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Phocoena dioptrica
Lahille, 1912
English: Spectacled porpoise
German: Brillenschweinswal
Spanish: Marsopa de anteojos
French: Marsouin à lunettes
Family Phocoenidae
Phocoena dioptrica
© Wurtz-Artescienza (see
links
)
1. Description
Most knowledge on the biology and ecology of the spectacled porpoise was obtained from stranded specimens, with less than fifteen confirmed sightings at sea. Published photographs of live animals in their natural environment are also very rare (Sekiguchi et al. 2006).
The spectacled porpoise is highly distinctive with its unusual pigmentation, small head and facial features and the large male dorsal fin. It is a robust animal with a rounded head and beak. The flippers are small and situated well forward. The dorsal fin is broadly triangular and grows much larger and rounded in males than in females. The flukes are small and have rounded tips. Adults are black dorsally, sharply separated from the white belly. Size ranges to 204 cm in females and 224 cm in males and mass to 85 kg in females and 115 kg in males (Goodall, 2002; 2009). Based on observations at sea and new photographs of live animals, a pale saddle around the dorsal fin is apparent (Sekiguchi et al. 2006).
Perrin et al. (2000) described osteological characteristics for specimens from Argentina and other areas of the Southern Hemisphere: tooth counts were16-26 and 17-23 in the upper and lower jaws, respectively. Total number of vertebrae was 66-70. The rostrum may be relatively smaller in the Auckland Islands than in other regions.
2. Distribution
There are records from widely separate locations; some of these may involve strays, or cases of mistaken identity. Records from offshore islands (mostly of dead animals and skulls), hint at a circumpolar distribution and suggest that the range may also include large areas of open sea. It is not known whether these represent isolated populations, or whether they mix with mainland coastal animals by migrating across the open sea (Carwardine, 1995).
Distribution of
Phocoena dioptrica
: coastal waters of southeastern South America and offshore islands around Antarctica (Hammond et al. 2008; © IUCN;
enlarge map
).
According to Goodall (2002, 2009),
P. dioptrica
is circumpolar in cool temperate, sub-Antarctic and low Antarctic waters. It ranges in coastal waters of south-eastern South America, from Santa Catarina in southern Brazil (32°S; Pinedo et al. 2002) south to Tierra del Fuego; Falkland Islands (Islas Malvinas); South Georgia; Iles Kerguélen; Heard Island; Tasmania; Macquarie Island; Auckland Islands; Antipodes Islands (Rice, 1998), South Island, New Zealand (Baker, 1999) and South Australia (Kemper and Hill 2001). The southernmost sighting was at 64°33'S (Goodall, 2009). The suggested circumpolar and offshore distribution of the species was extended further south than previously thought, into Antarctic waters south of the Antarctic Convergence (Brownell and Clapham, 1999; Van Waerebeek et al, 2004; Sekiguchi et al. 2006).
3. Population size
Nothing is known on the abundance of this porpoise (Goodall, 2009; Hammond et al. 2008). It was the most commonly encountered species during preliminary beach surveys undertaken on Tierra del Fuego by R.N.P. Goodall, but once the beaches had been cleared it was exceeded in frequency of occurrence by Commerson's dolphin (Brownell and Clapham, 1999).
4. Biology and Behaviour
Habitat
:
P. dioptrica
is mainly an oceanic species sighted in deep offshore waters. However, some have been sighted in coastal habitat, including in channels and even river estuaries (Goodall, 2009; Jefferson et al. 1993). Spectacled porpoises seem to occur only in cold temperate waters and where recorded, water temperatures associated with sightings ranged from 5.5°C to 9.5°C (Brownell and Clapham, 1999). However, this temperature range has recently be extended to 0.9-10.3 °C, with most of the sightings (52.0%) in waters of 4.9-6.2 °C (Sekiguchi et al. 2006).
Behaviour
: Spectacled porpoises are very inconspicuous when surfacing (Jefferson et al. 1993). They generally show fast swimming behaviour when approached by a vessel, resembling the swimming behaviour of harbour porpoises (Sekiguchi et al. 2006).
Schooling
:
P. dioptrica
appears to live mainly alone (most of the strandings and sightings are of solitary animals), but may also live in small groups (Carwardine, 1995; Jefferson et al. 1993). In southern waters, group size was small, averaging 2 animals per group. A total of six cow-calf pairs were observed and all such pairs were accompanied by one or two additional adults, always including a mature male (Sekiguchi et al. 2006).
Reproduction
: Births appear to occur in the southern spring to summer (Jefferson et al. 1993). Nothing is known on pregnancy rates, interbirth intervals or duration of lactation in this species (Brownell and Clapham, 1999).
Food
: Based upon its dentition, it is likely that, like other phocoenids, this species feeds upon fish and squid. Records of prey remains are scarce: anchovy (
Engraulis
sp.) and small crustaceans (possibly stomatopods) as well as squid (Brownell and Clapham, 1999; Goodall, 2009).
5. Migration
Nothing is known on the seasonal movements, if any, of this species (Brownell and Clapham, 1999; Goodall, 2009). Most sightings were pelagic, but strandings around Tierra del Fuego suggest at least some neritic activity of the species.
6. Threats
Direct catch
: In the past, spectacled porpoises were killed deliberately for food. In Argentina and Chile, spectacled porpoises are taken in gillnets, and they may have been taken deliberately for crab (centolla;
Lithodes santolla
) bait off southern Chile. The effects of these catches on spectacled porpoise populations are not known (Jefferson et al. 1993).
Incidental catch
: At least 34 animals were killed incidentally between 1975 and 1990 in coastal gill nets set in Tierra del Fuego, and there was a co-occurrence of strandings and fishing activity in south-eastern Chile, suggesting additional undocumented mortalities from this source. Some mortality of spectacled porpoises was also reported from bottom and mid-water trawls off the coast of Chubut, Argentina (Brownell and Clapham, 1999, and refs. therein). Jefferson and Curry (1994) summarise that the effects of incidental takes on the population are unknown.
Potential threats include also incidental captures in expanding fisheries in the Southern Ocean, especially in areas adjacent to subantarctic islands; disturbance and pollution resulting from coastal and offshore oil and mineral exploration (Argentina); pollution of preferred habitats, leading to accumulation of toxic substances in body tissues (Klinowska 1991; Bannister et al. 1996).
7. Remarks
Range states
:
Argentina; Australia (Macquarie Is., Tasmania); Brazil; Chile; Falkland Islands (Malvinas); French Southern Territories (the) (Kerguelen); Heard Island and McDonald Islands; New Zealand (Antipodean Is.); South Georgia and the South Sandwich Islands; Uruguay
IUCN Status: "Data Deficient" (Hammond et al. 2008).
P. dioptrica
is included in Appendix II of CMS. The species is listed in Appendix II of CITES.
According to Jefferson and Curry (1994), gillnets represent the single most important threat to porpoises as a group, and this may be an example of a "no technical solution problem". They conclude that better documentation of catches and new approaches to dealing with porpoise/gillnet interaction problems are needed in order to prevent the loss of several species and populations. See further recommendations and conclusions on South American stocks in Hucke-Gaete (2000) in
Appendix 1
.
8. Sources
· Baker, A.N. 1999. Whales and dolphins of New Zealand and Australia: an Identification Guide. Victoria University Press, Wellington. 133 pp.
· Bannister JL, Kemper CM, Warneke RM (1996) The Action Plan for Australian Cetaceans. Australian Nature Conservation Agency: Canberra vii 242 pp.
· Brownell RL, Clapham PJ (1999) Spectacled porpoise -
Phocoena dioptrica
Lahille, 1912. In: Handbook of Marine Mammals (Ridgway SH, Harrison SR, eds.) Vol. 6: The second book of dolphins and porpoises, pp.379-392.
· Carwardine M (1995) Whales, Dolphins and Porpoises. Dorling Kindersley, London, UK, 257 pp.
· Goodall RNP (2002) Spectacled porpoise -
Phocoena dioptrica
. In: Encyclopedia of marine mammals (Perrin WF, Würsig B, Thewissen JGM, eds.) Academic Press, San Diego, pp. 1158-1161.
· Goodall RNP (2009) Spectacled porpoise -
Phocoena dioptrica
. In: Encyclopedia of marine mammals (Perrin WF, Würsig B, Thewissen JGM, eds.) Academic Press, San Diego, pp. 1087-1091.
· Hammond PS, Bearzi G, Bjørge A, Forney K, Karczmarski L, Kasuya T, Perrin WF, Scott MD, Wang JY, Wells RS, Wilson B (2008)
Phocoena dioptrica
. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2.
· Hucke-Gaete R ed. (2000) Review on the conservation status of small cetaceans in southern South America. UNEP/CMS Secretariat, Bonn, Germany, 24 pp.
· Jefferson TA, Curry BE (1994) A global review of porpoise (Cetacea: Phocoenidae) mortality in gillnets. Biol Conserv 67: 167-183.
· Jefferson TA, Leatherwood S, Webber MA (1993) FAO Species identification guide. Marine mammals of the world. UNEP/FAO, Rome, 320 pp.
· Kemper C, Hill M (2001) First records of the spectacled porpoise
Phocoena dioptrica
in continental australian waters. Mar Mamm Sci 17: 161-170.
· Klinowska M (1991). Dolphins, Porpoises and Whales of the World: The IUCN Red Data Book. IUCN, Gland and Cambridge vii 429 pp.
· Perrin WF, Goodall RNP, Cozzuol MA (2000) Osteological variation in the spectacled porpoise (
Phocoena dioptrica
). J Cetacean Res Manag 2: 211-215
· Pinedo MC, Barreto AS, Lammardo MP, Andrade ALV, Geracitano L (2002) Northernmost records of the spectacled porpoise, Layard's beaked whale, Commerson's dolphin, and Peale's dolphin in the southwestern Atlantic Ocean. Aquat Mamm 28: 32-37
· Rice DW (1998) Marine mammals of the world: systematics and distribution. Society for Marine Mammalogy, Special Publication Number 4 (Wartzok D, ed.), Lawrence, KS. USA.
· Sekiguchi I, Olavarria C, Morse L, Olson P, Ensor P, Matsuoka K, Pitman R, Findlay K, Gorter U (2006) J Cetacean Res Manag 8: 265-271
· Van Waerebeek K, Leaper R, Baker AN, Papastavrou V, Thiele D (2004) Odontocetes of the Southern Ocean Sanctuary. IWC Scientific Committee Document SC/56/SOS1. 25pp.
© Boris Culik (2010) Odontocetes. The toothed whales: "
Phocoena dioptrica
". UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.
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