Gulper shark

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Gulper shark
Taiwan gulper shark female.jpg
Status iucn3.1 CR.svg
Critically Endangered  (IUCN 3.1)Europe and Mediterranean population assessments
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Squaliformes
Family: Centrophoridae
Genus: Centrophorus
Species:
C. granulosus
Binomial name
Centrophorus granulosus
Centrophorus granulosus distmap.png
Range of gulper shark (in blue)
Synonyms

Centrophorus acusGarman, 1906
Centrophorus niaukangTeng, 1959

Contents

The gulper shark (Centrophorus granulosus) is a long and slender dogfish usually about three feet in length generally found in deep, murky waters all around the world. It is a light grayish brown, paler ventrally, with a long snout and large greenish eyes. [2] This deep water shark has two dorsal fins with long, grooved spines and the second dorsal fin smaller than the first. Its upper teeth are blade-like and lower have finely serrated edges. [2] This tertiary consumer feeds on mainly fish such as bony fish, but also cephalopods such as squid and other invertebrates like crustaceans. [2] The gulper shark is currently an endangered species mainly because of exploitation by humans and their abnormally long gestation period and low fecundity, preventing their population from recovering.

Development and reproduction

Gulper sharks reach maturity at around age 12 to 16 years for females, and age 7 to 8 years for males. [3] The maturity of a gulper shark can be determined by the seven-stage maturity scale for aplacental and placental viviparous sharks. [4] This scale is good for practical field use, but may not be as accurate as other maturity scales that have more than seven stages. Maturity for gulper sharks is considered when they are at stage 3 or above, which for males is when gonads are enlarged and filled with sperm, and sperm ducts are tightly coiled. For females, stage three is when ovaries are large and well rounded. [4]

On average, male gulper sharks are smaller than females. [5] The size of an average adult male is 80 to 95 cm. The size of an average adult female is from 90 to 100 cm long. [5] Differences in size between the sexes may be due to the need for space to support offspring. [5] It has been hypothesized that gulper sharks display a “depth distribution pattern associated with size” based on random human observation. [5]

Male gulper sharks tend to outnumber females 2:1, which is common for many fish species. The life expectancy, longevity, of female gulper sharks ranges between 54 and 70 years. [5] Having a long life expectancy but a low net reproduction rate suggests that the population of gulper sharks would be at a very high risk if too many of them were killed from excessive fishing.

Female gulper sharks typically have between 2 and 10 pups in their lifetime, with generally one pup per pregnancy, this is considered to be a low fecundity. [5] Once fertilized, females can hold up to 6 mature egg cells, or oocytes, in their body at a time. The length of time these egg cells are kept inside the female's body is called the gestation period. Gulper sharks have a long gestation period, around two years. Gulper sharks can have long resting periods between pregnancies. [2]

They are ovoviviparous, meaning the only parental care they give their young is during the incubation period. [4] Since not all oocytes form into pups, when a pup or two is formed inside the female, they eat the remaining fertilized eggs, known as oophagy. [2] After they are born, they are on their own. Having a low fecundity, a long gestation period, breaks between pregnancies, and a late age of maturity all contribute to the gulper shark having a very low net reproduction rate. [2] It is believed that the gulper shark has the lowest reproduction rate of any elasmobranch species. [2]

Geographic range

The gulper shark is a deepwater oceanic species, living in waters ranging between 100 and 1490 meters in depth, with the juveniles being the main occupant of the lower half of the depths. [6] Acceptable habitats for gulper populations are found globally, wherever temperate and tropical waters are found. The gulper shark is most commonly found in the 300 to 800 meter depth range, inhabiting the upper continental slopes and outer continental shelves, the gulper is highly migratory species and has schooling habits based on multiple sharks being present around baited cameras. [7]

Due to the frequency and patterns of migration the gulper shark population estimates may be inaccurate with some sharks being counted twice, which are exacerbated by inappropriate tagging techniques. There are multiple species of gulper sharks, which has contributed to misidentification in the past. For example, populations of the gulper shark in the Southeast Atlantic Ocean may represent a separate species. Therefore, taxonomic confusion may influence current geographical range. The gulper sharks like deep, murky waters.

Human interaction

Fishing and bycatch

Human interaction with the gulper shark exists mainly in the form of fishing. Longline fishing is a typical method for fishing at the depth required to catch gulper sharks, and the broad distribution of gulper habitat leads to this method being used to catch gulpers around the world. However, gulper sharks are not always caught intentionally. The deep waters in which the gulper and similar shark species live is difficult to harvest, and longlines are an unspecific form of fishing. Longlines intended for other species can easily catch gulper sharks. [8]

Gulper shark that has been caught by a fishing boat Centrophorus granulosus noaa.jpg
Gulper shark that has been caught by a fishing boat

When a fish species other than the intended catch is caught, it is called bycatch. Although bycatch is not always a significant cause of loss to population size, it highlights the unpredictable nature of deepwater fish exploitation. [9] Rules and regulations regarding bycatch treatment are difficult to enforce by the nature of the bycatch being unintentional. Bycatch is often not treated as a serious issue until a species has declined to a point where small bycatch has a large effect, so data on the effect of bycatch on gulper populations is not abundant. Gulper shark populations have dropped as much as 80% in some areas, so bycatch is only recently becoming a big issue for them.

Consumables

Fins and meat are generally taken from gulper sharks, but it is of particular interest because of the quantity of liver oil it contains: compared to similar species such as the dogfish shark, the gulper has a larger liver with more oil. Traditionally, shark oil is a folk remedy for a variety of ailments, but also has been shown to contain compounds of contemporary medicinal value, most notable squalene, although the compound can also be extracted from plants. [10] This compound makes the liver of the gulper shark very valuable and is a large part of gulper-specific fishing.

Ecology

Life history

The life history of an organism describes the timing of important events for the typical individual of a species. The life history of the gulper shark shows that vulnerability to harvesting is inherent in its biology. The slow rate of gulper growth and development leads to a life strategy that is more centered on competition with one another than escaping predation, especially from humans. This is demonstrated from even the earliest part of an individual gulper's life history where it consumes other fertilized eggs inside its parent's body. [2]

A long gestation period, later maturity, and long lifespan all contribute to a K-selected tendency that favors intraspecific competition, or competition with similar species, over survival defenses having to do with predation. Harvesting is a form of predation that slow, invested reproduction does not easily alleviate. The long gestation, low fecundity, and breaks in individual reproduction lead to slow repopulation ability. [2] Slow reproduction is a part of the species biology, and cannot be changed in one generation based on sudden predation pressure. A group of gulper sharks that undergoes predation by humans may take fifteen years or longer to recover, if at all, based on their maturation time of twelve to sixteen years. [3] Large populations of gulper sharks must be built over long periods of time.

Gulper life strategy is also consistent with their trophic level and place in the deepwater community. They are tertiary consumers with no apparent predators, so their biological gear toward competition is an ecologically sound strategy. [11] The introduction of human interaction with gulper sharks is the introduction of a higher trophic level, and presents a relationship that current gulper biology is not equipped to handle while maintaining steady or growing population size.

While the fishing of gulper sharks and utilization of squalene from their livers is not inherently an activity that drives them toward extinction, overexploitation of the species can be a problem. The status of gulper sharks on the ICUN red list is currently only vulnerable rather than endangered. The squalene taken from the gulper liver is in high demand as a possible cancer therapy component among other uses, leading to unchecked harvesting of the species. When the populations are declining due to overexploitation, each viable individual is important. As much as 80% of the gulper population has been depleted in some areas, so any harvesting can have a large effect on the decline of the species or possible recovery.

The key to overexploitation in gulper sharks is that they require nearly as much time as humans to mature and reproduce. Their life strategy indicates that the frame of view for gulper fishing plans needs to be based on longer amounts of time, to allow for the consideration of the next generation of individuals. Gulper shark do not mature much faster than humans, so they need to be exploited based on a schedule that reflects this. However, being harvested by a species with similar growth patterns means that the gulper shark is unlikely to be considered in this way. It is highly susceptible to overexploitation leading to widespread population decline and its status and a species vulnerable to endangerment.

Conservation efforts and legislation

The gulper shark has been classified as vulnerable status by the IUCN since 2000 due to heavy overfishing and exacerbated through bycatch and low reproductive rates. The General Fisheries Commission for the Mediterranean (GFCM), which is in charge of almost all intergovernmental fishery management decisions, mandated in 2005 to stop expanding deep water fishing beyond 1,000 meters. [12] This mandate however, does not support the main population of gulper sharks, which generally live 300–800 meters below the surface. This decision also does not stop any current deepwater fishing; it simply stops any further expansion. This is an insufficient conservation attempt, as it does not help gulper populations under stress, it simply stops more stress from accumulating. The current level of fishing may already be enough to render that population critically endangered in that region, especially considering the low reproductive rate of gulpers.

Shark fins confiscated from the King Diamond II Shark fins confiscated from King Diamond II.jpg
Shark fins confiscated from the King Diamond II

Other areas of gulper shark populations have no current regulations. The Northwest Atlantic Ocean currently has no rules in regard to the harvesting of gulper sharks, and has already seen a decrease in gulper population of 80–95% since 1990. [13]

While not many laws apply to gulper sharks specifically, some blanket laws covering many different species have been created. The United States Government passed the Shark Conservation Act in 2010, which prohibited removing fins from sharks that were usually caught as bycatch and then sold to Chinese markets for shark fin soup. This law seals many of loopholes by requiring that any fins or tails brought to land must be “naturally attached to the corresponding carcass” and that no U.S. ship in foreign waters is allowed to possess shark fins. [11] This act protects all species of sharks within 50 nautical miles of the U.S. coast. [11] This is a much more effective law than that by the GFCM, because it addresses shark finning directly and cuts down on the amount of gulpers killed for their fins. Since this law point-blank cuts down on bycatching, it should be an effective effort at the conservation of shark species off U.S. coasts.

Conservation

Morphological similarities in Centrophorus Gulper shark comparisons.png
Morphological similarities in Centrophorus

While conservation attempts are being made, certain issues like fishery guidelines and catch verification pose problems for furthering conservation attempts.

The fisheries concept is a closely regulated way to harvest gulpers, while monitoring the species population to ensure it does not crash. They generally use body mass as an indicator of when to harvest the sharks to allow growth of the population. When these ratios are incorrect, the fishery can easily crash because sharks are harvested before they can reproduce. This is especially true with the gulper shark, which has a two-year-long gestational period and a twelve to sixteen year maturity for females. Biery and Daniel Pauly from UBC Fisheries Centre in Canada executed a review on species-specific fin to body-mass ratios in 2012. Their paper concludes that current regulated ratios are not appropriate for all species and that regulations based on a general ratio for all species is inadequate and may be harming fisheries. The ratios used by many fisheries were originally compiled by a politically affiliated group called The Regional Fishery Management Organizations, RFMO. Biery and Pauly collected fin to body-mass ratios for 50 different species and eight different countries and observed that actual fin to body-mass ratios varied by species and location. Species specific mean ratios ranged from 1.1% to 10.9% and estimated mean ratios by country ranged from 1.5% to 6.1% indicating that current regulations will crash fisheries and not promote population growth. [14]

Away from the commercial side of conservation, there are tagging efforts to monitor gulper populations. Tagging is a common ecological tool to study the species characteristics. A large problem with monitoring the populations of Australian and Indonesian dogfish is that discriminating between the seven local species by morphological attributes alone is unreliable. In 2012 a study conducted by Ross Daley, Sharon Appleyard, and Matthew Koopman from the CSIRO Marine and Atmospheric Research Center in Hobart, Australia aims to help monitored recovery plans by implementing a new catch data verification plan. Their study focuses on using the 16s mitochondrial gene region to differentiate these species and when sequenced, all but C. harrissoni and C. isodon were distinguishable. [15] They concluded that 16s gene is a strong marker suitable for fishery catch verification and that using this technique is a reliable and efficient system for routine testing. However, specialized primers needed for trials are sensitive to decay. Therefore, preservation problems need to be researched to further the prospective use of a 16s mitochondrial classification. This system for routine testing is only available to scientists and would require substantial training for fishermen to be able to use this technique. [15]

Uncertainties and inconsistency in data

While information concerning gulper sharks exists, there is no place to centrally compile the information so that other researchers may easily obtain it. This leads to repetition in basic data and less depth into the subject matter. Information presented may also be inaccurate as many genus of Centrophorus are morphologically similar. While attempts are being made to make it easier to identify different genus, such as Daley's use of 16s mitochondrial DNA listed above, [15] older data listed for gulper sharks could be for ones other than C. granulosus, such as the dumb gulper shark. This also means that current populations numbers could account for other dogfish than just the gulper sharks. Lastly, due to the frequency and patterns of migration, the recorded gulper shark populations may be inaccurate.

Related Research Articles

The Centrophoridae are a family of squaliform sharks. The family contains just two genera and about 15 species. They are sometimes called gulper sharks, but this is also the name of a specific species in the family, Centrophorus granulosus. These are generally deepwater fish. While some, such as the gulper shark C. granulosus, are found worldwide and fished commercially, others are uncommon and little-known. Their usual prey is other fish; some are known to feed on squid, octopus, and shrimp. Some species live on the bottom (benthic), while others are pelagic. They are ovoviviparous, with the female retaining the egg-cases in her body until they hatch.

<span class="mw-page-title-main">Dusky smooth-hound</span> Species of shark

The dusky smooth-hound, also called the smooth dogfish or the dog shark, is a species of houndshark in the family Triakidae. This shark is an olive grey or brown in color, and may have shades of yellow or grayish white. Females live to 16 years and males have a lifespan of 10 years. M. canis was the first shark recognised to have viral infections.

<span class="mw-page-title-main">Spiny dogfish</span> Species of shark

The spiny dogfish, spurdog, mud shark, or piked dogfish is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order.

Centrophorus is a genus of squaliform sharks. These deep-water sharks, found in temperate and tropical oceans throughout the world, are characterized by grey or brown bodies, large green eyes, and spines on both dorsal fins. These spines give them their name, from Greek κεντρον, kentron meaning "thorn" and φέρειν, pherein meaning "to bear".

<span class="mw-page-title-main">Dumb gulper shark</span> Species of shark

The dumb gulper shark is a rare and endangered deepwater dogfish, known from only along the east coast of Australia and isolated spots north and west of New Zealand. It is also known as the dumb shark, Harrison's deep-sea dogfish, or Harrison's dogfish.

<span class="mw-page-title-main">Lowfin gulper shark</span> Species of shark

The lowfin gulper shark is a large deepwater dogfish in the family Centrophoridae.

<span class="mw-page-title-main">Smallfin gulper shark</span> Species of shark

The smallfin gulper shark or endeavour dogfish, is a medium-sized deepwater dogfish in the family Centrophoridae.

<span class="mw-page-title-main">Mosaic gulper shark</span> Species of shark

The mosaic gulper shark is a small rare deepwater dogfish, found in the Pacific Ocean around Honshū, Japan and the Hawaiian Islands at depths between 260 and 728 m. It is one of 13 described species in the genus Centrophorus.

<span class="mw-page-title-main">Little gulper shark</span> Species of shark

The little gulper shark is a small, deepwater dogfish of the family Centrophoridae.

<span class="mw-page-title-main">Black dogfish</span> Species of shark

The black dogfish is a species of dogfish shark in the family Etmopteridae. It is common over the outer continental shelf and continental slope at depths of 180–2,250 m (590–7,380 ft). Females generally inhabit deeper water than males, and depending on the region, smaller sharks may occur at different depths than larger ones. This species is distributed widely in the Atlantic Ocean, from Greenland and Iceland to Virginia and West Africa in the north, and off southwestern Africa and Argentina in the south. The largest member of its family, the black dogfish, typically measures 60–75 cm (24–30 in) long. It has a stocky, dark brown body that is darker below than above, and bears scattered, minute bioluminescent organs. Its two dorsal fins are preceded by stout spines, and the anal fin is absent.

<span class="mw-page-title-main">Kitefin shark</span> Species of shark

The kitefin shark or seal shark is a species of squaliform shark in the family Dalatiidae, and the type species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of 200–600 m (660–1,970 ft). With a sizable oil-filled liver to maintain neutral buoyancy, this shark is able to cruise slowly through the water while expending little energy. The kitefin shark, the largest luminous vertebrate on record, has a slender body with a very short, blunt snout, large eyes, and thick lips. Its teeth are highly differentiated between the upper and lower jaws, with the upper teeth small and narrow and the lower teeth large, triangular, and serrated. Its typical length is 1.0–1.4 m (3.3–4.6 ft), though examples as long as 5.9 ft (180 cm) have been encountered.

<span class="mw-page-title-main">Salmon shark</span> Species of shark

The salmon shark is a species of mackerel shark found in the northern Pacific ocean. As an apex predator, the salmon shark feeds on salmon, squid, sablefish, and herring. It is known for its ability to maintain stomach temperature (homeothermy), which is unusual among fish. This shark has not been demonstrated to maintain a constant body temperature. It is also known for an unexplained variability in the sex ratio between eastern and western populations in the northern Pacific.

<span class="mw-page-title-main">Blackfin gulper shark</span> Species of shark

The blackfin gulper shark is a dogfish of the family Centrophoridae in the Northwest Pacific. Threats are not entirely clear but they may be bycatching from deepwater trawling and line fisheries and may also be used for cod liver oil and fish meal.

<span class="mw-page-title-main">Portuguese dogfish</span> Species of shark

The Portuguese dogfish or Portuguese shark, is a species of sleeper shark of the family Somniosidae. This globally distributed species has been reported down to a depth of 3,675 m (12,057 ft), making it the deepest-living shark known. It inhabits lower continental slopes and abyssal plains, usually staying near the bottom. Stocky and dark brown in color, the Portuguese dogfish can be distinguished from similar-looking species by the small spines in front of its dorsal fins. Its dermal denticles are also unusual, resembling the scales of a bony fish. This species typically reaches 0.9–1 m (3.0–3.3 ft) in length; sharks in the Mediterranean Sea are much smaller and have distinct depth and food preferences.

<span class="mw-page-title-main">Smooth lanternshark</span> Species of shark

The smooth lanternshark or slender lanternshark is a species of dogfish shark in the family Etmopteridae, found widely in the Atlantic and Pacific Oceans. It inhabits benthic environments at a depth of 274–1,000 m (899–3,281 ft), and pelagic environments at a depth of 0–708 m (0–2,323 ft). The smooth lanternshark forms a species group with the larger blurred lanternshark, both of which are distinguished from other members of their family by small, irregularly arranged dermal denticles with a truncated shape. This species has a slender, dark brown body with an indistinct black band on the sides over the pelvic fins, and reaches 50 cm (20 in) in length. This slow-growing, ovoviviparous shark feeds on smaller squid, fishes, and fish eggs. Smooth lanternsharks are often caught as bycatch in eastern Atlantic and Japanese commercial fisheries. The International Union for Conservation of Nature (IUCN) has evaluated this species as of Least Concern because of its wide distribution and limited threats.

<span class="mw-page-title-main">Velvet belly lanternshark</span> Species of shark

The velvet belly lanternshark is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 20–2,490 m (66–8,169 ft). A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. The ventral photophores are thought to function in counter-illumination, which camouflages the shark against predators and prey. The bioluminescent flank markings may play a role in intraspecific communication.

<span class="mw-page-title-main">Humpback smooth-hound</span> Species of shark

The humpback smooth-hound is a species of houndshark and a part of the family Triakidae.The most noticeable difference between Mustelus whitneyi and its relatives, is the slight curvature, causing a "humpback" appearance located in front of its primary dorsal fin. It is found on the continental shelves of the tropical southeast Pacific, from Peru to southern Chile, between latitudes 3° S and 54° S. These sharks are demersal feeders but range from depths between 15 and 210 metres. Humpback smooth-hound sharks are small sharks, reaching a maximum size of 118cm in total length. Mustelus whitneyi typically feed on teleosts and invertebrates in the benthic and pelagic ecosystems, most important prey being the peruvian anchovy. These humpback smooth-hound sharks are placental viviparious sharks, meaning that the embryo forms inside the mother tethered by the placental cord. The threats currently causing population decline to humpback smooth-hound sharks surround issues with local fisheries and management.

<span class="mw-page-title-main">Dwarf lanternshark</span> Species of shark

The dwarf lanternshark is a species of dogfish shark in the family Etmopteridae and is the smallest shark in the world, reaching a maximum known length of 20 cm (8 in). It is known to be present only on the upper continental slopes off Colombia and Venezuela, at a depth of 283–439 m (928–1,440 ft). This species can be identified by its small size at maturity, long flattened head, and pattern of black ventral markings and a mid-dorsal line. Like other members of its genus, it is capable of producing light from a distinctive array of photophores. Reproduction is aplacental viviparous, with females gestating two or three young at a time. The dwarf lanternshark is not significant to commercial fisheries, but could be threatened by mortality from bycatch; the degree of impact from human activities on its population is unknown.

<span class="mw-page-title-main">Pacific spiny dogfish</span> Species of shark

The Pacific spiny dogfish is a common species of the Squalidae (dogfish) family of sharks and are among the most abundant species of sharks in the world. This species is closely related to Squalus acanthias and for many years they were treated as a single species. Recent research, using meristic, morphological and molecular data led to the resurrection of Pacific Spiny Dogfish as a separate species. The American Fisheries Society recommends the common name "Pacific Spiny Dogfish" for Squalus suckleyi over alternatives such as "Spotted Spiny Dogfish" and "North Pacific Spiny Dogfish" and "Spiny Dogfish" for Squalus acanthias.

The gill plate trade is the buying and selling of stingray gill plates for their use in traditional Chinese medicine. The gill plates are harvested from stingrays that are caught intentionally, or caught as bycatch. The plates are sold whole or in a powder form. A single kilogram of the gill plate can be sold for up to US$350, though the price varies by ray species.

References

  1. ↑ Finucci, B.; Bineesh, K.K.; Cheok, J.; Cotton, C.F.; Dharmadi, Kulka, D.W.; Neat, F.C.; Pacoureau, N.; Rigby, C.L.; Tanaka, S. & Walker, T.I. (2020). "Centrophorus granulosus". IUCN Red List of Threatened Species . 2020: e.T162293947A2897883. doi: 10.2305/IUCN.UK.2020-3.RLTS.T162293947A2897883.en . Retrieved 24 August 2023.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. 1 2 3 4 5 6 7 8 9 ARKive, Gulper shark (Centrophorus granulosus) Archived 2016-11-18 at the Wayback Machine .
  3. 1 2 Clarke, M. W.; Connolly, P. L.; Bracken, J. J. (2002). "Age estimation of the exploited deepwater shark Centrophorus squamosus from the continental slopes of the Rockall Trough and Porcupine Bank". Journal of Fish Biology. 60 (3): 501. doi:10.1111/j.1095-8649.2002.tb01679.x.
  4. 1 2 3 Ungaro, N. (2008) Field manual on macroscopic identification of maturity stages for the Mediterranean fishery resources. FAO
  5. 1 2 3 4 5 6 Severino, Ricardo B.; Afonso-Dias, Manuel; Afonso-Dias, Isabel; Delgado, João (2009). "Aspects of the biology of the leaf-scale gulper shark Centrophorus squamosus (Bonnaterre, 1788) off Madeira archipelago" (PDF). Life and Marine Sciences. 26: 57–61.
  6. ↑ Guallart, Furio Javier (1997) Contribucion al conocimiento de la biologia y la taxonomia del tiburon batial c entrophorus granulosus (bloch y schneider, 1801) en el mar balear (mediterraneo occidental). PhD Thesis, Universitat de Valencia
  7. ↑ Gilat, E.; Gelman, A. (1984). "On the sharks and fishes observed using underwater photography during a deep-water cruise in the eastern Mediterranean". Fisheries Research. 2 (4): 257. doi:10.1016/0165-7836(84)90029-8.
  8. ↑ Seafood Watch. Fishing Methods Fact Card.
  9. ↑ Hogan, Michael (2010) “Overfishing” in Encyclopedia of Earth, Sidney Draggan and C. Cleveland (eds.). Washington DC.
  10. ↑ Owen, James (December 29, 2009) Sharks Killed for Oil Used in Swine Flu Vaccine. National Geographic
  11. 1 2 3 H.R.81 - Shark Conservation Act of 2009. opencongress.org
  12. ↑ Report of the Working Group on Fish Ecology (WGFE), 13–17 March 2006, ICES Headquarters, Copenhagen. ICES WGFE Report 2006.
  13. ↑ GFCM (2005) GFCM Recommendations on Mediterranean fisheries management
  14. ↑ Biery, L.; Pauly, D. (2012). "A global review of species-specific shark-fin-to-body-mass ratios and relevant legislation". Journal of Fish Biology. 80 (5): 1643–1677. doi:10.1111/j.1095-8649.2011.03215.x. PMID   22497402.
  15. 1 2 3 Daley, Ross K.; Appleyard, Sharon A.; Koopman, Mathew (2012). "Genetic catch verification to support recovery plans for deepsea gulper sharks (genus Centrophorus, family Centrophoridae) – an Australian example using the 16S gene". Marine and Freshwater Research. 63 (8): 708. doi:10.1071/MF11264.
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