Offshore killer whale (Orcinus orca) management plan: chapter 1

1.0 Species Information

1.1 Species Assessment Information from COSEWIC

The following information was obtained from the update COSEWIC status report on Killer Whales in Canada (COSEWIC 2008).

Date of Assessment: November 2008.

Common Name (population): Killer Whale - Offshore population
 
Scientific Name: Orcinus orca

COSEWIC Status: Threatened

Reason for Designation: This population has a very small number of mature individuals (~120). It is subject to threats from high levels of contaminants, acoustical and physical disturbance, and potential oil spills. However, the population is monitored and appears to be stable.

Canadian Occurrence: Pacific Ocean 

COSEWIC Status History: The “North Pacific Resident populations” were given a single designation of Threatened in April 1999. Split into three populations in November 2001. The Offshore population was designated Special Concern in November 2001. Status re-examined and designated Threatened in November 2008. Last assessment based on an update status report.

1.2 Description

Killer Whales are primarily black with a white-coloured abdomen, a large white patch behind each eye, and a grey saddle patch below and posterior to the black dorsal fin. The dorsal fin is large and distinctive in males (often 1.8m tall), while small and curved in females and juvenile animals (less than 0.9m tall).  Each Killer Whale has a uniquely shaped dorsal fin and saddle patch, with naturally acquired nicks and scars.  To the untrained eye, it is extremely difficult to distinguish between the three ‘assemblages’ of Killer Whales found on the west coast of North America; Resident, Transient and Offshore Killer Whales.  The physical appearance of Offshore Killer Whales (also called ‘Offshores’) is considered most similar to that of Resident Killer Whales (Ford et al. 2000).  Compared with those of Resident and Transient Killer Whales, the tips of Offshores’ dorsal fins tend to be rounded on the leading edge and over the apex of the fin, giving the dorsal fin a blunt appearance.  Dorsal fins tend to be less angled at the trailing edge and have many more nicks and notches than those of Resident Killer Whales.  The saddle patches are usually uniformly grey, although on some animals it may contain a black region (Black et al. 1997; Ford et al. 2000). 

Killer Whales are the largest members of the dolphin family, Delphinidae.  In general, maximum recorded lengths for male Killer Whales are 9.0 m, whereas females are smaller at 7.7 m (Dahlheim and Heyning 1999). Yamada et al. (2007) recently recorded the maximum weight-to-length ratio for Killer Whales at 6600kg in a 7.65m male, and 4700kg in a 6.58kg female.  In adult males, the paddle-shaped pectoral fins and tail flukes are noticeably longer and broader and fluke tips curl downward (Bigg et al. 1987).

Though they are a genetically distinct group, Offshores are thought to be more closely related to Resident Killer Whales than to the Transients due to similarities in appearance, vocalizations and genetics (Barrett-Lennard and Ellis 2001).  Offshore Killer Whales are most often observed in groups of 20 or more individuals (Barrett-Lennard and Ellis 2001). 

1.3 Populations and Distribution

The three assemblages of Killer Whales on the west coast are genetically distinct from one another, though preliminary genetic studies suggest that there may be some degree of mating between Transient and Offshore Killer Whales (Barrett-Lennard 2000).  The Transient and Resident populations in British Columbia are well studied, while detailed information on the life history of Offshore Killer Whales is lacking.  Behavioural and cultural differences have been observed in the Transient and Resident populations.  Resident Killer Whales live in stable, matrilineal associations (up to 50 individuals), while Transient Killer Whales travel in small groups (5 to 7 individuals) that may have fluid membership (i.e. animals often immigrate to and emigrate from these groups).  An additional distinction between Transients and Residents is dietary preference.  Resident Killer Whales feed exclusively on fish and squid, with particular preference for chinook and chum salmon (Ford and Ellis 2006), while Transients are mammal-eaters (Bigg et al. 1987).

There are no abundance estimates for any Killer Whale populations in British Columbia prior to 1976.  Since the early 1970’s, studies of Resident and Transient Killer Whales have increased our understanding of Killer Whale distributions and population dynamics.  Offshores were only recently described and review of historic records shows that the first  sighting in Canada was in 1979 off the Queen Charlotte Islands (Ford et al. 1992). 

The current known range of Offshore Killer Whales is from southern California to the southeastern Aleutian Islands (Black et al. 1997; Matkin et al. 2007), with documented occurrence in marine waters along the continental shelf off the coast of British Columbia (Figure 1). Encounters with these whales have occurred mostly around the Queen Charlotte Islands; however in recent years, sightings of Offshores in coastal and inshore waters have increased (e.g. in the lower Strait of Georgia and western Johnstone Strait (Ford et al. 1992; Fisheries and Oceans Canada-Cetacean Research Program (DFO-CRP) unpublished data)) suggesting that usage of coastal habitat may be higher than in the past.  It is likely that distribution is influenced by oceanographic conditions and distribution of prey. 

 

Figure 1.  Offshore Killer Whale sightings recorded within the Pacific coastal waters of North America from 1988 to 2007 (DFO-CRP unpublished data)

Figure 1.  Offshore Killer Whale sightings recorded within the Pacific coastal waters of North America from 1988 to 2007 (DFO-CRP unpublished data).  Sightings are not corrected for survey effort, therefore concentrations of occurrence cannot be inferred from this map.

 

The COSEWIC update status report (2008) notes that photo-identifications from 86 encounters with Offshore Killer Whales in B.C. between 1988 to mid-2008 provided a total estimate of 288 unique individuals found in B.C. waters (DFO-CRP unpublished data). The rate of discovery of new, unidentified Offshores is slowing, while the rate of re-sights of known Offshores is increasing (DFO-CRP unpublished data).  This suggests that much of the population in B.C. has been catalogued, however the current estimate is accepted as a conservative abundance estimate and the COSEWIC report (2008) suggests that there may be a low number of reproductive age animals (at least 120 mature individuals) in this population.  Reliable population estimates for Offshore Killer Whales throughout the northeast Pacific are unavailable at this time, and currently there is no evidence of occurrence outside of northeast Pacific waters.  Further research effort is necessary to address clarify population size and demographics.

Under the federal Species at Risk Act (SARA), this population is designated as ‘special concern’, meaning it is vulnerable to decline (i.e. becoming threatened or endangered) due to a combination of biological characteristics and identified threats.  The most recent COSEWIC report (2008) has re-assessed the population as ‘threatened’ due to the low number of mature individuals and threats from contaminants, acoustic and physical disturbance as well as oil spills. A change in the legal SARA status of the population in Canada is currently being considered.  Provincially, the population in B.C. is blue-listed with an S3 ranking (CDC 2007).  With this ranking the population is considered vulnerable to extirpation or extinction, as a result of a low number of populations, widespread, recent declines, or other factors (CDC 2007). Since October 1998, the international conservation status for Offshore Killer Whales is G4G5TUQ, indicating that there is some uncertainty regarding the species global abundance (i.e. ranges from somewhat abundant to abundant), and some question regarding taxonomic status.  Thus the population is unable to be globally ranked in further detail (CDC 2007).

1.4 Requirements of the Offshore Killer Whale

1.4.1 Habitat and Biological Needs

In general, there are serious data deficiencies on Offshore Killer Whale biology and habitat needs.  Documentation of core areas or home ranges is not yet possible given these data gaps.  However, as with all species, adequate availability of high-quality prey and freedom of movement within valuable habitat areas is necessary for survival.  Echolocation and social vocalizations are an important aspect of Killer Whale behaviour for all three assemblages, and an acoustic environment that allows for successful communication and foraging is undoubtedly important.

1.4.2 Ecological Role

Killer Whale populations around the world often have highly specialized foraging strategies, and target very specific prey species (Hoelzel 1991; Simila and Ugarte 1993; Guinet and Bouvier 1995; Ford et al. 1998; Visser 1999; Saulitis et al. 2000; Pitman and Ensor 2003; Ford and Ellis 2006).  On the west coast of B.C., Transient Killer Whales feed on marine mammals, while Resident Killer Whales are salmon-eaters (Bigg et al. 1987; Ford et al. 1998). 
Recent studies including feeding observation (Jones 2006), analysis of stomach contents (Heise et al. 2003), fatty acid and isotope analysis of blubber (Herman et al. 2005; Krahn et al. 2007) suggest that the diet of Offshores is fish-based, and includes halibut and sharks.  At this time, it is unclear whether mammals or other species also comprise a portion of their diet.  Crude examination of the dentition of dead Offshores indicates that the teeth of this type of Killer Whale are more worn and blunt than those of the other assemblages (G. Ellis pers. comm., 2007.), which coupled with chemical isotope analysis from Krahn et al. (2007) indicate a diet distinct from that of the Residents or Transients. 

Though there was no documented distinction between Killer Whale assemblages, First Nations peoples have long held these whales in high cultural and spiritual regard as protectors of the oceans.  Killer Whales were not traditionally hunted by First Nations, though bones were discovered at an Ozette midden (J. Scordino pers. comm., 2007).  At present, some First Nations groups are developing initiatives to monitor marine mammals and gather traditional knowledge on historic occurrence of Killer Whales within traditional territories.

1.4.3 Limiting Factors

The factors limiting population growth of apex predators such as the Offshore Killer Whale, can be broadly categorized as intrinsic, bottom-up processes mediated by the availability and quality of prey.  Factors that are intrinsic to the biology of the species can not be mitigated or managed.  However, human activities may contribute pressures which alter the balance of these limiting factors, and thus threaten the population.  In such cases, actions are necessary to ensure that human activities do not place undue stress on limiting factors. 

Resident Killer Whales are the most intensively studied Killer Whale assemblage in British Columbia (Ford et al. 2005).  Since there is a paucity of information on Offshores, general information on life span and reproductive parameters gathered from Residents was used for the purposes of illustrating potential environmental and biological limiting factors for Offshore Killer Whales (Table 1).  Life history parameters of this population could be similar to those limiting other Killer Whale assemblages, but caution should be taken when inferring similarities between the different assemblages. 

Table 1. Biological and environmental factors which may potentially limit the northeast Pacific Offshore Killer Whale population. 

Limiting Biological Factor Specific Attributes Description
Longevity* Females:  50 years, maximum 80-90 years
Males:  29 years, maximum 50-60 years
Reproduction Late age of sexual maturity* Approximately 15 years for both males and females, though males do not reproduce until over 20 years of age
Long gestation period* 16 to 17 months
Low number of calves per pregnancy* One calf per pregnancy
Low rate of reproduction* Interval between calving is typically 5 years, but can range from 2 to 12 years, thereby limiting population growth
Reproductive senescence* Females’ reproductive period is about 25 years, with last calf born at approx. 40 years of age 
i.e. Most females only give birth to a total of 5 calves in their lifetimes, thereby limiting the potential rate of population growth
Neonate mortality* Possibly up to 50% between 0 and 6 months of age
Limited dispersal Physical dispersal Dispersal of Offshore Killer Whales from family groups is unknown
Genetic dispersal Breeding behaviours are unknown at this time, though genetic study suggests some mating may occur between Transient and Offshores
Small population 288 individuals are currently identified in this genetically-distinct population
Learned behaviour(s)  (i.e. traditional or cultural) Unique vocalizations, likely accompanied by highly structured social behaviours
Prey Type Top predator, specific prey species are unknown at this time.  However, preliminary observations include feeding on halibut and shark
May acquire diseases through prey, esp. if they are feeding on high trophic level animals
Availability There is evidence that prey limitation reduced survival and reproductive success in Resident Killer Whales (Ford et al. 2005)
As Offshores are a top predator, limitation of food supply is a primary threat to population growth and survival
Prey may be limited by an ecosystem regime shift, climate change, and/or by harvesting 
Disease Naturally occurring diseases within the population can affect population viability 
Diseases may also be acquired through prey, esp. if they are feeding on high trophic level animals (see ‘Diet’)
Extensive tooth wear observed in Offshore Killer Whales may increase the risk of infection by prey-based pathogens 
Stranding or Entrapment Animals may accidentally beach themselves, or become entrapped in coves, lagoons or saltwater lakes (e.g. Bain 1994)
Ecosystem Regime Shift Natural shift in ecosystem processes may affect these whales (e.g. via changes to prey abundance or quality, occurrence of disease)

References used for information presented in this table: Ford 1989; Bigg et al. 1990; Olesiuk et al. 1990;, Ford 1991; Bain 1994; Barrett-Lennard 2000; Ford et al. 2000; Herman et al. 2005; Jones 2006; DFO-CRP unpublished data.
* Description utilizes data from studies on Resident Killer Whales.

 

1.5 Threats

Threats may either be of anthropogenic origin, such as incidental-take in fishing gear or toxic contamination, or they may be natural processes, such as an ecosystem regime shift, resulting in population decline. Limiting factors are environmental or biological factors (e.g. longevity) that may naturally limit population size or slow population growth, and are typically not considered a threat unless altered by human activities (EC 2007).  Threat assessments (Table 2) allow for prioritization of recommended management and other actions to prevent this population from becoming threatened or endangered, and provide an indication of the mitigation feasibility for a threat.  Definitions of the terms used for rankings are available in Appendix I (Table 5).  

1.5.1 Threat Classification

Threats were assessed based on their current likelihood of occurrence and severity of effect to thispopulation.  In addition, the certainty of a population-wide effect was incorporated into the assessment to provide a measure of confidence in the rating of ‘level of concern’ and provide an indication of areas where further monitoring or study may be useful in addressing uncertainties or knowledge gaps (Table 2).  Where certainty of effect on the Offshore Killer Whale population is not demonstrated, weight of scientific evidence for other cetaceans may be deemed adequate to contribute to the assessment of the level of concern for a threat. 
Mitigation potential refers to the likelihood that measures (future or existing) will adequately mitigate or prevent negative effects to the population.  It should be noted that the level of concern rating reflects the current concern for impacts from a threat at this time, and future assessments may result in levels of concern which differ from those presented here.  Therefore the importance of long-term monitoring of the population can not be overstated.

Table 2.  Summary of threat classifications and mitigation potential for identified threats to the northeast Pacific Offshore Killer Whale population.

Mitigation potential refers to the likelihood that measures (future or existing) may mitigate or prevent negative effects to the population.  This assessment is a current view of the state of threats to the population, and as such assessment ratings may change over time. (*) are naturally occurring threats to the population (i.e. limiting factors whose effects can be increased by human activities).


Category
Stress to the Population Severity of population-level impacts Uncertainty Current Level of Concern Mitigation Potential

Prey Reduction

  • Competition for resources
  • Ecosystem Regime Shift*
Prey availability
Reproductive rate Mortality
Disease
Synergistic effects of threats
Potentially High Low, based on weight of evidence on prey limitation for Residents Currently, UNKNOWN
Potentially HIGH
None, if due to natural fluctuation
Moderate to High, if due to anthropogenic effects
Toxic Spills Reproductive rate Mortality
Disease
High, but is dependent on location and timing Low, based on weight of evidence for Residents HIGH Moderate
Chemical Contamination Reproductive rate
Mortality
Disease
Moderate Medium MEDIUM-HIGH Low to Moderate
Acute Noise Displacement
Stranding?
Moderate Medium-High MEDIUM High
Chronic Noise Displacement
Prey availability (e.g. foraging success)
Unknown High LOW Low
Physical Disturbance Displacement Unknown High NEGLIGIBLE Moderate to High
Boat Collisions Mortality Unknown, dependent on vessel size and speed High UNKNOWN Low
Entanglement and Entrapment Mortality Unknown High UNKNOWN Unknown
Climate Change Ecosystem regime shift
Prey availability
Disease
Unknown High UNKNOWN Unknown
Biological Pollutants Disease
Reproductive rate
Mortality
Stranding?
Unknown High UNKNOWN Low to Moderate
Naturally occurring Disease Agents* Disease
Reproductive rate
Mortality
Stranding?
Unknown, usually Low High UNKNOWN None
Mass Stranding or Natural Entrapment* Mortality Has potential to impact local abundance High UNKNOWN On a case-by-case basis

 

1.5.2 Description of Threats

Prey Reduction

The potential for altered prey availability for this apex predator is one of the key attributes which prompted the initial designation of this population as ‘special concern’ by COSEWIC (Baird 2001).  For Resident Killer Whales, a decline in prey abundance is believed to have caused reduced survival and reproductive success (Ford et al. 2005), providing weight of evidence for effects to other Killer Whale assemblages.

There remains high uncertainty regarding the diet of Offshore Killer Whales, and the update status report (COSEWIC 2008) indicates that “the food habits of Offshore Killer Whales are too poorly known to judge whether changes in prey availability are likely to affect them in the foreseeable future”.  Recent studies including feeding observation (Jones 2006), analysis of stomach contents (Heise et al. 2003), fatty acid and isotope analysis of blubber (Herman et al. 2005; Krahn et al. 2007) suggest that the diet of Offshores is fish-based, and includes halibut and sharks.  If dietary requirements for Offshores are found to include significant proportions of commercially important fish such as halibut (Jones 2006), competition with fisheries could become an important threat (Table 2).  However, this threat could be mitigated by Fisheries and Oceans Canada through updating the integrated fishery management plan(s) for relevant species to recognize the feeding needs of these whales.  The potential for mitigation of fisheries competition is moderate to high, as fisheries extractions are managed directly by Fisheries and Oceans Canada.  As Offshore Killer Whales and likely their prey, are trans-boundary species, additional collaboration and cooperation with U.S. fisheries management may be necessary for effective management of the population.

Natural shifts in ecosystem processes (also termed ‘regime shifts’) as a result of large scale events, such as El Niño or the Pacific decadal oscillation, occur on a recurrent basis and may affect species composition, or other intrinsic processes within Offshore Killer Whale habitat (Francis et al. 1998; Hare and Mantua 2000).  Significant effects to marine mammals due to regime shifts have not been observed in B.C., and as such effects on prey supply and quality are largely speculative.  The mitigation potential for prey limitation as a result of an ecosystem regime shift is nonexistent.

The proposed effect of food limitation on the Resident Killer Whale population in B.C. (Ford et al. 2005) and Jones’ (2006) observation of an Offshore consuming market-sized halibut, suggest that fisheries competition may be a potentially important threat to the population.  It should be noted that synergistic effects on prey availability due to changing ocean conditions coupled with fisheries competition, have the potential to result in more significant effects than either factor acting alone.  Due to the high degree of uncertainty regarding prey, the current level of concern for general reduction in prey availability has been rated unknown, but potentially high (Table 2). 

Toxic Spills

Killer Whales do not avoid toxic spills and have been observed traveling through oil slicks (Matkin et al. 1999; DFO 2007, 2008).  After the Exxon Valdez oil spill (1989), there was a dramatically higher than normal observed mortality within the Killer Whale group that encountered spilled oil (Matkin et al. 1999, 2008).  Analyses from Matkin et al. (2008) reveal that two groups that encountered the spill, one Resident and one Transient group, exhibited losses of 41 and 33%, respectively.  To date, neither Killer Whale group has recovered their numbers, and the Transient group has been listed as ‘depleted’ under the U.S. Marine Mammal Protection Act (Matkin et al. 2008).  The loss of many reproductive-aged females from a population can impede recovery from catastrophic events.  Records from several encounters with Offshores have estimated greater than 50 animals clustered in one area (DFO-CRP unpublished data), suggesting that a single spill could affect a significant percentage of this small population. 

Given that spills are accidental in nature, they are likely to occur on a recurrent basis within Canadian waters.  Offshore Killer Whalesinhabit areas adjacent to major shipping routes (O’Hara and Morgan 2006; EC 2006) and increasing vessel traffic raises the likelihood of ship-based spills in their habitat. 

Currently there are measures in place to minimize the risk of spills (e.g. Transportation of Dangerous Goods Act) as well as multi-jurisdictional spill response plans (e.g. Can-US Dix Plan, B.C. Marine Oil Spill Contingency Plan) to implement clean-up and other mitigation measures.  However, ships carrying mixed goods (i.e. toxic and non-toxic goods) are not required to provide Canadian authorities with ships’ manifests, and therefore transport of toxic materials through Canadian waters may not always be recorded.  Spills which occur far offshore may be under-reported and are typically more difficult to coordinate responses for mitigation.
The data on Killer Whale mortalities and population recovery following the Exxon Valdez oil spill (Matkin et al. 1999, 2008), and clustering behaviour of Offshores, illustrates high concern (Table 2) regarding potentially severe population-wide effects.  Measures to prevent and mitigate effects of spills are currently in place, but once a spill occurs the effectiveness of clean up measures typically falls between 5 to 15% (Graham 2004).  Mitigation potential considers both prevention and clean-up of spills and is ranked moderate. 

Figure 2. Effects of chemicals on Killer Whales may occur by 1) consuming contaminated prey, 2) impacts on the quality or quantity of their prey, and/or 3) direct exposure to a toxic spill (e.g. oil). 

Figure 2. Effects of chemicals on Killer Whales may occur by 1) consuming contaminated prey, 2) impacts on the quality or quantity of their prey, and/or 3) direct exposure to a toxic spill (e.g. oil). 
This figure is courtesy of Dr. P. Ross, DFO Institute of Ocean Sciences.

 

Chemical Contamination

Preliminary sampling suggests that Offshores contain very high levels of the persistent bioaccumulative toxic chemicals (PBTs), such as DDT1 and PBDE (Krahn et al. 2007).  These contaminants are of particular concern as they persist for long periods in the environment and bioaccumulate within food webs (Christensen et al. 2005; Ross 2006).  Chronic contamination by PBTs is linked to long-term health effects and reduced reproduction in marine mammals (Ross 2000; Ross et al. 2004).  Killer Whales’ long life span and role as top predator make them vulnerable to PBT contamination (Rayne et al. 2004; Ross 2006), and they are some of the most contaminated mammals on the planet (Ross et al. 2000; Ross 2002). 

‘Legacy pollutants’ include those PBTs whose use and production has been discontinued, but which continue to persist in the environment.  High concentrations of these chemicals are found in the environment (Ross et al. 2000; 2004; Garrett and Ross, in press), long after local production has been terminated.  Therefore, reversal of contamination is likely to occur over several decades (Hickie et al. 2007). 

New generations of PBT chemicals are currently produced locally, nationally and on a global scale.  These chemicals have similar properties to legacy pollutants (Ross 2006) and their use and production is increasing, while remaining inadequately regulated (DFO 2008).  The main current concern for emerging pollutants stems from the polybrominated di-phenyl ethers (PBDEs), and their presence in B.C. ecosystems is rapidly increasing (Rayne et al. 2004; Elliott et al. 2005).  The toxic effects of PBDEs are still unclear, but there is growing scientific evidence to suggest that these chemicals may have similar environmental persistence and toxic effects to that of polychlorinated bi-phenyls (PCBs) (Ross 2006).

The widespread historic and current use of PBT chemicals has resulted in chronic contamination of the environment.  Preliminary research findings of high levels of contamination in Offshores (Krahn et al. 2007) support this theory.  The persistent nature of legacy chemicals and the increased presence of new emerging persistent chemicals lead to medium-high concern for impacts to this population.  Though point sources of contamination can be regulated and monitored, the potential to implement mitigation measures for this threat is rated low to moderate (Table 2), due to the difficulty in mitigating or managing non-point sources of contamination.  Additionally, sources of contamination which originate in Canada may be mitigated, whereas for contamination that originates from international waters, the mitigation potential is very low from a Canadian management perspective. 

Acute Noise

Acute noise typically refers to impulsive sounds produced in the mid to low frequency range, including those produced during military tactical sonar use, seismic surveying, explosions, and the use of acoustic deterrent devices2.  Many of these impulsive sounds are capable of traveling great distances through unrestricted open ocean areas (Nieukirk et al. 2004).  Offshore habitats may be more vulnerable as activities generating acute noise may occur more frequently in these areas (for example; seismic surveying) as compared to in-land or nearshore marine habitats.  Sonar sounds, such as those produced during the USS Shoup incident have been documented to cause behavioural changes in Resident Killer Whales (Fromm 2006; J. Ford pers. comm., 2007).  Currently, there is a Canadian military marine range off the west coast of Vancouver Island, within the known range of the Offshore population in Canada. 

Globally, acute noise is implicated in negative impacts on other marine mammal species including behavioural changes, displacement from habitat and in extreme cases, injury and mortalities (for example Crum and Mao 1996; Schrope 2002; Jepson et al. 2003; Fernández et al. 2004; Buck and Calvert 2005).  Predicting sound propagation using models is strongly dependent on adequate data regarding bottom type and sound speed profiles (Lawson and McQuinn 2004).  While care must be taken when extrapolating effects between species or populations, the lack of specific information for Offshore Killer Whales requires use of the growing weight of evidence from other cetaceans in order to estimate effects.   Generation of acute noise (such as explosive, seismic, or sonar noise) in the presence of Offshore Killer Whales could result in displacement from habitat, physical damage to hearing structures, or in extreme cases, mortality. 

The Canadian military has developed an internal operational protocol which aims to mitigate acute noise effects on marine mammals.  Proposals and protocols for seismic surveying (e.g. for research, industrial or other applications) are reviewed by DFO to ensure mitigation measures are in place to reduce the risk of negative effects.  

Seismic and sonar activity currently occur in Pacific Canadian waters on a recurrent basis, and in some cases information is not clear regarding application of, and effectiveness of mitigation.  The weight of evidence from other cetaceans, and the tendency for Offshores to travel in large aggregations (DFO-CRP unpublished data), indicates the potential for moderate effects to the population should acute noise be generated in the presence of these whales.  Therefore, overall concern is rated medium for this threat (Table 2).  Requirements for permitting and protocols for generation of acute noise result in high mitigation potential for this threat.

Chronic Noise

Shipping pressure is increasing along the B.C. coast (O’Hara and Morgan 2006), and existing shipping lanes and occurrence of Offshores tend to overlap (See ‘Populations and Distribution’; O’Hara and Morgan 2006; EC 2006).  Thirty years of data on underwater sound off the coast of California show an average increase of 10dB from the 1960s to the 1990s (which is a two-fold increase in noise level), most of which is attributed to increased shipping activity (Andrew et al. 2002).  Some mitigation of tanker traffic-related noise is provided by Canada’s Economic Exclusion Zone (EEZ), which requires that large tanker traffic remain at minimum 200nm off Vancouver Island and the mainland coast of B.C., and 80nm off the west coast of the Queen Charlotte Islands3.  However, many other large vessels (e.g. cruise ships, commercial goods traffic to Alaska, Department of National Defence (DND), Coast Guard and other large vessels) frequently travel within the EEZ boundary.

Determining the specific effects of chronic noise on wild marine mammals is difficult, and these effects often cannot be separated from those resulting from other stimuli (Morton and Symonds 2002).  Williams et al. (2002a; b) observed altered behaviour patterns of Resident Killer Whales in the presence of whale watching vessels, but could not separate responses due to physical versus acoustic disturbance.  Killer Whales are a vocally rich species, known to rely on echolocation or passive listening for effective foraging (Barrett-Lennard et al. 1996, Deecke et al. 2005).  Any noise that masks this ability may result in the whales being unable to detect communication signals required for effective foraging, or for socializing (Erbe 2002).  This could lead to decreased ability to capture prey, attract mates, or maintain cohesion of social groups.

Concern for chronic noise impacts is rated low at present (Table 2).  Though this threat occurs currently and continuously in Canada’s EEZ, the certainty and severity of population level impacts are unknown.  Mitigation potential is quite low, given that traffic density in offshore areas is difficult to monitor or mitigate the noise effects of, particularly for large vessels (e.g. tankers). 

Physical Disturbance

The majority of whale watching activities in British Columbia focus on Resident Killer Whales in the Georgia, Haro and Johnstone Straits.  Offshoresare seldom observed by researchers, or by whale watchers in British Columbian waters.  However, the rate of encounters with Offshores in coastal areas has increased in recent years (DFO-CRP unpublished data), and should this trend continue, animals may be exposed to whale watch pressure, or other physical disturbance from small vessels.  Williams et al. (2006) recorded altered activity budgets of Residents in the presence of vessel traffic, indicating some level of energetic cost of disturbance.  As Offshores are unaccustomed to close or targeted approaches by vessels, there remains some concern for the safety of boaters and whales alike, should such circumstances arise.  The Fisheries Act Marine Mammal Regulation (MMR) legally protects all marine mammals from disturbance.  Additionally, the ‘Be Whale Wise: Marine Wildlife Guidelines for Boaters, Paddlers and Viewers’ guidance for a minimum viewing distance of 100m may not be sufficient to mitigate potential impacts from small vessels, given these whales’ naiveté to targeted small boat disturbance. 

Currently, the rare exposure of Offshores to targeted vessel disturbance in coastal waters results in negligible level of concern for this threat at the present time.  The potential for mitigation of this threat is moderate to high (Table 2) given that guidelines and regulations are currently in place to dictate targeted vessel behaviour around whales, and occurrence of whale watching disturbance is primarily near coastal, urban centres that are relatively easy to monitor. 

Boat Collisions

Large vessels (e.g. passenger ships) travel at high speeds within Canada’s EEZ on the West Coast.  As Offshore Killer Whales also inhabit these regions, there is potential for interactions with vessels.  While the MMR legally protects marine mammals from disturbance, monitoring vessel interactions in offshore areas is not feasible. 

Historically, there are few reports of collisions between Killer Whales and vessels. However, from 2003 to 2007 there were six collisions reported in B.C., three of which were fatal for Residents (DFO-CRP unpublished data).  In 2005, DFO cetacean research surveys encountered a previously identified Offshore Killer Whale, whose dorsal fin was completely severed at the base (DFO-CRP unpublished data).  This individual survived, and its injuries are consistent with those that could be sustained from a propeller blade.  As Offshores do not typically utilize habitat near urban areas, they are not exposed to high densities of small vessel traffic on a regular basis (as Resident Killer Whales are).  Therefore these whales may behave quite differently around small boat traffic than other Killer Whale assemblages (see ‘Physical Disturbance’).

As there is no information regarding the frequency of vessel strikes, nor a complete census of the population, it is unclear what level of threat to population viability is posed by vessel strikes. The observed injury indicates that vessel strikes currently impact at least individual Offshores, and the recorded mortalities of other Killer Whales indicate that impacts can be severe.  At present, several knowledge gaps regarding the occurrence of this threat remain unaddressed; therefore level of concern for this threat remains unknown.  Vessel strikes are accidental and once an animal is struck, mitigation of effects to that individual is not feasible; however regulations and guidelines aim to increase awareness of Killer Whales and dictate vessel behaviour in the presence of whales.  Therefore, mitigation potential for this threat is rated as low (Table 2). 

Entanglement

Seine-, gill-, or driftnet fisheries may pose threat to this population by way of potential interaction and entanglement in fishing gear.  Entanglement or entrapment within fishing gear or other man-made devices may cause harm to individual animals, and in rare cases may result in death.  While there have been no recorded incidents of entanglement involving Offshore Killer Whales, there is one recorded incident involving natural entrapment of Offshores.  In 1994, a group of Offshore Killer Whales was trapped in semi-tidal Barnes Lake, Alaska for 2 to 3 months (Bain 1994), ultimately exiting the area only as a result of human intervention. 
Gillnet, driftnet and long-line fishing currently occurs within the known range of Offshore Killer Whale (DFO 2007a).  Information on any occurrences of Offshores outside of the northeastern Pacific may address knowledge gaps on interactions with offshore or foreign fisheries, as well as potential range for these animals.  Further insight into the current rate of entanglement, prey, habitat use and range of this population will address the high degree of uncertainty regarding this threat to the population of Offshore Killer Whales in B.C. 

As a result of extreme data deficiency surrounding both entanglement rates and the certainty and severity of effects to the population, the level of concern for this threat is unknown (Table 2).  Modification of fishing gear has been successful in mitigating entanglement rates for cetaceans elsewhere (i.e. U.S. or Atlantic Canada); recommendations to enact cost-effective modifications to gear should be considered.

Climate Change

Changes in global climate may affect distribution of Offshore Killer Whales and their prey, within and outside Canadian political boundaries.  Global climate change has the potential to alter oceanographic conditions (e.g. ocean acidification), as well as predator-prey dynamics.  Macdonald et al. (2005) suggests that large changes in natural processes may affect the behaviour of chemicals in the environment, as well as the potential for alterations in vectors for transmission of disease.  In addition, other contaminants and stressors can have interactive effects resulting in decreased ability to counteract effects of biological pollutants (Sih et al. 2004). 

Level of concern for this threat is unknown (Table 2).  However, environmental changes such as climate change should be considered in the context of potential interactive or synergistic effects.  The mitigation potential for addressing effects of climate change on the population is unknown; further study is required to understand the potential effects of this threat on Offshore Killer Whales.

Biological Pollutants

Nutrient loading from terrestrial runoff may create environments where naturally occurring diseases or harmful algal blooms flourish in greater density.  Urban and agricultural runoff often contain antibiotics, hormones, viruses or biological materials that have the potential to affect marine mammals, such as Offshores.  Introduction of foreign diseases into a population of highly social cetaceans, like Killer Whales, may result in disease outbreaks leading to population decline (Guimarães et al. 2007).  The occurrence of large aggregations of Offshore Killer Whales makes them particularly sensitive to virulent disease outbreaks.  Some terrestrially based pathogens are known to affect marine mammals (Raverty et al. 2007, Conrad et al. 2005), though presence of biological pollutants in the Offshore population has not been extensively studied, leaving significant uncertainty regarding potential population-scale impacts. The mitigation potential for this threat is considered low to moderate for point-sources of pollution within Canada (Table 2).  For further detail on effects of disease and pathogens on Killer Whales, see ‘Naturally occurring Disease Agents’.

1.5.3 Natural Threats

Natural threats are those limiting factors whose effects on Offshores may be exacerbated by anthropogenic activities (EC 2007).  For example, disease effects may be compounded by acute or chronic biological or toxic pollution.  While natural threats are unlikely to be managed or mitigated, in and of themselves, they can impact the population viability for Offshore Killer Whales, and thus should be monitored to detect trends and additional research needs.

Naturally occurring Disease Agents

Naturally occurring diseases and pathogens affect cetaceans around the world.  These diseases, while endemic to populations, may be exacerbated by synergistic or compounding effects with other threats or limiting factors.  See ‘Biological Pollutants’.

Preliminary investigation of infectious diseases indicates that Salmonella newport septicemia, Edwardsiella tarda septicemia, Erysipelothrix rhusiopathiae, and marine Brucella are present in Killer Whales on the west coast of North America (Raverty et al. unpublished).  Marine Brucella and cetacean poxvirus may have particular significance as infection may result in decreased fecundity, reproductive success and increase neonate mortality (Gaydos et al. 2004).

In addition, Offshores may also be exposed to naturally occurring diseases through transmission from prey species.  The cracks on Offshores’ teeth may allow bacteria to more easily enter the bloodstream making transfer of pathogens from prey to predator a possibility.
While the level of disease or infection within the population is unclear, the weight of evidence provided for other Killer Whales, as well as overlapping distribution of the three populations, would suggest at minimum general exposure to a similar suite of naturally occurring diseases. Gaydos et al. (2004) recommends further study of four priority pathogens likely to affect Resident Killer Whale populations either through intra- or inter-specific interactions; marine Brucella, cetacean poxvirus, cetacean morbilliviruses and herpesviruses.  While studies focusing on these four pathogens may address concerns regarding population level effects to Killer Whale assemblages, there are 16 other pathogens which have also been identified to potentially affect Killer Whales (Gaydos et al. 2004).  Level of concern for this threat is unknown (Table 2), given the uncertainties surrounding disease prevalence in the Offshore population. 

Mass Stranding and Entrapment

Mass stranding or entrapment of Killer Whales were listed by COSEWIC (2008) as potential sources of natural mortality.  Since 1992, there have been three recorded strandings of Killer Whales in British Columbia (DFO-CRP unpublished data). While no strandings of Offshores have been reported, the coastal habitat of B.C. is such that stranding events which occur outside of highly populated areas are less likely to be encountered.  The cause of stranding events for cetaceans is poorly understood, however anthropogenic effects, such as tactical sonar noise, have been implicated in several mass stranding incidents involving beaked whales (e.g. Schrope 2002; Jepson et al. 2003), suggesting that anthropogenic pressures may contribute to mass stranding events. 

In general, records of entrapment in inlets or bays indicate an inability of the group to adapt to exit from the area (examples listed in Baird 2001). There is one recorded incident involving natural entrapment of Offshores.  In 1994, a group of Offshore Killer Whales was trapped in semi-tidal Barnes Lake, Alaska for 2 to 3 months (Bain 1994).  The group ultimately exited the area only as a result of human intervention.  This event resulted in the mortality of one adult female and one sub-adult male (Bain 1994). 

While mitigation measures were taken in the Barnes Lake incident, mitigation potential for stranding and entrapment events will be highly dependent on each individual situation, and will require assessment on a case-by-case basis, and involvement of trained personnel.

1.5.4 Cumulative or Synergistic Effects of Threats and/or Limiting Factors

The effects of threats and limiting factors can be difficult to distinguish from one another, making conclusions regarding causes of population decline often difficult to ascertain.  Synergistic effects between multiple stressors on a population have been suggested to result in a ‘snowball effect’ enhancing the effects of otherwise benign limiting factors (e.g. Sih et al. 2004; Macdonald et al. 2005). 

There is considerable uncertainty as to the occurrence and total impact of threats on the population in Canadian waters.  Nonetheless a species, like Killer Whale, with a long maturation period and low reproductive rate would be expected to be sensitive to increases in human-caused mortality, particularly if oceanographic conditions deteriorate, or if combined with other threats.

1.6 Actions Already Completed or Underway

1.6.1 Current Management and Stewardship Actions

Canada’s federal Species at Risk Act [SARA] requires that a management plan be developed for the management of a species of special concern, such as Offshore Killer Whales.  While no other management actions have been initiated to specifically address conservation of Offshores, several existing actions to protect and preserve other marine species and ecosystems may prove useful for management of this population.  These actions and initiatives may mitigate stresses, or provide valuable opportunities to gain knowledge or promote awareness of the population.  Actions currently underway may also be listed in Section 2.3 (‘Actions’) in order to promote their completion, or to increase their effectiveness for protection of this population. 
Offshore Killer Whales are currently protected under the following legislation and guidelines:

  • Protection from trade under the Convention on International Trade in Endangered Species of Wild Fauna and Flora [CITES], Appendix II;
  • Canada’s federal Fisheries Act contains provisions for protection of fish and marine mammal habitat (S. 35, 36), and the Marine Mammal Regulation, protects all marine mammals from disturbance and injury;
  • Fisheries and Oceans Canada Statement of Canadian Practice with respect to the Mitigation of Seismic Sound in the Marine Environment (DFO 2007)
  • Department of National Defence [DND] ‘Maritime command order: marine mammal mitigation procedures’ (DND 2007) mitigates disturbance from tactical sonar use;
  • Environmental Quality Guidelines for water, air, sediment and tissues are published by the Canadian Council of Ministers for the Environment [CCME] and the B.C. Ministry of Environment [MoE];
  • By-laws, Codes of practice and Action groups are developed and implemented regionally and municipally for mitigation of environmental stresses;
  • Regional Environmental Emergency Teams [REET], regional, national and international spill response programs manage toxic spills and monitoring of contaminated sites (e.g. Can-US Dix Plan, B.C. Marine Oil Spill Contingency Plan).
  • Canadian Environmental Protection Act, Polybrominated Diphenyl Ethers (PBDEs) Regulations and Environment Canada’s Risk Management Strategy for PBDEs.  To view the regulations, visithttp://canadagazette.gc.ca/rp-pr/p2/2008/2008-07-09/html/sor-dors218-eng.html

I.  Regulatory development and review, currently underway

  • Fisheries Act ‘Marine Mammal Regulation’ [MMR] is being amended to increase prevention and mitigation of disturbance to marine mammals
  • Pacific North Coast Integrated Management Area [PNCIMA] aims to combine protection of habitat with sustainable use of resources in Queen Charlotte Basin and mitigate stress to species at risk found on the north coast of B.C.
  • Development of the proposed National Marine Conservation Area [NMCA] off Gwaii Haanas may protect potential habitat for Offshore Killer Whales around the Queen Charlotte Islands

II.  Stewardship measures currently in place

  • ‘Be Whale Wise: Marine Wildlife Guidelines for Boaters, Paddlers and Viewers’ provides guidelines for human behaviour and minimum vessel distances around wild marine mammals
  • Information on sightings of marine mammals are collected by the B.C. Cetacean Sightings Network (1-866-I-SAW-ONE; www.wildwhales.org ), a partnership between the Vancouver Aquarium and DFO
  • Information on incidents (e.g. strandings, entanglements) and marine mammal sightings are collected by the B.C. Marine Mammal Response Network [BCMMRN] (1-800-465-4336) program and other organizations
  • Straitwatch, Robson-Bight (Michael Bigg) Ecological Reserve Warden program, and the B.C. Cetacean Sightings Network, educate boaters on marine mammal viewing guidelines and threats to marine mammals
  • Public and industry initiatives such as, ‘Toxic Smart’ or ‘Clean Print B.C.’, increase awareness of chemical stress to marine habitats
  • Remediation programs can be carried out on a case-by-case basis for disturbed habitat
  • Pacific Whale Watch Association has implemented Best Management Practices (http://pacificwhalewatch.org) for all its members to ensure that operators behave in a manner which respects the spirit of the Be Whale Wise: Marine Wildlife Guidelines for Boaters, Paddlers and Viewers’

III.  Conservation strategies currently under development
With the legislation of the SARA in 2003, marine conservation strategies for ‘at-risk’ marine mammals have been drafted.  These documents include recommended actions for protection of marine mammal species.  In a larger context, these management actions may also benefit Offshores.  Please refer to Section 4.0 ‘Associated Plans’ for specific recovery plans with actions relevant to the protection and management of Offshore Killer Whales in British Columbia.

1.6.2 Current Research Actions

Due to the inherent difficulties of marine field research on wide-ranging and uncommon species, data are often collected on an opportunistic basis.  Researchers with DFO, universities and other organizations4, collect and share sightings and incident information for all marine mammals, including Offshores, and necropsy work is completed when possible.  During ship-based surveys, independent researchers and organizations collect information on cetaceans via:

  • Photo-identification of individual whales
  • Acoustic sampling of vocalizations
  • Biopsy (tissue) sampling of individuals, when possible

Aerial surveys complement these processes by providing abundance estimates for many marine mammals.  Fatty acid profiling of tissue samples address questions regarding prey types and contamination levels.  Potential prey species are being acquired and analyzed, which may support field studies in identification of the prey of Offshore Killer Whales via chemical isotope analysis (Krahn et al. 2007).

To date, relatively little targeted research on life history and ecology has been conducted on Offshores.  Their unpredictable patterns of occurrence and open ocean habitat have made directed research efforts impractical.  Future research should address concerns and knowledge gaps regarding threats. 

1.7 Knowledge Gaps

There is a considerable amount of detailed knowledge on the population dynamics and life history of the Resident Killer Whale communities in British Columbia.  It is unclear how much, if any, of these data are applicable to an understanding of the Offshore population in Canada.  Encounters with this population have been relatively few, and efforts to catalogue members of this population have been challenging given infrequent sightings, elusive behaviour, and their largely open ocean habitat. 

There are significant gaps in knowledge of nearly all aspects of the general biology and ecology of the Offshore Killer Whale, and increase in research effort is necessary to address these deficiencies.  The highest priority for research efforts are studies to address knowledge gaps on: diet (including nutritional needs), population abundance (e.g. long-term trends), demographics, distribution, range and seasonal occurrence, habitat requirements, and social organization.

Additional research programs on mating patterns, genetic associations and toxic or biological contaminant levels and magnitude of listed threats (Table 2), are also relevant.

 

1 Naming and properties of chemicals are available in Appendix I (Table 6).

2 Use of acoustic deterrent devices in British Columbia is no longer permitted.

3 80nm EEZ limit is based on the vessel traffic requirements for the protected area surrounding Bowie Seamount.

4 A list of organizations and independent researchers carrying out research programs on Offshore Killer Whales are listed in Appendix II.

 

 

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