Habitat:  Shelf-slope

Large boisterous groups of common dolphins are often seen whipping the ocean's surface into a froth as they move along at high speed. Herds range in size from about 10 to over 10,000. Associations with other marine mammal species are not uncommon. Active and energetic bowriders (except in prime tuna fishing zones of the eastern tropical Pacific), common dolphins are very familiar to most seagoers in low latitudes. They are often aerially active and highly vocal; sometimes their squeals can be heard above the surface as they bowride.

Reproduction:

Adult females calve every two or three years, gestating ten to eleven months and nursing up to nineteen months. At birth, common dolphins are 80-85 cm long. Age at sexual maturity varies greatly among populations. The lifespan of common dolphins is believed to be between twenty and thirty years. 

Broad diet dominated by:  Fish>squid

The prey of common dolphins consists largely of small schooling fishes and squid.

Large groups of common dolphin often feed in areas of prominent bottom topography. In some areas, common dolphins feed mostly at night on creatures associated with the deep scattering layer (DSL), which migrates toward the surface in the dark. In other areas, they feed mainly on epipelagic schooling fish.

Known prey species:

Cephalopods:Loligo spp., Sepia sp., Unidentified Sepiidae, Sepiola atlantica, Unidentified Sepiolinae, Alloteuthis sp., Unidentified Loliginidae, Octopoteuthis sicula, Illex coindetii, Brachioteuthis sp., Chiroteuthis sp.

Invertebrates: Pasiphaea sp., Acantephyra sp., Meganyctiphanes norvegica

Fish:Sardinops ocellatus, Sardinops pilchardus, Engraulis encrasicolus, Myctophum sp., Macroramphosus sp., Merluccius merluccius, Gadiculus argenteus, Micromesistius poutassou, Trisopterus sp., Capros aper, Cepola macrophthalma, Trachurus trachurus, Trachurus sp., Boops boops, Diplodus vulgaris, Unidentified Sparidae, Hyperoplus lanceolatus, Scomber japonicus, Scomber scombrus, Scomber spp., Deltentosteus quadrimaculatus, Gobius niger, Unidentified Gobiidae, Callionymus lyra, Liza ramada, Atherina sp., Arnoglossus imperialis, Arnoglossus laterna, Unidentified Bothidae, Microchirus variegatus, Maurolicus muelleri, Notoscopelus kroyeri, Ceratoscopelus maderensis, Diaphus sp.. Paralepis sp., Scomberesox saurus, Stomias boa, Chauliodus sloani

Main threats include:

Harvest

Fisheries bycatch

Entanglement in debris/fishing gear

Conservation status:

The IUCN lists specific populations of common dolphins of particular concern the Bulgarian population is “vulnerable”, the Ukrainian stock is “data deficient”, and the Romanian stock is “endangered”. In the U.S., the short-beaked common dolphin is not listed as endangered or threatened.

Although the species as a whole is not at risk, particular populations are of concern. In the Black Sea a fishery for common dolphins decimated their numbers, once killing up to 200,000 annually. Common dolphins continued to be taken in large numbers in the Black Sea until 1973, and even after this date a direct fishery existed to a lesser extent. Effects on the common dolphins of the Black Sea, with numbers thought to historically exceed one million, were severe and this population is of greatest concern for conservationists. Common dolphins are also taken in gillnet, trawl, tuna purse seine, and longline fisheries. Prey depletion and poor habitat quality are a concern for the population in the Mediterranean. U.S. stock estimates are 318,795 common dolphins in the eastern North Pacific off California, Oregon, and Washington and 22,215 in the western North Atlantic.

For current information on the conservation status of this species, please consult the following websites.

IUCN Species Redlist

CITES webpage

U.S. FWS Threatened and Endangered Species System (TESS)

International Whaling Commission

U.S. NMFS Stock Assessment Reports

Convention on Migratory Species (Appendix II)

Genetics Genbank

Sounds Scripps Institution of Oceanography

Museum Collections Smithsonian Institution

Amaha, A. 1994. Geographic variation of the common dolphin, Delphinus delphis (Odontoceti Delphinidae). Ph.D. thesis, Tokyo University of Fisheries.

Dizon, A.E., W.F. Perrin, AND P.A. Akin. 1994. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern tropical Pacific a phylogeographic classification. NOAA Technical Memorandum NMFS 119:20 PP.

Evans, W.E. 1994. Common dolphin, white-bellied porpoise Delphinus delphis Linneaus, 1758. Pp. 191-224 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5 The first book of dolphins. Academic Press.

Ferrero, R.C., and W.A. Walker. 1995. Growth and reproduction of the common dolphin, Delphinus delphis Lineaus, in the offshore waters of the North Pacific Ocean. Fishery Bulletin 93:483-494.

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb, and J.U. Caretta. 2000. U.S. Pacific marine mammal stock assessments 2000. U.S. Department of Commerce, NOAA technical memorandum, SWFSC-300.

Hassani, S., L. Antoine, and V. Ridoux. 1997. Journal of Northwest Atlantic Fisheries Science 22 119-123.

Heyning, J.E., and W.F. Perrin. 1994. Evidence for two species of common dolphins (genus Delphinus) from the eastern North Pacific. Natural History Museum of Los Angeles County, Contributions in Science 442:35 pp.

Pauly, D., A.W. Trites, E.Capuli, and V.Christensen. 1998. Diet composition and trophic levels of marine mammals. ICES Journal of Marine Science, 55467-481.

Perrin, W.F. 2002. Common dolphins Delphinus delphis, D. capensis, and D. tropicalis. Pp. 245-248 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.

Silva, M.A. 1999. Diet of common dolphins, Delphinus delphis, off the Portuguese continental coast. Journal of the Marine Biological Association of the United Kingdom, 79 531-540.

Waring, G.T., D.L. Palka, P.J. Clapham, S. Swartz, M.C. Rossman, T.V.N. Cole, K.D. Bisack, and L.J. Hansen. 1998. U.S. Atlantic marine mammal stock assessments 1998. U.S. Department of Commerce, NOAA technical memorandum, NMFS-NE-116.