Warning This Web page has been archived on the Web.

Archived Content

Information identified as archived on the Web is for reference, research or recordkeeping purposes. It has not been altered or updated after the date of archiving. Web pages that are archived on the Web are not subject to the Government of Canada Web Standards, as per the Policy on Communications and Federal Identity.

Skip booklet index and go to page content

Recovery Strategy for the Northern and Southern Resident Killer Whale

Polybrominated Diphenylethers ( PBDEs)

Preliminary evidence suggests that flame retardants may be a significant and emerging concern for resident killer whales (Ross 2006).  Moderate levels of the as-yet largely unregulated PBDEs were observed in 39 biopsy samples collected between 1993-1996 from southern resident and transient killer whales, and relatively low levels were observed in northern residents (Rayne et al. 2004).  Unlike an earlier study on PCB levels in resident killer whales (Ross et al. 2000), Rayne et al. (2004) did not find any significant age-related trends in PBDE levels, but that may have been an artefact of their small sample size or the fact that PBDEs were relatively new in the environment in the 1990s.  In a sample of 70 long-finned pilot whales in the North Atlantic, Lindstrom et al. (1999) found that juveniles had two to three times higher levels of PBDEs than did adults (Lindstrom et al. 1999), suggesting that reproductive females may pass PBDEs on to their offspring during gestation and lactation.

Although the toxicity of PBDEs is not well understood, they have been associated with endocrine disruption in laboratory animals (Darnerud, 2003).  While no conclusive link could be established as a result of the numerous other lipophilic contaminants present, PBDE concentrations were negatively associated with thyroid hormones in grey seals (Halichoerus grypus, Hall et al. 2003).  As more than 10 years have passed since some of the killer whale samples were collected, and since PBDE levels persist in the environment and their use has been increasing exponentially (Hooper and McDonald 2000), it is likely that killer whales today in 2007 are carrying significantly higher concentration loads of these contaminants than were found in whales sampled in the mid 1990s.  Numerous captive and semi-field studies of pinnipeds provide evidence that POPs are affecting immune function (hence, resistance to disease), hormone levels, and reproductive health (Ross 2000; Reijnders 1986; Nyman et al. 2003; De Swart e al., 1996).

Using this weight of evidence as a foundation, it is not possible to ignore the substantial risks that PCBs and other POPs present to killer whales in the northeast Pacific.  Transients from Prince William Sound, Alaska (AT1 population) are highly contaminated, and have had no successful reproduction since 1984, providing perhaps a population-level glimpse into the effects of high POP burdens (Ylitalo 2001). High levels of toxic chemicals may also make killer whales more vulnerable to disease (Ross, 2002).  Jepson (1999) found that harbour porpoises that died from infectious diseases had two to three times higher concentrations of PCBs than those that died from trauma. 

Biological Pollutants 

Biological pollution may also threaten the health of resident killer whales, their habitat and their prey.  These pollutants may take the form of ‘spill-over’ pathogens from human activities (e.g. pets, livestock, migrations, habitat change) virulent, antibiotic- resistant  l strains arising as a result of the use of antibiotics bacteria or exotic species.  Emerging infectious diseases are a growing concern for marine life, as naturally occurring host-pathogen relationships are altered through human activities such as disturbance, over-fishing, habitat destruction, climate change or pollution (Ross 2002).  Killer whales whose immune system is compromised through chemical contaminants may be increasingly vulnerable to biological pollutants.  Although no disease-related mass mortalities have been observed among BC’s marine mammals, Morbillivirus has been detected in marine-dwelling river otters (Mos et al. 2003), highlighting the potential risk of this or related pathogens to killer whales.  In other areas, Morbillivirus outbreaks have caused mass mortalities of seals (Grachev et al. 1989, Kennedy et al. 2000) and dolphins (Aguilar and Borrell 1994).  Pathogens such as Morbillivirus are capable of spreading extremely quickly (3000 km/yr), likely because in the marine environment there are few barriers to dispersal (McCallum et al. 2003).

The introduction of exotic species has changed habitats in other areas (e.g. zebra mussels in the Great Lakes, Eurasian milfoil into freshwater lakes) and introduced species have the potential to impact local ecosystems here.  In British Columbia, Atlantic salmon that have escaped from aquaculture operations have successfully spawned in freshwater (Volpe et al. 2000). The extent to which this is occurring and how Atlantic salmon would compete with Pacific salmon, the preferred prey of residents (Ford et al. 1998), is not well known at this time. 

Trace Metals

Trace metals occur naturally in the marine environment, but elevated concentrations sufficient to be a concern to marine mammals may be found in localized areas such as urban and industrial centers (Grant and Ross 2002).  Some, such as cadmium, mercury, copper and lead may have toxic effects even at relatively low concentrations, and could impact killer whales, although effects on their prey and/ or habitat are more likely.

Little information is available on the levels and effects of trace metals on marine mammals in the Pacific. However, in a small sample of stranded killer whales, residents showed higher levels of mercury than transients (Langelier et al. 1990). In the western Pacific, all odontocete meat sampled from Japanese markets contained amounts of mercury that exceeded the level permitted for human consumption (Endo et al. 2003). However, the historical exposure of high trophic level marine mammals to naturally elevated concentrations of mercury in prey has resulted in their evolved ability to detoxify this toxic metal through the formation of mercury-selenium crystals in the liver (Martoja and Berry, 1980).

Sources of Contaminants

Monitoring the sources and levels of environmental contaminants is particularly challenging given that each year, up to 1000 new chemicals are released into the environment globally (Haggarty et al. 2003).  The high contaminant levels found in southern residents may arise from consuming prey that are from industrialized areas near the BC-Washington border, which may be more contaminated than the prey of northern residents (Ross et al. 2000).  In Japan, odontocetes that travelled in more industrialized areas carried higher contaminant loads than those found in more remote areas (Endo et al. 2003).  In a study of harbour seals in British Columbia and Washington, Ross et al. (2004) found that although PCB levels were a concern in all areas, seals from Puget Sound are seven times more PCB-contaminated than were seals from the Strait of Georgia. This suggests that the food web within Puget Sound has been contaminated with PCBs, such that killer whales consuming prey items from this region may be vulnerable to increased contaminant exposure. Chinook salmon, one of the resident killer whales’ preferred prey species (Ford et al. 1998, Ford and Ellis 2005), feed in the upper trophic levels in the food web, and those from Puget Sound are relatively contaminated with PCBs (O’Neill et al. 1998). Studies suggest that most salmonids are ‘importing’ contaminants from their time at sea, reflecting global environmental contamination (O’Neill et al 1998; Ewald et al 1998).

Although DDT was banned in Canada in 1989 and over 30 years ago in the United States, it continues to enter the ocean from terrestrial runoff (Hartwell 2004) as well as from atmospheric transport from countries where it is still in use.  Dioxins (PCDDs) and furans (PCDFs) represent highly toxic by-products of chlorine bleaching and associated wood treatment, and incomplete combustion.  Source controls and regulations have greatly reduced their input in to the coastal environments of BC and Washington over the past 15 years.

Contaminants enter the marine environment from local, regional and international sources.  These are discussed in detail in Haggarty et al. (2003).  Local point sources of contaminants into the marine environment include:

  • pulp and paper mills,
  • wood treatment facilities,
  • municipal effluent outfalls,
  • petrochemical facilities, and
  • mines. 

Indirect sources (non-point source pollutants) include

  • sewer overflows (e.g. organic wastes, household products, pharmaceuticals and personal care products)
  • urban runoff and storm-water drainage (e.g. pesticides, metals, hydrocarbons, herbicides, and animal wastes)
  • agriculture (e.g. pesticides, herbicides, animal wastes and antibiotics),
  • forestry (e.g. pesticides, herbicides, fire-control chemicals, anti-sapstain chemicals, log booms and storage areas), and
  • aquaculture (e.g. organic wastes , chemical contaminants [antibiotics, feed additives, pharmaceuticals, pesticides and antifouling on nets]). 

Garrett and Ross (in press) describe the Canadian and US federal, provincial and state agencies responsible for the monitoring, mitigation and regulation of environmental contaminants and their sources.

Shipping also represents a risk to the ecological integrity of coastal regions. Both intentional and unintentional discharge of chemicals and biological waste are added sources of pollution in all coastal areas, but particularly in high traffic zones.  In addition,  the  introduction of exotic and invasive species carried on ship hulls and in ballast water have the potential to dramatically altered the habitats they have colonized (e.g. European green crabs, zebra mussels, the alga Caulerpa taxifola).  Numerous invasive invertebrates have been found in the ballast water of ships at anchor in Vancouver Harbour (Levings et al. 2004), although the ecological significance of such introductions is unclear. 

In addition, some pollutants such as PCBs, DDT and other chemicals, are transported through atmospheric processes and ocean currents, and may travel to the west coast of North America from as far away as Asia in less than 5-8 days (Wilkening et al. 2000).  Consequently, the northeastern Pacific may be a sink for globally produced POPs (Ross et al. 2000, 2004, 2006). 

Certain ‘legacy’ POPs such as PCBs and DDT have been phased out of industrialized countries and their concentrations are slowly decreasing in the marine environment (Muir et al. 1999), although these declines have levelled off (Addison and Stobo 2001).  However, levels of other ‘new’ POPs such as the flame retardant PBDEs have increased exponentially over the past 25 years, and represent the PCBs of the future (Hooper and McDonald 2000; Ross 2006).  Unlike PCBs, which were generally used in a limited range of applications such as electrical transformers and capacitors, PBDEs are widely used in many industrial and consumer applications and are incorporated into plastics, textiles and foam. 

2.2.2 Reduced Prey Availability

Answering the question as to whether killer whales may be prey limited is complex.  While the complete diet of resident killer whales is not known, at certain times of the year salmon, particularly chinook and chum, appear to be important prey (see Section 1.5.1. Diet).  Ford et al. (2005) found that trends in the mortality rates of southern and northern resident killer whales were correlated with each other, and that both were strongly related to fluctuations in the abundance of chinook salmon, but not chum salmon.  Birth rates were also correlated with chinook salmon abundance, but more weakly than mortalities.

Unfortunately, there is very little known about the prey of resident killer whales and their distribution and abundance during the months of November to April. This is due to the inherent challenges of studying whales during the winter months, and because the whales move from their ‘core areas’ and range widely along the exposed coast during the winter and early spring.  Thus when considering the availability of prey to resident killer whales, it should be noted that we have very little knowledge of what other prey species may be important to them, and the discussion below focuses on species that are known to be important.

Changes in Salmon Abundance and Availability

Assessing the status of salmon stocks and their availability to resident killer whales is challenging to interpret and often fraught with controversy.  Until the middle of the 20th century, many wild salmon stocks experienced significant declines due to overfishing, habitat degradation, restrictions in access to spawning grounds due to landslides, and changes in ocean productivity (summarized in Krahn et al. 2002 and Wiles 2004).  The situation changed between 1975 and 1993, and the total abundance of North Pacific salmon doubled (Bigler et al. 1996) due to hatchery enhancement, changes in fisheries management practices and a favourable climatic regime (Bigler et al. 1996, Beamish et al. 1997).  Since the early 1990s many of these stocks have declined in number, and controversy as to whether hatchery fish are detrimental to wild stocks of salmon has arisen (Beamish et al. 1997, and reviewed in Gardner et al. 2004).  At present 26 of 52 different wild Pacific salmon stocks in the lower 48 states of the US are considered at risk under the US Endangered Species Act (NWR 2004).  In British Columbia, salmon from one-third of the spawning rivers in southwestern BC had been lost or were seriously depleted by 1990 (Riddell 1993).  Recognizing that many salmon stocks are under threat, Fisheries and Oceans Canada announced a new wild salmon policy in December 2004 (DFOb 2005), designed to restore and maintain healthy and diverse wild salmon populations and their habitat.  If these actions are successful, salmon may gradually become more available to resident killer whales. 

Resident killer whales tend to be found in ‘core areas’ (discussed in 1.5.1 Diet and in Section 3 critical habitat) during the period when salmon are returning to rivers to spawn.  This likely reflects the fact that salmon are not as widely dispersed at this time as they are during the rest of their life cycle.  There is a great deal of diversity in the timing of the spawning period for salmon.  For example, the Upper Columbia River has a spring run and a summer/fall run of chinook.  These runs are considered distinct stocks because they do not interbreed. The spring run is endangered under the ESA in the US, yet the summer/ fall run is not at risk (NWR 2004).  This illustrates the need to consider the timing of the spawning period of each salmon stock when assessing the availability of salmon for killer whales, in order to ensure an adequate year-round food supply.  Chinook salmon are longer lived than other salmon species and spawn at different ages (Healey 1991).  It is likely that their year-round availability in nearshore waters is a key factor, along with body size and lipid content, in chinook being the preferred salmonid prey of resident killer whales (Ford and Ellis 2005).

While traditionally the main sources of reduced salmon abundance are considered to be over-fishing, habitat degradation and unfavourable climatic conditions, new concerns warrant further investigation.  Recent investigation suggests that salmonid aquaculture may be contributing to the decline of wild salmon stocks due to the high occurrence of sea lice associated with open net pen salmon farms within the northern resident range (Gardner and Peterson 2003, Morton et al. 2004).  Wild juvenile pink and chum salmon in the vicinity of fish farms in the Broughton Archipelago carried injurious or lethal loads of sea lice (Morton et al. 2004).  Juvenile chinook salmon in the area have also been recorded with sea lice (Morton and Williams 2003).  Sea lice associated with salmon farms have been implicated in the declines of wild fish stocks in both Norway and Scotland (Bjorn et al. 2001, Penston et al. 2004).  With the lifting of the moratorium on new fish farm licenses in British Columbia in September 2002, the impact of the expansion of this industry on the health of juvenile salmon populations and the potential impact on resident killer whale survival warrants examination.  This is of particular concern because of the importance of chinook and chum salmon in the diet of resident killer whales.

Depressed Chinook Stocks

Chinook salmon, the principal prey of BC’s resident killer whales, is one of the least abundant species of salmon in BC (Riddell 2004).  However, unlike other salmon, many populations of chinook remain in nearshore waters during the ocean phase of their life cycle.  As a result they are available on a more year-round basis to killer whales, but are also more vulnerable to pollution (discussed in 2.2.1 Environmental Contaminants).  

Chinook abundance dropped in the 1970s and 1980s, but escapements increased until the early 1990s in some rivers, primarily due to hatchery production (Beamish et al. 1997).  In Washington, hatchery fish now account for about 75% of all harvested chinook (Mahnken et al. 1998 in Wiles 2004).  In un-enhanced river systems in central and northern British Columbia, chinook numbers remain depressed (Riddell 2004) and 10 of 17 chinook stocks in Washington, Oregon and California are listed under the ESA (NWR 2004).  Thus it is plausible that chinook may be limiting for killer whales (Ford et al. 2005).  This may explain why southern resident killer whales have appeared in places as distant as off the Columbia River and off northern California to the south and off Langara Island in the north (unpublished data CRP-DFO).  Their presence was associated with unusually large returns of chinook salmon, which they may have had to seek out because of less abundant prey within their traditional range.   When prey availability is reduced, killer whales may be forced to spend more time and travel greater distances to forage for their food, or switch to less profitable prey, which could lead to lower reproductive rates and higher mortality rates.

In addition to reduced chinook abundance, the quality of individual fish appears also to have declined over recent decades.  Average weights of chinook salmon in nine populations from British Columbia to California declined by up to 45% between 1975 and 1993 (Bigler et al. 1996).  Thus, the nutritional yield of each chinook salmon is significantly less today than it was in past years, which may have an impact on the overall foraging energetics of resident killer whales.

2.2.3 Disturbance

All cetaceans, including resident killer whales, are being subjected to increasing amounts of disturbance from vessels, aircraft, and anthropogenic noise (IWC 2004).  Both private and commercial boat traffic have increased dramatically in recent years, and killer whales must navigate in increasingly busy waters (Osborne 1999, Foote et al. 2004).  Industrial activities such as dredging, drilling, construction, seismic testing, and military sonar and other vessel use of low and mid-frequency sonars also impact the acoustic environment (Richardson et al. 1995, NRC 2003).  The means by which physical and/ or acoustic disturbance can affect resident killer whales at both the individual and population level are not well understood, but may depend on whether the disturbance is chronic (such as whale watching) or acute (such as seismic surveys).  Other factors, including the animal’s condition, previous exposure (potentially causing sensitization or habituation), age, sex, and behavioural state also influences how disturbance affects whales.  In addition, environmental factors, such as El Niño events that may change the availability of prey, may make animals more vulnerable to disruption than they would be otherwise.  The sources of both physical and acoustic disturbance and their potential impact on resident killer whales are discussed in greater detail below.

A current challenge in studying the effects of disturbance is in finding informative ways to describe and measure them, and to date the question of whether a source of disturbance is likely to result in effects at the population level can be difficult to answer.  Responses to disturbance may range from slight differences in surfacing and breathing rates to active avoidance of an area.  Even if the disturbance causes immediate death, carcasses are rarely recovered.  (Regardless of the cause of death, only 6% of killer whale carcasses are recovered, unpublished data CRP-DFO).  As well, animals may show no obvious behavioural responses to disturbance, yet still be negatively affected.  For example, Todd et al. (1996) found that humpback whales remained in the vicinity of underwater explosions, and showed no obvious behavioural responses to them.  However they experienced significantly higher entanglement rates during this time, and necropsies of two whales that drowned in nets revealed acoustic trauma (Ketten et al. 1993).  Thus a lack of a measurable behavioural response to a stimulus does not necessarily imply the disturbance does not have negative consequences.  A parallel may exist with humans, since people exposed to chronic noise lose their hearing more quickly than those that are not exposed to chronic noise.  The consequences of hearing loss for cetaceans are likely fatal.

Measures for changes in behaviour may also not be subtle enough to detect disturbance.  Whitehead (2003) re-analyzed data that were reported to show that sperm whales did not show behavioural responses to surveys using high-intensity sound.  He segregated the responses according to whale density in the area and found that contrary to earlier conclusions, when whale density was low, sperm whales avoided seismic activity.  When densities were high, whales remained in the vicinity.  He suggested that whales may have been reluctant to leave a rich feeding area despite the disturbance.

Whale Watching

Commercial whale watching has grown dramatically in British Columbia, with just a few boats carrying less than 1,000 passengers per year in the late 1970s and early 1980s to 80 boats carrying half a million passengers per year in 1998 (Osborne 1991, Baird 2002, Osborne et al. 2003).  Whale watchers tend to target resident killer whales in their most predictable locations, Haro Strait and Johnstone Strait. In the summer, an average of 19-22 boats have been observed near southern resident killer whales in Haro Strait, commonly from 9 am to 9 pm (Osborne et al. 2003) although some begin as early as 6 am (personal communication David Bain, February 2005).  These include privately owned kayaks, sailboats and powerboats as well as commercial whale watch vessels. While the benefits of public education and increased awareness that can be achieved through guided whale watching are well established, concern over the effects of whale watching on killer whales has grown with the industry itself.  This concern has prompted the  development of industry initiated watching guidelines and has resulted in studies that have attempted to measure responses of the whales to such focused attention (Kruse 1991, Williams et al. 2002a, b), as well as the behaviour of boaters around whales (Jelinski et al. 2002).  Whale watching activities have the potential to disturb marine mammals through both the physical presence and activity of boats, as well as the increased underwater noise levels boat engines generate. 

Under the Fisheries Act in Canada and the MMPA in the US, disturbance (harassment) of marine mammals, including killer whales, by the public is prohibited.  No special provisions or exemptions to this prohibition have been made for commercial whale watch operators and the commercial fleet is subject to the same regulatory restrictions as recreational boaters.  It is not known what the biological significance of disturbance is to resident killer whales, but voluntary whale watching guidelines for Canadian vessels have been developed (Be Whale Wise, DFO 2004).  From June through to November, an additional set of guidelines has been developed to minimize disturbance to whales when whales are in the Special Management Zone in Johnstone Strait (see www.straitwatch.org for details).  The Whale Watch Operators Association Northwest (WWOANW) has developed an even more comprehensive ‘Best Practices Guidelines’ for commercial operators to follow when observing southern residents (WWOAN 2004).  These guidelines have evolved over a 10 year period to reflect new knowledge and minimize the negative effects of vessel traffic.  They remain a work in progress and will evolve as further research reveals if and how whale watching may have population level consequences for resident killer whales.

There are several projects that focus on educating the boating public both on and off the water about appropriate conduct in the vicinity of marine mammals.  They also monitor vessel activity in the presence of whales.  Current projects include the Soundwatch Boater Education Program in the San Juan Islands, and Straitwatch in Johnstone Strait, while past projects include the Marine Mammal Monitoring Project in Victoria, BC,.  All these programs are run by non-profit organizations that do not have guaranteed funding.  Smith and Bain (2002) found that commercial operators increased their compliance with a voluntary 0.4 km ‘no boat’ zone in the San Juan Islands from less than 80% to over 90% when Soundwatch was present on the water.  

Boat activity has been linked to short-term behavioural changes in resident killer whales (Kruse 1991, Smith and Bain 2002, Williams et al. 2002a, b).  They have been known to swim faster, travel in less predictable paths, alter dive lengths, move into open water, and alter normal behaviour patterns at the surface in response to vessel presence (Kruse 1991, Williams et al. 2002a, b).  Foote et al. (2004) found that southern resident killer whales significantly increased the duration of their calls when boats were present, and suggested that this was an adaptation to the masking effects caused by increased noise levels.

Although studies have shown short- term responses of killer whales to whale watching vessels, the long- term effects of whale watching on the health of killer whale populations are not known (Trites et al. 2002).  Increased whale watching operations between the mid-1980s and 2001 may have resulted in a potential 20% increase in energetic expenditures of killer whales due to increased swimming velocity (Kriete 1995, 2002).  Bain (2002) found that although the decline of southern residents followed the increase in commercial whale watching, the relationship was much more complex.  He suggested that other variables, such as changes in the availability of prey, were also likely significant.  Whether whale watching is a significant threat to killer whales or not, both the northern and southern resident populations continue to return to their traditional summer ranges despite increased whale watching activity.  This may reflect their strong cultural behaviours or the distribution of their prey.