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 Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

, with a long snout and large greenish eyes. 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. This tertiary consumer feeds on mainly fish such as bony fish, but also

cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

s such as

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

and other invertebrates like

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 ...

s. The gulper shark is currently a vulnerable species mainly because of exploitation by humans and their abnormally long

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...

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. The maturity of a gulper shark can be determined by the seven-stage maturity scale for aplacental and placental

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

sharks.Ungaro, N. (2008
Field manual on macroscopic identification of maturity stages for the Mediterranean fishery resources
FAO 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 A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sperm ...

are enlarged and filled with sperm, and sperm ducts are tightly coiled. For females, stage three is when

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

are large and well rounded. On average, male gulper sharks are smaller than females. 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. Differences in size between the sexes may be due to the need for space to support offspring. It has been hypothesized that gulper sharks display a “depth distribution pattern associated with size” based on random human observation. Male gulper sharks tend to outnumber females 2:1, which is common for many fish species. The life expectancy,

longevity The word " longevity" is sometimes used as a synonym for "life expectancy" in demography. However, the term ''longevity'' is sometimes meant to refer only to especially long-lived members of a population, whereas ''life expectancy'' is always d ...

, of female gulper sharks ranges between 54 and 70 years. Having a long life expectancy but a low

net reproduction rate In population ecology and demography, the net reproduction rate, ''R''0, is the average number of offspring (often specifically daughters) that would be born to a female if she passed through her lifetime conforming to the age-specific fertility ...

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 Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the natural capability to pr ...

. Once fertilized, females can hold up to 6 mature egg cells, or

oocytes An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female g ...

, 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 In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it ...

. Gulper sharks have a long gestation period, around two years. Gulper sharks can have long resting periods between pregnancies.ARKive
Gulper shark (''Centrophorus granulosus'')
. They are

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

, meaning the only parental care they give their young is during the incubation period. 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 Oophagy ( ) sometimes ovophagy, literally "egg eating", is the practice of embryos feeding on eggs produced by the ovary while still inside the mother's uterus. The word oophagy is formed from the classical Greek (, "egg") and classical Greek (, ...

. 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

. It is believed that the gulper shark has the lowest reproduction rate of any

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gil ...

species. Centrophorus granulosus SI2.jpg Centrophorus granulosus SI3.jpg Centrophorus granulosus SI4.jpg Centrophorus granulosus jaws.jpg, Jaws Centrophorus granulosus upper teeth.jpg, Upper teeth Centrophorus granulosus lower teeth.jpg, Lower teeth

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.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 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 A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

, the gulper is highly migratory species and has

schooling A school is an educational institution designed to provide learning spaces and learning environments for the teaching of students under the direction of teachers. Most countries have systems of formal education, which is sometimes compuls ...

habits based on multiple sharks being present around baited cameras. 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 Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

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 Longline fishing, or longlining, is a commercial fishing angling technique that uses a long ''main line'' with baited hooks attached at intervals via short branch lines called ''snoods'' or ''gangions''.Seafood Watch
Fishing Methods Fact Card
Centrophorus granulosus noaa

When a fish species other than the intended catch is caught, it is called

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

. Although bycatch is not always a significant cause of loss to population size, it highlights the unpredictable nature of deepwater fish exploitation.Hogan, Michael (2010
“Overfishing”
in ''Encyclopedia of Earth'', Sidney Draggan and C. Cleveland (eds.). Washington DC. 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 Squalene is an organic compound. It is a triterpenoid with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). A ...

, although the compound can also be extracted from plants.Owen, James (December 29, 2009
Sharks Killed for Oil Used in Swine Flu Vaccine
National Geographic 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. A long gestation period, later maturity, and long lifespan all contribute to a

K-selected In ecology, ''r''/''K'' selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of indivi ...

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. 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. Large populations of gulper sharks must be built over long periods of time. Gulper life strategy is also consistent with their

trophic level The trophic level of an organism is the position it occupies in a food web. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it i ...

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.H.R.81 - Shark Conservation Act of 2009
opencongress.org 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

from their livers is not inherently an activity that drives them toward extinction,

overexploitation Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term app ...

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 A general officer is an officer of high rank in the armies, and in some nations' air forces, space forces, and marines or naval infantry. In some usages the term "general officer" refers to a rank above colonel."general, adj. and n.". OED O ...

(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.Report of the Working Group on Fish Ecology (WGFE), 13–17 March 2006, ICES Headquarters, Copenhagen
ICES WGFE Report 2006. 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 King Diamond II

Shark fins confiscated from King Diamond II

Other areas of gulper shark populations have no current regulations. The Northwest

Atlantic Ocean 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 ...

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.GFCM (2005
GFCM Recommendations on Mediterranean fisheries management
/ref> 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 The Shark Conservation Act of 2009 (SCA) (, ) was passed by the 111th United States Congress that amended the High Seas Driftnet Fishing Moratorium Protection Act and the Magnuson–Stevens Fishery Conservation and Management Act to improve the con ...

in 2010, which prohibited removing fins from sharks that were usually caught as

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. This act protects all species of sharks within 50 nautical miles of the U.S. coast. 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

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

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

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 Daniel Pauly is a French-born marine biologist, well known for his work in studying human impacts on global fisheries and in 2020 was the most cited fisheries scientist in the world. He is a professor and the project leader of the Sea Around Us ...

from

UBC Fisheries Centre The UBC Institute for the Oceans and Fisheries (IOF) is a research unit at the University of British Columbia The University of British Columbia (UBC) is a public research university with campuses near Vancouver and in Kelowna, British Co ...

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

. 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. 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 attributesalone 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. 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.

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, older data listed for gulper sharks could be for ones other than the ''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.

References

{{Taxonbar, from=Q592572 Centrophorus Fish described in 1801