey abundance on thyroid hormone concentrations. The noninvasive method for measuring POP concentrations in killer whales through scat employed in this study may improve toxicant monitoring in the marine environment and promote conservation efforts.

Fluctuating Asymmetry in the Saddle Patch Shape of the Pacific Ocean Killer Whale (Orcinus orca) Populations

The killer whale (Orcinus orca) is a top predator and one of the most contaminated marine mammal species in the world. Due to different prey preferences and life styles, killer whale populations accumulate persistent pollutants differently, and therefore are exposed differently to this stress. Stress may express itself in a population as an increase in the relative number of individuals with asymmetric presentation of a trait that is normally symmetrical. This phenomenon is called fluctuating asymmetry. There are many environmental and genetic factors that can cause fluctuating asymmetry. We have used the symmetry of the killer whale's saddle patch pattern behind the dorsal fin as an indicator of fluctuating asymmetry in six Pacific Ocean populations. The southern resident killer whale population seems to be remarkably more asymmetrical than the other studied populations. Although many possible environmental factors could cause asymmetry, we suggest that small population size, development of reproductively isolated ecotypes and possible inbreeding as genetic factors are causing asymmetry in the southern resident population.

Species and stock identification of prey consumed by endangered southern resident killer whales in their summer range

Recovery plans for endangered southern resident killer whales Orcinus orca have iden- tified reduced prey availability as a risk to the population. In order to better assess this risk, we stud- ied prey selection from 2004 to 2008 in 2 regions of the whales' summer range: San Juan Islands, Washington and the western Strait of Juan de Fuca, British Columbia. Following the whales in a small boat, we collected fish scales and tissue remains from predation events, and feces, using a fine mesh net. Visual fish scale analysis and molecular genetic methods were used to identify the species con- sumed. Chinook salmon, a relatively rare species, was by far the most frequent prey item, confirming previous studies. For Chinook salmon prey, we used genetic identification methods to estimate the spawning region of origin. Of the Chinook salmon sampled, 80 to 90% were inferred to have origi- nated from the Fraser River, and only 6 to 14% were inferred to have originated from Puget Sound area rivers. Within the Fraser River, the Upper Fraser, Middle Fraser, South Thompson River and Lower Fraser stocks were inferred to currently be sequentially important sources of Chinook salmon prey through the summer. This information will be of significant value in guiding management actions to recover the southern resident killer whale population.

The social dynamics of southern resident killer whales and conservation implications for this endangered population

Quantitatively characterizing the social structure of a population provides important insight into the forces shaping key population processes. Moreover, long-term social dynamics provide an avenue for understanding population-level responses to changes in socioecological conditions. This is particularly true for species that show natal philopatry and highly stable hierarchically structured social units, such as the piscivorous resident killer whales of the northeast Pacific. The southern resident killer whale population is a small, demographically closed population, comprising three commonly recognized pods (J, K and L pods), that has recently been listed as endangered throughout its range in both Canadian and U.S.A. waters. In this study, we quantitatively assessed social structure in this population from 29 years of photo-identification data to characterize significant temporal changes in sociality. Preferential affiliation among killer whales within both genealogical matrilines and pods was supported by two different analytical methods and, despite interannual variability, these social clusters persisted throughout the study. All three pods experienced fluctuations in social cohesion over time, but the overall rate of intrapod affiliation was consistently lowest within L pod, the largest of the southern resident pods. The most recent increase in fluidity within social units, occurring in the mid to late 1990s, was coincident with a significant decline in population size, suggesting a possible common response to external stressors. Quantifying these trends in social structure is the first step towards understanding the causes and consequences of long-term changes in killer whale social structure.