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Recovery Strategy for the Northern and Southern Resident Killer Whale

5. Recovery

5.1 Recovery Feasibility

Resident killer whale populations are not expected to achieve high abundances that might automatically trigger a de-listing due to their ecological position as upper trophic-level predators coupled with their apparent propensity to live in relatively small populations.  Despite this, and despite gaps in our knowledge, the recovery team views the recovery of both populations to a more robust and sustainable status as technically and biologically feasible.  Both populations have males, reproductive and pre-reproductive females, and the capacity to grow.  During past periods of population growth, annual increases of approximately 3% have been recorded (see 1.4.2 in Population Status and Trends).  Growth is unlikely to exceed these levels due to the low reproductive rate of the species, and the recovery of northern and southern resident killer whales can be expected to take more than one generation.  The southern resident killer whale population will be vulnerable to catastrophic events and continue to have a high risk of extinction during this period.

Technologies and methodologies currently exist to reduce many of the threats facing killer whales, their prey and their habitat.  As well, the identification of additional core areas and the protection of critical habitat areas from further degradation will ensure that resident killer whales have sufficient habitat for recovery.  Effective implementation of initiatives such as Environment Canada’s Georgia Basin Action Plan (EC-GBAP 2005) and Fisheries and Oceans Canada’s Wild Salmon Policy (DFO 2005) will complement the objectives in this recovery strategy, to improve both the quality and abundance of killer whale prey and their habitat.  There are also individuals and interest groups that have already shown initiatives in mitigating threats to killer whales, such as the ‘Best Practices Guidelines’ developed by the industry based Whale Watch Operators Association- Northwest (WWOANW 2004). These are designed to reduce the impact of whale watching on southern resident killer whales. As killer whales travel regularly across international borders, it is timely that both the Washington State and the United States federal governments are engaged in developing a conservation plan for the southern resident population that should complement and enhance Canadian efforts towards population recovery.  

5.2 Recovery Goal

Ensure the long-term viability of resident killer whale populations by achieving and maintaining demographic conditions that preserve their reproductive potential, genetic variation, and cultural continuity.

The recovery goal reflects the complex social and mating behaviour of resident killer whales and the key threats that may be responsible for their decline.  In the absence of historical data, it does not identify a numerical target for recovery because our current understanding of killer whale population demographics is not adequate for setting a meaningful value at this time.  However, because maintaining the demographic conditions that will preserve their reproductive potential, genetic variation, and cultural continuity is fundamental to these populations recovering, a number of demographic indicators are expressed herein that will serve as interim measures of recovery success.  The setting of a quantitative recovery goal will be revisited in five years, when the recovery strategy is re-evaluated.

Killer whales are top-level predators, and as such will always be far less abundant than most other species in their environment.  In addition, they are segregated into small populations that are closed to immigration and emigration, such as the northern and southern resident communities.  Furthermore, their capacity for population growth is limited by a suite of life history and social factors, including late onset of sexual maturity, small numbers of reproductive females and mature males, long calving intervals, and dependence on the cultural transmission of ecological and social information.  Unfortunately, little is known concerning the historic sizes of killer whale populations, or the factors that ultimately regulate them.  Genetic diversity is known to be low in both populations, particularly the southern residents, but the consequences of this lack of diversity have not been examined.  In light of these inherent characteristics and uncertainties, the following have been identified as interim measures of recovery success:

5.2.1 Interim Measures of Recovery Success

  1. Long-term maintenance of a steady or increasing size for populations currently at known historic maximum levels and an increasing size for populations’ currently below known historic maximum levels;
  2. Maintenance of sufficient numbers of females in the population to ensure that their combined reproductive potential is at replacement levels for populations at known historic maximum levels and above replacement levels for populations below known historic maximum levels;
  3. Maintenance of sufficient numbers of males in the population to ensure that breeding females have access to multiple potential mates outside of their own and closely related matrilines;
  4. Maintenance of matrilines comprised of multiple generations to ensure continuity in the transmission of cultural information affecting survival. 

5.2.2 Monitoring and Research Strategies

  1. The following monitoring and research programs are essential to define and evaluate the success of the interim indicators of recovery success and will be vital to the establishment of a quantitative recovery goal in five years’ time.
  2. Routinely monitor resident killer whale population numbers, sex- and age-composition, social structure and genetic diversity.
  3. Develop models of resident killer whale population dynamics and demographics, including social and genetic structure.
  4. Develop a quantitative framework to better understand how key anthropogenic and naturally occurring factors, particularly those identified as threats, affect the dynamics of resident killer whale populations.
  5. Undertake studies to identify the role of cultural transmission in the foraging ecology, sociobiology and maintenance of genetic diversity in resident killer whales.

Because killer whale populations are closed and animals individually identifiable, routine monitoring provides accurate, detailed life history information, which will be used to determine trends, and to refine and test populations models.  These models will lead to a better understanding of achievable targets for population recovery.  A better understanding of the anthropogenic and naturally occurring factors that regulate or limit killer whale populations, and of the role and importance of culture, will make it possible to rank threat factors and prioritize recovery actions. 

5.3 Recovery Objectives and Strategies to Achieve Recovery

Given our current knowledge, the prime anthropogenic threats to the long-term survival of northern and southern resident killer whales appear to be 1) reduced prey availability, 2) environmental contaminants, 3) disturbance, and 4) degradation of critical habitat.  We have identified four objectives that directly address these threats and contribute to achieving the recovery goal of population viability and sustaining genetic diversity and maintaining cultural continuity (as stated above).  The numerical values do not reflect any priority among the objectives.  These objectives provide direction for the broad strategies that can be used to specifically mitigate and/or eliminate each of the threats facing resident killer whales, and to better address gaps in our knowledge. 

5.3.1 Objective 1

Ensure that resident killer whales have an adequate and accessible food supply to allow recovery

This objective identifies the need to learn more about the year-round diet of killer whales, and to understand and mitigate the threats to key prey populations and their habitat.  Food supply can limit the growth and recovery of any population, and there are concerns about both the quality and quantity of resident killer whale prey, as well as their habitat.  In some areas of the US, for example, runs of chinook salmon, a principal prey species for residents during the summer, have been listed as either endangered or threatened (NWR 2004).  We know very little about what killer whales eat during the winter and spring, and this information is critical to understanding whether the quantity or quality of their food supply could be responsible for the recent decline in killer whale numbers, and may prevent their populations from recovering.

Objective 1 Strategies
  • Determine the seasonal and annual diet and energetic requirements of resident killer whales.
  • Identify key prey populations and feeding areas for resident killer whales.
  • Establish long-term monitoring programs capable of detecting changes in the abundance, distribution and quality of resident killer whale prey.
  • Protect the access of resident killer whales to important feeding areas.
  • Ensure that resident killer whale prey populations and their habitat are adequately protected from anthropogenic factors such as exploitation and degradation, including contamination, which will allow for the recovery of resident killer whales.

Protecting key prey populations and their habitat will also be addressed by strategies in Objective 3 below.

5.3.2 Objective 2

Ensure that chemical and biological pollutants do not prevent the recovery of resident killer whale populations.

Ross et al. (2000) showed that southern resident killer whales are among the most contaminated mammals known, and that northern residents also carry significant pollutant loads.  These pollutants are known to impair both immune responses and reproduction in other species, at lower concentrations than currently seen in killer whales.  The strategies listed below are intended to improve our understanding of, and mitigate, the contaminant risks that resident killer whales and their prey are exposed to.  They also acknowledge the serious risks that pathogens, introduced species, and catastrophic events such as oil spills present to killer whales and their prey.

Objective 2 Strategies
  • Investigate the effects of chemical and biological pollutants on the health and reproductive capacity of resident killer whales.
  • Monitor chemical and biological pollutant levels in resident killer whales and their prey.
  • Identify (and prioritize) key chemical and biological contaminants and their sources.
  • Reduce the introduction into the environment of pesticides and other chemical compounds that have the potential to adversely affect the health of killer whales and/or their prey, through measures such as national and international agreements, education, regulation, and enforcement.
  • Mitigate the impacts of currently and historically used ‘legacy’ pollutants in the environment.
  • Reduce the introduction of biological pollutants, including pathogens and exotic species, into the habitats of killer whales and their prey.

These strategies are intended to protect and restore the prey populations and habitat of resident killer whales.  In order for them to be successful, it is important that contaminant levels be measured, so as to provide a baseline that can be used to monitor changes in contaminant profiles over time, and to quantify whether attempts at mitigation are successful.  Mitigation must occur on scales that range from the local consumer to the international level, as many pollutants originate from sources outside of Canada. Regulations, guidelines, and best practices for the manufacture, storage, transport, use and disposal of hazardous compounds must be followed, and evolve to reflect changing knowledge of contaminants and their adverse health effects on resident killer whales, their prey and their habitat.  Education at individual, corporate and government levels (again ranging from local to international) will play an important role in reducing the rate at which contaminants are introduced into the environment.  New international treaties, similar to the Stockholm Convention on Persistent Organic Pollutants, which Canada ratified in 2001 (but the US has not), should be endorsed.

5.3.3 Objective 3

Ensure that disturbance from human activities does not prevent the recovery of resident killer whales.

Both physical and acoustic disturbance from human activities may be key factors causing depletion or preventing recovery of resident killer whale populations.   Sources of acoustic disturbance range from high-intensity sound produced by seismic surveys to chronic sources such as vessel traffic.  During periods of high boating activity in the summer months, disturbance may occur from vessel congestion, impairing the ability of whales to move freely and/ or forage effectively.  Physical disturbance can be caused by boat or air traffic close to whales, especially during certain behavioural states such as feeding or beach rubbing (Williams 1999).  Research to date has identified various immediate responses of whales to disturbance; however we know little about potential long-term effects on whale behaviour, health, and foraging efficiency. The National Research Council (NRC 2005) has recently put forward a detailed listing of approaches to better understand how noise impacts marine mammals, which will be worth examining as the resident killer whale action plan moves forward.  The strategies listed here more generally address the need for more knowledge about how noise and physical disturbance affect resident killer whales and also provide for mitigation of disturbance as a precautionary measure.

Objective 3 Strategies
  • Determine the short and long-term effects of chronic and immediate forms of disturbance, including vessels and noise, on the physiology, foraging and social behaviour of resident killer whales.
  • Determine baseline ambient and anthropogenic noise profiles and monitor sources and changes in the exposure of resident killer whales to underwater noise.
  • Develop and implement regulations, guidelines, sanctuaries and other measures to reduce or eliminate physical and acoustic disturbance of resident killer whales.
  • Develop protocols, regulations, guidelines and/or other measures for the use of underwater seismic survey tools and high energy sonar testing, as most appropriate and in collaboration with stakeholders, to reduce disturbance or injury to resident killer whales, where such activities are permitted.

In order to be effective, these strategies will require education and stewardship activities promoting compliance with best practice guidelines, the protection of sanctuaries, and the enforcement of regulations. New technologies, such as those that reduce noise may also contribute to reductions in disturbance over the long-term.  Existing regulations, guidelines, protocols and other measures should be evaluated for their efficacy in protecting resident killer whales, particularly as new information becomes available.

5.3.4 Objective 4

Protect critical habitat for resident killer whales and identify additional potential core areas for critical habitat designation and protection.

Two coastal areas, used consistently by resident killer whales, are designated as critical habitat.  One, the trans-boundary waters of Haro Strait and Boundary Pass, is used by southern residents year-round.  The other, the waters of Johnstone and Queen Charlotte Straits and their adjoining channels, is used by many of the northern residents during the summer and fall.  These areas represent a relatively small proportion of the total range of each population.  Preliminary data suggest that other core areas may exist in other locations and at different times of the year, but are not sufficient to warrant proposing these habitats as critical without further research. The strategies listed here provide measures for the protection of the critical habitats referred to above, as well as direction for the identification of additional critical habitat. 

Objective 4 Strategies
  • Develop a year-round comprehensive survey program for resident killer whales.
  • Identify key feeding areas and other critical habitat of resident killer whales throughout the year.
  • Protect the access of resident killer whales to their critical habitat.
  • Protect critical habitat areas through assessment and mitigation of human activities that result in contamination, and physical and acoustical disturbance.
  • Ensure that prey are available to killer whales in their critical habitat.
  • Ensure trans-boundary cooperation in the identification and protection of critical habitat.

The first two strategies listed above focus on determining whether additional areas should be proposed for critical habitat designation.  The remaining strategies, as well as those in Objectives 2, 3 and 4, will help to preserve and protect designated critical habitat.