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Recovery Strategy for the Transient Killer Whale [Proposed]

2. Recovery

2.1 Recovery Feasibility

Transient killer whale populations are not expected to achieve high abundances due to their ecological position as upper trophic-level predators and their apparent propensity to live in relatively small populations.  It is presumed that population abundance is limited by prey availability, and whether the current population is below or at carrying capacity is unknown.  Regardless, the threat of decline due to the strikingly high contaminant burden that this population carries as a result of bioaccumulation through its prey, along with other potentially significant threats such as disturbance and prey reduction, warrants the protection of Species at Risk Act prohibitions and the implementation of recovery actions that will address threats, so that transient killer whales do not decline to an Endangered status.  (See section 1.5.2 for the classification of threats and associated risk).  As technologies and methodologies currently exist to reduce many of the threats facing killer whales, their prey and their habitat, recovery is considered feasible.   

Contaminants are considered a high priority threat that must be addressed, and sources of these chemicals are widespread and diffuse.  Accordingly, cooperation among federal, provincial and municipal governments, industries that produce or use these chemicals, and action at a citizen level, will be necessary to mitigate the effects of this threat.  Effective implementation of initiatives such as Environment Canada’s Georgia Basin Action Plan (EC-GBAP 2005), Environment Canada’s regulatory review of these chemicals, and non-governmental programs such as the Green Boater Program and Pesticide Free Lawns, will complement the objectives in this recovery strategy to improve the quality of killer whale prey and their habitat, and reduce disturbance to important life processes.  The decline of PCBs, DDT, dioxins and furans in the local marine environment since their source control and regulation demonstrates that actions taken can have tangible results and should serve as a model for the management of persistent, bioaccumulative and toxic (PBTs) chemicals, such as the largely unregulated PBDEs.

As prohibitions on the killing of pinnipeds since the early 1970s have resulted in pinniped populations approaching or at historic levels of abundance, there appears to be no immediate threat of prey limitation.  However, further research on the dietary needs of the transient population is required.  

Finally, measures to address the threat of disturbance have resulted in a reduction in disturbance from some priority activities.  The successful implementation of monitoring programs for boaters viewing and operating vessels around all marine mammals, including transient killer whales, indicate a greater awareness and compliance to appropriate boating practices (e.g., ‘Be Whale Wise’ boating guidelines developed by DFO and the US National Oceanic and Atmospheric Administration).  Ecotourism operators in British Columbia have shown leadership and initiative in developing codes of practices, such as the ‘Best Practices Guidelines’ developed by the industry-based Whale Watch Operators Association- Northwest (WWOANW 2006), which have also evolved to consider new information regarding activities that cause disturbance.  Protocols for the mitigation of acute noise from both military active sonar and seismic have similarly reduced the threat of disturbance or injury from these activities (see Section 1.6.3).

2.2 Recovery Goal

To attain long-term viability of the West Coast transient killer whale population by providing the conditions necessary to preserve the population’s reproductive potential, genetic variation, and cultural continuity

2.3 Population Objectives

This recovery goal reflects the complex social and behavioural dynamics of transient killer whales and the key threats that may lead to their decline.  In the absence of historical data, it does not identify a numerical target for a “viable” population because the current understanding of killer whale population demographics is inadequate for setting a meaningful value at this time.  However, because maintaining the demographic conditions that will preserve the population’s reproductive potential, genetic variation, and cultural continuity is fundamental to the population’s continued existence, population objectives, in the form of demographic indicators, have been expressed herein that will serve as interim measures of recovery success.

There are three population objectives for the five-year time span of this recovery strategy: 

  • P1   The population size, averaged over the next five years, will remain at or above the current level.
  • P2   The number of breeding females in the population, averaged over the next five years, will remain at levels that will provide a neutral or positive growth rate.
  • P3  Studies will be undertaken to determine numerical and demographic population objectives that represent long-term viability for this population. 

2.4 Distribution Objectives

Transient killer whales currently range widely throughout British Columbia, and into southeastern Alaska and Washington state waters.  This range likely reflects the whales’ hunting strategies and the wide distribution of their prey.  At the same time, little is understood about how transient killer whales associate and how groups range and utilize the known habitat. The following distribution objectives are directed at understanding these relationships and ensuring that the population, as a whole, has access to adequate quantities of their known prey species throughout their range. 

There are three distribution objectives for the five-year time span of this recovery strategy: 

  • D1  Transient killer whales will continue to utilize their known range.
  • D2  Prey will be available, in quantities adequate to support recovery, throughout the currently known range of transient killer whales.
  • D3   Studies will be undertaken to determine how the range is utilized at a population and sub-population level. 

2.5 Recovery Objectives

To achieve protection (recovery) of this population, studies to understand conservation threats and the development of measures to address the threats are necessary. Given our current knowledge, the primary anthropogenic threats to the long-term survival of transient killer whales appear to be environmental contaminants and disturbance.  However, while some of the key prey species of pinniped are currently at historic high levels, the potential for these populations to decline because of human activities dictates the need for objectives to ensure prey remains available at sufficient quantities and of adequate quality so as not to limit transient killer whale population maintenance and/or increases. 

Recovery objectives for the next five years of this recovery strategy, which directly address these threats and contribute to achieving the overarching long term recovery goal and the population and distribution objectives, are outlined below.  The first four objectives provide direction for the strategies and approaches that can be used to mitigate and/or eliminate each of the threats facing transient killer whales.  The remaining four objectives focus on obtaining information needed to develop a more comprehensive understanding of these threats, which will allow for the refinement of mitigation measures. 

  • R1  Minimize the exposure to transient killer whales to legacy and emergent pollutants.
  • R2  Minimize the risk of prey population reductions from anthropogenic activities, until precise prey needs can be determined.
  • R3  Current measures to protect transient killer whales from vessel disturbance will be maintained or modified, if determined necessary from further studies.  
  • R4  Minimize the exposure of transient killer whales to acute or chronic sound levels in excess of those considered to cause behavioural or physical harm in cetaceans.
  • R5  The quantity, quality and distribution of transient killer whale prey necessary to sustain or increase the current population level will be determined.
  • R6  A greater understanding of the impacts of contaminants and other biological and non-biological pollutants on transient killer whales will be developed.  
  • R7  The effects of vessel disturbance on transient killer whales will be evaluated. 
  • R8  A more comprehensive understanding of the impacts of chronic and acute noise on transient killer whales will be developed.