(DRAFT) - Taxonomy
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
TAXONOMY
NAME - sea lion, northern
OTHER COMMON NAMES - stellar sea lion
ELEMENT CODE -
CATEGORY - Marine Mammals
PHYLUM AND SUBPHYLUM - ,
CLASS AND SUBCLASS - Mammalia,
ORDER AND SUBORDER - , Pinnipedia
FAMILY AND SUBFAMILY - Otariidae,
GENUS AND SUBGENUS - Eumetopias,
SPECIES AND SSP - jubatus,
SCIENTIFIC NAME - Eumetopias jubatus
AUTHORITY - Gill, 1866
TAXONOMY REFERENCES - 125, 178 and 170
COMMENTS ON TAXONOMY -
There are several genera in this group, two of which occur in Alaskan
waters: the northern fur seal, Callorhinus ursinus, and the Steller sea
lion. Steller sea lions are the largest representatives of the family
Otariidae and show pronounced sexual dimorphism.*170*
Also known as Steller Sea Lions.*125*
Taxonomy - 1 (DRAFT) - Status
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
STATUS
Coded Status
T: Federal Threatened
Migrant
Subsistence
See Comments
REFERENCES FOR STATUS - 170, 179 and 274
COMMENTS ON STATUS -
Prior to 1972, the Alaska Department of Fish and Game funded an ongoing
program to monitor the population status of sea lions in the Gulf of Alaska.
When management authority was rescinded in 1972, the State continued to
address management concerns such as the impacts of coastal development and
the interactions with fisheries, under funding from a variety of sources,
as available. However some of the programs have been terminated. The
responsible Federal agency (National Marine Fisheries Service) has not
developed an adequate management program on sea lions.*170*
Based on a preliminary review of a status report on the Northern (Steller)
sea lion in Alaska, NMFS has published an advance notice of proposed
rulemaking (May 6, 1988) to consider designating this population as
depleted. If this population stock is designated as depleted, the MMPA
requires the application of certain additional restrictions on taking and
importation. In this instance, based on recent court decisions,
restrictions on commercial fishing in the North Pacific Ocean and Bering Sea
are possible consequences.*179*
Steller sea lions directly interact with fisheries by taking fish off gear
and by damaging gear, especially nets. During such interactions, sea lions
may be caught and killed incidentally. Although interactions are poorly
quantified, sea lions interact with most major Alaskan finfish fisheries,
including salmon gillnet, troll, and purse seine fisheries, halibut
(Hippoglossus stenolepis) and sablefish (Anoplopoma fimbria) longline
fisheries, and groundfish trawl net fishery (Mate 1980, Strombom 1981,
Loughlin et al. 1983, Loughlin and Nelson 1986).*125*
Status - 1 (DRAFT) - Distribution
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine BB2
Marine RB.
Marine OW0
REFERENCES FOR NWI - 125
Habitat Associations - 1 (DRAFT) - Food Habits
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 125
LIFESTAGE FOOD FOOD PART
General Molluscs
General Bivalve Molluscs
General Snails
General Squid, Octopus
General Chondrichthyes
General Osteichthyes
REFERENCES FOR GENERAL FOOD - 125
COMMENTS ON FOOD -
Steller sea lions eat a wide variety of invertebrates and fishes. In early
studies in the Gulf of Alaska, (1945-1960) invertebrates (primarily clams,
mussels, and snails), greenling and Pacific sand lance were the more
dominant species in the diet of sea lions. In most recent studies
(1975-1978), herring and walleye pollock were the most important species.
The seven most important prey found in recent studies in the Gulf of Alaska
in order of their importance were: walleye pollock, herring, squids,
capelin, salmon, Pacific cod, and sculpins. Although salmon and herring
were among the top seven, they are seasonally abundant fishes and are only
available to most sea lions at limited times and in specific locations. Most
of the top ranked prey of sea lions are off-bottom schooling species. Use
of this prey type may be important in minimizing foraging effort and
conserving energy; energy expenditure may be higher in procuring more
solitary species.*170*
Food Habits - 1 (DRAFT) - Environment Associations
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Bottom Type [Aquatic]: Sand
G Bottom Type [Aquatic]: Gravel
G Bottom Type [Aquatic]: Rubble
G Bottom Type [Aquatic]: Boulders
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 125
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
In California, increasing water temperatures (potentially affecting the
distribution of prey and/or the distribution and expansion of California
sea lion populations) have been suggested to have caused the loss of the
southernmost rookery on San Miguel Island during the late 1970s
(Bartholomew and Boolootian 1960, Bartholomew 1967, Antonelis and Fiscus
1980, Bonnel et al. 1983).
Habitats used for haulouts and rookeries include rock shelves, ledges, or
slopes and boulder, cobble, gravel, or sand beaches. The locations where
sea lions haul out may be determined by the season, suitable exposure,
proximity to food sources, tradition of use, and proper substrate (Clkins
and Pitcher 1982a). Sea lions use specific locations according to their
age and the season of the year. Adults and dependent young tend to
concentrate on breeding rookeries from May throught October, dispersing to
other haulouts the remainder of the year. Nonbreeding adult and subadult
males may congregate on areas adjacent to rookeries during the summer
whereas independent juveniles tend to avoid rookeries (Gentry 1970,
Sandegren 1970, Calkins and Pitcher 1982a).*125*
Environment Associations - 1 (DRAFT) - Life History
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
LIFE HISTORY
PHYSICAL DESCRIPTION:
Steller (or northern) sea lions belong to the family Otariidae or "eared
seals." Steller sea lions, particularly large adult males, have short manes
and extremely large necks and front shoulders which give the appearance of
the mained terrestrial lion.*170*
At birth sea lion pups have a chocolate brown coat with a frosty appearance
since the tips of the hairs are colorless. There appears to be a gradual
lightening in coloration as the animals get older. Most adults show a
yellowish cream coloration on the back, although some may remain darker.
Nearly all males remain darker on the front of the neck and chest. Some
animals may even have a red coloration.*170*
Steller sea lions are the largest representatives of the family Otariidae
and show pronounced sexual dimorphism. In females growth is rapid during
the first four years but slows by the fifth year with little growth after
age six. Males continue to grow until the eleventh year. Although there
is great variability between year classes, all females probably reach
adult size and maximum skeletal growth by their sixth year and males reach
adult size as indicated by maximum skeletal growth in their eleventh year.
*170*
REPRODUCTION:
Throughout the Steller sea lion's range, births occur from mid-May to
mid-July, peaking in June (Scheffer 1945, Pike and Maxwell 1958, Mathisen et
al. 1962, Thorsteinson and Lensink 1962, Gentry 1970, Sandegren 1970, Mate
1973, Pitcher and Calkins 1981, Withrow 1982). Nearly 70% of the births on
Sugarloaf and Marmot islands occur from 5 to 16 June (Pitcher and Calkins
1981). The daytime (0500-2100 hours) birth rate is twice that at night
(2100-0500 hours), and births occur most frequently in the morning and
evening (Gentry 1970).*125*
Births generally take place at sites above high water and away from
territoral males. These sites may be actively competed for by the
preparturient females (Gentry 1970, Sandegren 1970, Edie 1977).*125*
Sea lions are able to give birth to single pups annually; twin births are
rare (Gentry 1970). Newborn pups are highly precocial. They are born with
their eyes open and are able to crawl and swim, if necessary, a few minutes
after birth (Gentry 1970, Sandegren 1970, Higgins 1984). Both vocal and
olfactory cues are important for mother-pup recognition (Gentry 1970,
Sandegren 1970, Ono 1972). Females accept only their own pups and are
highly aggressive toward others, often lifting and tossing alien pups that
approach them (Gentry 1970, Sandegren 1970). Pups are less discriminating
and occasioanlly will approach females other than their mothers (Higgins
1984).*125*
Females with pups less than 2 months old feed at sea between visits to the
rookery to nurse their pups. After birth the mother remains at the rookery
for roughly 5-13 days (Sandegren 1970). Sandegren (1970) observed that pups
cared for less than 6 days before the female went to sea had a lower chance
Life History - 1 (DRAFT) - Life History
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
of survival than those cared for longer. He observed females remaining at
sea for 9-40 hours (average =16.7 hours) before returning to the rookery for
9-42 hours (average =17 hours).*125*
Sandegren (1970) attributed variation between females in the amount of time
spent at sea to female size and dominance. However, food availablity may be
a strong factor. Observations by Gentry (1970) and Gisiner (1985) on Ano
Nuevo Island were repeated in 1983 when the El Nino ocean-temperature
anomaly was particularly strong, potentially reducing prey availability
(Higgins 1984). In all three studies, females bred about 12 days after
parturition. Gentry (1970) and Gisiner (1985) observed that most females
copulated while departing from or returning to the rookery from their first
feeding trip. Higgins (1984), however, found that females made an average
of four feeding trips before breeding. Those females spent an average of
20.2 hours at sea (range =6-62 hours) during the first trip and stayed at
sea for progressively longer periods during later feeding trips.*125*
Pups develop rapidly. During their mother's absence they gather in pods
where they play and avoid aggressive encounters with adult sea lions. Pups
first enter tide pools or shallow water at about 2 weeks of age. By 24-32
days of age the mothers begin to take them out to sea. At 36-41 days old,
the pups have become proficient swimmers, using the synchronous swimming and
breathing patterns of adults (Gentry 1970, Sandegren 1970).
Most females appear to retain parental bonds with offsping somewhat less
than a year, weaning the young prior to returning to the rookery the
following year or just before parturition. Calkins and Pitcher (1982a)
found that from June through March, 81-83% of mature females were lactating
whether or not they were pregnant; by April and May the proportion
lactating dropped to 61%, indicating an increase in weaning. Young sea
lions, 1-3 years old, are often observed suckling adult females at rookeries
and haulouts (Gentry 1970, Sandegren 1970, Perlov 1980, Calkins and Pitcher
1982a). If a juvenile continues to accompany an adult female after she
gives birth, the mother will either wean the juvenile and care for the
newborn, abandon the newborn and retain the bond with the juvenile, or
nurse both offsprings (Sandegren 1970, Withrow 1982). Nonpregnant females
may retain bonds with previous offsping longer than a year. Rarely (<1% of
nursing observations on Sugarloaf rookery) do females nurse two individuals
simultaneously (Pitcher and Calkins 1981).*125*
Dominant males, usually 9 years old and older, establish breeding
territories on rookeries in early May, maintaining them for about 40 days
(range =20-68 days) without feeding (Thorsteinson and Lensink 1962, Gentry
1970, Sandegren 1970, Gisiner 1985). On rock substrates, territorial
boundaries are rigid, generally following topographic features; on sand
beaches, territories are mobile, following tidal fluctuations (Gentry 1970,
Smith 1981, Gisiner 1985). Individual males hold territories an average of
2 years (range =1-7+ years). The reproductive success of males increases
significantly the first 3 years they maintain territoires while aggressive
interactions with neighbors decrease (Gisiner 1985). Reproductive success
is greatest for those males holding territories with access to water
frequented by females (Gentry 1970, Sandegren 1970, Gisiner 1985).*125*
Life History - 2 (DRAFT) - Life History
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
Females with pups undergo a brief (probably <48 hours ) estrus about 11-12
days (range =6-16 days) after the birth of their pups; nulliparous females
are thought to breed early in the season, from early to mid-June (Gentry
1970, Sandegren 1970, Gisiner 1985). Copulations are most frequent in the
morning (0500-1300 hours) and evening (1600-2100 hours) and least frequent
at night (Gentry 1970, Gisiner 1985).*125*
A female does not necessarily breed with the male on whose territory she
previously rested or cared for her pup. Edie (1977) observed 20% of the
females copulating more than 10 m from the site where they were last seen
with their pups. Gisiner (1985) observed that 54% of 119 females bred on a
territory other than one they just previously rested on or that their pups
were located on.*125*
Soon after fertilization, further development of the embryo ceases. The
blastocyst remains dormant in the uterus for about 3 months whereupon in
late September or October it implants (Vania and Klinkhart 1967, Pitcher and
Calkins 1981).*125*
Two indices used to indicate the onset of sexual maturity for females are
the age of first pregnancy and the age of first ovulation. The age of first
pregnancy is more meaningful with respect to population dynamics but
requires more interpretation of the reproductive tract than the age of first
ovulation. In the Gulf of Alaska the mean age of females at first ovulation
was 4.6 years and at first pregnancy was 4.8 years; the range in both cases
was 3-8 years (Pitcher and Calkins 1981). Primiparous females in the Kuril
Islands were 4-6 years old, and multiparous females 6-12 years old (Pevlov
1980). Of the females collected in the Gulf of Alaska between 1975 and
1978, 41% from 3 to 5 years old and 84% from 6 to 20 years old were pregnant
(Pitcher and Calkins 1981). Pregnancy rates appear to drop after 20 years
of age (Perlov 1980, Pitcher and Calkins 1981).*125*
Males may reach physical maturity as early as 3 years of age although most
mature at 5-7 years of age (Parlov 1971, Pitcher and Calkins 1981). Most
males, however, are unable to successfully defend territories (therefore
potentially breed) until they are between 9 and 13 years old (Thorsteinson
and Lensink 1962).*125*
BEHAVIOR:
Steller sea lions are distributed around the North Pacific rim from 34
degrees N latitude to 66 degrees N latitude. In North America, the breeding
range includes the Pribilof and Aleution islands and extends southward
around the Gulf of Alaska, and continuously along the coast to California.
The southern breeding limit is San Miguel Island, one of the Channel Islands
in southern California. In the Bering Sea, there appears to be a summer
movement of males toward the Bering Strait, although no pupping takes place
north of the Pribilofs. In the Soviet Union, sea lions are found in the
Kuril Islands, the Okhotsk Sea, the Commander Islands, and the western
Bering Sea. They have also been recorded from Hokkaido and northern Honshu
islands of Japan where 1,000-3,000 are found seasonally in coastal waters,
and from the northern coast of the Korean Peninsula. Breeding occurs in the
Commander Islands, Kamchatka and Japan.*170*
Life History - 3 (DRAFT) - Life History
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
Historically, shifts in distribution and movements of Steller sea lions have
been noted throughout their range. Some areas are used to haul out and rest
and are referred to as haulouts. Others are used for pupping and breeding
and are termed rookeries. There was early recognition of marked seasonal
movements in California, particularly those involving males moving northward
after the breeding season. Long distance movements were also indicated by
the recovery of spear points from sea lions in California which probably
were implanted by Natives of southeastern Alaska. Movements of males along
the west coast from the California Channel Islands to British Columbia and
southern Alaska were recorded. An absence of adult males in the winter in
California and the presence of either young males or females all year
suggested seasonal migratory movements correlated with age and sex.
Movements of sea lions onto Oregon rookeries also have been documented.
Seasonal shifts in distribution of sea lions in Prince William Sound have
been recorded as have movements of males between the Commander Islands and
Kamchatka in the Southwestern Bering Sea.*170*
There has been extensive documentation of movements of Steller sea lions in
the Gulf of Alaska. Juvenile sea lions often move away from the rookeries
of their birth, dispersing widely. Most eventually return to those same
rookeries, but generally not until after the third year. Long distance
movements of up to 1,500 km have beeen documented. These include movements
from northern British Columbia to Prince William Sound and from the northern
Kodiak Island region to the vicinity of Baranof Island in southeastern
Alaska. In 1977 there apparently was a major shift eastward of juveniles
across the northern Gulf of Alaska, away from the major pupping rookeries in
the Kodiak and Kenae Peninsula area. Such movements appear to be dispersal
of subadults not correlated with any particular season, rather than
definitive migration. There have been no detectable seasonal movements by
subadults less than four years of age.*170*
The evidence available at this time indicates that many adult females return
to the large rookeries where they were born to bear their young and breed.
In the northern Gulf of Alaska, a total of 15 identifiable branded cows bore
pups at two rookeries where branding took place. Only one of these cows
gave birth at a rookery other than where she was born.*170*
Steller sea lions range all along the coast and seaward as far as the
continental shelf break. They utilize specific well-defined locations on
shore to haul out and rest, bear their young, and breed. During the period
when pupping and breeding do not occur (August through April), most
rookeries are used by sea lions as haulouts. During the breeding and
pupping season from May through July, most of the sea lions present on a
rookery are adult females, adult males, and newborn pups. Generally,few
subadults of either sex are present within the rookery, particularly during the peak of
pupping from June 10 through June 21. Nearly all adult females present on a
rookery during the breeding season will give birth to a pup. Most of the
adult males present on the rookery during the breeding season defend
territories. Occasioanlly, where large rookeries are located , nonbreeding
males can be found congregated at the fringes of the rookery proper.*170*
LIMITING FACTORS:
Known predators include killer whales (Orcinus orca) and sharks (Mate 1973,
Life History - 4 (DRAFT) - Life History
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
Stroud 1978). The impact of these predators on sea lion populations is
unknown.*125*
Three diseases have been considered as potential causal or contributing
agents in the current population decline of Steller sea lions:
leptopirosis, San Migual Sea Lion Virus (SMSLV), and chlamydiosis.
Leptospirosis is caused by a spirochete bacteria which, in California sea
lions (Zalophus californianus), may contribute to the mortlaity of adults
and pups, and may be a contributing factor or causative agent of abortions
(Gilmartin et al. 1976, Morton 1981, Britt and Howard 1983). Chlamydial
antibodies have recently been discovered in sea lions (Goodwin and Calkins
1985). Chlamydia potentially could interfere with the upper respiratory
tract and/or genital tract; however, the effect of chlamydiosis on sea
lions is unknown. In otariid pinnipeds it may cause vesicles to appear on
hairless regions of the skin but does not appear to otherwise debilitate
them (Gelberg 1981). Although SMSLV has been associated with abortions in
California sea lions, a cause and effect relationship has not been shown
(Gilmbartin et al. 1976, Gelberg 1981).*125*
Other limiting factors:
Reduced prey availability due to increased commercial fishing on important
prey (e.g., pollock, herring, cod, salmon, and flatfishes); direct kills of
sea lions as a result of previous commercial harvests, continued subsistence
harvest, and intentional and incidental kills by fisheries; entanglement in
marine debris; disease; and disturbance. Less likely causes might include
chronic exposure to organochlorine compounds, predation by sharks and killer
whales, and movements out of the survey areas (Braham et al. 1980, Kuzin et
al. 1984, Calkins 1985b).*125*
Three factors may cause the declining numbers of sea lions observed during
surveys: (1) movements out of the areas surveyed, including changes in
haulout schedules affecting the proportion of sea lions on shore; (2)
increased mortality, both natural and human-related; and (3) decreased
recruitment, or fewer successfully reproducing females due to previous
harvests, decreased fertility, decreased ability to carry pup to full term,
or decreased ability to succussfully wean a pup.*125*
REFERENCES FOR LIFE HISTORY- 170 and 125
Life History - 5 (DRAFT) - Management Practices
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Regulating commercial harvest gear types
Adverse Drilling
Existing Prohibiting harvest of species being described
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 125
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 125
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 125
COMMENTS ON MANAGEMENT PRACTICES -
Based on a preliminary review of a status report on the Northern (Steller)
sea lion in Alaska, NMFS has published an advance notice of proposed
rulemaking (May 6, 1988) to consider designating this population as
depleted. If this population stock is designated as depleted, the MMPA
requires the application of certain additional restrictions on taking and
importation. In this instance, based on recent court decisions,
restrictions on commercial fishing in the North Pacific Ocean and Bering Sea
are possible consequences.*179*
Commercial fishermen are allowed to kill sea lions involved in fisheries
conflicts under terms of permits issued by the National Marine Fisheries
Service by authority of the Marine Mammal Protection Act (PL92-522). Each
year approximately 1,000 sea lions are killed in the nearshore salmon
fishery, and 800 to 1,600 are killed in the high sea fishery.*170*
Management Practices - 1 (DRAFT) - References
Species sea lion, northern
Species Id M120106
Date 26 AUG 96
References
*170* Burns, J.J., K.J. Frost, L.F. Lowry (ed.)1985. (7). Marine Mammal
Species Accounts. Alaska Department of Fish and Game:96.
*125* Lentfer, J.W. (ed.). 1988. Selected Marine Mammals of Alaska,
Species Accounts with Research and Management Recommendations.
Marine Mammal Commission Washington, D.C pp 275.
*179* U.S. Department of Commerce. 1988. Marine Mammal Protection Act
of 1972 Annual Report 1987/88. Marine Mammal Protection Act of
1972. U.S. Department of Commerce Miami, Florida:38.
(Note: Ref. 179 is Ref. 195 in marine references)
276 * Harvey, James T., David L. Stein. 1986. The State of
Scientific Information Relating to the Biology and Ecology of
the Gorda Ridge Study Area, Northeast Pacific Ocean: Nekton.
(0-86-7) (ed.). Oregon Department of Geology and Mineral
Industries Portland, Oregon:131.
References - 1