(DRAFT) - Taxonomy
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
TAXONOMY
NAME - seal, ribbon
OTHER COMMON NAMES -
ELEMENT CODE -
CATEGORY - Marine Mammals
PHYLUM AND SUBPHYLUM - ,
CLASS AND SUBCLASS - ,
ORDER AND SUBORDER - ,
FAMILY AND SUBFAMILY - ,
GENUS AND SUBGENUS - Phoca,
SPECIES AND SSP - fasciata,
SCIENTIFIC NAME - Phoca fasciata
AUTHORITY -
TAXONOMY REFERENCES - 125 and 170
COMMENTS ON TAXONOMY -
Although once considered a member of a separate genus, Histriophoca, recent
studies have shown that the ribbon seal is a member of the genus Phoca.
This indicates the close relationship between ribbon seals and other
members of the genus Phoca including ringed, spotted, harbor, and harp
seals.*170*
Taxonomy - 1 (DRAFT) - Status
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
STATUS
Coded Status
Marine Mammal
Furbearer
Subsistence
See Comments
REFERENCES FOR STATUS - 170 and 125
COMMENTS ON STATUS -
Only Native subsistence hunters harvest ribbon seals in Alaskan waters.*125*
Present provisions of the MMPA (Marine Mammal Protection Act) preclude
actual management of the ribbon seal population and regulation of its users.
*170*
No major problems are anticipated with regard to future State (Alaska)
management of ribbon seals. In the absence of large commercial or
subsistence harvest, and given the secure status of the population, the
amount of biological data gathered would be small. Emphasis would continue
to be placed on monitoring harvest levels.*170*
Status - 1 (DRAFT) - Distribution
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
REFERENCES FOR HABITAT - 125 and 170
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine
COMMENTS ON HABITAT ASSOCIATIONS -
Although they spend many months in ice-free waters, sea ice is vital to the
life cycle of ribbon seals. For pupping, ribbon seals select areas of
moderately thick large floes commonly 10-60 km north of the ice fringe and
open sea.*170*
Ribbon seals seem to select an ice type that seldom occurs near shore, and
tend to be 50-250 km offshore during the pupping and nursing periods and
move to within 20-100 km of shore during the molt. Ribbon seals have been
reported in highest densities in areas of 60-80% ice coverage. In April
they have been found throughout the ice front, but most abundant south of
the continental shelf over deep water.*125*
Habitat Associations - 1 (DRAFT) - Food Habits
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
REFERENCES FOR TROPHIC LEVEL - 170
LIFESTAGE FOOD FOOD PART
General Squid, Octopus Not Specified
General Crustaceans Not Specified
General Fish Not Specified
General See Comments; Food Not Applicable
Adult Squid, Octopus Not Specified
Adult Fish Not Specified
Adult See Comments; Food Not Applicable
Juvenile Crustaceans Not Specified
Juvenile See Comments; Food Not Applicable
Important Crustaceans Not Specified
Important Squid, Octopus Not Specified
REFERENCES FOR GENERAL FOOD - 170
REFERENCES FOR IMPORTANT FOOD - 170
REFERENCES FOR ADULT FOOD - 170
REFERENCES FOR JUVENILE FOOD - 170
COMMENTS ON FOOD -
The foods of ribbon seals are known only for the months of February to June.
Most samples are from April to June, a time of reduced feeding, but the
types of foods in ribbon seal stomachs during spring undoubtedly shed some
light on foods eaten at other times of year.
In general, ribbon seals eat a variety of fishes, cephalopods (octopus and
squid), and crustaceans (primarily shrimp and mysids).*170*
COMMENTS ON ADULT FOOD -
Based on food remains in stomachs of animals taken in spring, fishes and
cephalopods comprise the bulk of the adult diet.*170*
COMMENTS ON JUVENILE FOOD -
Soviet researchers have suggested that crustaceans are the main food of
young seals.*170*
Food Habits - 1 (DRAFT) - Environment Associations
Species seal, ribbon
Species Id M120104
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 Substrate: Specified in Comments
G Relation to Substrate: Specified in Comments
G Aquatic Habitat Zonation: Open water [pelagic zone]
G Aquatic Habitat Zonation: Specified in Comments
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 125
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
In Alaskan waters ribbon seals are found in the open sea, on the pack ice,
and only rarely on shorefast ice. Clean ice that is not discolored by
sediment or algae seems to be preferred. Except for occasional moribund
individuals, they do not haul out on land. It has been noted that ribbon
seals seem to select an ice type that seldom occurs near shore.*125*
Environment Associations - 1 (DRAFT) - Life History
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
LIFE HISTORY
Physical description: Adult males are easily recognized by the
characteristic banding of their pelage, from which the species' name is
taken. Four nearly white bands contrast with a brown to black background.
One band encircles the neck and base of the head, another encircles the
posterior portion of the trunk, and each forflipper in encircled by an oval
extending generally from the lower neck to the midsection of the trunk.
These "ribbons" are most distinct in adult males; most females show much
less contrast between the markings and background coloration. The pattern
is indistinct in young seals and becomes progressively clearer with
successive molts up to the age of marturity.*125*
In addition to their distinctive coloration, ribbon seals can be recognized
by their relatively short snout, long neck, slender trunk, and seemingly
long foreflippers. The ribbon seal skull is characterized by a short
rostrum, broad cranium, and small, widely spaced teeth. Notable in soft
tissue anatomy is an air sac extending from the posterior end of the trachea
over the ribs on the right side. The inflatable sac is well developed only
in adult males, and its function is unknown. It has been speculated that
the air sac functions as a buoyancy device, for storage of air during
diving, and in sound production.*125*
Mature ribbon seals average 1.50-1.75 m in standard length and weigh up to
148 kg. Weight declines substantially in spring when the blubber thichness
decreases by 50-60%.*125*
Reproduction:
Mating takes place from late April to early May in the Bering and Okhotsk
seas. At that time of year the seals inhabit the southern ice front, where
they apparently prefer to haul out on floes about 20 m in diameter.*125*
Implantation of the blastocyst occurs approximately 2.5 months after
fertilization and gestation lasts 8.5 months, so parturition occurs 11
months after mating. A single pup is born on the ice in April or May; the
majority of births take place between April 5 and 15.*125*
Population size:
The most recent estimate of the worldwide population of ribbon seals is
240,000, from surveys conducted in the mid-1970s. Ribbon seals are
difficult to enumerate because they occur in a remote and harsh environment
and spend much time out of sight, underwater. Estimates of their numbers
are based on aerial surveys conducted in spring when the breeding seals haul
out on the ice.*125*
Population trends:
A decline in the numbers of ribbon seals in the Bering Sea was believed to
be the result of overharvest by Soviet commercial sealers in the early
1960s. The catch per unit of effort dropped by more than 50% between the
first commercial harvest in 1961 and 1963. The Bering Sea population was
believed to have decreased from 80,000-90,000 in 1964 to 60,000 in
1969.*125*
Predation:
Potential predators of ribbon seals include man, polar bears, walruses,
killer whales, eagles, and gulls.*125*
Life History - 1 (DRAFT) - Life History
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
Parasites:
Ribbon seals harbor low numbers of anopluran lice. It has been suggested
that the scarcity of the ectoparasites is related to the seal's low level of
gregariousness.*125*
More than a dozen species of helminths occur in ribbon seals. Helminth
damage to the intestines, stomach, lungs, and possibly liver of ribbon seals
has been reported, but the contribution of helminth infestations to ribbon
seal mortality is not known.*125*
Other causes of morbidity and mortality:
Dermatitis is fairly common in ribbon seals. Molting seals especially may
be vulnerable to microbial infections of the skin.*125*
Ribbon seals are occasionally found traveling over ice and land after
losing access to the water because of sudden freeze-ups or ice movements.
Undoubtedly, some ribbon seals die as a result.*125*
Ribbon seals are incidentally taken in groundfish trawls and salmon gill
nets. The numbers of seals killed in this manner are unknown, but the
incidence may be increasing, as is thought to be the case for other
pinnipeds.*125*
Organochlorine compounds and heavy metals have been found in high
concentrations in some phocids, but the occurrence of pollutants in ribbon
seals has not been investigated. The tendency of ribbon seals to remain
away from coastal waters may decrease the risks of encountering some
pollutants.*125*
Offshore oil development in the Bering and Chukchi seas presents several
potential causes of morbidity or mortality. Well blowouts or shipping
accidents could bring ribbon seals into direct contact with crude oil. The
effects on ribbon seals have not been studied. There is some evidence that
seals may be most adversely affected by contact with oil during periods of
naturally occurring stress such as the molt, reproduction, scarcity of food,
or illness.*125*
LIFE HISTORY CODES -
Breeding Spawning Season: April
Breeding/Spawning Season: May
Gestation/Incubation Period: Greater than 8 months
Average Number of Offspring/Reproductive Effort: 1
Number of Broods/Litters (Reproductive Efforts) Per Ye
REFERENCES FOR LIFE HISTORY- 125 and 170
Life History - 2 (DRAFT) - Management Practices
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Regulating harvest of species being described
Beneficial Restricting/regulating human use of habitats
Beneficial Other management practices [specified in comments]
Adverse Other management practices [specified in comments]
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 125
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 125
COMMENTS ON MANAGEMENT PRACTICES -
Management of ribbon seals should be directed toward monitoring and
regulating harvests and reducing potential threats from commercial fishing
and offshore industrial development activities. The population and
ecological data necessary for developing effective management plans
currently are lacking. Harvest monitoring should be a routine part of
management activities and should include analysis of the age and sex
composition of the kill and the reproductive history of harvested
seals.*125*
Ribbon seals are incidentally taken in groundfish trawls and salmon gill
nets. The numbers of seals killed in this manner are unknown, but the
incidence may be increasing, as is thought to be the case for other
pinnipeds.*125*
Organochlorine compounds and heavy metals have been found in high
concentrations in some phocids, but the occurrence of pollutants in ribbon
seals has not been investigated. The tendency of ribbon seals to remain
away from coastal waters may decrease the risks of encountering some
pollutants.*125*
Offshore oil development in the Bering and Chukchi seas presents several
potential causes of morbidity or mortality. Well blowouts or shipping
accidents could bring ribbon seals into direct contact with crude oil. The
effects on ribbon seals have not been studied. There is some evidence that
seals may be most adversely affected by contact with oil during periods of
naturally occurring stress such as the molt, reproduction, scarcity of food,
or illness.*125*
Management Practices - 1 (DRAFT) - References
Species seal, ribbon
Species Id M120104
Date 26 AUG 96
References
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.
170* Burns, John J., K.J. Frost, L.F. Lowry (ed.)Marine Mammal Species
Accounts. 1985. (7). Alaska Department of Fish and Game:96.
References - 1