''Dissostichus'', the toothfish, is a genus of marine
ray-finned fish
Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species.
The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...
belonging to the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Nototheniidae
: ''In some scientific literature, the term "cod icefish" is used to identify members of this family. This should not be confused with the term "icefish," which refers to the "white-blooded" fishes of the family Channichthyidae. See Icefish (disam ...
, the notothens or cod icefish. These fish are found in the
Southern Hemisphere. Toothfish are marketed in the United States as Chilean sea bass (or Chilean seabass) or less frequently as white cod. "Chilean sea bass" is a
marketing name coined in 1977 by Lee Lantz, a fish wholesaler who wanted a more attractive name for selling the
Patagonian toothfish
The Patagonian toothfish (''Dissostichus eleginoides'') is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around most ...
to Americans.
[ Retrieved on 16 May 2015.][G. Bruce Knecht, ''Hooked: Pirates, Poaching, And the Perfect Fish", 2006. . p. 9''] In 1994, the U.S.
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA) accepted "Chilean sea bass" as an "alternative market name" for Patagonian toothfish.
The toothfish was remarkably successful in the United States, Europe and Asia, and earned the nickname "white gold" within the market.
Toothfish are vital to the ecological structure of
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s. For this reason, on 4 September a national day is dedicated to the toothfish in
South Georgia.
Taxonomy
''Dissostichus'' was first described as a genus in 1898 by the Swedish zoologist
Fredrik Adam Smitt
Fredrik Adam Smitt, (9 May 1839 in Halmstad – 19 February 1904 in Stockholm), was a Swedish zoologist.
Biography
Smitt studied in Lund and Uppsala
Uppsala (, or all ending in , ; archaically spelled ''Upsala'') is the county seat of Up ...
, he was
describing a new species from waters off
Tierra del Fuego
Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla ...
, ''Dissostichus eleginoides'', which he placed as the only species in the new genus.
Some authorities place this taxon in the
subfamily Pleuragrammatinae,
but the 5th edition of ''
Fishes of the World'' does not include subfamilies in the Nototheniidae.
The name of the genus ''Dissostichus'' is a compound of ''dissos'' which means "twofold" or "double" and ''stichus'' which means "row" or "line". an allusion to the two
lateral lines of ''D. eleginoides''.
Species
Two species in this genus are recognized:
*''
Dissostichus eleginoides
The Patagonian toothfish (''Dissostichus eleginoides'') is a species of notothen found in cold waters () between depths of in the southern Atlantic, Pacific, and Indian Oceans and Southern Ocean on seamounts and continental shelves around mos ...
''
Smitt, 1898 (Patagonian toothfish)
*''
Dissostichus mawsoni''
Norman
Norman or Normans may refer to:
Ethnic and cultural identity
* The Normans, a people partly descended from Norse Vikings who settled in the territory of Normandy in France in the 10th and 11th centuries
** People or things connected with the Norm ...
, 1937 (Antarctic toothfish)
Distribution
The Patagonian toothfish is distributed
circumpolarly near the
Antarctic Convergence
The Antarctic Convergence or Antarctic Polar Front is a marine belt encircling Antarctica, varying in latitude seasonally, where cold, northward-flowing Antarctic waters meet the relatively warmer waters of the sub-Antarctic. Antarctic waters pr ...
, spanning the
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
,
Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
and
Indian
Indian or Indians may refer to:
Peoples South Asia
* Indian people, people of Indian nationality, or people who have an Indian ancestor
** Non-resident Indian, a citizen of India who has temporarily emigrated to another country
* South Asia ...
sectors of the Southern Ocean, with a few populations near the
Antarctic Peninsula as well as the coasts of
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
and
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
. The Antarctic toothfish is distributed around the
Antarctic continental shelf and in the
Ross Sea
The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who ...
, generally south of 60°S.
Both species are
benthopelagic
The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...
as adults. The Patagonian toothfish has been found between 600 and 1500 m, and the Antarctic toothfish tends to be found between 1300 and 1900 m. The Patagonian and Antarctic toothfish populations overlap geographically in the southern Indian Ocean, north of the
Ross Sea
The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who ...
and several south Atlantic islands.
[Roberts, J.; et al. (2011). "The diet of toothfish species" ''Dissostichus eleginoides'' and ''Dissostichus mawsoni'' with overlapping distributions. ''J. Fish Bio.'' 79, 138–154.] The Southern Ocean has not yet been fully sampled, so both species may extend further throughout the region.
[Collins M.A., et al. (2010). "The Patagonian toothfish: biology, ecology and fishery". ''Adv. Mar. Bio.'' 58, 227–300.]
Morphology and body size
The Patagonian toothfish and the Antarctic toothfish are markedly similar in appearance, but can be identified via several morphological features. The Patagonian toothfish has a characteristic scaleless patch between the eyes and a longer visible
lateral line.
Both species are long-lived and relatively slow-growing. The Patagonian toothfish can live up to at least 50 years of age and the Antarctic toothfish can live to at least 35 years of age.
[Horn P.L. (2002). "Age and growth of Patagonian toothfish (''Dissostichus eleginoides'') and Antarctic toothfish (''D. mawsoni'') in waters from the New Zealand subantarctic to the Ross Sea, Antarctica". ''Fish. Res.''56, 275–287.] Both species show the fastest growth in the first 10 years of life, and reach maximum body size around 20 years of age.
The Patagonian toothfish grows at an average rate of 2 cm and 1 kg per year. Toothfishes are large in size, with both species reaching maximum sizes exceeding 100 kg. This trait distinguishes the toothfishes from other
notothenioids.
History
The Patagonian toothfish was initially captured in the 1970s as
bycatch via
trawl fishing vessels around
South Georgia Island
South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east†...
and off the coast of
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...
. Most of the individuals caught using this method were juveniles.
[Constable A.J. et al. (2000). Managing fisheries to conserve the Antarctic marine ecosystem: practical implementation of the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). ''J. Mar. Sci.'' 57, 778-791.] In 1987, the Patagonian toothfish was caught as bycatch via
longline fishing
Longline fishing, or longlining, is a commercial fishing angling technique that uses a long ''main line'' with fish bait, baited fish hook, hooks attached at intervals via short branch lines called ''snoods'' or ''gangions''.[< ...]
, a technique that captured the larger adults.
The fish, marketed as "Chilean Sea Bass," became widely successful in restaurants due to its large size and white, oily flesh, which can be cooked in numerous ways.
Fish were collected in massive numbers, first in
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
and later in
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
after the Chilean population declined abruptly in 1994.
Exploratory fisheries for the Antarctic toothfish were established in the Ross Sea in 1996/1997. The fisheries for the two toothfish species are intended to be distinct; however, there is some concern that the species may be indistinguishable to commercial fishermen. In 2013, the FDA eliminated market distinctions between the species, meaning that the Antarctic toothfish, like its
congener, could also be marketed as Chilean Sea Bass. Previously, the Antarctic toothfish was sold under the name "toothfish."
Commercial fisheries
All
fisheries south of the Antarctic Convergence are regulated by the
(CCAMLR), which is a subset of the international
Antarctic Treaty System designed to prevent exploitation of the region’s natural resources. CCAMLR currently oversees thirteen licensed toothfish fisheries, including seven exploratory fisheries and one research fishery.
[Ccamlr.org. Toothfish fisheries. Accessed 29 January 2019.] The five established fisheries target the Patagonian toothfish exclusively, and the exploratory fisheries, mostly concentrated in the Ross Sea, target the Antarctic toothfish primarily.
The research fishery targets both species.
The Patagonian toothfish, which has been caught and sold since 1977, is currently being removed legally from the Southern Ocean at an estimated rate of 12,000 to 17,000 tons per year.
The Antarctic toothfish, which has been caught and sold since 1988, is currently being removed legally from the Southern Ocean at an estimated rate of 4,000 tons per year.
All known Antarctic toothfish and most Patagonian toothfish populations fall within the CCAMLR Convention Area.
[Lack M. and Sant G. (2001). Patagonian toothfish: Are conservation and trade measures working? ''TRAFFIC Bul.''19, 1-18.] Northern Patagonian toothfish populations are managed by the nations that control the respective regions in which the populations reside; however, these nations are required to adhere to CCAMLR regulations.
Illegal, unreported and unregulated fishing
As of 2014, CCAMLR was allowing fisheries to remove the Antarctic toothfish at rates that would reduce the population to 50 percent of its current biomass. However, some scientists are concerned that estimations of toothfish biomass may be inaccurate due to a number of factors, including
illegal, unreported and unregulated (IUU) fishing activities.
[Abrams, P.A. (2014). How precautionary is the policy governing the Ross Sea Antarctic toothfish (''Dissostichus mawsoni'') fishery? ''Antarc. Sci.'' 26, 3-13.]
IUU activities can be challenging to prevent and prove.
However, centralized international collaborative efforts (between
Australia,
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
and
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
) to mitigate IUU activities have been reported as successful. As of 2012, measures included CCAMLR’s catch-documentation scheme along with on-sea, satellite and aerial surveillance. A 2012 report indicated that implementation of these measures has reduced IUU activity by 90 percent. However, in 2014 others stated that these numbers may be inaccurate, as IUU fishing in the Southern Ocean is difficult to prove.
Diet and ecological importance
Both species occupy similar
ecological niche
In ecology, a niche is the match of a species to a specific environmental condition.
Three variants of ecological niche are described by
It describes how an organism or population responds to the distribution of resources and competitors (for ...
s. They are
piscivorous
A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...
at all life stages. Juveniles mostly prey on small notothenioids,
krill
Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish.
Krill are consi ...
,
squid and
pelagic fish
Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that do live on or near the bottom, and reef fish that are associated with coral re ...
es. Prey range increases with maturity.
As adults, both species consume a variety of fishes,
cephalopods and
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...
s.
The Patagonian toothfish is
opportunistic
Opportunism is the practice of taking advantage of circumstances – with little regard for principles or with what the consequences are for others. Opportunist actions are expedient actions guided primarily by self-interested motives. The term ...
, and sometimes scavenges penguin and fish remains that sink from the
epipelagic zone
The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...
. The toothfishes may compete with
Adélie penguins for prey such as
silverfish and krill.
Toothfish are important prey for large mammals. Patagonian toothfish predators include
elephant seal
Elephant seals are very large, oceangoing earless seals in the genus ''Mirounga''. Both species, the northern elephant seal (''M. angustirostris'') and the southern elephant seal (''M. leonina''), were hunted to the brink of extinction for oi ...
s,
sperm whales, and
killer whale
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus ''Orcinus'' and is recognizable by its black-and-white ...
s.
Antarctic toothfish predators include
Weddell seal
The Weddell seal (''Leptonychotes weddellii'') is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. The Weddell seal was discovered and named in the 1820s during expeditions led by British seali ...
s and whales, especially killer whales. Some data suggests that the overfishing of toothfish may stress whale populations. Hucke-Gaete et al. observed that when toothfish were removed from via longline capture, killer whales were more likely to prey on nearby sperm whales.
Migration and reproductive cycle
Much remains unknown regarding the life cycles of both toothfish species, particularly the Antarctic toothfish. Much of the existing data has been collected by reports from commercial fishing vessels. Current research suggests that both the Patagonian and Antarctic toothfishes tend to form discontinuous populations, meaning that little
gene flow exists between populations.
Both species migrate during spawning season. However, the specific duration and distance of these migrations have not been fully characterized.
Tag-and-release experiments on the Patagonian toothfish have indicated that most individuals migrate an average of 15 miles from their habitat, and that any migratory movement generally occurs after the fishes reach maturity. However, some anecdotal evidence demonstrates that the Patagonian toothfish may be capable of migrating between the northern and southern poles, likely by submerging beneath tropical and temperate waters.
Patagonian toothfish
The Patagonian toothfish spawns in deep waters during the austral winter and early spring, between June and September.
Discontinuous
oogenesis development patterns suggest that Patagonian toothfish do not
spawn
Spawn or spawning may refer to:
* Spawn (biology), the eggs and sperm of aquatic animals
Arts, entertainment, and media
* Spawn (character), a fictional character in the comic series of the same name and in the associated franchise
** '' Spawn: ...
annually.
Individuals migrate to spawn in shallower waters (800–1000 m), although migration patterns can vary widely between different geographic populations. Some data suggest that spawning yields decrease at higher latitudes.
Egg development occurs over a period of approximately three months, with hatching occurring in October or November. After hatching, the
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
ic larvae drift for a period of time, likely until February. Around this time, the fish reach a critical size and become
bathypelagic. They gradually inhabit deeper waters as they grow, migrating down the
continental slope
A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...
. Adult fish are generally found at depths greater than 500 m.
Antarctic toothfish
The life cycle of the Antarctic toothfish is less well-characterized. Researchers and fisheries are limited to collecting this species during the austral summer and autumn (December to May) due to harsh polar conditions during the austral winter (June to August). Scientists have not yet collected any juvenile or larvae Antarctic toothfish
[Young, P. (2012). The last ocean: The toothfish and the battle for Antarctica’s soul''.'' ''Fisheye Films.'' Documentary.] and have not yet verified the location, season or frequency of spawning activity. Hanchet et al. used all previously collected data from 1996 to 2008 to generate an updated model for the life cycle of the Antarctic toothfish within the Ross Sea fishery, although the authors note that much of this model is based on speculation and much of the data has not yet been collected fully.
[Hanchet S.M. et al. (2008). A hypothetical life cycle for Antarctic toothfish (''Dissostichus mawsoni'') in the Ross Sea region. ''CCAMLR Sci''. 15, 35-53.] They estimated that the Antarctic toothfish adults spawn between June and November, and that spawning likely occurs north of 70°S, beyond the Ross continental shelf and slope.
Eggs likely have a development period of four to five months and hatch between November and February, developing more slowly than their Patagonian toothfish counterparts.
Current data suggests that spawning requires a large amount of reproductive tissue, and may not occur annually.
Planktonic larvae undergo larval drift for a period of several months, likely into late summer or early autumn. Researchers predict that the Antarctic toothfish inhabit benthic regions after reaching 15 cm.
Sub-adult individuals develop within the Ross Sea and gradually inhabit deeper waters over a period of two to three years.
Conservation efforts
In June 2010, 500 scientists formed the
Antarctic and Southern Ocean Coalition
The Antarctic and Southern Ocean Coalition (ASOC) is a global coalition of environmental non-governmental organizations with more than 150 members in 40 countries worldwide. ASOC has worked since 1978 to ensure that the Antarctica, Antarctic Conti ...
(ASOC), advocating to CCAMLR for special protection of the entire Ross Sea. Chilean Sea Bass has been placed on the Red Lists of
Greenpeace International
Greenpeace is an independent global campaigning network, founded in Canada in 1971 by Irving Stowe and Dorothy Stowe, immigrant environmental activists from the United States. Greenpeace states its goal is to "ensure the ability of the Earth t ...
and the
One World One Ocean
MacGillivray Freeman Films is an American film studio based in Laguna Beach, California and founded in the mid-1960s by Greg MacGillivray and Jim Freeman. It produces documentaries, feature films, and IMAX films.
History
MacGillivray Freeman ...
Campaign. As a result, a number of restaurant and grocery owners have publicly opted not to prepare or sell Chilean Sea Bass. Furthermore, advocacy projects have been undertaken to increase the scope of public awareness. The New Zealand documentary ''The Last Ocean'' was created to communicate the issue of toothfish fisheries, conveying the need to protect the Southern Ocean’s native biodiversity.
In October 2016, a 1.55 million km
2 region of the Ross Sea was designated as a
marine protected area
Marine protected areas (MPA) are protected areas of seas, oceans, estuaries or in the US, the Great Lakes. These marine areas can come in many forms ranging from wildlife refuges to research facilities. MPAs restrict human activity for a conse ...
by the CCAMLR, meaning that most fishing is banned in the area. The area will remain protected until 2052.
See also
*
Toothfish Day
Toothfish Day is a public holiday celebrated in the British Overseas Territory of South Georgia and the South Sandwich Islands. It is annually on 4 September, but if that falls on a weekend it may be observed on a weekday. It is one of eleven ...
References
*
{{Taxonbar, from=Q2369129
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Nototheniidae
Illegal, unreported and unregulated fishing