In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.
|EPBC Act Listing Status||Cetacean|
|Adopted/Made Recovery Plans|
Australian National Guidelines for Whale and Dolphin Watching (Department of the Environment and Heritage, 2005e) [Information Sheet].
|Non-statutory Listing Status||
|Scientific name||Delphinus delphis |
This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.
Scientific name: Delphinus delphis (Linneaus 1758)
Common name: Common Dolphin
Other names: Common Dolphin, Offshore Common Dolphin, Saddle-backed Dolphin
The taxonomy of the genus Delphinus is controversial. There are currently three species recognised within the genus; Delphinus delphis, D. capensis and D. tropicalis (Rice 1998). The short-beaked offshore form (D. delphis) and the long-beaked coastal form (D. capensis) are separated based on differences in morphology (Heyning & Perrin 1994) and mtDNA sequences (Rosel et al. 1994). In the Indo-Pacific, a longer-beaked form (D. tropicalis) is differentiated from the two other forms based on osteological measures and tooth counts (Heyning & Perrin 1994). More recently, however, this form was suggested to be a sub-species of D. capensis, which hybridise or intergrade with the long-beaked form of southeast Asia and possibly the east coat of Africa (Jefferson & van Waerebeek 2002).
Common Dolphins are slender, with a long beak protruding sharply from the melon (face and forehead). The dorsal fin is high and curves backwards. Common Dolphins are easily distinguished from other dolphin species by a unique crisscross colour pattern on the top of the animal. This colour pattern is formed by the interaction of the dorsal overlay and the cape. This yields a four-part colour pattern, with dark grey to black over the back of the animal, buff to pale yellow forming an anterior thoracic patch, light to medium grey on the flank and white abdominal field (Perrin 2002). The colour pattern is crisp, the thoracic patch rather yellowish, and the sub-cape stripe is anteriorly narrow and faint (Perrin 2002).
Like other dolphins, male Common Dolphins are slightly larger than females. In California, adult males measured between 172 and 201 cm while adult females measured between 164 and 193 cm (Perrin 2002). Body mass is about 200 kg (Perrin 2002).
Common Dolphins are found in medium-sized groups to extremely large schools, ranging from about 2030 to hundreds and thousands of individuals (Evan 1994). Within schools they may be segregated by age and sex (Perrin 2002).
Common Dolphins are found in offshore waters. They have been recorded in waters off all Australian states and territories, but are rarely seen in northern Australian waters (Jefferson & Waerebeek 2002; Ross 2006). Common Dolphins appear to occur in two main locations around Australia, with one cluster in the southern south-eastern Indian Ocean and another in the Tasman Sea.
Neither the extent of occurrence nor the area of occupancy of the Common Dolphin have been estimated.
Due to its offshore distribution, it is unlikely that Common Dolphin populations are severely fragmented in Australia (Möller 2006, pers. comm.).
Globally, Delphinus dolphins are found in tropical, subtropical and temperate waters of the Atlantic, Pacific and Indian Oceans (Rice 1998) occurring in both shallow and deep offshore waters (Evans 1994). However, there some uncertainty regarding the distribution of each of the three recognised species as in many cases records were not identified to the species level.
Based on species specific records, Common Dolphins are known to occur:
- from southern Norway to west Africa in the eastern Atlantic
- from Newfoundland to Florida in the western Atlantic
- from southern Canada to Chile in the eastern Pacific
- in the central North Pacific
- from central Japan to Taiwan, and around New Caledonia, New Zealand, and Tasmania in the western Pacific (Perrin 2002).
Global population size estimates are available for only a few regions:
- eastern tropical Pacific: 3 000 000 individuals (Evans 1994)
- off the Californian coast: 226 000 individuals (Barlow 1995)
- Black Sea: 96 000 (Sokolov et al. 1997).
In the Mediterranean Sea, Common Dolphins have declined in numbers. This decline is thought to be a consequence of prey depletion, among other factors (Bearzi et al. 2003). The population in the Mediterranean Sea is listed as Endangered on the IUCN Red List of Threatened Species. It is thought that the population in this area has declined by more than 50% over a three-generation period (i.e., the past 3045 years) (Bearzi 2003).
Main threats to the species globally include direct catch, incidental catch, culling, pollution, habitat degradation, environmental changes (such as increase in water temperatures), and competition with fisheries.
In the Black Sea a large fishery operated from 1870 to 1983, taking a large number of Common Dolphins. Direct catches are still known to occur in small numbers in several areas (Jefferson et al. 1993; Reyes 1991).
Incidental catches occur in purse-seine, drift nets, gillnets, and trawl nets in many areas around the world. In the eastern tropical Pacific about 16 000 Common Dolphins were killed in 1988 alone in the tuna purse-seine fishery (Evans 1994).
High loads of contaminants, including PCBs and heavy metals have been reported in Common Dolphins (Reyes 1991, Evans 1994, Holsbek et al. 1998). In southern Australia high levels of cadmium and histological abnormalities were found in the kidneys of stranded Common Dolphins (Long et al. 1997).
In the Mediterranean Sea, competition with schooling fish fisheries is thought to have contributed to the decline of Common Dolphins in the area. However, habitat degradation, pollution, environmental changes and indirect catch in gillnets are also thought to have contributed (Bearzi et al. 2003).
There is no information on movements of Common Dolphins in and out of the Australian jurisdiction, or studies on stock structure of this species in Australia and neighbouring areas. The relationship between Australian Common Dolphins and those inhabiting other regions is thus not known.
Common Dolphins have not been well surveyed in Australia, and specific range and population sizes are currently unknown.
There are no estimates of population size for Common Dolphins in Australian waters. Similarly, there is no information on population trends for this species.
Although the nature of population fluctuations in Australian waters is unknown, seasonality in distribution and abundance of Common Dolphins has been reported for several other areas around the world. Substantial seasonal and inter-annual changes in abundance have been observed in the eastern North Pacific, and may be related to north-south or inshore-offshore movements (Forney & Barlow 1998). In New Zealand a seasonal offshore shift appears to be correlated with sea surface temperature (Neumann 2001). In South Africa, the occurrence of Common Dolphins off Natal is strongly associated with the annual sardine run (Young & Cockcroft 1994). In the Gully, off Nova Scotia, the arrival of Common Dolphins to the area appears to be seasonal, and associated with an increase in water temperature (Gowans & Whitehead 1995). These movements may correspond to noted fluctuations in the abundance of this species.
The generation length of the Common Dolphin has been estimated at 1015 years (Bearzi 2003). However, as the age of sexual maturity varies between region, the generation length may also be dependent on region (Perrin 2002).
All cetaceans are protected within the Australian Whale Sanctuary under the EPBC Act. The Sanctuary includes all Commonwealth waters from the 3 nautical mile state waters limit out to the boundary of the Exclusive Economic Zone (i.e. out to 200 nautical miles and further in some places). Common Dolphins are also subject to IWC regulations and protected within the Indian Ocean Sanctuary and Southern Ocean Sanctuary (Ross 2006).
Information on the species' habitats is only available from outside of Australia. In most areas where they have been studied, Common Dolphins appear to occur mainly in medium water depths over the continental shelf (Cañadas et al. 2002; Evans 1994; Forcada & Hammond 1998), but little is known about those living near or on the edge of the shelf. Common Dolphins have been observed to travel over specific ocean features such as seamounts, ridges and escarpments (Evans 1994). In the tropical eastern Pacific they are primarily associated with upwelling-modified habitats (Reilly 1990). In the Mediterranean Sea they are known to occur in both neritic (over the shelf) and pelagic (open ocean) environments (Bearzi et al. 2003).
Common Dolphins are usually found in areas where surface water temperatures are between 10°C and 20°C, and in habitats also inhabited by small epipelagic fishes such as anchovies and sardines.
Common Dolphins associate with several other dolphin species. In the Mediterranean Sea, they occur with Striped, Bottlenose and Risso's dolphins (Frantzis & Herzing 2002). In New Zealand, Common Dolphins have been observed to feed in association with Australasian gannets, and on rare occasions, with Minke, Sei and Bryde's Whales (Neumann & Orams 2003).
Females usually attain maturity earlier than males, although some variation exists between areas. In the Black Sea for example, males reach sexual maturity from three years, and females two to four years. In the eastern Pacific however, sexual maturity occurs between seven and 12 years for males and six to seven years for females (Perrin 2002). Variation between regions may be partly a result of density-dependent effects, and may thus have been affected by the population decline in the Mediterranean. The maximum estimated age is 22 years (estimated from the Black Sea population) (Bearzi 2003).
Information on reproduction is only available for populations outside of Australia. Calving occurs year-round, with peaks in spring and autumn. Gestation is about 1011 months long and the interbirth interval is about one to three years (Perrin 2002). No specific calving areas in Australia are known (Bannister et al. 1996).
Common Dolphins feed on a variety of small prey, mainly on epipelagic schooling and mesopelagic fishes and squids, but also on other cephalopods and crustaceans (Bearzi et al. 2003; Evans 1994; Perrin 2002). Diet may vary with season as well as region (Evans 1994). In South Australia, the diet of Common Dolphins has been reported to consist of fish and cephalopods, including fishes of the families Clupeidae and Carangidae, Southern Calamari, Arrow Squid and octopus (Kemper & Gibbs 2001).
The feeding preferences and behaviours of Common Dolphins puts them at risk of incidental capture on nets and other fishing gear. In the eastern tropical Pacific, Common Dolphins feed in association with tuna, and are often caught in large numbers in the purse-seine nets (Evan 1994). In the Mediterranean Sea, there are records of Common Dolphins feeding on anchovies as they are caught in gillnets, and causing damage to fishing gear (Bearzi et al. 2003). In South Australia, Common Dolphins become entangled in anti-predator nets (eg. shark nets) when they presumably come to feed near tuna aggregations (Kemper & Gibbs 2001). They are also caught in this area in purse-seine nets set for pilchards. The rate of capture led to a temporary closure of the South Australian pilchard fishery in 2005 (Advertiser 2005).
In many areas around the world Common Dolphins show shifts in distribution and abundance, suggesting seasonal migration. In the eastern North Pacific this movement may be either north-south or inshore-offshore (Forney & Barlow 1998). In New Zealand, a seasonal offshore-shift correlated with sea surface temperature has been reported (Neumann 2001). In South Africa, the occurrence of Common Dolphins off Natal is strongly associated with the annual sardine run (Young & Cockcroft 1994). In the Gully, off Nova Scotia, Common Dolphins appear to occur in the area seasonally, associated with an increase in water temperature (Gowans & Whitehead 1995).
Common Dolphins can be easily distinguished from other dolphin species by the unique crisscross colour pattern formed by interaction of the dorsal overlay and cape. Common Dolphins, however, can be confused with the Long-beaked Common Dolphin in areas where their distributions narrowly overlap, such as off the Californian coast. The Common Dolphin has a shorter beak, a crisper colour pattern, more yellowish thoracic patch, and an anteriorly narrow and faint sub-cape stripe (Perrin 2002). They also tend to be found further offshore than the long-beaked species. Common Dolphins may also be confused with Clymene Dolphin (Stenella clymene), particularly when viewed from above.
Due to the offshore distribution of Common Dolphins, the recommended methods for abundance surveys include vessel-based and aerial line-transects. Time of the year for conducting surveys should coincide with the season with most favourable weather conditions, such as prevailing light winds. It is recommended that researchers should take into consideration the potential movement north-south and inshore-offshore of these animals when designing the surveys (Möller 2006, pers. comm.).
Main threats likely to affect Australian Common Dolphin populations include indirect catches in purse-seine, gillnet, and trap fisheries, entanglements in debris (Shaughnessy et al. 2003), intentional killing (Kemper & Gibbs 2001), and pollution (Ross 2006). Death in fishing nets has been recorded in South Australia, Tasmania and Western Australia (Ross 2006). They are also caught in anti-predator nets set around tuna feedlots in South Australia (Kemper & Gibbs 2001) and in shark meshing to protect bathers in NSW.
In South Australia high levels of cadmium and histological abnormalities were found in the kidneys of stranded Common Dolphins (Long et al. 1987).
In the past, Common Dolphin meat was used as bait for craypots, and individuals were captured for aquariums (Ross 2006).
The low reproductive rate of the Common Dolphin, with an interbirth interval of about one to three years and a late age of sexual maturity, means that population recovery would be a very slow process (Perrin 2002).
By-catch action plans for several fisheries managed by the Australian Fisheries Management Authority were initiated in 2001, to reduce the by-catch of dolphins and other marine animals (Ross 2006). Pingers used to warn cetaceans away from nets are currently employed on shark nets positioned to protect bathers in Australia.
Recommendations for minimising entanglements in marine aquaculture facilities, such as tuna feedlots, have also been proposed and include:
- an observer program
- collection of baseline information on the species/populations affected
- a review on the use of anti-predator nets
- use of acoustic harassment devices (Kemper & Gibbs 2001; Kemper et al. 2004).
The Action Plan for Australian Cetaceans (Bannister et al. 1996) and the Review of the Conservation Status of Australia's Smaller Whales and Dolphins (Ross 2006) provide brief overviews of the species and some management recommendations. Mitigating measures, such as the use of pingers, escape panels in purse seine nets, and handling methods for animals brought aboard vessels have been proposed by Leadbitter and colleagues (1998). In addition, The Australian National Guidelines for Whale and Dolphin Watching (DEH 2005c) have been published.
No threats data available.
Bannister, J.L., C.M. Kemper & R.M. Warneke (1996). The Action Plan for Australian Cetaceans. [Online]. Canberra: Australian Nature Conservation Agency. Available from: http://www.environment.gov.au/resource/action-plan-australian-cetaceans.
Barlow, J. (1995). The abundance of cetaceans in California waters: Part I. Ship surveys in summer and fall of 1991. US National Marine Fisheries Service Fishery Bulletin. 93:1-14.
Bearzi, G, R.R. Reeves, G. Notarbartolo di Sciara, E. Politi, A. Canadas, A. Frantzis & B. Mussi (2003). Ecology, status and conservation of Common Dolphins Delphinus delphisin the Mediterranean Sea. Mammal Review. 33:224-252.
Bearzi, G. (2003). Delphinus delphis (Mediterranean subpopulation). IUCN Red List of Threatened Species. [Online]. International Union for the Conservation of Nature and Natural Resources. Available from: http://www.iucnredlist.org/search/details.php/41762/all. [Accessed: 18-Jul-2007].
Department of the Environment and Heritage (2005e). Australian National Guidelines for Whale and Dolphin Watching. [Online]. Available from: http://www.environment.gov.au/resource/australian-national-guidelines-whale-and-dolphin-watching-2005.
Evans, W.E. (1994). Common dolphin, White-bellied Porpoise Delphinus delphis Linnaeus, 1758. In: Ridgway, S.H. & R. Harrison, eds. Handbook of Marine Mammals Vol 5: The First Book of Dolphins. Page(s) 191-224. Academic Press, London.
Forcada, J. & P. Hammond (1998). Geographical variation in abundance of striped and common dolphins of the western Mediterranean. Journal of Sea Research. 39:313-325.
Forney, K.A. & J. Barlow (1998). Seasonal patterns in the abundance and distribution of California cetaceans, 1991-1992. Marine Mammal Science. 14:460-489.
Frantzis, A. & D.L. Herzing (2002). Mixed-species associations of striped dolphins (Stenella coeruleoalba), Common Dolphins (Delphinus delphis), and Risso's dolphins (Grampus griseus) in the Gulf of Corinth (Greece, Mediterranean Sea). Aquatic Mammals. 28:188-197.
Gowans, S. & H. Whitehead (1995). Distribution and habitat partitioning by small odontocetes in the Gully, a submarine canyon on the Scotian Shelf. Canadian Journal of Zoology. 73:1599-1608.
Heyning, J.E. & W.F. Perrin (1994). Evidence for two species of common dolphins (genus Delphinus) from the eastern North Pacific. Contributions in Science, Los Angeles County Museum of Natural History. 442:1-35.
Jefferson, T.A. & K. Van Waerebeek (2002). The taxonomic status of the nominal dolphin species Delphinus tropicais Van Bree, 1971. Marine Mammal Science. 18:787-818.
Jefferson, T.A., S. Leatherwood & M.A. Webber (1993). FAO species identification guide. Marine Mammals of the World. [Online]. Rome: United Nations Environment Programme, Food and Agricultural Organization. Available from: ftp://ftp.fao.org/docrep/fao/009/t0725e/t0725e00.pdf. [Accessed: 15-Aug-2007].
Kemper, C.M. & S.E. Gibbs (2001). Dolphin interactions with tuna feedlots at Port Lincoln, South Australia and recommendations for minimising entanglements. Journal of Cetacean Research and Management. 3:283-292.
Kemper, C.M., D. Pemperton, M. Cawthorn, S. Heinrich, J. Mann, B. Wursig, P. Shaughnessy & R. Gales (2004). Aquaculture and marine mammals: Co-existence or conflict?. In: Gales, N.J., M.A. Hindell, & R. Kirkwood, eds. Marine mammals: fisheries, tourism and management issues. CSIRO Publishing, Collingwood.
Leadbitter, D., I. Gordon & M. McKechnie (1998). Circle of dependence: Protected species handing manual. Sydney, Ocean Watch.
Long, M., R.J. Reid & C.M. Kemper (1997). Cadmium accumulation and toxicity in the bottlenose dolphin Tursiops truncates, the common dolphin Delphinus delphis, and some dolphin prey species in South Australia. Australian Mammalogy. 20:25-33.
Neumann, D.R. (2001). Seasonal movements of Common Dolphins (Delphinus delphis) in the north-western Bay of Plenty, New Zealand: influence of sea surface temperature and El Nino/La Nina. New Zealand Journal of Marine and Freshwater Research. 35:371-374.
Neumann, D.R. & Orams (2003). The feeding behaviours of Common Dolphins, Delphinus delphis, in New Zealand. Aquatic Mammals. 29:137-149.
Perrin, W.F. (2002). Common dolphins. In: Perrin, W.F., B. Würsig, & J.G.M. Thewissen, eds. Encyclopedia of Marine Mammals. Academic Press, San Diego.
Reilly, S.B. (1990). Seasonal changes in distribution and habitat differences among dolphins in the eastern tropical Pacific. Marine Ecology Progress Series. 66:1-11.
Reyes, J.C. (1991). The conservation of small cetaceans: a review. Report prepared for the Secretariat of the Convention on the Conservation of Migratory Species of Wild Animals. UNEP/CMS Secretariat, Bonn.
Rice, D.W. (1998). Marine mammals of the world. Systematics and distribution. Special publication number 4. Kansas: Society for Marine Mammalogy.
Rosel, P.E., A.E. Dizon & J.E. Heyning (1994). Genetic analysis of sympatric morphotypes of common dolphins (genus Delphinus). Marine Biology. 119:159-167.
Ross, G.J.B. (2006). Review of the Conservation Status of Australia's Smaller Whales and Dolphins. Page(s) 124. [Online]. Report to the Australian Department of the Environment and Heritage, Canberra. Available from: http://www.environment.gov.au/resource/review-conservation-status-australias-smaller-whales-and-dolphins.
Shaughnessy, P., R. Kirkwood, M. Cawthorn, C. Kemper & D. Pemberton (2003). Pinnipeds, cetaceans and fisheries in Australia: A review of operational interactions. In: Gales, N., M. Hindell, & R. Kirkwood, eds. Marine Mammals: Fisheries, Tourism and Management Issues. Collingwood: CSIRO Publishing.
Sokolov, V.E., V.A. Yaskin & V.L. Yukhov (1997). Distribution and numbers of the Black Sea dolphins surveyed from ships. Zoologicheskii Zhurnal. 76:364-370.
Young, D.D. & V.G. Cockcroft (1994). Diet of common dolphins (Delphinus delphis) off the south-east coast of southern Africa: Opportunism or specialization?. Journal of Zoology London. 234:41-53.
This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.
Citation: Department of the Environment (2014). Delphinus delphis in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Tue, 23 Sep 2014 04:05:10 +1000.