Shark liver oil

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Sharks typically targeted for their liver oil include the school and gulper shark, and the basking shark (pictured). All three of these species are either endangered or critically endangered due to overfishing according to the IUCN, although a legal targeted fishery for basking sharks no longer exists. Cetorhinus maximus by greg skomal.JPG
Sharks typically targeted for their liver oil include the school and gulper shark, and the basking shark (pictured). All three of these species are either endangered or critically endangered due to overfishing according to the IUCN, although a legal targeted fishery for basking sharks no longer exists.

Shark liver oil is an oil obtained from the livers of sharks. It has been used for centuries as a folk remedy to promote the healing of wounds and as a remedy for respiratory tract and digestive system problems. [5] [6] It is still promoted as a dietary supplement, and additional claims have been made that it can treat other maladies such as cancer, HIV, radiation sickness, swine flu, and the common cold. [5] [7] To date, none of these claims has been medically validated and shark liver oil (alone) is not a medication prescribed or utilized by American physicians. [7] However, it is a component of some moisturizing skin lotions [6] and hemorrhoid medications. [8] [9]

Contents

Function in the shark

Many fish maintain buoyancy with swim bladders. However sharks lack swim bladders, and maintain their buoyancy instead with large livers that are full of oil. [10] This stored oil may also function as a nutrient when food is scarce. [11] Deep sea sharks are usually targeted for their oil, because the livers of these species can account for up to 5–10% of their total weight. [1]

Composition

A principal component of many shark oils is squalene, a triterpenoid (C30H50), ranging up to 90% of the oil, depending on the species. In Centrophorus species squalene may account for 15% of the total body weight. Pristane, another terpenoid (C19H40), is often a minor component, ranging up to nearly 8% of the oil. [12]

Medicinal use

Most shark liver oil supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Although many people have taken shark liver oil, the issue of potential toxicity at the usual doses has not been well studied. Some mild digestive problems such as nausea, upset stomach, and diarrhea have been reported. The safe range of doses for shark liver oil has not yet been determined, though overdosing can have toxic consequences. [5] [13]

Some animal studies have found that shark liver oil and its components may raise blood cholesterol levels. A Japanese study found some shark liver oil supplements to be contaminated with polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). [14] PCBs can have harmful effects in humans, and may increase the risk of some types of cancer. [5] People with seafood allergies may also react to shark liver oil. [5]

Shark liver oil has been misleadingly promoted as a treatment for cancer. In addition, it has been confused with the word "Charcoal" in multiple translations. Despite claims that the alkoxy-glycerols derived from shark liver oil could reduce tumor growth, there is not sufficient evidence to prove this to be a viable treatment option. [15]

Shark oil barometers

Traditionally, the people of Bermuda rely on shark-oil based "barometers" to predict storms and other severe weather. Small bottles of oil are hung outside. If the bottle is clear then the weather will be good, while, if it is cloudy, it is advisable to take cover. They are not true barometers, and how they work is disputed. [16]

See also

Related Research Articles

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<span class="mw-page-title-main">Elasmobranchii</span> Subclass of fishes

Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks, rays, skates, and sawfish. Members of this subclass are characterised by having five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil.

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

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

The dumb gulper shark is a rare and endangered deepwater dogfish, found along the east coast of Australia and in 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">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">Leafscale gulper shark</span> Species of shark

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

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<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">Gulper shark</span> Species of shark

The gulper shark 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. 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 cephalopods such as squid and other invertebrates like crustaceans. 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. Because of the depth of their habitat, they are considered little to no threat to humans.

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

The longnose velvet dogfish is a sleeper shark of the family Somniosidae, found circumglobally in southern hemisphere subtropical seas, at depths of between 230 and 1,500 m. It reaches a length of 130 cm. It has a diet consisting of predominantly mesopelagic fishes and squids.

<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.

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

The dwarf gulper shark is a dogfish of the family Centrophoridae found in the Indo-West Pacific oceans, from the Gulf of Aden, Japan, Taiwan, and northern Papua New Guinea, living and feeding at dephts exciding 656 ft (m), marine, deep-water dogfish most commonly found between 328 ft and 3937 ft

<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">Knifetooth dogfish</span> Species of shark

The knifetooth dogfish, is a harmless sleeper shark of the family Somniosidae, found in the eastern Atlantic, from Scotland to Spain, Portugal, and Senegal, and the southwest Pacific from New Zealand, between latitudes 58°N and 15°N, at depths of between 200 and 1,600 m. Its length is up to 1.1 metres (3.6 ft).

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

The velvet dogfish, the only member of the genus Zameus, is a small sleeper shark of the family Somniosidae, found around the world between latitudes 64°N and 48°S, from the surface to 2,000 m.

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

The salamander shark or salamander catshark is a little known catshark that inhabits a range from Japan and the East China Sea, on the upper to middle continental slope at depths of 358–895 m. Specimens of this species can attain a total length of at least 64 cm. This catshark is a potential bycatch of trawl fisheries operating within its range, but no details are available. There are high levels of squalene in this catshark's liver. The reproduction of this catshark is oviparous.

The deepwater catshark is a catshark of the family Scyliorhinidae, found in the western Atlantic from Delaware Bay to Suriname, and in the eastern Atlantic from Morocco to northwest Africa. An important key factor to understanding these creatures is ageing, many deepwater Apristurus profundorum have poorly calcified vertebrae that lack visible growth bands, and most do not have dorsal fin spines that can be used for ageing. Other methods, such as captive growth and tag-recapture, are also limited in their suitability for deepwater chondrichthyans due to difficulties in the deep sea.

References

  1. 1 2 Vannuccini, Stefania (2002) Shark liver oil products In: Shark Utilization, Marketing and Trade, Fisheries Technical paper 389, FAO, Rome. ISBN   92-5-104361-2.
  2. 1 2 Rigby, C.L.; Barreto, R.; Carlson, J.; Fernando, D.; Fordham, S.; Francis, M.P.; Herman, K.; Jabado, R.W.; Liu, K.M.; Marshall, A.; Romanov, E.; Kyne, P.M. (2021) [amended version of 2019 assessment]. "Cetorhinus maximus". IUCN Red List of Threatened Species . 2021: e.T4292A194720078. doi: 10.2305/IUCN.UK.2021-1.RLTS.T4292A194720078.en . Retrieved 11 May 2024.
  3. ↑ 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 11 May 2024.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ↑ Walker, T.I.; Rigby, C.L.; Pacoureau, N.; Ellis, J.; Kulka, D.W.; Chiaramonte, G.E.; Herman, K. (2020). "Galeorhinus galeus". IUCN Red List of Threatened Species . 2020: e.T39352A2907336. doi: 10.2305/IUCN.UK.2020-2.RLTS.T39352A2907336.en . Retrieved 11 May 2024.
  5. 1 2 3 4 5 American Cancer Society . Retrieved 28 March 2013.
  6. 1 2 Gupta P, K Singhal, AK Jangra, V Nautiyal and A Pandey (2012) "Shark liver oil: A review" Archived 2013-01-23 at the Wayback Machine Asian Journal of Pharmaceutical Education and Research, 1 (2): 1-15.
  7. 1 2 Shark liver oil WebMD . Retrieved 28 March 2013.
  8. ↑ PE-shark liver oil-cocoa buttr Rect WebMD . Retrieved 28 March 2013.
  9. ↑ Hemorrhoidal suppository Daily Med. Retrieved 28 March 2013.
  10. ↑ Oguri, M. (1990). "A review of selected physiological characteristics unique to elasmobranchs". In Pratt Jr., H.L.; Gruber, S.H.; Taniuchi, T. (eds.). Elasmobranchs as living resources: Advances in the biology, ecology, systematics and the status of the fisheries (PDF) (Report). US Department of Commerce. pp. 49–54. NOAA technical report NMFS 90. Retrieved 11 May 2024.
  11. ↑ Bone Q and Roberts BL (1969) "The density of elasmobranchs" Journal of the Marine Biological Association, 49: 913–937.
  12. ↑ Ackman, RG. Marine Biogenic Lipids, Fats and Oils, Vol 1. CRC Press 1989, pages 42-43.
  13. ↑ S Kilincalp S, M Deveci, O Basar, F Ekiz, S Coban and O Yuksel (2012) Shark liver oil: hidden dangers" Annals of Hepatology, 11 (5): 728–730.
  14. ↑ Akutsu K; Tanaka Y; Hayakawa K (2006). "Occurrence of polybrominated diphenyl ethers and polychlorinated biphenyls in shark liver oil supplements". Food Addit. Contam. 23 (12): 1323–1329. doi:10.1080/02652030600892966. PMID   17118876. S2CID   33249788.
  15. ↑ Sheldon Saul Hendler; David Rorvik, eds. (2008). PDR for Nutritional Supplements. Montvale, NJ: Physician's Desk Reference Inc. p. 22. ISBN   978-1-56363-710-0.
  16. ↑ Bermuda Traditions & Their Sources
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