National Recovery Strategy for the Sea Otter (Enhydra lutris) in British Columbia
 

DRAFT

December 2002

EXECUTIVE SUMMARY

Sea otters once ranged from Northern Japan to central Baja California, but were hunted almost to extinction during the European fur trade in the 1700s and 1800s. As few as 2000 animals, less than 3% of the pre-fur trade population are thought to have remained in 13 remnant populations by 1911. In British Columbia, the last sea otter was shot in Kyuquot in 1929. Between 1969 and 1972, 89 sea otters from Amchitka and Prince William Sound Alaska were released in Checleset Bay on the west coast of Vancouver Island. The British Columbia sea otter population is presently estimated to includes a minimum of 2000 animals along the west coast of Vancouver Island and 500 animals on the central British Columbia coast. Sea otters are listed as threatened (since 1996), down-listed from endangered (1978) by COSEWIC, the Committee on the Status of Endangered Wildlife in Canada.  Oil spills are a significant threat that could easily decimate this population at any time because of its small size and localized distribution and sea otters inherent vulnerability to oil. In June of 2002, a Recovery Team was formed to develop a National Recovery Strategy for sea otters in British Columbia

The Recovery Team identified threats and knowledge gaps that should be addressed to ensure recovery of sea otters. The Recovery Team determined that there is a need to establish a target population size and distribution along the British Columbia coast that would be sufficient to ensure recovery of the species even in the event of a spill or some other catastrophic event that killed a portion of the population. These targets are unknown and efforts to fill this knowledge gap were considered crucial by the Recovery Team.  In addition to this knowledge gap lack of information about critical habitat was also identified. With regard to threats, the Recovery Team identified several threats to sea otters and their habitat in addition to oil spills. These were; disease and parasites, contaminants, entanglement in fishing gear, illegal killing and, potentially low genetic diversity.

The goal of the Recovery Strategy is to:

… Ensure that the sea otter population in British Columbia is sufficiently large and adequately distributed so that threats, including catastrophic events, such as an oil spill, would be unlikely to cause extirpation of the species or diminish the population such that recovery to pre-event numbers would be very slow.

To achieve this goal the Recovery Team identified the need for:

·        research to determine a target population size and distribution;

·        research to clarify threats and limiting factors to sea otter recovery;

·        research to identify and delineate critical habitat;

·        protection of sea otters and their habitat through education, enforcement and habitat protection.

Table of Contents

I.     INTRODUCTION

II.    BACKGROUND

1.     CURRENT STATUS

1.1      Species Description

1.2      Distribution

1.3      Population Size And Trends

2.     FACTORS AFFECTING VULNERABILITY AND CONTRIBUTING TO THREATENED STATUS   

2.1      Habitat Requirements

2.2      Biological Limiting Factors

2.3      Threats

2.4      Ecological Role

2.5      Socio-Economic Considerations

2.6      Knowledge Gaps

III.   RECOVERY

1.     RECOVERY GOAL

2.     SHORT-TERM RECOVERY OBJECTIVES (~ 5years)

3.     APPROACHES TO ACHIEVE RECOVERY

3.1      Research

3.2      Protection

3.3      Communications

4.     CONSIDERATIONS FOR RECOVERY

4.1      Recovery Potential and Rationale

4.2      Recommended Approach/ Scale of Recovery

4.3      Anticipated Conflicts or Challenges

5.     ACTIONS ALREADY COMPLETED AND/OR UNDERWAY

6.     STATEMENT OF WHEN ONE OR MORE ACTION PLANS IN RELATION TO THE RECOVERY STRATEGY WILL BE COMPLETED

7.     EVALUATION

IV.   REFERENCES CITED

V.    GLOSSARY OF TERMS

VI.   SEA OTTER RECOVERY TEAM MEMBERS

I.                  INTRODUCTION

Hunted during the European fur trade (late 1700s), sea otters (Enhydra lutris) were driven to the brink of extinction by the mid 1800s.  Found along the Northeastern Pacific Rim, sea otters today occupy roughly half their historic range.  In Canada, sea otters are found in coastal British Columbia (BC) and are listed Threatened by the Committee on the Status for Endangered Wildlife in Canada (COSEWIC). 

With input from First Nations, stakeholders and those interested in the recovery of sea otters, the Sea Otter Recovery Team is co-ordinating the drafting of this National Recovery Strategy, which represents a legal requirement under the emerging Species at Risk Act (SARA) and will form the scientific basis for recovering the sea otter population in BC. 

The purposes of the Act are:

“to prevent wildlife species from being extirpated or becoming extinct, to provide for the recovery of a wildlife species that are extirpated, endangered or threatened as a result of human activity and to manage species of special concern to prevent them from becoming endangered or threatened”. 

As such, this strategy is being developed from the perspective of benefits to sea otters and activities that lead to recovery of the population. Socio-economic factors are identified in this strategy, but will be further evaluated for costs and the benefits to be derived from implementation in the subsequent Action Plan. Under the Act, the development of an Action Plan will follow the drafting of the Recovery Strategy. The Sea Otter Action Plan will list the measures for 5 years that are to be taken in implementing the Recovery Strategy.

II.               BACKGROUND

1.      CURRENT STATUS

1.1       Species Description

Sea otters are the smallest marine mammals, but the largest of the Mustelidae or weasel family. Worldwide there are 12 species of otters. All have streamline bodies, thick fur and amphibious habits, but the sea otter, is the only species that carries out all aspects of its life in the marine environment. The sea otter possesses several important adaptations. These include development of hind flippers for aquatic locomotion, flattened premolars and molars for crushing the hard-shelled marine invertebrates (Reviewed in Riedman and Estes 1990), and enlarged kidneys to process the large amounts of ingested sea salt (Costa 1982).

Sea otters weigh, on average between  19.5 kg and 39.5 kg (reviewed in Riedman and Estes 1990). Adult male sea otters tend to weigh slightly more than females and can weigh as much as 50 kg and reach lengths of 1.5 m (R. Jameson pers. comm. 2002). Males tend to have a larger head and the neck is more muscular, however presence of the penial and testicular bulge is the only reliable method for determining sex when observing free-ranging otters. Newborn pups are characterized by a light brown, or yellowish, woolly natal fur that is completely replaced by adult fur by 13 weeks (Payne and Jameson 1984).

Three subspecies of sea otter are recognized. Enhydra lutris kenyoni, which is thought to have historically ranged from the coast of Oregon to the Aleutian Islands, Enhydra lutris nereis occurs along the California coast and Enhydra lutris lutris, ranges from the Kuril Islands to the Kamchatka Peninsula and the Commander Islands (Wilson et al. 1991).

Sea otters have little or no body fat. To survive in an aquatic environment, they maintain an exceptionally high metabolic rate and rely on their dense fur for insulation.  The fur consists of an outer layer of protective guard hairs below which is an extremely fine dense under fur of approximately 100,000 hairs per cm² (Kenyon 1969). Oil from glands in the skin helps to enhance the water repellency of the fur. Sea otters must groom their fur frequently to maintain its insulative quality and water repellency. During grooming, the fur is cleaned, hair shafts are straightened and aligned to maintain loft, oil is distributed and air is blown through the fur where it is trapped as tiny bubbles that enhance the insulative capacity of the fur (reviewed in Riedman and Estes 1990).

The metabolic rate of the sea otter is 2.4 to 3.2 times higher than that of terrestrial mammals of a similar size. To fuel this internal heat production, free-ranging sea otters consume the equivalent of 23 to 33% of their body weight per day (Reviewed in Riedman and Estes 1990).

1.2       Distribution

Global Distribution

Sea otters are found in coastal areas throughout the North Pacific. The species once ranged fairly continuously from Northern Japan to central Baja California (Kenyon 1969), but the European fur trade caused near extinction of the species by the mid 1800s.

Today, the sea otter occupies about half of its historical range. In California, the sea otter population has grown from a small remnant population that survived the fur trade on the central California coast. Similarly, sea otters in southwestern Alaska have descended from small remnant populations that survived. Large areas to the south of the Gulf of Alaska, with the exception of California remain unoccupied except where sea otters were intentionally re-introduced. (Figure 1)

Figure 1. Distribution of historic and current populations of sea otters in the North Pacific.

Canadian Distribution

In British Columbia sea otters certainly occurred historically wherever there was suitable habitat. Since re-introduction of the sea otter to the British Columbia coast between 1969 and 1972, the population range has expanded beyond Checleset Bay; the site of re-introduction. Currently, the established sea otter range, extends along the west coast of Vancouver Island from Estevan Point to Cape Scott, then north east from Cape Scott to Hope Island. A second area extends from the Goose Islands to Cape Mark, at the edge of Milbanke Sound on the central coast of British Columbia (Figure 2). Individuals and groups of sea otters have been reported outside these ranges seasonally.

Figure 2. Distribution of sea otters in British Columbia.

Percent of Global Distribution in Canada

Not more than 5 to 10% of the global distribution of sea otters is in Canada. This is a crude estimate based on inspection of the sea otter distribution map in Watson et al. (1997). In terms of population size, British Columbia sea otters represent 3 to 4 % of the global population, however should declines in the sea otter populations of southwestern Alaska and California continue, this percentage could increase.

1.3       Population Size and Trends

Global

Estimates of the historic number of sea otters throughout the North Pacific range from 150,000 to 300,000 (Kenyon 1969; Riedman and Estes 1990). Midden remains indicate native people exploited sea otters before the arrival of Europeans and may have extirpated local populations (Simenstad et al 1978). Massive over exploitation during the European fur trade drove sea otters to the brink of extinction by the mid 1800s. Sea otters were protected in 1911 under the International Fur Seal Treaty. By that time less than 2000 otters remained scattered amongst 13 remnant populations (Kenyon 1969). Several of these remnant populations declined to extinction, perhaps as a result of their small size (Watson et al. 1997).

Currently less than 100,000 sea otters are estimated throughout the North Pacific. Until recently, the estimated world population was thought to be more than 100,000 animals (Estes et al. 1996) but dramatic declines in southwestern Alaska have reduced this estimate (Estes et al. 1998; USFWS 2002a).

The North Pacific sea otter populations include several remnant populations that have rebounded (California, southcentral and southwestern Alaska) and several re-introduced populations (southeast Alaska, British Columbia and Washington) founded by animals translocated from remnant populations in Alaska. The following discussion does not include any information about Russian sea otter stocks.

Remnant populations

The California sea otter population has generally experienced a positive growth trend of 5 to 7% per year although with two notable periods of decline. In the mid 1970s the population began to decline from 1789 individuals at about 5% per year. The decline was attributed to high rates of mortality from entanglement in submerged fishnets. This trend reversed following restrictions on net use and the population grew at about 5% per year, a rate that is notably lower than most other populations of sea otters (Estes 1990). In 1995 the population numbered 2377 but has since declined. Disease caused mortality appears to be higher than in other populations and is thought to be an important factor (see threats) (California Sea Otter Recovery Plan 2000).

In southcentral Alaska sea otters have recolonized most of their former range; however, the population was significantly affected by the Exxon Valdez oil spill in 1989. An estimated 750 (Garshelis 1997) to 2,650 (Garrot et al. 1993) sea otters died. Since the spill, the sea otter population in Prince William Sound has increased but not appreciably and larger than expected numbers of sea otter carcasses wash ashore periodically (USFW 2002b). The minimum population estimate for southcentral Alaska is 13,955. The adjusted estimate is 16,552 sea otters (USFW 2002b).

In southwestern Alaska sea otters re-established to a large population size as early as the late 1950s and the Aleutian Islands population  represented the greatest concentration of sea otters in the world (Kenyon 1969). By the 1980s the Aleutian Island sea otter population numbered between 55,100 and 73,700 (Calkins and Schneider 1985), however since then it has declined  precipitously . In 1992 the population in the Aleutians had declined to about 8,042 animals and by year 2000, the total uncorrected count was only 2,442 animals indicating a decline of 70% since 1992  (USFW 2002a). Surveys of other parts of southwestern Alaska indicate declines are widespread. The minimum population estimate is 33,203. The adjusted estimate is 41,474 (USFW 2002a).

Translocated populations

The occurrence of sea otters today in southeast Alaska, British Columbia and Washington is the result of sea otter translocations. Between 1965 and 1970, 708 sea otters from Prince William Sound and Amchitka Island in Alaska were re-introduced to southeast Alaska, Washington, Oregon and British Columbia. Only the Oregon re-introduction was not successful. In 1969 and 1970, 59 sea otters were re-introduced to Washington State. The Washington sea otter population currently includes more than 500 animals and since 1988 has grown at 8.8% a year (Jameson and Jeffries 2001). Between 1965 and 1969, 467 sea otters were released in southeast Alaska (Jameson et al. 1982). The minimum population estimate is 9,266, the adjusted estimate is 12,632 animals (USFWS 2002c). Between 1969 and 1972, 89 sea otters were released in British Columbia during three transplant attempts.

The success of the Washington and British Columbia re-introductions may have been improved by the addition of animals that emigrated from other re-introduction sites. The Washington population may have been  augmented by otters from the Oregon re-introduction that may have swam north in an attempt to return home, or in search of more suitable habitat. Likewise, the British Columbia re-introduction may have been augmented by otters from the Washington re-introduction that swam northward (Jameson et al. 1982). Recent genetic analysis that includes the British Columbia sea otter population may support this theory (Bodkin et al. 1999).

Population size and trends in British Columbia

No estimates exist of the number of sea otters that historically inhabited coastal British Columbia although they likely occupied most coastal marine waters. Following the intense fur trade of the 19^th Century, the last verified sea otter was  shot off Kyuquot in 1929 (Cowan and Guiguet 1960). After that, there are no confirmed sightings of sea otters on the British Columbia coast until re-introduction. Between 1977 and 1996, the British Columbia sea otter population increased at 18.6% per year (Watson et al. 1997). In areas near the site of re-introduction, the sea otter population has been at equilibrium density for sometime and (Watson et al. 1997) and the overall population growth rate is thus likely less than 18.6% per year. In 1998 the population was estimated to include 2000 animals along the west coast of Vancouver Island between Cape Scott and Estevan Point and an additional 500 animals off the central coast of British Columbia (Watson 2000).

2.      FACTORS AFFECTING VULNERABILITY AND CONTRIBUTING TO THREATENED STATUS

2.1       Habitat Requirements

Sea otters occur in shallow coastal waters not generally deeper than 40 m and seldom range beyond 1-2 km of shore, although in areas where shallows extend well offshore they have been found several miles out (Riedman and Estes 1990).

In British Columbia, rocky shorelines and reefs in exposed coastal areas are typical sea otter habitat. Specific kelp beds are used habitually as rafting sites for groups of otters, as well as for individuals (Loughlin 1977; Jameson 1989). Kelp beds are also used for foraging and are important habitat components. Soft-bottom communities are also very important foraging habitat for otters (Kvitek et al. 1992; Kvitek et al. 1993).

Sea otter density in an area may be related to substrate characteristics; areas with irregular rocky substrate appear to support more otters than areas with little relief. Certainly this is true in California (Riedman and Estes 1990; Laidre et al. 2001). Rocky substrate probably supports a greater variety of invertebrate prey species (Riedman and Estes 1990). In British Columbia, sea otters generally occur along stretches of coastline characterized by complex shorelines with small islets and offshore rocky reefs. Weather and sea conditions may influence use of habitat. During periods of calm weather, sea otters tend to move to offshore reefs but aggregate inshore during storms (Morris et al. 1981; Watson 1993).

Foraging behaviour, diet, social organization, reproduction and maternal care are influenced by and have influence on habitat use and requirements and for this reason are summarized here.

Foraging

Sea otters forage along the bottom as well as in kelp beds. Most foraging takes place in subtidal areas, although some otters, particularly young otters also forage in intertidal areas at high tide (Estes 1980; Harrold and Hardin 1986; VanBlaricom 1988). Intertidal foraging is common in British Columbia (J. Watson pers. comm. 2002). The depth at which sea otters forage may vary geographically and depends on prey availability. In California, sea otters typically forage in depths of less than 25 m and rarely exceed 40 m whereas in parts of Alaska, sea otters may forage in deeper waters (Riedman and Estes 1990).

Sea otters capture their prey with their forelimbs, often storing prey in the loose flaps of skin under the forelimb. Dives to obtain prey can range from 50 seconds to more than 3 minutes (reviewed in Riedman and Estes 1990). Prey are consumed at the surface. Sea otters use objects such as rocks as tools to break the shells of various clams and snails and are among only a few animals known to use tools.

Diet

Sea otters eat a wide variety of prey species and diet varies geographically, by duration of residency and also by individual.  In recently occupied rocky habitats, where sea urchins are abundant these are consumed preferentially probably because of ease of capture. As the abundance of preferred prey is reduced, the diet of the sea otter population in an area diversifies to include a larger array of invertebrates including various bivalves, snails, chitons, crabs, sea stars and even fish (Estes et al. 1981). Fish are important prey in some parts of the Aleutian, Commander and Kurile Islands (Estes and VanBlaricom 1985; Watt et al. 2000). Within a population, however, sea otters display a great deal of individual prey preference, and these preferences can persist for long periods of time (Estes et al. 1981).

Social Organization

Sea otters segregate by gender with males and females occupying spatially distinct areas. During the breeding season adult males occupy territories that overlap female areas (Garshelis et al 1984; Jameson 1989; Riedman and Estes 1990; Watson 1993). Male rafts occur in the range of established populations but occur at the periphery of the range of expanding populations (Jameson 1989; Watson 1993). During the breeding season, male rafts are composed largely of sub-adult males because the adult males have established territories closer to female raft areas. Breeding males re-join the male rafts outside the breeding season (Garshelis et al. 1984; Jameson 1989). Males generally expand into new areas first (Loughlin 1980; Garshelis et al 1984; Wendell et al 1986) while females use areas which have been occupied by sea otters for longer periods and expand into areas vacated by male groups (Garshelis et al 1984).

Movements and Home Range

Individual otters typically remain within an area known as a home range, which varies in size depending on  season, reproductive status, sex and age. In California adult male territories average 40 ha. Female home ranges are larger (Jameson 1989) but on an annual basis adult males may use a much larger area.  In California adult males on an annual basis utilized over 80 kilometres of coastline (Ribic 1982; Jameson 1989). Home ranges of males may be comprised of several heavily used areas interconnected by travel routes (Ribic 1982; Garshelis and Garshelis 1984; Jameson 1989). In Prince William Sound, sea otters were reported to travel as much as 100 km over several days (Garshelis and Garshelis 1984) and in California 127 km ( Jameson 1989), while one male moved 75 km in less than 23 hours (Jameson 1989).

Reproduction and Maternal Care

Female sea otters reach sexual maturity at three to five years (Bodkin et al. 1993) and males between 5 and 6 years of age (Riedman and Estes 1990). By five years of age all females have given birth (Bodkin et al. 1993; Jameson and Johnson 1993). Sea otters remain reproductive until death. In Alaska, female sea otters live 15 to 20 years whereas males live only 10 to 15 years (Riedman and Estes 1990).

Mating occurs year-round, however, in British Columbia peak pupping appears to occur in March and April (Watson 1993) and gestation, including a period of delayed implantation, last 6 months and thus most mating occurs in the fall. Sea otters are polygynous, males form pair bonds consecutively with several females throughout the year. Female sea otters produce one pup per year. Gestation is followed by birth in the water or on land of a single pup, twins are rare (Kenyon 1969; Jameson 1983; Jameson and Bodkin 1986; Jameson and Johnson 1993).

At birth a sea otter pup weighs 1.4 to 2.3 kg (Riedman and Estes 1990). Pups remain dependent on their mothers for the first 6 months after which they are weaned (Payne and Jameson 1984; Jameson and Johnson 1993). Throughout the 6 months of pup dependency, care is provided entirely by the female. During the first month the pup depends exclusively on its mother’s milk, by 4 months it feeds almost exclusively on prey provided by the mother, and by 5 months a pup can dive, capture and break open prey, and groom itself.

2.2       Biological Limiting Factors

It is thought that sea otter populations are limited by prey abundance (Riedman and Estes 1990). Other sources of natural mortality are predation and disease. Pup carcasses found at eagle nests suggest this may be a significant source of pup mortality in British Columbia (Watson et al. 1997). In the Aleutian Islands sea otter pups are found to comprise 5 to 20% of the eagle diet during the sea otter breeding season (Anthony et al. 1998). Killer whales, are an insignificant source of mortality in British Columbia, but have been observed pursuing and consuming sea otters in Kyuquot Sound (Watson 1993). In Alaska, however, killer whale predation is suspected of causing dramatic population declines in sea otters in the Aleutian Islands. Mammal eating killer whales may have switched to preying on sea otters because blubber rich seal and sea lion populations have declined in response to large-scale ecosystem changes (Estes et al. 1998). The situation in the Aleutian Islands and other parts of southwestern Alaska serves to illustrate that shifts in one part of an ecosystem can have far-reaching and unexpected effects on other parts of the system.

Various diseases have been documented in sea otters (Thomas and Cole 1996; Reeves 2002), but generally, disease is not thought to be a significant source of mortality in most sea otter populations. In California, however disease may be a major source of mortality and human activities may be a contributing factor (see threats).

 2.3      Threats

Oil Spills

Oil is the single most serious threat to sea otter populations. Oil can have both immediate and long-term effects on sea otters. Oil is a particular threat to sea otters because:

1)      Sea otters depend upon their fur for insulation. Oil destroys the water-repellent nature of the fur. As it penetrates the pelage it eliminates the air layer and reduces insulation by 70% (Williams et al. 1988). This usually results in hypothermia.

2)      Once the fur is fouled, sea otters ingest oil as they groom themselves. Ingested oil damages internal organs, which in turn has chronic and acute effects on sea otter survival.

3)      Sea otters prey upon benthic invertebrates, which can accumulate and store toxic hydrocarbons, during and after an oil spill.

4)      Sea otters are nearshore animals with strong site fidelity, and will remain in or return to oiled areas, additionally, they often rest in kelp beds, which collect and retain oil.

5)      Sea otters are often found in single sex aggregations, which can include hundreds of  animals. Thus large numbers of sea otters, (representing a substantial portion of the reproductive potential of a population) can become simultaneously fouled by oil.

Disease and Parasites

In general, disease is not thought to be a major cause of mortality among most sea otter populations (Riedman and Estes 1990). The southern sea otter population, however, has declined since 1995 and disease is now considered a significant contributing factor.

Over the past decade, a large variety of diseases including some that usually cause only sporadic mortality in other species have been reported in southern sea otters (Thomas and Cole 1996). Of recent concern are a large number of deaths from protozoal encephalitis caused by Toxoplasma gondii associated with waste from domestic cats (Lafferty and Gerber 2002; Miller et al. 2002). The prevalence of disease and variety of disease documented in the southern sea otter may be related to reduced immune competence, which could result from contaminants, genetic factors, or habitat/nutrition stress, or massive exposure to novel diseases (Thomas and Cole 1996; Reeves 2002). 

Among sea otters in Washington State several diseases have recently been detected.

Protozoal encephalitis was recently reported as cause of death in one of seven dead sea otters tested in 2000 and one of nine dead sea otters tested in 2002 (D. Lynch pers. comm. 2002). Leptosporosis, a disease usually associated with sea lions was confirmed as the cause of death of five of the nine animals test in 2002. An additional 18 carcasses were found in 2002, but have not been tested (D. Lynch pers. comm. 2002).  Of 16 sea otters live-captured in 2001, 14 tested positive for exposure to Morbillivirus, however, no  animals appear to have died from a Morbillivirus disease in 2002 (D. Lynch pers. comm. 2002).

Canine Distemper Virus (CDV), is a member of the genus Morbillivirus, and has recently been detected in river otters living in the marine environment in British Columbia. Transmission is thought to have been from terrestrial hosts (Mos et al. 2002). The disease can be deadly to populations that have not previously been exposed and persistent organic pollutants that suppress immune function are thought to exacerbate morbillivirus-related outbreaks in other marine mammals (Ross 2002).

Contaminants

Contaminant levels of British Columbia sea otters have not been assessed. Organochlorine contamination has been assessed in sea otters from California, southeast Alaska and the Aleutian Islands (Jarman et al. 1996). Total polychlorinated biphenyls (PCB) were found to be highest in sea otters from the Aleutian Islands (310mg/kg), followed by California (170mg/kg) and negligible in southeast Alaska. DDT was high in California (850mg/kg), but negligible in Alaska. There is concern that contaminants may affect sea otter populations in California and in the Aleutian Islands (Estes et al.1997). Immune suppression resulting from contaminants is a potential cause of the higher than expected frequency and variety of disease now documented in the southern sea otter, but there may be other factors as well (Thomas and Cole 1996; Reeves 2002).

Marine Biotoxins

The toxin responsible for Paralytic Shellfish Poisoning (PSP), produced by a dinoflagellate, can accumulate to toxic levels in filter-feeding bivalves. Butter clams, which tend to accumulate the biotoxin PSP, form an important component of the sea otter diet. A large die-off of sea otters in the Aleutian Islands in the summer of 1987 was in part attributed to PSP poisoning (DeGange and Vacca 1989). One study has shown that sea otters may be able to detect PSP and avoid clams with lethal concentrations (Kvitek et al. 1991), but more extensive study of this topic is warranted (R. Jameson pers. comm. 2002).

Domoic acid, a biotoxin produced by a diatom can accumulate to lethal levels in both invertebrates and fish. First detected on the west coast of North America in 1991, it has been identified as the cause of several large die-offs of sea birds and sea lions in California. So far only one case has been confirmed of a sea otter in California dying from domoic acid poisoning.

Threats resulting from human activities within the sea otter range

Entanglement in fishing gear

Incidental drowning in sunken gill nets was a significant threat in California during the late 1970s and early 1980s and contributed to a population decline (Wendell et al.1985). As a result, restrictions in the use of gill and trammel nets in waters less than 30 fathoms (65 metres) were implemented (Riedman and Estes 1990) and the population decline reverse. Incidental entanglements in fishing gear have also been reported in Alaska (USFWS 1994) and Washington. At least 3 sea otters have been accidentally taken in the Makah tribal set-net fishery for salmon (Gerber and VanBlaricom 1998). The extent of accidental drowning of otters in fishing gear in British Columbia is unknown, although as the sea otter population expands into areas of gill-net fisheries, there may be local effects (Watson et al. 1997).  Seventeen sea otters are known to have died in various crab pots and fish traps in California and Alaska (reviewed in Richardson and Allen 2000). Crab pots may present a threat to sea otters, particularly since they are set in shallow waters within the species diving depth range.

Collisions with vessels

One otter carcass recovered from Kyuquot Sound had injuries that could have been caused by a boat propeller (Watson et al. 1997). This threat is probably minor and localized at this time.

Illegal kill

There are no statistics on illegal kill of sea otters in British Columbia, although it is suspected in some areas. 

Disturbance

The extent of disturbance of resting and foraging otters from boat traffic is largely unknown but unlikely to be significant at this time. Disturbance may become a more significant local effect in the future as the sea otter population expands its range into more populated areas, and public awareness and interest in the British Columbia sea otter population grows.

Genetic Diversity

Genetic diversity is of concern to conservation of species that have been reduced to a small size and then allowed to increase; a phenomenon called a bottleneck. The loss of genetic diversity through inbreeding in small populations will reveal deleterious recessive alleles, resulting in lower fecundity, higher rates of juvenile mortality and an overall reduction in population growth rate. Furthermore loss of diversity reduces a population’s ability to respond to unexpected environmental or biological events.

A recent genetic study shows that current sea otter populations have significantly less genetic variation than their pre-fur trade ancestors (Larson et al. 2002a). This is attributed to the severe population bottleneck that resulted when as much as 99% of the sea otter population was lost to the fur trade (Kenyon 1969; Riedman and Estes 1990). Among the current populations there are no significant differences in genetic variation between remnant populations and translocated populations, even though translocated populations experienced two bottlenecks (Larson et al. 2002b).

That reduced genetic diversity is apparent in extant populations compared to pre-fur trade ancestors (Larson et al. 2002b) indicates genetic diversity should remain cause for concern in the long-term as it increases the risk of extinction from random events. A case in point, is the current situation in California. There, the decline observed in the southern sea otter population since 1995 seems to be the result of disease. Loss of genetic diversity and contaminants, however, are factors speculated to contribute to the higher than expected rates of disease susceptibility (Reeves 2002).

2.4       Ecological Role

Sea otters play a key role in structuring rocky nearshore benthic communities throughout their range (Estes and Palmisano 1974). Sea otter predation affects the abundance and distribution of a variety of invertebrate species. However, their effect on sea urchins and the secondary effects on habitat have important consequences for nearshore benthic communities. Where sea otters are absent, sea urchins dominate much of the rocky nearshore habitat and graze kelp and other seaweeds. These habitats, often known as sea urchin barrens, are characterized by a lack of seaweed. Sea otters prey on sea urchins, and by doing so, release fleshy algae, particularly kelp, from intense grazing pressure. The result is the growth of kelp, which creates a very different nearshore community; areas with sea otters are dominated by seaweed, and large invertebrates such as sea urchins are restricted to areas inaccessible to sea otters. The relationship between sea otters, sea urchins and kelp was first described  in the Aleutian Islands (Estes and Palmisano 1974). Since then studies in British Columbia (Morris et al. 1981; Breen et al. 1982; Watson 1993), Washington State (Kvitek et al. 1989; Kvitek 1998) and California (Laur et al. 1988) have provided supporting evidence for this general paradigm in rocky subtidal habitats. 

The physical structure and the biological productivity of kelp have significant consequences for coastal food webs. In Alaska and California kelp forests enhance nearshore productivity, becoming a significant source of food particularly in the form of detritus from drift algae. Where sea otters and kelp forests occur, kelp-derived carbon accounts for more than half the carbon in kelp forest food webs. In these habitats nearshore productivity, measured as growth of invertebrates, is 2 to 5 times higher than in areas where sea otters and kelp are absent (Duggins et al. 1989). Kelp also enhances the structure of the water column by creating a complex three-dimensional habitat that supports a large variety of invertebrate and fish species (Bodkin 1988; Ebeling and Laur 1988; Laur et al. 1988; Duggins et  al. 1990; Carr 1991). Nearshore fish have been shown to be more abundant in areas with kelp beds than in urchin barrens or in areas without kelp. Furthermore stands of kelp dampen tidal currents and wave height and influence dispersal, settlement rates and recruitment of benthic invertebrates and rockfish that live within them (Duggins et al. 1990; Carr 1991).

Not only does kelp contribute significantly to nearshore productivity where it grows, but a recent study has shown that kelp beds may have far reaching implications for marine productivity and provide significant amounts of carbon to deep benthic areas, through dispersal of drift kelp (Harrold et al. 1998). Further research is needed to assess the generality of this finding and the significance this may have for deepwater fisheries resources.

Sea otters also exert ecological effects on soft bottom communities although their role in these communities is less well understood. Where sea otters prey on clams, they can limit the size, abundance and distribution of these species. As well as influencing these species through direct predation, sea otters may exert secondary community level effects. By disturbing the sea floor and adding shell litter (hard substrate) sea otter predation may support settlement and recruitment of various species that require hard substrate (Kvitek et al. 1992; Kvitek et al. 1993;).

2.5       Socio-Economic Considerations

The section provides a brief summary of the prevailing dichotomy of views regarding sea otters and their recovery. Historically the sea otter was hunted by First Nations and used for clothing, regalia and gifts. In the 1700 and 1800s the luxuriant fur was highly prized by European fur traders, who hunted and bartered for pelts which were sold in Asia. This trade resulted in an intensive commercial fur trade that led to the near extinction of the species. In 1911 when sea otters were protected under the International Fur Seal Treaty, the total North Pacific population was not more than 3% of pre-exploitation levels. Since 1911, the sea otter has been protected from commercial harvest throughout much of its range. Under the United States, Marine Mammal Protection Act, only First Nations in Alaska may harvest sea otters for subsistence purposes and for creating handicraft and traditional clothing for sale and trade (USFW 1994; Lianna Jack pers. comm. 2002).

For many people the re-introduction of the sea otter represents a return to the pristine natural order of the marine ecosystem (Gerber and VanBlaricom 1998). While for others, the presence of sea otters also underlines the fragility of the marine ecosystem and the need for greater protection of this environment (Watson and Root 1996), particularly from oil spills. For other people, the re-introduction of the sea otter is viewed as a threat to socially and economically valuable invertebrate resources, such as sea urchins, Dungeness crab, butter clams, geoducks and abalone.

There are two predominant views regarding the effects of sea otters on nearshore marine communities. One view, based on studies of the community ecology of sea otters, recognizes the ecologically important role of sea otters. Collectively, these studies demonstrate that the presence of sea otters results in increased diversity and productivity of nearshore marine ecosystems. The second view focuses on the direct effects sea otters  have on the abundance of invertebrates. This view is of particular concern to the commercial shellfish industry, to the First Nations along the west coast of Vancouver Island, to recreational harvesters and, potentially in the future, to the shellfish aquaculture industry.

Concern over the effects of sea otters on invertebrate abundance arises because present-day commercial and recreational invertebrate fisheries developed over the past 100 years, as many invertebrate populations flourished in the absence of sea otter predation. As the sea otter population recovers and re-populates its historic range, declines in the abundance of many invertebrates are expected. Commercial fisheries in British Columbia for invertebrate species such as sea urchins, butter clams and sea cucumbers will not be possible in areas with sea otters.

In British Columbia, members of the commercial shellfish industry are concerned about declines in the abundance of economically important invertebrate resources in areas occupied by sea otters and about declines anticipated in areas not yet inhabited by sea otters. First Nations of the west coast of Vancouver Island are concerned with the impact sea otters are having on invertebrate food resources formerly available to their communities. The Nuu-chah-nulth First Nation, of the west coast of Vancouver Island, hold the view that sea otters should be managed to control their numbers in certain areas as a means of protecting local subsistence shellfish resources from sea otter predation and to make sea otters available for cultural and ceremonial uses.

Declines in the abundance of abalone, sea urchins and pismo clams were documented in California with the expansion of sea otters in the 1970s and 1980’s but concerns about their impact on the shellfish industry in California date back to the 1950s (Silva 1982; Estes and VanBlaricom 1985).

Although it is evident sea otters can and have reduced the abundance of many invertebrate populations (Estes and Palmisano 1974; Morris et al. 1981; Breen et al. 1982; Watson 1993; Watson and Smith 1996), invertebrate stocks can and do decline in the absence of sea otters. For example abalone populations in California and in British Columbia (reviewed in Watson 2000). These examples may serve as cautionary reminders that ecosystems are complex. Estes and VanBlaricom (1985) point out that in addition to understanding how sea otters affect invertebrate abundance, it is also important to understand other factors that can strongly affect invertebrate populations.

Although the economic cost of sea otters is understood, there has been little effort made to identify the economic benefits of sea otters. Studies show that kelp beds support a greater abundance of fish and invertebrates and one study suggests kelp may contribute significantly to the productivity of offshore habitats. In Washington State it has been suggested that sea otters may benefit recreational and commercial fisheries for rockfish and lingcod by increasing kelp bed habitat. Currently it seems evident that both marine eco-tourism and the herring-spawn-on-kelp fishery should benefit from the recovery of the sea otter population.

Eco-tourism is a valuable industry in British Columbia and one that continues to grow.  Sea otter viewing is included in the itinerary of eco-tour operators on the west and northeast coasts of Vancouver Island.  In California sea otters are a major tourist attraction in Monterey and Santa Cruz. Tourism generated almost 1/3 of all jobs in the area during the late 1970s (Silva 1982).

The herring-spawn-on-kelp fishery depends on a reliable supply of suitable quality kelp. Kelp abundance and quality can in fact limit the value of this fishery (Shields et al. 1985).  An increase in the abundance of giant kelp (Macrocystis integrifolia) could benefit this industry and provide increased opportunities to export kelp for this and other purposes (Watson and Smith 1996).

2.6       Knowledge Gaps

The following describes key knowledge gaps regarding population, biology and ecology of sea otters in British Columbia.

Survey Requirements

Counts of the British Columbia sea otter population are required to be able to assess population growth rates, estimate population size and coastal distribution. Sea otters are challenging to count and sufficient time series data from routine population counts using consistent methods are required to be able to estimate growth rates, population size and distribution, parameters needed to assess the status of the population.

Biological/Ecological Research Requirements

Significant knowledge gaps exist with regard to understanding habitat use, particularly seasonal habitat use by sea otters. Sea otters are thought to remain primarily in exposed coastal areas, however use of inlets and protected areas may occur in winter and during inclement weather. Understanding habitat use is key to identifying and delineating critical habitat, as defined under the Species At Risk Act.

Little is known of the genetic diversity of the British Columbia sea otter population. Lack of genetic diversity could affect recovery of the population, by increasing susceptibility of the population to random environmental or biological events, and/or reducing population growth rates. Knowledge of levels of genetic diversity among BC sea otters, including comparing west coast Vancouver Island sea otters and central BC coast sea otters and comparing these with other remnant and translocated populations would determine whether genetic diversity among BC sea otters is cause for concern

Threat Clarification Research Requirements

Oil spills are the single biggest threat to sea otter populations. While the effect of an oil spill to sea otters is well documented, research is needed to assess options for protecting the population and its habitat from oil. There are other threats as well that may be significant but are less well understood. Clarification of these threats is needed. These include, disease, contaminant levels, entanglement in fishing gear, illegal kills and human disturbance. Interactions with human-related activities can be expected to increase as the sea otter population expands into areas previously unoccupied. These are threats that have been identified and in some cases quantified in other sea otter populations. For example, entanglement in fishing gear was cause for concern in California in the 1970’s  and resulted in a population decline. Presently, the southern sea otter population is declining again, this time disease, contaminants and genetics are implicated. There may be additional limiting factors that have not been identified. Sea otter populations have the capacity to decline precipitously for reason poorly understood but are related to complex ecosystem changes as a result of ocean regime shifts, e.g. the situation in southwestern Alaska. There is a need to support research on potential limiting factors and to maintain information exchange or collaboration with researchers and managers working on populations of sea otters in other jurisdictions.

III.           RECOVERY

RECOVERY GOAL

Ensure that the sea otter population in British Columbia is sufficiently large and adequately distributed so that threats, including catastrophic events, such as an oil spill, would be unlikely to cause extirpation of the species or diminish the population such that recovery to pre-event numbers would be very slow.

SHORT-TERM RECOVERY OBJECTIVES (~ 5years)

To be able to achieve the goal of the sea otter recovery strategy all of the objectives should be met.

1.      Specify a minimum population size that would correspond to a viable, sufficiently large population no longer at risk. If this can not be achieved within 5 years, then a best estimate will be made following the precautionary approach.

2.      Identify the adequate geographic distribution that is needed to ensure the population would survive a catastrophic event such as an oil spill, and be able to rebound demographically within a relatively short period of time to pre-catastrophe numbers. If this can not be achieved within 5 years, then a best estimate will be made following the precautionary approach.

3.      Mitigate threats to sea otters and their habitat to ensure adequate protection and recovery of the population.

      APPROACHES TO ACHIEVE RECOVERY

The approaches identified by the Recovery Team can be broadly grouped into three categories – Research, Protection, and Communication. As information from these approaches becomes available, the Sea Otter Recovery Strategy will be updated and specific measurable goals and objectives will be made as well as new strategies with which to achieve them.

3.1       Research

In order to achieve a minimum size and adequate distribution of the sea otter population, research is needed to:

·        determine the current size and the target population size,

·        determine the current distribution and the target distribution,

·        determine the critical habitat sea otters need,

·        determine and/or clarify the threats to sea otters,

·        fill knowledge gaps (including other factors that may be limiting population recovery).

Population monitoring and research

·        Develop a census method suitable for the British Columbia coast and undertake regular counts of sea otters. Use these data to monitor population size, growth rate and distribution and as a key input to defining a minimum population size and distribution as identified in Objectives 1 and 2.

Sea otters are difficult to count and results are strongly influenced by sea state, weather, time of day and sensitivity of the animals to approach. There can be considerable variation among multiple counts, with the result that estimating population size and population growth may require regular counts and a long time series to detect trends.

·        Develop a sea otter carrying capacity model for the British Columbia coast as an input to estimating a minimum population size.

·        Develop a model to determine an adequate geographic distribution of the sea otter population in British Columbia.

·        Assess the feasibility of translocating sea otters to achieve this distribution.

Habitat

·        Develop a method to assess and identify critical habitat for sea otters.

·        Identify important rafting and foraging areas and seasonal variations in these as part of identifying and delineating critical habitat.

·        Carry out research on the movements and home range patterns of sea otters.

·        Develop models using sea otter distribution, rafting and foraging area data as well as oil spill trajectory information to identify areas of the coast where sea otters are particularly susceptible to oil from spills.

Clarify threats and limiting factors to population recovery

Sea otter populations in both California and southwestern Alaska are declining. Predation and disease are suspected causes and without adequate research these factors may have gone undetected. An important strategy to ensure recovery of the British Columbia sea otter population is then to support research that clarifies threats and factors that may limit population growth and range expansion. Such research could include, but is not limited to, the following:

·        Develop a program to monitor the health of the sea otter population by documenting body condition, disease and contaminant burdens in live-captured sea otters and through necropsy of fresh carcasses when the opportunity arises.

·        Assess the genetic diversity of the British Columbia sea otter population and monitor population measures that are indicative of fitness.

·        Prey abundance is thought to be the main factor limiting growth in most sea otter populations. Research should be carried out to assess the effect or potential effect of prey abundance reduction by invertebrate fisheries on the rate, or extent of geographic expansion of the sea otter range.

·        Assess the occurrence and significance of sea otter entanglement in fishing gear.

·        Assess the occurrence and significance of illegal killing of sea otters in British Columbia.

3.2       Protection

There is a need for greater efforts to protect sea otters and their habitat from acute and chronic threats to achieve recovery of the population. Approaches to protection should include, but are not limited to the following:

·        Develop an oil spill response plan specifically for sea otters. Oil spills remain the single biggest threat to sea otters. Such a strategy should include several response options depending on the severity of the oil spill. It should include detailed response procedures and identify equipment, training, personnel and facilities required.

·        Ensure a readiness of sufficient funds, equipment and personnel to carry out the oil spill response plan.

·        Assess the feasibility of protecting sea otter habitat in areas where susceptibility to oil contamination or other threats exist, for example, areas in proximity to tanker routes and proposed exploration and drilling sites.

·        Identify opportunities to make designations for habitat protection e.g. MPAs or protected areas to protect critical habitat.

·        Ensure there is adequate levels of protection to enforce regulations and procedures in response to threats, including new or previously less well known threats should these prove to be significant, e.g. mortality from entanglement in fishing gear or illegal kills.

3.3       Communications

Communication to the public and others is important to garner support and understanding for the need to protect sea otters and their habitat. Until recently sea otters were absent for almost one hundred years from Canada’s fauna. With their return, there is a need to raise the level of understanding and appreciation of the role of sea otters in structuring nearshore ecosystems and of the threats to them and to their habitat. This approach should include, but is not limited to the following:

q          Public communications materials, school curricula, booklets, brochures, and websites to inform the public of the status of sea otters, and threats to their recovery.

q          Sea otter watching guidelines for eco-tour operators and the general public. Human disturbance of sea otters from vessels and people are not yet considered to be significant threats, but as the sea otter population expands, this threat may become significant.

·        Establish and maintain collaboration or information exchange about research and protection of sea otters and their habitat.

CONSIDERATIONS FOR RECOVERY

4.1       Recovery Potential and Rationale

Ecological and Technical feasibility of species recovery

Sea otter recovery is ecologically feasible. The sea otter has a strong inherent capacity to rebound demographically from a small founding population, as illustrated by the growth of several translocated populations including the population in British Columbia. Food is generally viewed as the main factor that limits population growth. Much of the British Columbia coast remains unoccupied by sea otters and for this reason population recovery is unlikely to be limited by food. One of the largest threats to sea otters, however, is an oil spill. Such an event could occur at anytime and could significantly impede recovery of the population. In addition, concerns about the reduction of socially and economically valuable invertebrate resources, by sea otters, could also prove to be a technical challenge to gaining support for sea otter recovery. Finally, sea otter populations can decline from threats that are not well understood, as is occurring in California, or from complex ecosystem changes associated with ocean regime shifts as is occurring in southwestern Alaska.

4.2              Recommended Approach/ Scale of Recovery

The single species approach has been chosen because the issues that threaten sea otters are somewhat unique to the species. However, sea otters eat abalone and limit their size and abundance and occupy a range that overlaps that of abalone. A multi-species approach may be required in the future.

4.3              Anticipated Conflicts or Challenges

As the sea otter population expands to reoccupy its former range and preys on populations of various shellfish, conflicts with recreational, commercial and aboriginal (food, social, ceremonial) invertebrate fisheries are likely to occur. Calls to manage sea otter abundance can be expected from First Nations or others.

Additional challenges may be; determining the minimum population size and an adequate distribution and addressing the threat of oil spills.

ACTIONS ALREADY COMPLETED AND/OR UNDERWAY

Surveys

Sea otter counts have been made since 1977. Between 1977 and 1987 counts were made  by Fisheries and Oceans Canada. Between 1988 and 2000, most counts were made by Dr. Jane Watson as part of her Ph.D. work and on-going study of the effects of sea otters on nearshore communities, although see Watson et al. (1997) for a summary of survey effort and results between 1977 and 1995. In 2001 and 2002, Fisheries and Oceans Canada began work to develop a survey method suitable for on-going assessment of the sea otter population in BC and has made aerial and boat-based counts throughout the range of the sea otter population. As part of a Habitat Stewardship project in 2002, the Nuu-cha-nulth Tribal Council (NTC) biologist made boat-based counts in areas along the west coast of Vancouver Island in 2002.

Oil spill response for protection of sea otters

A symposium was held in 1995 at the Vancouver Aquarium Marine Science Centre, to discussed procedures necessary in the event of a spill to effectively protect the population.

Watson J.C. 1995. Sea Otters and Oil: An overview. Summary of a meeting held February 22, 1995 at the Vancouver Aquarium. 85pp.

Education

As part of a Habitat Stewardship project in 2002, the NTC developed and presented workshops to their community members to inform them of the biology and ecology of the sea otter and conflicting views about their role in the ecosystem.

As part of a Habitat Stewardship project in 2002, the Johnstone Strait Marine Mammal Interpretative Society, created a museum in Telegraph Cove depicting local marine mammals. Sea otters are a component of the display.

Listing Status

Sea otters in British Columbia were listed by COSEWIC as Endangered in 1978, re-assessed and down-listed to Threatened in 1996, and re-assessed as Threatened in May 2000 based on the 1996 status report.

Scientific documents and publications

Monroe, W. T. 1985. Status of the sea otter, Enhydra lutris in Canada, Canadian Field-Naturalist 99: 413-416

MacAskie I.B. 1987. Updated status of the sea otter (Enhydra lutris) in Canada. Canadian Field-Naturalist 101:279-283.

Watson, J.C. 1993. The effects of the sea otter (Enhydra lutris) foraging on shallow rocky communities off northwestern Vancouver Island, British Columbia. Ph.D. dissertation. Univ. of California, Santa Cruz. 169 pp.

Watson, J.C. 1990. The effects of the Nestucca oil spill on the British Columbia sea otter population and its environment. Unpublished report submitted to the Canadian Department of Fisheries and Oceans. DSS Contract No. FP597-9-0478/01-XSA.

Watson, J.C., G.M. Ellis,  T.G. Smith, J.K.B. Ford. 1997. Updated status of the sea otter, Enhydra lutris, Canada. Can. Field-Nat. 111(2): 277-286.

Watson, J.C. and T.G. Smith. 1996. The effect of sea otters on shellfisheries in British Columbia: A review. Ed. by C.M. Hand and B.J. Waddell. Can. Tech. Rep. Fish. Aquat. Sci. No. 2089 pp 262-303.

Sea Otter Recovery Team

Formed in June 2002, the team includes representatives from Fisheries and Oceans Canada, Parks Canada, BC Ministry of Water, Land and Air Protection, BC Seafood Alliance, the U.S. Fish and Wildlife Service, the Washington State Department of Fish and Wildlife, the Sierra Club of British Columbia, World Wildlife Fund Canada, Nuu-cha-nulth Tribal Council, the Underwater Harvesters Association, Malaspina College and an expert (retired) from the U.S. Geological Survey.

STATEMENT OF WHEN ONE OR MORE ACTION PLANS IN RELATION TO THE RECOVERY STRATEGY WILL BE COMPLETED.

A Sea Otter Recovery Action Plan that outlines specific programs, costs and timelines will be completed within 2 years of approval of the sea otter recovery strategy.

EVALUATION

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Personal Communications 

Lianna Jack  - Alaska Sea Otter Commission

Ron Jameson  – sea otter biologist (retired), formerly United States Geological Survey

Deanna Lynch  - United States Fish and Wildlife Service

Jane Watson  - Malaspina University College

V.               GLOSSARY OF TERMS

Acute effect – An adverse effect resulting from a single exposure to a substance.

Benthic – A term that refers to the ocean bottom or seabed. Benthic animals are those which live on or in the seafloor.

Carrying capacity – This is the maximum population size that can be supported by an area or environment. This is a theoretical concept. In reality carrying capacity changes as conditions change. This is also known as “K”. Also see equilibrium density.

Chronic effect - An adverse effect resulting from long-term exposure to a substance.

Critical habitat – The ecosystems upon which a species (usually a species at risk) depends.

Deleterious recessive alleles – Alleles are alternate forms of genes (brown, blond, red and black hair represent different alleles of the same gene). The effect of a single recessive allele is masked by a dominant allele, however when an individual inherits two recessive alleles it is potentially harmful. This often occurs due to inbreeding in small populations. Also see genetic diversity.

Demography – A term that refers to the characteristics of a population. Usually processes which affect the size of the population, birth rates, death rates, immigration, and emigration.

Dinoflagellate – A microscopic organism that drifts in the water. Some species cause red tide.

Equilibrium density – The density of a population at carrying capacity. This is the state at which the population size remains almost steady with birth and immigration rate equal to the death and emigration rate.

Extant population – A population in existence.

Extinct – A species that no longer exists.

Extirpated – A species that no longer exists in part of its range, for example, in Canada, but still exists elsewhere.

Endangered – COSEWIC defines this as a species facing imminent extirpation or extinction.

Fecundity – The number of offspring produced by an individual during some period of time

Genetic diversity – This is a measure of the number of alternate forms (alleles) of genes in a population. Populations that have become small generally have low genetic diversity. Genetic variability is what ultimately allows individuals to cope with changing environments. Also see deleterious recessive alleles

Hypothermia – a condition in which the body core temperature drops to a dangerously low level.

Immune suppression – The ability of the immune system to fight off infection or disease is reduced. Contaminants such as PCBs, lead and mercury may cause immune suppression in many animals.

Invertebrates – Animals without backbones, for example shellfish.

Metabolic rate – The rate at which an animal uses energy to maintain body temperature and activity. Sea otters, which must consume 25-33% per day of their body weight in food to maintain their elevated body temperature and activity level, have high metabolic rates.

Polygynous – In a polygynous mating system the male mates with more than one female.

Precautionary approach – An approach to management that says we must be very cautious when making decisions about systems we do not fully understand.

Raft – An aggregation of resting sea otters

Recruitment – Increases to a population caused by the addition of young animals to the adult population.

Soft-bottomed communities – The animals (often invertebrates) and plants that live in and on gravel, mud and sand bottoms. Organisms such as clams, worms and sea pens are members of soft-bottomed communities

Special Concern – COSEWIC defines this as a species of concern because of characteristics that make it particularly sensitive to human activities or natural events.

Threatened – COSEWIC defines this as a species that is likely to become endangered if limiting factors are not reversed.

I.                  SEA OTTER RECOVERY TEAM MEMBERS