|Scientific Name:||Dosidicus gigas (D'Orbigny, 1835)|
Ommastrephes gigas D'Orbigny, 1835
|Taxonomic Notes:||D. gigas is a well defined species that cannot be confused with any other squid. Within its geographic range, however, there is great variation in the size and age at maturity and size frequency distribution. But there is no evidence at present (2009) that any subpopulations are genetically distinct although Nigmatullin et al. (2001) suggest that they may be separate stocks.|
|Red List Category & Criteria:||Data Deficient ver 3.1|
|Assessor(s):||Barratt, I. & Allcock, L.|
|Reviewer(s):||Vecchione, M., Young, R. & Böhm, M.|
|Contributor(s):||Staaf, D., Stewart, J., Field, J. & Carrete-Vega, G.|
We consider Dosidicus gigas to be Data Deficient since there are no reliable estimates of total biomass or stock stock size despite it being the target of the largest invertebrate fishery in the world.
|Range Description:||Historical habitat for Dosidicus gigas is the Eastern Tropical Pacific (Young and Vecchione 2009). In some years, as at present, the population extends along the coast south to about 47 °S and north to Alaska (60 ºN) (Young and Vecchione 2009). Its historical distribution ranged from 26 ºS to mid-Baja California, with occasional range extensions attributed to El Niño Southern Oscillation events (Wormuth 1998, Young and Vecchione 2009).|
Native:Canada; Chile; Colombia; Costa Rica; Ecuador; El Salvador; Guatemala; Honduras; Mexico; Nicaragua; Panama; Peru; United States (Alaska)
|FAO Marine Fishing Areas:|
Pacific – eastern central; Pacific – northeast; Pacific – southeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population size of this species is unknown.|
|Current Population Trend:||Unknown|
|Habitat and Ecology:||Dosidicus gigas is the largest member of the Ommastrephidae and one of the most abundant nektonic squids in the world (Nigmatullin et al. 2001). It ranges from neritic to distant oceanic waters and from the surface to probably over 1,000 m depth in some areas. Unlike other members of its family, it has extremely attenuate arm tips with hundreds of tiny suckers. This, presumably allows it to capture very small prey while still retaining the ability to capture large prey with the tentacles and proximal regions of the arms. It is very tolerant of low oxygen waters which may provide an advantage over some predators since oxygen minimum layers in the ocean are common in its general habitat.|
Offshore populations appear to undergo diel vertical migrations while those inshore do not with individuals occurring in fairly shallow waters both by day and night (Wormuth 1998). It has been proposed that the population consists of three size groups at maturity: 1) small, males 130-260 mm in mantle length (ML) and females 140-340 mm ML; 2) intermediate, males 240-420 mm ML and females 280-600 mm ML; 3) large, males 400-500 mm ML and females 550-1,200 mm ML (Young and Vecchione 2009). Whilst other researchers propose that just two size groups exist: 1) small 520 mm ML (Young and Vecchione 2009). Spawning appears to occur throughout the year with a peak in the austral spring-summer (October-January) (Nigmatullin et al. 2001). Growth is rapid and unvalidated statolith increment analysis suggests a life span of a single year (Young and Vecchione 2009).
The presence of large numbers of protoplasmic oocytes and oocytes at all stages of development even in mature females suggests spawning may occur intermittently over a prolonged period of time (Nigmatullin and Markaida 2009). Eggs are spawned into a large gelatinous matrix (3-4m in diameter), which may contain a million eggs or more (Staaf et al. 2008). The average potential fecundity of females ranged between 18 and 21 million eggs which is the highest of any living cephalopod (Nigmatullin and Markaida 2009). Mature ovarian oocytes measure between 0.7 and 1 mm in length (Nigmatullin and Markaida 2009).
This species is an active predator preying on a range of pelagic fish (e.g. lanternfish and sardines), crustaceans as well as other squid including its conspecifics (Roper et al. 2010). Predators include pelagic fish such as sharks and the striped marlin, Makaira mitsukurri, and cetaceans like sperm whales and porpoises (Roper et al. 1984, Wormuth 1998).
|Use and Trade:||Dosidicus gigas is currently the largest invertebrate fishery in the world, and has grown to this size very quickly. In 1965, the first year of reported catch according to FAO statistics, 100 tons were caught globally. The catch reached 1,000 tonnes in 1976, 10,000 tonnes in 1980, 100,000 tonnes in 1992, and in 2010 was over 800,000 tonnes. The core range of D. gigas comprises the tropical and subtropical waters off the west coast of North and South America, where it is fished by artisanal and commercial boats from Peru and Mexico and by overseas fleets from China, South Korea, and Japan. This range expands sporadically into the temperate and subpolar waters of Chile, the United States, and Canada. When present in Chile, the species is subject to a substantial commercial target fishery, while in the United States it is generally targeted only by recreational fishermen and sometimes encountered as bycatch in other fisheries, such as hake and rockfish. There are no reliable estimates of total biomass or stock size. Genetic evidence suggests two separate populations, one in the northern hemisphere and one in the southern hemisphere. Peru set the first quota of any governing body for this species in 2012, for 500,000 tonnes. The recent rapid increase in the scale of the fishery and uncertainties over the potential risk of overharvesting highly variable populations with high turnover rates could be cause for some concern, particularly given the important role of D. gigas in oceanic food webs.|
|Major Threat(s):||Dosidicus gigas is the target of the largest invertebrate fishery in the world.|
|Conservation Actions:||There are no species-specific conservation measures in place for this species. Further research is recommended in order to determine the precise distribution, population dynamics, life history and ecology of this species.|
|Citation:||Barratt, I. & Allcock, L. 2014. Dosidicus gigas. The IUCN Red List of Threatened Species 2014: e.T162959A958088.Downloaded on 23 July 2018.|
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