|Scientific Name:||Grampus griseus|
|Species Authority:||(G. Cuvier, 1812)|
|Infra-specific Taxa Assessed:|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J.K.B., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L.|
|Reviewer/s:||Hammond, P.S. & Perrin, W.F.|
As with similar species, threats that could cause widespread declines include high levels of anthropogenic sound, especially military sonar and seismic surveys, and bycatch. Threats that could cause declines include entanglement in fisheries and competition with squid fisheries. The combination of the large global range and high abundance with possible declines driven by these more localized threats is believed sufficient to rule out a 30% global reduction over three generations (60 years; Taylor et al. 2007) (criterion A).
|Range Description:||This is a widely-distributed species, inhabiting primarily deep waters of the continental slope and outer shelf (especially with steep bottom topography), from the tropics through the temperate regions in both hemispheres (Kruse et al. 1999). It also occurs in some oceanic areas, beyond the continental slope, such as in the eastern tropical Pacific. It is found from Newfoundland, Norway, the Kamchatka Peninsula, and Gulf of Alaska in the north to the tips of South America and South Africa, southern Australia, and southern New Zealand in the south. Its range includes many semi-enclosed bodies of water, such as the Gulf of Mexico, Gulf of California, Red Sea, Persian Gulf, Sea of Japan, and Mediterranean Sea.
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. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.
Native:Algeria; Angola (Angola); Anguilla; Antigua and Barbuda; Argentina; Aruba; Australia; Bahamas; Barbados; Bermuda; Brazil; Canada; Cayman Islands; Chile; China; Colombia; Comoros; Cook Islands; Costa Rica; Côte d'Ivoire; Croatia; Cuba; Curaçao; Denmark; Dominica; Ecuador; France; French Polynesia; French Southern Territories (Mozambique Channel Is.); Gabon; Gambia; Germany; Ghana; Gibraltar; Greece; Grenada; Guadeloupe; Guam; Guatemala; Guernsey; Guinea-Bissau; Haiti; India; Indonesia; Iran, Islamic Republic of; Ireland; Israel; Italy; Jamaica; Japan; Jersey; Korea, Republic of; Lebanon; Madagascar; Maldives; Malta; Mauritius; Mayotte; Mexico; Morocco; New Caledonia; New Zealand; Oman; Panama; Papua New Guinea; Peru; Philippines; Russian Federation; Samoa; Seychelles; Slovenia; Solomon Islands; Somalia; South Africa; Spain; Sri Lanka; Sweden; Syrian Arab Republic; Taiwan, Province of China; Tanzania, United Republic of; Tonga; Trinidad and Tobago; Tunisia; Turkey; United Arab Emirates; United Kingdom; United States; United States Minor Outlying Islands (Midway Is.); Uruguay; Venezuela, Bolivarian Republic of; Viet Nam; Yemen
|FAO Marine Fishing Areas:||
Atlantic – western central; Atlantic – southwest; Atlantic – eastern central; Atlantic – northeast; Atlantic – northwest; Atlantic – southeast; Indian Ocean – western; Indian Ocean – eastern; Mediterranean and Black Sea; Pacific – southwest; Pacific – western central; Pacific – northeast; Pacific – eastern central; Pacific – northwest; Pacific – southeast
|Range Map:||Click here to open the map viewer and explore range.|
There are no estimates of global abundance, but there are some estimates for specific areas. Forney and Barlow (1998) observed that the estimated abundance of Risso's Dolphins off California was almost an order of magnitude higher in winter (N= 32,376) than in summer (N= 3,980). However, the California, Oregon, Washington subpopulation is now estimated at only 16,066 (CV=28%) whales (Barlow 2003). Hawaiian waters are estimated to contain 2,351 (CV=65%) Risso’s Dolphins (Barlow 2006). Abundance estimates off Sri Lanka ranged from 5,500 to 13,000 animals (Kruse et al. 1999). In the eastern Sulu Sea, Dolar et al. (2006) estimated the abundance at 1,514 (CV=55%) individuals. There are an estimated 20,479 (CV=59%) Risso’s Dolphins off the eastern United States (Waring et al. 2006), 2,169 (CV=32%) in the northern Gulf of Mexico (Mullin and Fulling 2004), 83,300 (CV=17%) in three areas of concentrated occurrence off Japan (Miyashita 1993), and 175,000 in the eastern tropical Pacific (Wade and Gerrodette 1993).
In relative terms, there are several examples of long term changes in abundance and distribution, e.g. in the Southern California Bight (Kruse et al. 1999). In the late 1950s, Risso's Dolphins were rarely encountered in this area, and between 1975 and 1978 they were still considered to be a minor constituent of the cetacean fauna of the Bight, representing only 3% of the cetaceans observed. After the El Niño of 1982/83, however, numbers of Risso's Dolphins increased, especially around Santa Catalina Island where they came to be considered common (Shane 1995). There is no information on global trends in the abundance.
|Habitat and Ecology:||
Risso’s Dolphins inhabit deep oceanic and continental slope waters, generally 400-1,000 m deep (Baird 2002, Jefferson et al. 1993), mostly occurring seaward of the continental slope. They frequent subsurface seamounts and escarpments, where they are thought to feed on vertically migrant and mesopelagic cephalopods. In Monterey Bay, California, Risso's dolphins are concentrated over areas with steep bottom topography (Kruse 1989). Currents and upwelling causing local increases in marine productivity may enhance feeding opportunities, resulting in the patchy distribution and local abundance of this species worldwide (Kruse et al. 1999). Davis et al. (1998) and Baumgartner (1997) reported that in the Gulf of Mexico, Risso's dolphins were mostly found over deeper bottom depths, concentrating along the upper continental slope, which may reflect squid distribution. Most records of Grampus griseus in Britain and Ireland are within 11 km of the coast. In certain areas, such as in the southwest English Channel, Risso’s Dolphins are known to occur seasonally in shallow coastal waters to feed on cuttlefishes Sepia officinalis (Kiszka et al. 2004).
Long-term changes in the occurrence of Risso’s Dolphins in some areas (e.g., off Catalina Island and in central California) have been linked to oceanographic conditions and movements of spawning squid (Kruse et al. 1999). Risso's Dolphins feed on crustaceans and cephalopods, but seem to prefer squid. Squid bites may be the cause of at least some of the scars found on the bodies of these animals. In the few areas where feeding habits have been studied, they appear to feed mainly at night.
Occasional direct killing of Risso’s Dolphins has occurred. This is generally as a result of the dolphins removing fish from longlines, or in multi-species small cetacean fisheries, such as those that occur in Sri Lanka, the Caribbean, and Indonesia. One regular hunt occurs in Japan, where about 250–500 are taken per year in a drive fishery. Some Risso’s Dolphins have been captured for live display in oceanaria, although there are not many of them in oceanaria.
In Sri Lanka, Risso's Dolphins are apparently the second most commonly taken cetacean in fisheries, providing fish and meat for human consumption and fish bait; subpopulations there may be adversely affected (see Jefferson et al. 1993, Kruse et al. 1991). An estimated 1,300 Risso's Dolphins may be landed annually as a result of this fishery, and abundance estimates in these waters range only from 5,500 to 13,000 animals (Kruse et al. 1999). In Japan, Risso's Dolphins are taken periodically for food and fertilizer in set nets and as a limited catch in the small-type whaling industry (Kruse et al. 1999), with reported catches in recent years ranging from about 250–500. They are also a major target of artisanal hunting, and are taken often in gillnets and other fishing gear in the Philippines (Dolar 1994, Dolar et al. 1994). Off eastern Taiwan, Risso’s Dolphins are also taken by harpoon opportunistically and oceanic large-mesh driftnets for large pelagic fish appear to take considerable numbers incidentally (Wang pers. comm.).
There are reports of bycatches from the North Atlantic, the Mediterranean Sea, the southern Caribbean, the Azores, Peru, and the Solomon Islands. They are also a rare bycatch in the US tuna purse seine industry, and are taken occasionally in coastal gill net and squid seining industries off the US coast, or shot by aggravated fishermen (Kruse et al. 1999).
This species, like Beaked Whales that are also deep-divers that feed on squid, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).
Predicted impacts of global climate change on the marine environment may affect this species of whale, although the nature of impacts is unclear (Learmonth et al. 2006).
The species is listed in Appendix II of CITES. The North and Baltic Sea subpopulations are included in Appendix II of CMS.
This is a circumglobal species, which migrates between summering and wintering grounds. Off California, where these movements are best known, they may cross between US and Mexican waters. Data on abundance, bycatch, and behaviour needed in order to develop conservation measures that will enable protection of the natural habitat of the species
Baird, R. W. 2002. Risso's dolphin Grampus griseus. In: W. F. Perrin, B. Wursig and J. G. M. Thewissen (eds), Encyclopedia of Marine Mammals, pp. 1037-1039. Academic Press.
Barlow, J. 2003. Preliminary estimates of the abundance of cetaceans along the U.S. west coast: 1991-2001. Southwest Fisheries Center Administrative Report LJ-03-03: 31 pp.
Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. Marine Mammal Science 22(2): 446-464.
Baumgartner, M. F. 1997. The distribution of Risso's dolphin (Grampus griseus) with respect to the physiography of the northern Gulf of Mexico. Marine Mammal Science 13(4): 614-638.
Davis, R. W., Fargion, G. S., May, N., Leming, T. D., Baumgartner, M., Evans, W. E., Hansen, L. J. and Mullin, K. 1998. Physical habitat of cetaceans along the continental slope in the north-central and western Gulf of Mexico. Marine Mammal Science 14(3): 490-507.
Dolar, M. L. L. 1994. Incidental takes of small cetaceans in fisheries in Palawan, Central Visayas and northern Mindanao in the Philippines. Reports of the International Whaling Commission 15: 355-363.
Dolar, M. L. L., Leatherwood, S., Wood, C. J., Alava, M. N. R., Hill, C. L. and Arangones, L. V. 1994. Directed fisheries for cetaceans in the Philippines. Reports of the International Whaling Commission 44: 439-449.
Dolar, M. L. L., Perrin, W. F., Taylor, B. L., Kooyman, G. L. and Alava, M. N. R. 2006. Abundance and distributional ecology of cetaceans in the central Philippines. Journal of Cetacean Research and Management 8(1): 93-112.
Forney, K. A. and Barlow, J. 1998. Seasonal patterns in the abundance and distribution of California cetaceans, 1991-1992. Marine Mammal Science 14(3): 460-489.
IUCN. 2012. IUCN Red List of Threatened Species (ver. 2012.2). Available at: http://www.iucnredlist.org. (Accessed: 17 October 2012).
Jefferson, T. A., Leatherwood, S. and Webber, M. A. 1993. Marine Mammals of the World: FAO Species Identification Guide. United Nation Environment Programme and Food and Agricultural Organization of the UN.
Kiszka, J., Ersts, P. J. and Ridoux, V. 2007. Cetacean diversity around the Mozambique Channel island of Mayotte (Comoros archipelago). Journal of Cetacean Research and Management 9: 105-109.
Kiszka, J., Hassani, S. and Pezeril, S. 2004. Status and distribution of small cetaceans along the French Channel coast: using opportunistic records for a preliminary assessment. Lutra 47: 33-46.
Kruse, S., Caldwell, D. K. and Caldwell, M. C. 1999. Risso's dolphin Grampus griseus (G. Cuvier, 1812). In: S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, pp. 183-212. Academic Press, San Diego, California, USA.
Kruse, S. L. 1989. Aspects of the biology, ecology, and behavior of Risso's dolphins (Grampus griseus) off the California coast. University of California.
Kruse, S., Leatherwood, S., Prematunga, W. P., Mendes, C. and Gamage, A. 1991. Records of Risso's dolphins, Grampus griseus, in the Indian Ocean, 1891-1986. UNEP Marine Mammal Technical Report 3: 67-78.
Learmonth, J. A., Macleod, C. D., Santos, M. B., Pierce, G. J., Crick, H. Q. P. and Robinson, R. A. 2006. Potential effects of climate change on marine mammals. Oceanography and Marine Biology: An Annual Review 44: 431-464.
Miyashita, T. 1993. Abundance of dolphin stocks in the western North Pacific taken by the Japanese drive fishery. Reports of the International Whaling Commission 43: 417-437.
Mullin, K. D. and Fulling, G. L. 2004. Abundance of cetaceans in the oceanic northern Gulf of Mexico, 1996-2001. Marine Mammal Science 20(4): 787-807.
Poisson, F., Marjolet, C., Mété, K. and Vanpouille, M. 2001. Evaluation du phénomène de déprédation dû aux mammifères marins. In: Poisson, F. and Taquet, M. (eds), L’Espadon: de la Recherche à l’Exploitation Durable, pp. 231-247. Programme Palangre Réunionais. Rapport Final, Novembre 2001.
Shane, S. H. 1995. Behavior patterns of pilot whales and Risso's dolphins off Santa Catalina Island, California. Aquatic Mammals 21: 195-198.
Shane, S. H. 1995. Relationship between pilot whales and Risso's dolphins at Santa Catalina Island, California, USA. Marine Ecology Progress Series 123: 5-11.
Taylor, B. L., Chivers, S. J., Larese, J. and Perrin, W. F. 2007. Generation length and percent mature estimates for IUCN assessments of Cetaceans. Southwest Fisheries Science Center.
Wade, P. R. and Gerrodette, T. 1993. Estimates of cetacean abundance and distribution in the eastern tropical Pacific. Reports of the International Whaling Commission 43: 477-493.
Waring, G. T., Josephson, E., Fairfield, C. P. and Maze-Foley, K. (eds). 2006. U.S. Atlantic and Gulf of Mexico marine mammal stock assessments - 2005. NOAA Technical Memorandum NMFS-NE, pp. 346 pp..
|Citation:||Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J.K.B., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. 2012. Grampus griseus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 20 April 2014.|
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