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Overview

Distribution

Range Description

The two disjunct subspecies are separated by 130° of longitude and about 8,500 km.

C. c. commersonii - Falkland Islands / Islas Malvinas and the coastal waters of southern South America. On the Atlantic coast the northern limit is at approximately River Negro mouth (40°S) (Bastida and Rodríguez 2003). The range extends south near Cape Horn (56ºS) including the central and eastern Strait of Magellan and the Falkland (Malvinas) Islands (Goodall 1978, Goodall et al. 1988). Single dolphins and groups of up to hundreds were sighted in the late 1980s and early 1990s along the northern coast of Tierra del Fuego (Goodall 1994). Although sightings in the northern parts of the range often are of small groups or solitary individuals, overall numbers and group sizes increase to the south. In Chile the species is found: Strait of Magellan (Aguayo-Lobo 1975, Goodall 1978, Venegas and Sielfeld 1978, Sielfeld 1983, Venegas and Atalah 1987, Thielke 1984, Goodall et al. 1988, Leatherwood et al. 1988, Hucke-Gaete and Vallejos 1997, Aguayo-Lobo et al. 1998, Gibbons et al. 2000), Seno Skyring, Fitz Roy channel, seno Otway and seno Almirantazgo (Sielfeld and Venegas 1978, Gibbons et al. 2000). Genetic population structure revealed significant differentiation among different studied areas (within Tierra del Fuego and Santa Cruz provinces) over small geographic scales, considering these as subpopulations (Pimper et al. 2010, Cipriano et al. 2011).Two “ecological stocks” have been identified based on differences in parasite loads and patterns of prey consumption (Berón-Vera et al. 2001).

C. c. kerguelenensis - Shallow coastal waters around all of the Îles Kerguélen in the southern Indian Ocean (Rice 1998; Robineau et al. 2007). No sightings or specimens have yet been reported from islands between South America and Kerguélen, such as Crozet, Heard, Amsterdam or St Paul (Goodall 1994). Dolphins of the Kerguelen Islands subspecies are most commonly sighted in the Golfe du Morbihan, on the eastern side of Kerguélen. Reported vagrants (northernmost records) in the coast of South America. Buenos Aires province, Argentina (Brownell and Praderi 1985, Iñiguez et al. 2010), Chile (Capella and Gibbons 1991), Brazil (Pinedo et al. 2002).
Recently, a sighting of a single individual south of Cape Town, in South African waters, was reported, although this should be considered extralimital (de Bruyns et al. 2006). There are also unsubstantiated reports of this species at South Georgia, but these have been rejected (Brown 1988).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.
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Geographic Range

Commerson's dolphins are primarily found in the coastal waters of the southwest Atlantic Ocean near Patagonia, Tierra del Fuego, Cape Horn and the Falklands Islands. They are most commonly seen along the eastern coast of South American between 41˚30' S and 55˚ S latitude, though they have been found as far north as 31˚ S latitude in some areas.

There is also a disjunct population of Commerson's dolphins in the south Indian Ocean near Kerguelen Island. In this area, they range from 48˚30' S to 49˚45' S latitude and are most common around the Golfe du Morbihan and around Heard Island. They are the only common cetacean in these coastal waters.

Biogeographic Regions: neotropical (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

  • 2004. The Commerson's Dolphin Story. San Diego: Sea World, Inc.
  • 2006. Whales, Dolphins, and Other Marine Mammals of The World. United States: University Presses of California.
  • 2009. "The Ocean Biogeographic Information System" (On-line). Accessed March 15, 2010 at http://seamap.env.duke.edu/species/tsn/180449.
  • Goodall, R. 1994. Commerson's dolphin. Pp. 241-267 in S Ridgway, R Harrison, eds. Handbook of Marine Mammals, Vol. Volume 5: The First Book of Dolphins. San Diego: Academic Press Limited.
  • Goodall, R., A. Galeazzi, S. Leatherwood, K. Miller, I. Cameron, R. Kastelein, A. Sobral. 1988. Studies of Commerson's dolphins, Cephalorynchus commersonii, off Tieraa del Fuego, 1976-1984, with a review of information on the speices in the South Atlantic. Pp. 3-70 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).
  • Leatherwood, S., R. Reeves. 1983. he Sierra Club Handbook of Whales and Dolphins. San Francisco: Sierra Club Books.
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Physical Description

Morphology

Physical Description

Commerson's dolphins are mostly white and have black marked faces and bodies. This black and white pattern varies with geographic location as well as age and sex. These colors are more muted in coastal waters. The black color on the head extends behind the blowhole and down the sides of the body, including the flippers. Black also covers the dorsal fin and runs back to encircle the tailstock behind the anus and flukes. The black color on the chest ends in a posterior-facing point. Large black genital patches are oval or heart-shaped, with the narrow end pointing posteriorly in males. In females the narrow end is anterior, and may or may not include "ears" outside the mammary slits. The throat is generally white, as is the rest of the body. Individuals can be recognized by varying shape of the black "widow's peak" behind the blowhole as well as pigmentation on the side of the tailstock. Calves are born dark grey and black with vertical creasing as a result of fetal folding. These folds disappear after a week, and the dark grey portions become paler in the first few months and white within 4 to 6 months.

Coloration of Commerson's dolphins near Kerguelen Island is similiar to that of juveniles from the south Atlantic Ocean. Near Kerguelen, the surface in front of the dorsal fin is grey, as are the sides. The grey behind the blowhole is streaked with black and their "widow's peak" is not as well defined. The white throat patch is more asymmetrical than in individuals from the south Atlantic. Commerson's dolphins near Kerguelen generally have a narrow white line in the center of their chest, a feature seldom found in their counterparts in the south Atlantic Ocean.

Commerson's dolphins have a dark rounded dorsal fin that rises at a shallow angle and flippers with rounded tips. Their head is blunt and has a sloped forehead and little or no beak. A narrow cap extends on the rear half of body from dorsal fin to flukes. The tail flukes are slightly round tipped and notched, and the flippers are small and rounded. The flukes have concave edges with a slight hatch in the middle with dark coloring above and below. Commerson's dolphins have approximately 29 to 30 pairs of pointed teeth in the upper and lower jaws. Newborns range from 0.5 to 0.75 m in length and weigh 4.5 to 7.3 kg. Adults range from 1.2 to 1.5 meters in length and usually weigh 35 to 65 kg. Females are generally larger than males, and Commerson's dolphins from the Indian Ocean tend to be larger than those in the South Atlantic. Also, although Commerson's dolphins from both areas do not have well defined snouts, there is a distinct rostral depression in Kerguelen animals which individuals in the south Atlantic lack.

Range mass: 35 to 65 kg.

Range length: 1.2 to 1.5 m.

Sexual Dimorphism: female larger; sexes colored or patterned differently

  • 2006. Whale Watcher. United Kingdom: Firefly Books, Ltd..
  • Lockyer, C., R. Goodall, A. Galeazzi. 1988. Age and bodylength characteristics of Cephalorynchus commersonii from incidentally-caught specimens off Tierra del Fuego. Pp. 103-118 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).
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Ecology

Habitat

mostly coastal
  • UNESCO-IOC Register of Marine Organisms
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Habitat and Ecology

Habitat and Ecology
Commerson's dolphins are found in cold inshore waters along open coasts, in sheltered fjords, bays, harbours and river mouths, and occasionally the lower reaches of rivers. Their offshore limit is not very clear. Along the Atlantic shelf Commerson’s dolphins have been sighted more than 100 nmi offshore and in water deeper than 1000 m (Pedraza 2008). Within the Strait of Magellan, they prefer the areas with strongest currents, such as the Primera and Segunda Angostura (First and Second Narrows), where the current can reach or exceed 15 km/hr (Goodall 1994). Off South America, Commerson's dolphins appear to prefer areas where the continental shelf is wide and flat, the tidal range is great, and temperatures are influenced by the cool Malvinas Current. In coastal Patagonia, they are found principally in areas with continental runoff such as at the mouths of the Chubut and Santa Cruz Rivers and at Puerto Deseado. Around the Falklands/Malvinas and Kerguelen Islands, as well as off mainland Argentina, they are often seen swimming in or at the edge of kelp beds. Commerson's dolphins sometimes move very close to shore, even inside the breakers. However, they are also observed offshore in waters deeper than 50 m.

South American Commerson's dolphins appear to be opportunistic, feeding near the bottom on various species of fish, cephalopods, crustaceans, and benthic invertebrates in kelp beds but also on pelagic schooling fish in more open areas. In the Kerguelen Islands, they seem to have a more restricted diet, consisting mostly of fish.

Systems
  • Marine
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Commerson's dolphins inhabit shallow, inshore waters along coastlines, harbors, bays, and river mouths. The live in cold shallow waters, with temperatures ranging from 1˚ C to 16˚ C. They are rarely found at depths greater than 200 m. Commerson's dolphins prefer a neritic environment and are seldom found far offshore. Most sightings occur in the coastal regions near the mouths of bays and estuaries or over the wide shallow continental shelf where the tidal range is great. Commerson's dolphins move towards the shore with the tide. In some areas, dolphins prefer areas with the strongest currents - up to or greater than 15 km/hr. They are also frequently found in kelp beds and in narrow passages like those found in the Strait of Magellan. It is thought that most dolphins seasonally move away from the shore, following fish which move offshore during the winter. Commerson's dolphins in Kerguelen follow this trend and are less common inshore between June and December. In Kerguelen, they are most commonly observed over the Kerguelen shelf, but they are also found in open waters, kelp-ringed coastlines, and protected areas between islets.

Range depth: 200 (high) m.

Habitat Regions: temperate ; saltwater or marine ; freshwater

Aquatic Biomes: pelagic ; benthic ; rivers and streams; coastal

  • Clapman, P., R. Reeves, B. Stewart, J. Powell. 2002. National Audubon Society: Guide to Marine Mammals of the World. New York: Random House.
  • Leatherwood, S., R. Kastelein, K. Miller. 1988. Observations of Commerson's dophin and other cetaceans in south Chile, Janurary-February 1984. Pp. 71-84 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).
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Depth range based on 26 specimens in 1 taxon.
Water temperature and chemistry ranges based on 11 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 2.814 - 14.753
  Nitrate (umol/L): 5.959 - 24.558
  Salinity (PPS): 33.925 - 34.816
  Oxygen (ml/l): 5.834 - 7.355
  Phosphate (umol/l): 0.528 - 1.739
  Silicate (umol/l): 2.621 - 18.358

Graphical representation

Temperature range (°C): 2.814 - 14.753

Nitrate (umol/L): 5.959 - 24.558

Salinity (PPS): 33.925 - 34.816

Oxygen (ml/l): 5.834 - 7.355

Phosphate (umol/l): 0.528 - 1.739

Silicate (umol/l): 2.621 - 18.358
 
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Trophic Strategy

Food Habits

Commerson's dolphins are primarily carnivores but are often opportunistic coastal feeders. They rely on both pelagic and benthic prey. Their diet is mainly composed of mysid shrimp, and small fish like silversides, sardines, and Argentine hake. They are also known to eat squid, octopus, marine worms, tunicates, and even algae. Among 53 Commerson's dolphins in the Tierra del Fuego, 22.5% of their diet was composed of mysid shrimp, 20.4% of 3 species of fish, 14.1% of squid, and the rest of algea, isopods, and other benthic invertebrates. Other plant remains, seeds, sand, and pebbles were also found in their stomachs. Individuals found near the Kerguelen Island eat a high proportion of semipelagic chaennichthyid fish, as well as pelagic and benthic crustaceans. At times, Commerson's dolphins hunt together, as described in the behavior section. In captivity, Commerson's Dolphins consume 3 to 4 kg of Atlantic herring each day.

In areas of high tides, Commerson's dolphins feed in the shallow areas in or just beyond the advancing tide breakers in order to take fish, such as sardines and anchovies that are also feeding in the area, or other organisms that are dislodged by the turbulent water. Commerson's dolphins also feed for long periods in kelp beds, in open waters, around submarine banks, and near artificial structures such as piers and oil rigs.

Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans

Plant Foods: algae

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )

  • Bastida, R., V. Lechtschein, R. Goodall. 1988. Food habits of Cephalorynchus commersonii off Tierra del Fuego.. Pp. 143-161 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).
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Associations

Ecosystem Roles

Commerson's dolphins prey on small fish, mysid shrimp, as well as squid, octopus, marine worms, and tunicates. While natural predators are still unknown, killer whales and leopard seals may prey on them as they are found in the same geological area. Commerson's dolphins also act as hosts for roundworms (Nematoda) and flukes (Trematoda).

Commensal/Parasitic Species:

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Predation

The black and white coloration patterns of Commerson's dolphins breaks up the outline of their body, making them more difficult for predators to spot. Natural predators may include killer whales, sharks, and leopard seals that live within the same geographic range, but such predation has not been documented. Humans actively kill Commerson's dolphins for food, oil and bait and inadvertently through other fishing practices.

Known Predators:

  • Humans Homo sapien

Anti-predator Adaptations: cryptic

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Life History and Behavior

Behavior

Communication and Perception

Commerson's dolphins communicate using echolocation. They also rely on echolocation to navigate and hunt through dark waters. In captivity, they vocalize at frequencies ranging from 120 to 134 kHz for a duration of 180 to 600 μs.

Communication Channels: visual ; tactile ; acoustic

Other Communication Modes: choruses ; vibrations

Perception Channels: visual ; infrared/heat ; acoustic ; ultrasound ; echolocation ; vibrations

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Life Expectancy

Lifespan/Longevity

Commerson's dolphins generally do not live more than 10 years in the wild. In captivity, they commonly live to 18 years of age, and one individual at SeaWorld San Diego lived to be 25.8 years of age.

Range lifespan

Status: wild:
23 (high) years.

Range lifespan

Status: captivity:
25.8 (high) years.

Typical lifespan

Status: wild:
10 (high) years.

Typical lifespan

Status: captivity:
15 to 18 years.

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Lifespan, longevity, and ageing

Observations: These animals do not commonly live more than 10 years in the wild with the oldest animal ever found being 18 years old (Ronald Nowak 1999). One wild born animal was still living in captivity at 25.8 years of age (Richard Weigl 2005). Given the lack of detailed studies, however, their maximum longevity is classified as unknown.
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Reproduction

Little information is available regarding the mating systems of Commerson's dolphins. They have been observed copulating in a vertical, belly to belly position.

Commerson's dolphins breed between the months of September and February. After a gestation period of at most 12 months, females give birth to one individual in the winter. Calves are born tail first and are grey in color. Newborns range from 0.5 to 0.75 m in length and weigh 4.5 to 7.3 kg. Their dorsal fin and tail flukes are pliable at birth and gradually stiffen as they mature. The length of the nursing period in the wild is unknown. However, in captivity calves begin eating solid food by 2 months of age and take whole fish by 4 months. Males typically reach sexual maturity between 6 and 9 years of age, and females between 5 and 9 years. Individuals from the the south Atlantic Ocean, however, tend to reach sexual maturity at a younger age than populations from Kerguelen.

Breeding interval: Commerson's dolphins breed once yearly.

Breeding season: Mating occurs between late September and early February.

Range number of offspring: 1 (high) .

Range gestation period: 10 to 12 months.

Range birth mass: 4.5 to 7.3 kg.

Range age at sexual or reproductive maturity (female): 5 to 8 years.

Range age at sexual or reproductive maturity (male): 6 to 9 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average number of offspring: 1.

Mother Commerson's dolphins nurse their calves through abdominal mammary slits for about 9 months. Mothers are attentive to their calves, which swim close to their mother. Calves learn to swim by following in their mother's slip stream. Females also appear defensive of their young.

Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

  • 2004. The Commerson's Dolphin Story. San Diego: Sea World, Inc.
  • Goodall, R., A. Galeazzi, S. Leatherwood, K. Miller, I. Cameron, R. Kastelein, A. Sobral. 1988. Studies of Commerson's dolphins, Cephalorynchus commersonii, off Tieraa del Fuego, 1976-1984, with a review of information on the speices in the South Atlantic. Pp. 3-70 in R Brownell, Jr., G Donovan, eds. Biology of the genus Cephalorynchus. Reports of the International Whaling Commission (Special Issue 9).
  • Repetto, N., M. Wurtz. 2003. Underwater World: Dolphins and Whales.. Italy: While Star Publishers.
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2013

Assessor/s
Reeves, R.R., Crespo, E.A., Dans, S., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Pedraza, S., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K.

Reviewer/s
Brownell Jr., R.L. & Cooke, J.

Contributor/s

Justification
Although some progress has been made towards increasing what is known about this species since the previous 1996 listing as Data Deficient, the information is still insufficient for evaluation against the criteria, particularly with regard to population size, trends, and threats. There is reason to suspect that the species overall, and at least the South American subspecies, is continuing to decline in portions of its range. Further research is needed, especially to address the question of population structure within Argentina. In the future, separate assessments of the two recognized subspecies should be a priority. Similarly, population structure within South America may justify separate assessments of geographical populations. Further research is also needed to provide current abundance estimates for a larger proportion of the species’ total range, and quantitative information on recent and current human-caused mortality.

History
  • 1996
    Data Deficient
  • 1994
    Insufficiently Known
    (Groombridge 1994)
  • 1990
    Insufficiently Known
    (IUCN 1990)
  • 1988
    Insufficiently Known
    (IUCN Conservation Monitoring Centre 1988)
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Commerson's dolphins were hunted for their meat and oil and more recently for crab bait. Although these practices are now illegal, they are often entangled in gillnets and other fishing gear used in nearshore waters and are occasionally killed in midwater trawl nets used for shrimp. In Tierra del Fuego alone, at least 5 to 30 dolphins die each year as by-catch in nets set perpendicular to the shore.

Near Kerguelen Island, low levels of chlorinated hydrocarbons (DDT, PCB and HCB) were found in the blubber of Commerson's dolphins, confirming the presence of pollutants in oceans far from their main source. The levels of contaminants were 10 to 100 times that of cetaceans in the North Atlantic.

US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: data deficient

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Population

Population
Commerson's dolphin seems to be the most abundant species of the genus Cephalorhynchus (Dawson 2002) although much of its range has not been surveyed and there are only a few estimates of abundance. Leatherwood et al. (1988) conducted aerial surveys in the northern Strait of Magellan and estimated a minimum of 3,221 dolphins for that area. However, they did not observe Commerson's dolphins in some areas where the species had been recorded previously. It has been suggested that the reduced abundance of these dolphins in some areas of southern Chile was due to either depletion of the population or displacement of the animals eastward of the Strait of Magellan. In either case, potential causes include mortality in fishing gear and extensive hunting in the past. The practice of using dolphins and other marine mammals as bait is reported to have declined in recent years, due in part to the fact that legal bait has been more readily available and in part to measures taken by Chilean government agencies (Lescrauwaet and Gibbons, 1994; Reeves et al., 2003).

Venegas (1996) estimated the density of Commerson's dolphins during early summer (1989-1990) in the eastern sector of the Strait of Magellan, flying 79 transects corresponding to 1,320 km. The estimated total number within the study area was 718 ± 196 individuals. Venegas attributed the substantial difference between his figures and those of Leatherwood et al. (1988) to methodological factors and time of year. In Argentine waters, overall abundance in the early to mid-2000s was estimated at about 40,000, with at least half of that number in Tierra del Fuego and southern Patagonia (Pedraza 2008).

The status of the Kerguelen Islands subspecies is even less clear than that of the South American subspecies. As of 1985, there had been more than 100 reported sightings, the largest group of about 100 dolphins having been seen near the edge of the shelf (Goodall 1994; Robineau 1989). The Kerguelen subspecies is restricted in range and is therefore probably small and relatively vulnerable to any anthropogenic threats.

Population Trend
Unknown
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Threats

Major Threats
Until recently, various species of small cetaceans, mainly Commerson's dolphins and Peale's dolphins, were harpooned and used as bait in the southern king crab ("centolla") fishery in both Argentina and Chile (Lescrauwaet and Gibbons 1994). Because the centolla is overfished in the Magellan region, fishing effort has shifted to the false king crab, which is exploited principally farther west in the channels. Commerson's dolphins are not found there, but they are relatively abundant in the eastern part of the Strait. In Argentina, the crab fishery operates in the Beagle Channel, where there are relatively few Commerson's dolphins. Some animals have been killed for sport (Reyes 1991) and others have been live -captured for dolphinaria (Goodall 1994).

This is the odontocete species most frequently taken in fishing nets off southern South America, perhaps due to its coastal distribution which overlaps with trammel and artisanal gillnet fisheries (e.g. Iñiguez et al. 2003). It is taken most often in fairly large-mesh nets. Although the scale of the bycatch is unknown, at least 5-30 died each year in nets set perpendicular to the shore in eastern Tierra del Fuego alone during the 1980s and early 1990s (Goodall 1994). They are also taken in this type of fishing in the Argentinean provinces north of Tierra del Fuego and in the eastern Strait of Magellan and Bahia Inútil in Chile. Commerson’s dolphins are also killed at least occasionally in midwater trawl nets on the Argentine shelf (Crespo et al. 1997, 2000). Recent aerial surveys off Patagonia provided an estimate of 1,200 to 2,750 Commerson’s dolphins for Chubut Province (Pedraza 2008). The bycatch there in hake and shrimp fisheries (25 to 170 individuals per year, mostly females; Dans et al. 2003) could represent anywhere from 0.9 to 14% of the estimated abundance. Incidental mortality in gillnets was calculated as almost 180 animals for the fishing season 1999-2000 in a small area of the Santa Cruz Province, southern Argentina (Iñiguez et al. 2003).

The salmon farming industry in southern Chile plans to expand into the Southwestern Atlantic in an effort to meet the increasing demand for feeds based on anchovy, mackerel and other pelagic species of fish (Skewgar et al. 2007). Pelagic fish are captured by large vessels operating with trawls or purse seines, and those fish are then converted into meal to feed salmon. The rising global demand for fish meal could lead to unsustainable anchovy fishery expansion on the Patagonian coast. Global aquaculture, which uses feeds manufactured from fish meal, increased by 50% between 1998 and 2004, and will likely continue to grow (Skewgar et al. 2007). Uruguay recently approved a Chile-financed factory to process 200,000 tons of anchovy into fishmeal (Skewgar et al. 2007). In addition to uncontrolled fishing that will reduce populations of key prey species like the southern anchovy, substantial bycatches of several species of dolphins, including Commerson’s, off Patagonia have been documented over the last 15 years. Commerson’s dolphins are particularly susceptible to capture in pelagic trawls or purse seines (Dans et al. 2003; Crespo et al. 1997, 2000). Enforcement of fishery regulations in Argentina and other countries in southern South America is reportedly inadequate (E. Crespo pers. comm.).
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES.

Although Commerson’s dolphins may have been seriously affected by the illegal deliberate take for bait in the Chilean crab fishery, the pressure on them in the southern part of their range apparently was reduced beginning in the late 1980s. However, in various parts of their range, incidental mortality in gillnets and other fishing gear continues and represents an ongoing threat (Dans et al. 2003, Iniguez et al. 2003). Such mortality should be investigated in more detail.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Commerson's dolphins may affect fishermen, as they sometimes become entangled in fishing nets and may also deplete populations of small fish.

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Economic Importance for Humans: Positive

Humans living in Patagonia and Tierra del Fuego have traditionally harpooned Commerson's dolphins for their meat and oil. Crab fishermen in southern Argentina and Chile use the meat of Commerson's dolphins as bait, as it does not deteriorate in salt water. These practices are now illegal and have steadily declined. Commerson's dolphins can also be found in aquariums in Germany, Japan and the United States.

Positive Impacts: food ; ecotourism

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Risks

IUCN Red List Category

Data Deficient (DD)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Commerson's dolphin

Commerson's dolphin (Cephalorhynchus commersonii) is one of four dolphins in the genus Cephalorhynchus. The species has also the common names skunk dolphin, piebald dolphin and panda dolphin. The dolphin is named for Philibert Commerson, who first described them in 1767 after he sighted them in the Strait of Magellan.[3]

Physical description[edit]

A Commerson's dolphin in the Strait of Magellan

Commerson's dolphin has a very distinctive patterning. It has a black head, dorsal fin, and fluke, with a white throat and body. The demarcation between the two colours is very clear-cut. This stocky creature is one of the smallest of all cetaceans growing to around 1.5 m (5 ft). A mature female caught off of south Patagonia, at 23 kg (51 lb) and 1.36 m (4.5 ft), may be the smallest adult cetacean on record.[4] Its appearance resembles that of a porpoise, but its conspicuous behaviour is typical of a dolphin. The dorsal fin has a long, straight leading edge which ends in a curved tip. The trailing is typically concave but not falcate. The fluke has a notch in the middle. This dolphin has no rostrum. It is not known why their distribution is limited to the southern coast of South America and the Kerguelen Islands.

Sexes are easily distinguished by the different shape of the black blotch on the belly — it is shaped like a teardrop in males but is more rounded in females. Females reach breeding age at six to 9 years. Males reach sexual maturity at about the same age. Mating occurs in the spring and summer and calving occurs after a gestation period of 11 months. The oldest known Commerson's dolphin died at age 18.

Population and distribution[edit]

The species is distributed in two locations. The larger population is found inshore in various inlets in Argentina, in the Strait of Magellan and near the Falkland Islands. The second population (discovered in the 1950s) resides near the Kerguelen Islands, 8,000 km (5,000 mi) to the east of the main population. They prefer shallow waters. Global populations are unknown, but the species is accepted to be locally common. A survey in 1984 estimated there to be 3,400 individuals in the Strait of Magellan.

The dolphin is found in two geographically disparate areas:

Behavior[edit]

Commerson's dolphin is very active. It is often seen swimming rapidly on the surface and leaping from the water. It also spins and twists as it swims and may surf on breaking waves when very close to the shore. It will bow-ride and swim behind fast-moving boats. It is also known to swim upside-down, which is thought to improve the visibility of its prey.

This dolphin feeds on a mix of coastal and pelagic fish and squid. Those in the South American subpopulation supplement their diets with crustaceans.

Conservation[edit]

The IUCN lists Commerson's dolphin as Data Deficient in its Red List of Threatened Species. The proximity of the dolphin to the shore makes accidental killing in gillnets a common occurrence. The dolphin was killed for use as crab bait by some Argentinian and Chilean fishermen in the 1970s and 1980s, but this practice has since been curtailed.[2]

The Commerson's dolphin population of South America is listed on Appendix II[5] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II[5] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.[6]

Captivity[edit]

About two dozen Commerson's dolphins live in aquariums in the world, including SeaWorld San Diego, Aquatica in Florida, Duisburg Zoo in Germany (until 2004), and several aquariums in Japan.

See also[edit]

References[edit]

  1. ^ Mead, J. G.; Brownell, R. L., Jr. (2005). "Order Cetacea". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 723–743. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ a b Reeves, R.R., Crespo, E.A., Dans, Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Pedraza, S., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, JY. & Zhou, K. (2008). "Cephalorhynchus commersonii". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 January 2013. 
  3. ^ Sharks and Whales (Carwardine et al. 2002), p. 370.
  4. ^ Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0-85112-235-9
  5. ^ a b "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.
  6. ^ Convention on Migratory Species page on the Commerson's dolphin
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