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| Ecology and Behavior |
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Habitat: Coastal, with the exception of the ETP
The spinner dolphin is named for its habit of leaping from the water and spinning up to seven times on its long axis before falling back to the water. This is one of the most aerial of all dolphins, and in most areas they are active bowriders (the main exception is the ETP, where these dolphins have been harassed by fishermen, who encircle them to catch tuna swimming below). Herd sizes range from less than 50 up to several thousand. Associations with spotted dolphins are common in the ETP, and they occasionally associate with several other marine mammal species. Their association with spotted dolphins and yellowfin tuna results in their entanglement in tuna purse seines in the ETP.
The behavior of Hawaiian spinner dolphins has been well studied. Moderately-sized groups of dolphins move into shallow sandy bays to rest in the daytime, and then move offshore in the late afternoon/evening for nighttime feeding in nearby continental slope and oceanic waters. Dolphins are highly aerial during the ascent from rest to foraging.
Reproduction:
Calving peaks in different populations range from late spring to fall after a gestation of ~10.5 months. Females lactate 1-2 years, and the calving interval is about 3 years. Maximum age is thought to be 20 years. |
| Feeding and Prey |
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Feeding mode: Seizing
Broad diet dominated by: Fish>squid>other invertebrates
Most spinners feed predominantly at night, on midwater fish and squid, and rest during much of the day. Dwarf spinners are exceptional, however, and presumably feed during daylight hours on reef-associated organisms.
Known prey species:
Bathylagus sp., Bregmaceros bathymaster, Oxyporhamphus micropterus, Vinciguerria lucetia, Benthosema panamense, Diogenichthys laternatus, Hygophum sp., Lampanyctus idostigma, Lampanyctus parvicauda, Myctophum aurolaternatum, Myctophum asperum, Myctophum brachygnathum, Myctophum nitidulum, Myctophum sp. c.f. phengodes, Symbolophorus evermanni, Conger sp., Diretmoides parini, Melamphaes sp., Scopeloberyx sp., Caelorinchus sp., Coryphaenoides sp., Hymenocephalus sp., Bolinichthys spp., Ceratoscopelus warmingi, Diaphus fragilis, Diaphus garmani, Diaphus luetkeni, Diaphus parri, Diaphus rafinesquii, Diaphus sagamiensis, Diaphus suborbitalis, Diogenichthys atlanticus, Electrona risso, Gonichthys barnesi, Hygophum proximum, Lampadena c.f. luminosa, Lampanyctus alatus, Lampanyctus ater, Lampanyctus sp. c.f. nobilis, Notoscopelus resplendens, Symbolophorus evermanni, Symbolophorus sp. c.f. boops, Lestidiops sp. c.f. similus, Notolepis spp., Sudis sp., Scopeloarchus sp., Howella sp., Rexea sp. c.f. solandri, Aphanophus carbo, Cubiceps pauciradiatus, Cubiceps squamiceps, Bathylagus sp., Chauliodus sloani
Invertebrates: Abralia astrosticta, Abralia trigonura, Enoploteuthis chunii, Octopoteuthis banksi, Histioteuthis miranda, Brachioteuthis sp., Nototodarus sp. c.f. philippinensis, Chiroteuthis sp., Grimalditeuthis sp., Idioteuthis sp., Cranchia scabra, Galiteuthis sp., Helicocranchia sp., Leachia dislocata, Taonius sp., Sergia fulgens, Acanthephyra sp., Pusiphea spp., Oplophurus grimaldi, Acanthephyra quadrispinosa, Hemipenaeus sp. |
| Threats and Status |
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Main threats include:
Fisheries bycatch
Harvest
Conservation status:
The IUCN lists the spinner dolphin as lower risk/conservation dependent, in that conservation measures are in place that address the concerns for spinners. This is the second-most important species of dolphin involved in the ETP tuna purse seine fishery (after the pantropical spotted dolphin). The eastern spinner dolphin population is estimated to have been reduced to less than 1/3 its original size by the kill. Other incidental kills occur throughout the range in a number of different fisheries, including driftnets, purse seines, and trawls.
In some cases, human use of bycaught dolphins has led to direct fisheries. Direct kills occur in several areas, including the Caribbean, Sri Lanka, the Philippines, and Indonesia, and occasionally Japan. Their habit of resting in coastal waters leads to problems of harassment by dolphin-watching boats in a number of areas. In 2000, NMFS estimated the Hawaiian stock of spinners to be 3,184 (CV = 0.37) and in 1995, the Northern Gulf of Mexico population was likewise estimated at 6,316 (CV = 0.43). The population of spinner dolphins in the ETP is estimated to be 1,157,746 (CV = 0.43).
For current information on the conservation status of this species, please consult the following websites.
CITES web-page
Convention on Migratory Species (Appendix II, ETP populations and southeast Asian populations
International Whaling Commission
U.S. NMFS Stock Assessment Reports |
| References |
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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.
Dolar, M.L.L., W.A. Walker, G.L. Kooyman, W.F. Perrin. 2003. Comparative feeding ecology of spinner dolphins (Stenella longirostris) and Frasers dolphins (Lagenodelphis hosei) in the Sulu Sea. Marine Mammal Science 19 1-19.
Fitch J.E. and R.L. Brownell, Jr. 1968. Fish otoliths in cetecean stomachs and their importance in interpreting feeding habits. Journal of the Fisheries Research Board of Canada 25 2561-2574.
Gerrodette, T. 1999. Preliminary estimates of 1998 abundance of four dolphin stocks in the eastern tropical Pacific. U.S. Department of Commerce. SWFSC Administrative Report LJ-99-04.
Norris, K.S. and T.P. Dohl. 1980. Behavior of the Hawaiian spinner dolphin, Stenella longirostris. Fisheries Bulletin 77 821-849.
Norris, K.S., B. Wursig, R.S. Wells, and M. Wursig. 1994. The Hawaiian Spinner Dolphin. University of California Press.
Perrin, W.F. 1990. Subspecies of Stenella longirostris (Mammalia Cetacea Delphinidae). Proceedings of the Biological Society of Washington 103:453-463.
Perrin, W.F. 1998. Stenella longirostris. Mammalian Species 599:1-7.
Perrin, W.F. 2002. Spinner dolphin Stenella longirostris. Pp. 1174-1178 in W. F. Perrin, B. Würsig and J. G. M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Perrin, W.F., M.L.L. Dolar, and D. Robineau. 1999. Spinner dolphins (Stenella longirostris) of the western Pacific and Southeast Asia pelagic and shallow-water forms. Marine Mammal Science 15:1029-1053.
Perrin, W.F., and J.W. Gilpatrick Jr. 1994. Spinner dolphin Stenella longirostris (Gray, 1828). Pp. 99-128 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Volume 5 The first book of dolphins. Academic Press.
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