The family Haliotidae contains only one genus, Haliotis, which contains about 4 to 7 subgenera. The number of species recognized worldwide ranges between 30 and 130 with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies.
The shells of abalones have a low open spiral structure, and are characterized by several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre (mother-of-pearl), which in many species is highly iridescent, giving rise to a range of strong changeable colors, which make the shells attractive to humans as decorative objects, jewelry, and as a source of colorful mother-of-pearl.
The flesh of abalones is widely considered to be a desirable food, and is consumed raw or cooked in a variety of dishes.
The shell of abalones is convex, rounded to oval shape, and may be highly arched or very flattened. The shell is generally ear-shaped, presenting a small flat spire and two to three whorls. The last whorl (known as the body whorl) is auriform, meaning that the shell resembles an ear, giving rise to the common name "ear shell". The "ass’s ear" abalone has a somewhat different shape, as it is more elongated and distended. The shell of Haliotis cracherodii cracherodii Leach, 1814 is also unusual: it has an ovate form, it is imperforate, shows an exserted spire, and has prickly ribs.
A mantle cleft in the shell impresses a groove in the shell, in which are the row of holes characteristic of the genus. They are respiratory apertures for venting water from the gills and for releasing sperm and eggs into the water column. These holes make up what is known as the selenizone which form as the shell grows. This series of 8 to 38 holes is near the anterior margin. Only a small number are generally open. The older holes are gradually sealed up as the shell grows and new holes form. Each abalone species has a typical number of open holes in the selenizone. There are four to ten of these holes, depending on the species. Abalone have no operculum. The aperture of the shell is very wide and nacreous.
The exterior of the shell is striated and dull. The color of the shell is very variable from species to species, and may reflect the animal's diet. The iridescent nacre that lines the inside of the shell varies in color from silvery white, to pink, red and green-red, through to Haliotis iris, which shows predominantly deep blues, greens and purples.
The animal shows fimbriated[disambiguation needed] head-lobes. The side-lobes are fimbriated and cirrated. The rounded foot is very large. The radula has small median teeth, and the lateral teeth are single and beam-like. There are about 70 uncini, with denticulated hooks, the first four very large. The soft body is coiled around the columellar muscle, and its insertion, instead of being on the columella, is on the middle of the inner wall of the shell. The gills are symmetrical and both well developed.
These snails cling solidly with their broad muscular foot to rocky surfaces at sublittoral depths, although some species such as Haliotis cracherodii used to be common in the intertidal zone. Abalones reach maturity at a relatively small size. Their fecundity is high and increases with their size (from 10,000 to 11 million eggs at a time). The spermatozoa are filiform and pointed at one end, and the anterior end is a rounded head.
The larvae are lecithotrophic (i.e. feed off a yolk sac). The adults are herbivorous and feed with their rhipidoglossan radula on macroalgae, preferring red or brown algae. Sizes vary from 20 mm (Haliotis pulcherrima) to 200 mm (or even more) (Haliotis rufescens).
The haliotid family has a worldwide distribution, along the coastal waters of every continent, except the Atlantic coast of South America, the Caribbean, and the East Coast of the United States. The majority of abalone species are found in cold waters, off the Southern Hemisphere coasts of New Zealand, South Africa and Australia, and Western North America and Japan in the Northern Hemisphere.
The shell of the abalone is exceptionally strong and is made of microscopic calcium carbonate tiles stacked like bricks. Between the layers of tiles is a clingy protein substance. When the abalone shell is struck, the tiles slide instead of shattering and the protein stretches to absorb the energy of the blow. Material scientists around the world are studying this tiled structure for insight into stronger ceramic products such as body armor.
The dust created by grinding and cutting abalone shell is dangerous; appropriate safeguards must be taken to protect people from inhaling these particles. An N95-rated dust respirator, a ventilation system, and wet grinding are requirements to working abalone shell safely. The calcium carbonate dust is a respiratory irritant and the particles can penetrate into the lower respiratory tree and cause irritant bronchitis and other respiratory irritation responses. The usual symptoms are cough and sputum production, and secondary infections can occur. If there are proteins left in the shell matrix, it is also possible that they can trigger an allergic (asthmatic) attack. Allergic skin reactions can also occur.
Diseases and pests
Abalones are subject to various diseases. The Victorian Department of Primary Industries said in 2007 that abalone viral ganglioneuritis, or AVG, killed up to 90% of stock in affected regions. Abalone are also severe hemophiliacs as their fluids will not clot in the case of a laceration or puncture wound. Polydorid polychaetes are known as pests of abalone.
The meat (foot muscle) of abalone is used for food, and the shells of abalone are used as decorative items and as a source of mother of pearl for jewelry, buttons, buckles, and inlay. Abalone shells have been found in archaeological sites around the world, ranging from 75,000 year old deposits at Blombos Cave in South Africa to historic Chinese abalone middens on California's Northern Channel Islands. On the Channel Islands, where abalones were harvested by Native Americans for at least 12,000 years, the size of red abalone shells found in middens declines significantly after about 4000 years ago, probably due to human predation. Worldwide, abalone pearls have also been collected for centuries.
Farming of abalone began in the late 1950s and early 1960s in Japan and China. Since the mid-1990s, there have been many increasingly successful endeavors to commercially farm abalone for the purpose of consumption. Over-fishing and poaching have reduced wild populations to such an extent that farmed abalone now supplies most of the abalone meat consumed. The principal abalone farming regions are China, Taiwan, Japan, and Korea. Abalone is also farmed in Australia, Canada, Chile, France, Iceland, Ireland, Mexico, Namibia, New Zealand, South Africa, Thailand, and the United States.
In Japan, live and raw abalone are used in awabi sushi, or served steamed, salted, boiled, chopped, or simmered in soy sauce. Salted, fermented abalone entrails are the main component of tottsuru, a local dish from Honshū. Tottsuru is mainly enjoyed with sake.
In California, abalone meat can be found on pizza, sautéed with caramelized mango or in steak form dusted with cracker meal and flour.
Tasmania supplies approximately 25% of the yearly world abalone harvest. Around 12,500 Tasmanians recreationally fish for blacklip and greenlip abalone. For blacklip abalone, the size limit varies from between 138 mm for the southern end of the state and 127 mm for the northern end of the state.Greenlip abalone have a minimum size of 145 mm, except for an area around Perkin's Bay in the north of the state where the minimum size is 132 mm. With a recreational abalone licence, there is a bag limit of 10 per day, and a total possession limit of 20. Scuba diving for abalone is allowed, and has a rich history in Australia. (Scuba diving for abalone in the states of New South Wales and Western Australia is illegal; a free-diving catch limit of two is allowed).
Victoria has had an active abalone fishery since the late 1950s. The state is sectioned into three fishing zones, Eastern, Central and Western with each fisher required a zone allocated licence. Harvesting is performed by divers using surface supplied air "hookah" systems operating from runabout style, outboard powered boats. While the diver seeks out colonies of abalone amongst the reef beds the deckhand operates the boat, known as working "live" and stays above where the diver is working. Bags of abalone pried from the rocks are brought to the surface by the diver or by way of "shot line", where the deckhand drops a weighted rope for the catch bag to be connected then retrieved. Divers measure each abalone before removing from the reef and the deckhand re-measures each abalone and removes excess weed growth from the shell. Since 2002 the Victorian Industry has seen a significant decline in catches, with the total allowable catch (TAC) reduced from 1440 tonnes to 787 tonnes for the 2011/12 fishing year. This is due to dwindling stocks and most notably the abalone virus Ganglioneuritis which is fast spreading and lethal to abalone stocks.
Two highly endangered White Abalone. Prohibitions on commercial and recreational harvest of this species have been in place since 1996.
Sport harvesting of red abalone is permitted with a California fishing license and an abalone stamp card. New in 2008, the abalone card also comes with a set of 24 tags. Legal-size abalone must be tagged immediately. Abalone may only be taken using breath-hold techniques or shorepicking; scuba diving for abalone is strictly prohibited. Taking of abalone is not permitted south of the mouth of the San Francisco Bay. There is a size minimum of seven inches (178 mm) measured across the shell and a quantity limit of three per day and 24 per year. A person may be in possession of only three abalone at any given time.
Abalone may only be taken from April to November, not including July. Transportation of abalone may only legally occur while the abalone is still attached in the shell. Sale of sport-obtained abalone is illegal, including the shell. Only red abalone may be taken; black, white, pink, flat, green, and pinto (threaded) abalone are protected by law.
An abalone diver is normally equipped with a thick wetsuit, including a hood, bootees, and gloves, and usually also a mask, snorkel, weight belt, abalone iron, and abalone gauge. Alternatively, the rock picker can feel underneath rocks at low tides for abalone. Abalone are mostly taken in depths from a few inches up to 10 m (33 ft); less common are freedivers who can work deeper than 10 m (33 ft). Abalone are normally found on rocks near food sources (kelp). An abalone iron is used to pry the abalone from the rock before it can fully clamp down. Divers dive out of boats, kayaks, tube floats or directly off the shore.
The largest abalone recorded in California is 12.34 inches, caught by John Pepper somewhere off the coast of San Mateo county in September 1993.
In New Zealand, abalone is called pāua (/ˈpaʊə/, from the Māori language). Haliotis iris (or blackfoot pāua) is the ubiquitous New Zealand pāua; the highly polished nacre of which is extremely popular as souvenirs with its striking blue, green, and purple iridescence. Haliotis australis and Haliotis virginea are also found in New Zealand waters, but are less popular than H. iris.
Like all New Zealand shellfish, recreational harvesting of pāua does not require a permit provided catch limits, size restrictions, and seasonal and local restrictions set by the Ministry for Primary Industries (MPI) are followed. The legal recreational daily limit is 10 pāua per diver, with a minimum shell length of 125 mm (4.9 in) for Haliotis iris and 80 mm (3.1 in) for Haliotis australis. In addition, no person may be in possession, even on land, of more than 20 pāua or more than 2.5 kg (5.5 lb) of pāua meat at any one time. Pāua can only be caught by free-diving; it is illegal to catch pāua using scuba gear.
There is an extensive global black market in collecting and exporting abalone meat. This can be a particularly awkward problem where the right to harvest pāua can be granted legally under Māori customary rights. When such permits to harvest are abused, it is frequently difficult to police. The limit is strictly enforced by roving Ministry for Primary Industries fishery officers with the backing of the New Zealand Police. Pāua 'poaching' is a major industry in New Zealand with many thousands being taken illegally, often undersized. Convictions have resulted in seizure of diving gear, boats, and motor vehicles and fines and in rare cases, imprisonment. The Ministry of Fisheries expects in the year 2004/05, nearly 1,000 tons of pāua will be poached, with 75% of that being undersized.
The largest abalone in South Africa, Haliotis midae, occurs along approximately two-thirds of the country’s coastline. Abalone-diving has been a recreational activity for many years, but stocks are currently being threatened by illegal commercial harvesting. In South Africa all persons harvesting this animal need permits that are issued yearly, and no abalone may be harvested using scuba gear.
For the last few years, however, no permits have been issued for collecting abalone, but commercial harvesting still continues as does illegal collection by syndicates. In 2007, because of widespread poaching of abalone, the South African government listed abalone as an endangered species according to the CITES section III appendix, which requests member governments to monitor the trade in this species. This listing was removed from CITES in June 2010 by the South African government and South African abalone is no longer subject to CITES trade controls. Export permits are still required, however. The abalone meat from South Africa is prohibited for sale in the country to help reduce poaching; however, much of the illegally harvested meat is sold in Asian countries. As of early 2008, the wholesale price for abalone meat was approximately US$40.00 per kilogram. There is an active trade in the shells, which sell for more than US$1,400 per metric tonne. There is, however, speculation that local criminal gangs barter abalone illegally with Chinese nationals in exchange for chemicals used in the production of drugs, reducing the need for the use of money and hence avoiding money laundering difficulties.
Ormers (Haliotis tuberculata) are considered a delicacy in the British Channel Islands as well as in adjacent areas of France, and are pursued with great alacrity by the locals. This has led to a dramatic depletion in numbers since the latter half of the 19th century, and 'ormering' is now strictly regulated in order to preserve stocks. The gathering of ormers is now restricted to a number of 'ormering tides', from January 1 to April 30, which occur on the full or new moon and two days following. No ormers may be taken from the beach that are under 80 mm in shell length. Gatherers are not allowed to wear wetsuits or even put their heads underwater. Any breach of these laws is a criminal offence and can lead to fine of up to £5,000 or six months in prison. The demand for ormers is such that they led to the world's first underwater arrest, when Mr. Kempthorne-Leigh of Guernsey was arrested by a police officer in full diving gear when illegally diving for ormers.
The highly iridescent inner nacre layer of the shell of abalone has traditionally been used as a decorative item, in jewelry, buttons, and as inlay in furniture and in musical instruments such as guitars, etc.
Abalone pearl jewelry is very popular in New Zealand and Australia, in no minor part due to the marketing and farming efforts of pearl companies. Unlike the Oriental Natural, the Akoya pearl, and the South Sea and Tahitian cultured pearls, abalone pearls are not primarily judged by their roundness. The inner shell of the abalone is an iridescent swirl of intense colours, ranging from deep cobalt blue and peacock green to purples, creams and pinks. Therefore each pearl, natural or cultured, will have its own unique collage of colours.
The shells of abalone are occasionally used in New Age smudging ceremonies to catch falling ash. They have also been used as incense burners.
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