The Houtman Abrolhos (often informally called the Abrolhos Islands) is a chain of 122 islands, and associated coral reefs, in the Indian Ocean off the west coast of Australia. Coral reefs are Aragonite structures produced by living organisms found in marine waters with little to no nutrients in the water The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface For a topic outline on this subject see List of basic Australia topics. Nominally located at 28°43′S 113°47′E / -28.717, 113.783Coordinates: 28°43′S 113°47′E / -28.717, 113.783^[1], it lies about eighty kilometres (50 mi) west of Geraldton, Western Australia. A geographic coordinate system enables every location on the Earth to be specified in three coordinates using mainly a spherical coordinate system. Western Australia is a state occupying the entire western third of the Australian continent. ^[2] It is the southernmost true coral reef in the Indian Ocean, and one of the highest latitude reef systems in the world. It is one of the world's most important seabird breeding sites, and is the centre of Western Australia's largest single species fishery, the Western Rock Lobster fishery. Seabirds are Birds that have adapted to life within the marine environment The western rock lobster or western crayfish, Panulirus cygnus, is a Spiny lobster found off the west coast of Australia and It is also well known as the site of numerous shipwrecks, the most famous being the Dutch ships Batavia, which was wrecked in 1629, and Zeewijk, wrecked in 1727. A shipwreck can refer to a wrecked ship or to the event that caused the wreck such as the striking of something that causes the ship to sink the stranding of the ship on rocks The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Mutiny on the Batavia Departure On 29 October 1628, the newly built Batavia, commissioned by the Dutch East India Company Background The Zeewijk was built in 1725 with a tonnage of 140 lasten (275

Contents 1 Geography 2 History 2.1 Discovery and naming 2.2 Wreck of the Batavia 2.3 Wreck of the Zeewijk 2.4 Later history 3 Tenure, governance and management 4 Geology 5 Oceanography 5.1 Bathymetry 5.2 Currents 5.3 Temperature and salinity 5.4 Sea levels 6 Climate 7 Biogeography 8 Terrestrial flora 8.1 Flora 8.2 Vegetation 9 Terrestrial fauna 9.1 Birds 9.2 Mammals 9.3 Reptiles 9.4 Amphibians 10 Marine flora 10.1 Algae 10.2 Seagrass 11 Marine fauna 11.1 Fish 11.2 Marine mammals 11.3 Marine reptiles 11.4 Coral 11.5 Crustaceans 11.6 Molluscs 11.7 Echinoderms 11.8 Other invertebrates 12 Human uses 12.1 Fishing 12.1.1 Western rock lobster 12.1.2 Saucer scallops 12.1.3 Finfish 12.2 Aquaculture 12.3 Mineral exploration 12.4 Recreation 13 Cultural references 14 References 15 Further reading 16 See also

Geography

The Houtman Abrolhos is made up of three island groups, the Wallabi Group, Easter Group and Pelsaert Group. The Wallabi Group is the northern-most group of islands in the Houtman Abrolhos. The Easter Group is the central of three groups of islands that make up the Houtman Abrolhos island chain The Pelsaert Group is the southernmost of the three groups of islands that make up the Houtman Abrolhos island chain The Wallabi Group is the northern-most group of islands in the Houtman Abrolhos. The Easter Group is the central of three groups of islands that make up the Houtman Abrolhos island chain The Pelsaert Group is the southernmost of the three groups of islands that make up the Houtman Abrolhos island chain

The most northerly group, the Wallabi Group, consists of an island clump about 17 kilometres (10 mi) by 10 kilometres (6 mi), and also takes in the outlying North Island, located 14 kilometres to the northwest. North Island is the most northerly Island in the Houtman Abrolhos. The main islands of the Wallabi Group are North Island, West Wallabi Island, East Wallabi Island, Long Island and Beacon Island. ^[3] The group is best known for the shipwreck of the Batavia on Morning Reef near Beacon Island in 1629,^[4] and the subsequent mutiny and massacres that took place among the marooned survivors. Mutiny on the Batavia Departure On 29 October 1628, the newly built Batavia, commissioned by the Dutch East India Company Mutiny is a conspiracy among members of a group of similarly-situated individuals (typically members of the Military; or the Crew of any ship even Marooning is leaving someone behind on purpose in an uninhabited area such as an uninhabited island ^[5]

The Easter Group lies to the southeast of the Wallabi Group, from which it is separated by a 9 kilometres (5 mi) wide channel named Middle Channel. It is about 20 kilometres by 12 kilometres, and consists of a number of islands including Rat Island, Wooded Island, Morley Island, Suomi Island and Alexander Island. Alexander Island is one of the five largest Islands in the Easter Group of the Houtman Abrolhos.

Further to the southeast, across Zeewijk Channel, lies the Pelsaert Group, the most southerly true coral reef in the Indian Ocean. The main islands of this group are Middle Island, Square Island, Pelsaert Island and the Mangrove Group. A great many ships have been wrecked in the Pelsaert Group, most notably the Zeewijk, which was wrecked on the Half Moon Reef in 1727, the survivors staying on Gun Island for some time afterwards. Background The Zeewijk was built in 1725 with a tonnage of 140 lasten (275 Gun Island is one of the larger Islands in the Pelsaert Group of the Houtman Abrolhos. ^[6] Other wrecks include the Ocean Queen, wrecked on the Half Moon Reef in 1842; the Ben Ledi, wrecked off Pelsaert Island in 1879; and the Windsor, wrecked on the Half Moon Reef in 1908. The Windsor was a ship wrecked on Long Reef near Sydney, Australia in 1816 ^[7]

History

Discovery and naming

According to the surviving historical record, the first sighting of the Houtman Abrolhos was by the Dutch VOC ships Dordrecht and Amsterdam in 1619, only three years after Dirk Hartog made the first authenticated sighting of what is now Western Australia, and only 13 years after the first authenticated voyage to Australia, that of the Duyfken in 1606. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands The Dutch East India Company ( Vereenigde Oost-Indische Compagnie or VOC in old-spelling Dutch, literally "United East Indian Dirk Hartog (1582 — 1631 was a 17th century Dutch sailor and Explorer, Dirk Hartog's expedition was the second European group to land on Australian Voyages In 1596 a ship named "Duyfken" sailed in the first expedition to Bantam, the crew was captured by the islanders Discovery of the islands was credited to Frederick de Houtman, Captain-General of the Dordrecht, as it was Houtman who later wrote of the discovery in a letter to the directors of the Dutch East India Company:

"On the 29th do. Frederick de Houtman (1571 Gouda - 21 October 1627, Alkmaar) or Frederik de Houtman, was a Dutch explorer who sailed The Dutch East India Company ( Vereenigde Oost-Indische Compagnie or VOC in old-spelling Dutch, literally "United East Indian deeming ourselves to be in an open sea, we shaped our course north-by-east. At noon we were in 29° 32' S. Lat. ; at night about three hours before daybreak, we again unexpectedly came upon a low-lying coast, a level, broken country with reefs all round it. We saw no high land or mainland, so that this shoal is to be carefully avoided as very dangerous to ships that wish to touch at this coast. It is fully ten miles in length, lying in 28° 46. "^[8]

The word abrolhos is of Portuguese origin, making the Houtman Abrolhos one of only two Australian places with a Portuguese name, the other being Pedra Branca in Tasmania. Portuguese ( or língua portuguesa) is a Romance language that originated in what is now Galicia (Spain and northern Portugal. Pedra Branca is a 25 ha rock or small Island about 26 km (16 mi) south-south-east of South East Cape, Tasmania Tasmania is an Australian island and state of the same name It is located south of the eastern side of the Continent, being separated from it by Bass ^[9] The term is commonly reported to be a contraction of the Portuguese expression abro olhos ("open the eyes") or abri vossos olhos ("keep your eyes open"), but this has been shown to be a false etymology. A false etymology is an assumed or postulated Etymology that current consensus among scholars of Historical linguistics holds to be incorrect In the Portuguese language of the time, abrolhos meant "spiked obstructions", and served not only as a word for offshore reefs, but also as their word for caltrops and chevaux de frise. A caltrop (also known as Caltrap, galtrop,or in Japanese: Makibishi or Tetsubishi. The cheval de frise (plural chevaux de frise) was a Medieval defensive obstacle consisting of a portable frame (sometimes just a simple log covered with To Spanish ears, however, the word sounded like abre ojos ("open your eyes"), so they imputed this meaning, and this false etymology was later borrowed by English, Dutch and French writers. ^[10]

Another explanation has been proferred by Philippe Godard. He reports, without citation, that some authors have claimed that the word abrolhos comes from a 15th century Portuguese nobleman named Frederico de Abrolhos. Godard notes, however, that there is no trace of such a person in Lusitanian archives, and that Abrolhos is not known as a family name in Portugal, making this an unconvincing explanation. This article concerns the Roman province For the ship see RMS Lusitania. ^[11]

Why Houtman named the islands using a Portuguese word remains a subject of debate. John Forsyth states that the islands are named after the Abrolhos Archipelago off the east coast of Brazil, which was discovered and named by Portuguese navigators early in the 16th century. |utc_offset = -2 to -4 |time_zone_DST = BRST |utc_offset_DST = -2 to -5 |cctld This position is supported by the fact that Houtman was familiar with the Abrolhos Archipelago, having sailed through it in 1598. ^[10] Others assert that abrolhos was a Portuguese lookout's cry which, like many other Portuguese maritime terms, was taken up by sailors of other nationalities,^[12] becoming by Houtman's time a Dutch loan word for offshore reefs. A lookout or look-out is a person on a Ship in charge of the observation of the sea for hazards other ships land etc A loanword (or loan word) is a word directly taken into one Language from another with little or no translation ^[5] Finally, it has been argued by proponents of the theory of Portuguese discovery of Australia that the Portuguese name is evidence that the islands were charted by Portuguese navigators in the 16th century. Although most historians hold that the European discovery of Australia began in 1606 with the voyage of the Dutch navigator Willem Janszoon on board the Kenneth McIntyre, for example, claimed that Houtman was in possession of Portuguese maps of the west coast of Australia, and that he named the islands "abrolhos" in accordance with the name on his map. Kenneth Gordon McIntyre OBE ( August 22, 1910 &ndash May 20, 2004) was an Australian Lawyer, Historian ^[9] Charting of the islands was previously credited to Jorge de Menezes, but the notion that Menezes visited Australia is now thoroughly discredited, and no other candidate has been proffered. Jorge de Menezes was a Portuguese explorer who in 1526-27 landed on Waigeo Island (now Indonesian, taking shelter in the town of Wasai whilst

The primary piece of evidence for the claim of Portuguese priority is the 16th century Dieppe maps, some of which are said to show the west coast of Australia, including an island at the position of the Houtman Abrolhos. The Dieppe maps are a series of world maps produced in Dieppe, France, in the 1540s 1550s and 1560s This island is unlabelled on most of the Dieppe maps, but on Pierre Desceliers' 1550 map, it is labelled Arenes. Pierre Desceliers (~1500 ~1558 was a French cartographer of the Renaissance and an eminent members of the Dieppe School of Cartography. In 1895, George Collingridge suggested that Arenes was a corruption of Abrolhos,^[13] but this was mocked by Heeres in 1898,^[14] and according to J. S. Battye "this suggestion can scarcely be regarded seriously. George Collingridge (1847-1931 was an Australian writer and illustrator best known today for his early assertions of Portuguese discovery of Australia in the 16th Dr James Sykes Battye (1871-1954 was the first chief librarian of the Victoria Public Library (now the State Library of Western Australia) in Perth Western It certainly does not in any way add to the merit of the Portuguese claim". ^[15]

Setting aside the Portuguese claims, the Houtman Abrolhos first appears on a published map in 1622, on a little-known portolan by Hessel Gerritsz. A portolan (derived from the Latin word portus, port is an early modern European navigation chart, dating from the Thirteenth century or later Hessel Gerritsz (c 1581 Assum near Uitgeest – buried Sep 4 1632, Amsterdam) was a Dutch Engraver, Cartographer ^[10] They are unlabelled, however, being marked merely as a group of small circles. ^[11] They are first named in print in Gerritsz' 1627 map Caert van't Landt van d'Eendracht, where they bear the label Fr. Caert van't Landt van d'Eendracht ("Chart of the Land of Eendracht" is a 1627 map by Hessel Gerritsz. Houtman's abrolhos. On a map produced by him the following year, they are labelled Houtman's Abrolhos. ^[16]

On British Admiralty charts, the islands are labelled Houtman's Rocks.

Wreck of the Batavia

In 1629 and 1630 some of the islands were the scene of a spectacular shipwreck and mutiny. Mutiny on the Batavia Departure On 29 October 1628, the newly built Batavia, commissioned by the Dutch East India Company The Dutch ship Batavia under the command of Francisco Pelsaert ran aground and Pelsaert and some men went in an open boat to the town of Batavia (now Jakarta) in order to get help. Mutiny on the Batavia Departure On 29 October 1628, the newly built Batavia, commissioned by the Dutch East India Company Francisco Pelsaert (first name sometimes reported as "François" surname also spelled "Pelsart" (c Jakarta (also DKI Jakarta) is the Capital and largest city of Indonesia. A group of the men who stayed on some of the islets decided to terrorise and massacre many others, including women. When Pelsaert came back many culprits were executed.

Wreck of the Zeewijk

The Zeewijk was the last of the four Dutch East Indiamen to be wrecked on the west coast of Australia. Background The Zeewijk was built in 1725 with a tonnage of 140 lasten (275 An East Indiaman was a Ship operating under charter or licence to the Honourable East India Company. The Ship's Council having made the inexplicable decision to disregard sailing orders and actually seek out the west coast of Australia, the ship ran onto the Half Moon Reef at about 7:30pm on 9 June 1727. Events 53 - Roman Emperor Nero marries Claudia Octavia 62 - Claudia Octavia commits Year 1727 ( MDCCXXVII) was a Common year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Common It did not break up immediately, and the heavy swell made evacuation impossible until 18 June. The longboat was launched on that day, and the crew and stores were thereafter gradually transferred to nearby Gun Island. Not to be confused with Vikings ' Longships In the days of sailing ships a vessel would carry several boats for various uses Gun Island is one of the larger Islands in the Pelsaert Group of the Houtman Abrolhos. Later, the men landed ten chests of money, containing 315,836 guilders and weighing a total of three tons. Guilder is the English translation of the Dutch gulden — from Old Dutch for 'golden' ^[6]

The crew of the Zeewijk would be marooned in the Pelsaert Group for ten months, during which time they lived off seals, seabirds, eggs, and victuals salvaged from the wreck. They obtained some water from rainfall, but were forced to explore throughout the group in search of further supplies. A great many men died on the islands, including two boys who were accused of sodomy and marooned on separate islands of the Mangrove Group. Sodomy (ˈsɒdəmi is a term used today predominantly in Law (derived from traditional Christian usage to describe the act of Anal intercourse, Oral intercourse ^[6]

On 10 July the longboat, fitted for a voyage and crewed with eleven men, was sent to Batavia to obtain help. Events 48 BC - Battle of Dyrrhachium, Julius Caesar barely avoids a catastrophic defeat to Pompey in Macedonia. Batavia is the Latin name for the land of the Batavians during Roman time It never arrived there, and nothing is known of its fate. Four months later the castaways began building a 60-foot (18 m) boat, sufficient to carry all the men and the money chests. Completed in March 1728 and affectionately named the Sloepie ("little sloop"), it was the first ocean-going vessel built in Australian history. Background The Zeewijk was built in 1725 with a tonnage of 140 lasten (275 For the military definition of sloop see Sloop-of-war. For the open learning project see SLOOP Project. On 26 March 1728, the surviving men set sail for Batavia, arriving in Sunda Strait late the following month. Events 1026 - Pope John XIX crowns Conrad II as Holy Roman Emperor. Year 1728 ( MDCCXXVIII) was a Leap year starting on Thursday (link will display the full calendar of the Gregorian calendar (or a The Sunda Strait ( Indonesian: Selat Sunda) is the Strait between the Indonesian Islands of Java and the island of Sumatra ^[6]

Later history

During admiralty surveys of the north west coast in 1840, crew from HMS Beagle discovered a brass gun of about three pounds calibre, an iron swivel on which paint still adhered as well as numerous other artefacts signifying European occupation, on the largest island in the Pelsart Group. First Voyage On 27 September 1825 Beagle docked at Woolwich for repairs and fitted out for her new duties at a total cost of £5913 The commander, John Clements Wickham, named the place Gun Island and the passage between the Easter and Pelsart Groups, Zeewijk Channel. John Clements Wickham ( December 21 1798 &ndash January 6 1864) was naval officer and judge Gun Island is one of the larger Islands in the Pelsaert Group of the Houtman Abrolhos. ^[17]Later during the 19th century many islets were used by men collecting guano. Guano (from the Quechua 'wanu' via Spanish) is the Feces of Seabirds Bats and seals

Tenure, governance and management

The Houtman Abrolhos is Australian territory. There is no dispute about this, although it has been suggested that Australia claims the island chain under the UNCLOS by extending their continental baseline to encompass it, a breach of Article 7 of the Convention. The United Nations Convention on the Law of the Sea ( UNCLOS) also called the Law of the Sea Convention or the Law of the Sea treaty is the international agreement that resulted

The islands are a part of Western Australia. They are part of the Electoral district of Geraldton, and the Shire of Northampton. Geraldton is an electoral district of Western Australia As in other districts the Geraldton district elects a single person to the Western Australian Legislative Assembly. The Shire of Northampton is a Local Government Area in the Mid West region of Western Australia, about north of Geraldton and about north

Management is vested in the Department of Fisheries.

Geology

Some of the islands are considered to be remnants of the mainland isolated by rising sea level during the last 8,000 to 10,000 years. Others were more recently formed from coral rubble. Corals are Marine organisms from the class Anthozoa and exist as small Sea anemone –like Polyps typically in colonies of many

Oceanography

Bathymetry

The Houtman Abrolhos lays in the Indian Ocean about 60 kilometres (40 mi) off the coast of Western Australia, near the edge of Australia's continental shelf. The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface The continental shelf is the extended perimeter of each Continent and associated Coastal plain, which is covered during interglacial periods such At less than 50 metres (160 ft) deep, the shelf is quite shallow. It is also fairly level, the depth increasing to the west at a modest gradient of about 1. 3 metres per kilometre (7 ft/mi). About five kilometres (3 mi) to the east of the Houtman Abrolhos lies the shelf break, beyond which the seabed falls away much more steeply, averaging around 50 metres per kilometre (260 ft/mi). The continental shelf is the extended perimeter of each Continent and associated Coastal plain, which is covered during interglacial periods such ^[18]

The islands of each island group arise from a single carbonate platform, so the waters within an island group are mostly shallow. A carbonate platform is a sedimentary body which possesses Topographic relief and is composed of autochthonous calcareous deposits (Wilson 1975 The channels between groups, however, are 40 to 50 metres deep, and therefore no impediment to the exchange of offshore and inshore waters. ^[18]

Currents

The Houtman Abrolhos lies almost directly in the path of the Leeuwin Current, which draws warm, low-saline water of tropical origin southwards along the coast of Western Australia. Leeuwin Current is a warm Ocean current which flows southwards near the western coast of Australia. The Tropics are centered on the Equator and limited in Latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23 This current flows all year round, but is strongest during southern hemisphere winter months. Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' In general the Leeuwin Current runs along the shelf break, and thus passes close by the western edge of the Abrolhos. It meanders, however, sometimes passing well out to sea, and sometimes passing directly through the island chain, bathing it in warm tropical water;^[18] Although the direction of the Leeuwin Current is predominantly southerly, Shark Bay and the Houtman Abrolhos together act as a topographical trigger for the forming of eddies,^[19] so the Abrolhos can experience currents from any direction, even when the Leeuwin Current is flowing strongly. Topography ( topo-, "place" and graphia, "writing" is the study of Earth 's Surface features or those of Planets In Fluid dynamics, an eddy is the swirling of a Fluid and the reverse current created when the fluid flows past an obstacle ^[18]

Unlike most other major ocean currents, there is no large-scale coastal upwelling associated with the Leeuwin Current. Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense cooler and usually nutrient-rich water towards the ocean surface replacing the warmer Leeuwin Current is a warm Ocean current which flows southwards near the western coast of Australia. There is limited evidence for some sporadic, localised upwelling in the vicinity of the Abrolhos, but if so it appears to have little effect on the extremely low levels of nutrients in the water. ^[18]

Temperature and salinity

Sea temperature at the islands varies according to a diurnal cycle, with the water at its coldest between six and eight in the morning, and at its warmest between three and four in the afternoon. In summer the daily temperature range is around 1°C (2°F); in winter it is about half that. ^[18]

There is also an annual cycle, with sea temperature varying by a little less than 4°C (7°F) over the year, peaking at nearly 24°C (75°F) in March, and falling to around 20°C (68°F) in September. This variability is much less than in nearby coastal waters, which reaches a similar peak in summer but drops as low as 18°C (64°F) in winter. The relatively low variability in sea temperatures at the Abrolhos is largely attributable to the Leeuwin Current, which bathes the islands in warm tropical water during winter months. ^[18]

A similar annual pattern occurs in salinity. Salinity is the Saltiness or dissolved salt content of a body of Water. There is a clear seasonal variation, with values ranging from a summer high of around 35. 7 ppt, to a winter low of around 35. "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly 4 ppt. As with water temperatures, the variability in salinity is much smaller than in coastal waters, where summer salinity reaches 36. 4 ppt. This difference is partly due to the low-salinity waters of the Leeuwin Current, but there are a number of other factors involved, including high evaporation of coastal waters in summer. ^[18]

Temperatures can also vary substantially from year to year. Annual mean temperatures vary by as much as 1°C (2°F); with cooler years usually cooler throughout the year. There is evidence that annual mean temperatures are related to El Niño-Southern Oscillation events. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon ^[18]

The water column is generally well-mixed, with no evidence of a significant halocline or thermocline. A water column is a conceptual column of water from surface to bottom sediments In Oceanography, a halocline is a strong vertical Salinity Gradient. The thermocline (sometimes metalimnion) is a thin but distinct layer in a large body of water such as an ocean or lake in which temperature changes more rapidly with depth Mean differences in water temperature between sea surface and sea bed range from only half a degree (Celsius; 1°F) in summer to almost zero in winter, and differences in salinity are very small even when the Leeuwin Current is at its strongest. ^[18]

Sea levels

As with the rest of southwestern Australia, tides at the Houtman Abrolhos are small and irregular. Characteristics A tide is a repeated cycle of sea level changes in the following stages Over several hours the water rises or advances up a beach in the flood There is little tidal data available for the islands, but what there is accords very closely with the data for Geraldton. Geraldton tides follow a diurnal pattern, with maximum tidal ranges of around 1 metre (3 ft). ^[18]

Mean sea levels at Geraldton show seasonal fluctuations, being higher in winter when the Leeuwin Current is at its peak. There are also variations from year to year, which are strongly associated with the El Niño-Southern Oscillation (ENSO) cycle. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon Apparently, ENSO events induce a weaker Leeuwin Current, which results in lower sea levels. ^[18]

There is no published information on wave heights in the Abrolhos. In the open ocean, waves are typically a little over two metres high all year round. Nearer the mainland, they are usually less than 1. 2 metres, with a calmer period in March and April, and another in October and November. ^[18]

Climate

As of 2007, the Australian Bureau of Meteorology has not published climatic data for the Houtman Abrolhos. The Bureau of Meteorology is an Executive Agency of the Australian Government responsible for providing weather services to Australia and surrounding areas Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of However, an automatic weather station has been installed on North Island since 1990, and hourly measures of precipitation, air temperature, wind speed, wind direction, relative humidity and atmospheric pressure have been publicly available since then. An automatic weather station (AWS is an automated version of the traditional Weather station, either to save human labour or to enable measurements from remote areas North Island is the most northerly Island in the Houtman Abrolhos. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Wind speed is the Speed of Wind, the movement of air or other gases in an atmosphere Wind direction is the direction from which the Wind is blowing Relative humidity is a measurement of the amount of Water vapor that exists in a gaseous mixture of air and water Based on this and other data, researchers have put together a picture of the Abrolhos' climate.

The islands have a mediterranean climate, with warm dry summers and cooler, wet winters. A Mediterranean climate is one that resembles the Climate of the lands in the Mediterranean Basin, which includes over half of the area with this climate type world-wide Mean temperatures range from 9. 3°C to 19. 5°C in July, and from 19. 1°C to 32. 4°C in February. These temperatures have a substantially smaller range than on the mainland: the summer temperature is typically a degree cooler, while winter temperatures are a good deal warmer. This is due to the influence of the ocean, and to the Leeuwin Current.

86% of the rain falls between April and September; on average there are 89 raindays, resulting in 469 millimetres of rain. The wettest month is June, when over 100 millimetres typically falls. In contrast, only about 70 millimetres can be expected to fall between October and March.

It is nearly always windy. During summer a high pressure ridge lies to the south, causing persistent winds from the southeast or southwest, at speeds exceeding 17 knots almost half the time. KNOT (1450 AM) is a commercial Classic Country music Radio station in Prescott Arizona, broadcasting to the Flagstaff - Prescott During autumn and winter, the ridge moves northwards, increasing the atmospheric pressure over the islands, resulting in highly variable winds. Winter tends to produce both the strongest gales and the most frequent periods of calm.

In addition to these winds, there is daily pattern of land breezes in the morning, followed by the onset of south-westerly sea breezes in the afternoon. This pattern is caused by temperature differences between the land and the ocean, and is not as strong in the Houtman Abrolhos as on the mainland, but is present nonetheless.

Three classes of storm have been identified for the region. Brief squalls may occur between December and April. A tropical cyclone occurs in the area about once in three years, between January and April; these may generate extremely high wind speeds that are potentially destructive. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding During winter, extra-tropical cyclones sometimes pass south of Geraldton, generating winter gales with gusts of up to 35 metres per second, the wind direction from the northwest initially, then gradually moving around to southerly. Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low

Biogeography

Under the Interim Biogeographic Regionalisation for Australia (IBRA), the islands of the Houtman Abrolhos fall within the Geraldton Hills subregion of the Geraldton Sandplains region. The Interim Biogeographic Regionalisation for Australia ( IBRA) is a biogeographic regionalisation of Australia developed by the Australian Government's Department Geraldton Sandplains is an Interim Biogeographic Regionalisation for Australia (IBRA region in Western Australia. ^[20][21] The main biogeographic significance of the islands is their isolation, allowing them to provide refugia for such threatened fauna as Tammar Wallabies (Macropus eugenii), Australian Sea Lions (Neophoca cinerea) and rare breeding seabirds. Biogeography is the study of the distribution of Biodiversity over Space and Time. In biology a refugium (plural refugia is a location of an isolated or Relict Population of a once widespread animal or plant species The Tammar Wallaby ( Macropus eugenii) also known as the Dama Wallaby or Darma Wallaby, is a small member of the Kangaroo family and is the type The Australian Sea Lion ( Neophoca cinerea) is a species of Sea lion that breeds only on the south and west coasts of Australia. ^[22]

In marine terms, the Houtman Abrolhos is located within the Southwest Shelf Transition, an Integrated Marine and Coastal Regionalisation of Australia (IMCRA) biotone that takes in the continental shelf from Perth to Geraldton. Southwest Shelf Transition is a Marine biogeographic region of Australia. The Integrated Marine and Coastal Regionalisation of Australia ( IMCRA) formerly the Interim Marine and Coastal Regionalisation for Australia, is a biogeographic A biotone is a biogeographical region characterised not by distinctive biota but rather by a distinctive transition from one set of biota to another Perth is the capital and largest city of the Australian state of Western Australia. This province is defined as the area of shelf where tropical waters intergrade into temperate, thus supporting both tropical and temperate biota. ^[23][24] In addition, this area contains the highest concentration of west coast endemics. ^[25]

Consistent with this, the Houtman Abrolhos contains a mix of tropical, temperate and west coast endemic fauna, resulting in unusual associations such as the occurrence of tropical corals in close association with temperate macro-algae. The proportions of tropical, temperate and west coast endemic biota vary from taxonomic group to group, but in general the biota is dominated by tropical species. This is attributable to the location of the Houtman Abrolhos at the northern limit of the Southwest Shelf Transition, together with the warming influence of the Leeuwin Current. ^[25]

Under IMCRA, the Southwest Shelf Transition divides into two meso-scale bioregions. One is named Abrolhos Islands, and covers the shelf waters surrounding the Houtman Abrolhos, with an area of 6,645 square kilometres. The other bioregion, Central West Coast, covers the remaining area. ^[23][24]

Terrestrial flora

The flora of the Houtman Abrolhos islands is generally the same as the coastal flora of the adjacent mainland, with the exception of the islands' mangrove, saltbush and salt lake vegetation. ^[26]

Flora

The vascular flora of the Houtman Abrolhos has been thoroughly surveyed, and species lists have been published for 119 islands. Nitraria billardierei (also Nitraria schoberi) is a perennial salt tolerant shrub Adelaide is the capital and most populous city of the Australian state of South Australia, and is the fifth largest city in Australia with a Vascular plants (also known as tracheophytes or higher plants) are those Plants that have lignified tissues for conducting As of 2001, these lists totaled 239 species from 68 families. A further six species have been collected in the Houtman Abrolhos, but cannot be allocated to islands because insufficient location information was recorded. There have also been collections of mosses, liverworts and lichens, but no information has been published on these non-vascular groups. Mosses are small soft Plants that are typically 1–10  cm (0 Lichens (ˈlaɪkən or /lɪtʃən/ are symbiotic associations of a Fungus (the mycobiont with a photosynthetic partner (the photobiont also known as ^[26] For a complete list, see Flora of the Houtman Abrolhos. This is a list of the terrestrial flora of the Houtman Abrolhos.

The islands with the greatest floristic diversity are East and West Wallabi Islands, with 124 and 97 species respectively. 54 species occur in all three island groups. The most widely distributed species are Nitraria billardierei (Nitre Bush), which has been recorded on 106 islands; the exotic Mesembryanthemum crystallinum (Iceplant), on 88 islands; Threlkeldia diffusa (Coast Bonefruit), on 72 islands; and Atriplex cinerea (Grey Saltbush), on 70 islands. Nitraria billardierei (also Nitraria schoberi) is a perennial salt tolerant shrub Mesembryanthemum crystallinum is a prostrate Succulent plant that is native to Africa, Western Asia and Europe. Threlkeldia diffusa, also known as Coast Bonefruit, is a perennial herb which occurs in coastal areas and saline flats in Australia. Atriplex cinerea ( Grey Saltbush, Coast Saltbush or Barilla) is a species of Plant in the Chenopodiaceae family On the other hand, Eucalyptus oraria (Ooragmandee) and Acacia didyma occur only on East Wallabi Island. Eucalyptus oraria, also known as Ooragmandee, is a mallee species of Eucalyptus that is native to Western Australia, occurring Acacia didyma is a Shrub or small Tree which is native to Western Australia. ^[26]

As of 2001, 5 species of priority flora occurred on the islands. ^[26] One, Acacia didyma, is no longer considered a priority species. Acacia didyma is a Shrub or small Tree which is native to Western Australia. ^[27] The remaining priority species are Chthonocephalus tomentellus, which is rated Priority Two under the Department of Environment and Conservation's system of Conservation Codes for Western Australian Flora;^[28] Calocephalus aervoides and Galium migrans, both Priority Three;^[29][30] and Lepidium puberulum, Priority Four. Chthonocephalus tomentellus is an annual herb in the family Asteraceae. Calocephalus aervoides ( Woolly Beauty-heads) is a herb in the family Asteraceae. Galium migrans is a species of Flowering plant in the family Rubiaceae. Lepidium puberulum is an annual herb in the Brassicaceae family endemic to the west coast of Western Australia. ^[31]

95 exotic species from 29 families have been recorded. In general, islands that have or had human settlements are the weediest. Of greatest concern is the noxious weed Lycium ferocissimum (African Boxthorn), which has long spines that can trap birds. Lycium ferocissimum ( African Boxthorn or boxthorn) is a Shrub in the nightshade family ( Solanaceae) This weed was recorded on the islands as early as 1970. Efforts to eradicate it began in 1990,^[26] Other noxious weeds include Opuntia stricta (Prickly Pear),^[26] Verbesina encelioides and Echium plantagineum (Paterson's Curse). Opuntia stricta, commonly known known as Erect Prickly Pear, is a species of Cactus from southern North America and Central America Verbesina encelioides ( American dogweed, butter daisy, crown-beard, golden crown-beard or South African daisy) is Echium plantagineum ( Purple Viper's Bugloss) is a species of Echium, native to western and southern Europe (from southern ^[32]

Vegetation

The vegetation is mostly chenopod shrubs.

Terrestrial fauna

Birds

The Houtman Abrolhos is home to around 100 species of bird; for a complete list, see list of birds of the Houtman Abrolhos. Terns are Seabirds in the family Sternidae, previously considered a subfamily (Sterninae of the gull family Laridae (van Tuinen et al The Houtman Abrolhos, an island chain off the coast of Western Australia, is one of the most important areas in the world for breeding colonies of Seabirds Six species are land birds, and three are shore birds. The remainder, the vast majority, are seabirds. Seabirds are Birds that have adapted to life within the marine environment Most seabird species have a tropical distribution, but some occur in both tropical and warm-temperate seas, and a small number are warm-temperate only. ^[33]

When numbers of individuals are taken into account, the tropical birds overwhelmingly dominate. The islands are one of the most important breeding sites for tropical seabirds in Australia. They contain by far the largest colonies of Wedge-tailed Shearwater in the eastern Indian Ocean, with over a million breeding pairs recorded there in 1994. The Wedge-tailed Shearwater, Puffinus pacificus is a medium-large Shearwater in the Seabird family Procellariidae. ^[34] They also contain Western Australia's only breeding colonies of the Lesser Noddy, and the largest colonies in Western Australia of the Little Shearwater, White-faced Storm Petrel, Common Noddy, Caspian Tern, Crested Tern, Roseate Tern and Fairy Tern. A seabird colony is a site which Seabirds visit to breed typically during the summer UserPolbot. -->The Lesser Noddy ( Anous tenuirostris) is a species of Tern in the Sternidae The Little Shearwater ( Puffinus assimilis) sometimes called Southern Little Shearwater to distinguish it from the North Atlantic Little Shearwater The White-faced Storm-petrel, Pelagodroma marina also known as White-faced Petrel is a small Seabird of the Storm-petrel family The Brown Noddy or Common Noddy Anous stolidus is a Seabird from the Tern family. The Caspian Tern ( Hydroprogne caspia, formerly Sterna caspia; syn The Greater Crested Tern, Crested Tern or Swift Tern, ( Thalasseus bergii) is a Seabird in the Tern family which nests in dense The Roseate Tern ( Sterna dougallii) is a Seabird of the Tern family Sternidae The Fairy Tern ( Sterna nereis) is a small Tern which occurs in the southwestern Pacific. In addition, they contain important breeding areas for the Eastern Reef Heron, Pacific Gull, Bridled Tern, White-bellied Sea Eagle and Osprey. The Pacific Gull ( Larus pacificus) is a very large Gull, native to the coasts of Australia. The Bridled Tern ( Onychoprion anaethetus, formerly Sterna anaethetus - see Bridge et al The White-bellied Sea-eagle ( Haliaeetus leucogaster) and also known as the White-bellied Fish-eagle or White-breasted Sea Eagle, is a large The Osprey (Pandion haliaetus, also called Sea Hawk, is a diurnal, fish-eating Bird of prey. ^[33][35]

There are two subspecies of bird endemic to the islands. The Abrolhos Painted Button-quail occurs only on five islands in the Wallabi Group, and is protected as rare under the Wildlife Conservation Act 1950. The Wildlife Conservation Act 1950 is an act of the Western Australian Parliament that provides the statute relating to conservation of flora and fauna Also gazetted as rare, the Australasian subspecies of the Lesser Noddy, Anous tenuirostris melanops, breeds only on Wooded Island, Morley Island and Pelsaert Island. ^[35]

Mammals

Only two species of land mammal are indigenous to the Houtman Abrolhos, the Tammar Wallaby (Macropus eugenii) and the Bush Rat (Rattus fuscipes). The Tammar Wallaby ( Macropus eugenii) also known as the Dama Wallaby or Darma Wallaby, is a small member of the Kangaroo family and is the type The Tammar Wallaby ( Macropus eugenii) also known as the Dama Wallaby or Darma Wallaby, is a small member of the Kangaroo family and is the type The Bush Rat ( Rattus fuscipes) is a small Australian Nocturnal animal. Both are native only to West and East Wallabi Islands,^[36] although R.  fuscipes has not been collected on East Wallabi Island since August 1967, and is probably extinct there. ^[37] The Tammar Wallabi was seen on West Wallabi Island by survivors of the 1628 Batavia shipwreck, and recorded by Francisco Pelsart in his 1629 Ongeluckige Voyagie. Francisco Pelsaert (first name sometimes reported as "François" surname also spelled "Pelsart" (c This represents the first recorded sighting of a macropod by Europeans,^[38] and probably also the first sighting of an Australian mammal. Macropods are Marsupials belonging to the family Macropodidae, which includes Kangaroos wallabies, Tree-kangaroos Pademelons ^[39] Tammar Wallabies were introduced to North Island from East Wallabi Island by fishermen, probably in the 1950s, but failed to establish. In 1987 they were reintroduced again, this time successfully. By the 2000s, there were over 400 wallabies on the island, resulting in overgrazing of native vegetation and increased erosion. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Research into the effectiveness of controlling population levels by the use of implanted contraceptives was begun in 2005,^[40] but in July 2007 the research was discontinued and the population culled instead. ^[41]

Two introduced mammals are established on the islands. The Domestic Cat (Felis silvestris catus) was introduced to Rat Island around 1900, and the House Mouse (Mus musculus) was introduced onto North Island in the 1970s, presumably with food. WikipediaManual of Style (spelling, articles should conform to one overall spelling style of English typically the one most linked to the article topic (if it is geographic The House Mouse ( Mus musculus) is one of the most numerous species of the genus Mus commonly termed a Mouse. In 1995 the House Mouse was reported as also present on Rat Island for many years before 1987,^[36] but a recent report makes no mention of this. ^[42] In addition, three introduced mammals were previously established in the Houtman Abrolhos, but have since been eradicated. The Black Rat (Rattus rattus) was established on Pigeon and Rat Islands, but has been eradicated by poisoning. The European Rabbit (Oryctolagus cuniculus) has been introduced at various times onto Leo Island, Middle Island, Morley Island, Pelsaert Island and Wooded Island. The European Rabbit ( Oryctolagus cuniculus) is a species of Rabbit native to south west Europe (Spain and Portugal In the case of Pelsaert Island, it is not clear whether it ever established; in all other cases, established populations have been eradicated by poisoning. ^[36][42] The Domestic Goat (Capra aegagrus hircus) is also reported to have been present on East Wallabi Island, but is no longer. The domestic goat ( Capra aegagrus hircus) is a subspecies of goat Domesticated from the Wild goat of Southwest Asia and Eastern Europe ^[33]

Reptiles

23 terrestrial reptile species are known to occur on the islands of the Houtman Abrolhos. Pogona minor minima is an Agamid lizard found only on islands at Houtman Abrolhos, and commonly named for this location the Abrohlos Bearded ^[43] This relatively low biodiversity is apparently due to the homogeneity of habitat on the islands, which provide few distinct ecological niches. In Ecology, a niche (pronounced nich nēsh or nish A shorthand definition of niche is how an organism makes a living ^[44] The most significant terrestrial reptile species are the Spiny-tailed Skink (Egernia stokesii stokesii) and the Carpet Python (Morelia spilota imbricata), both of which are listed as rare and therefore afforded special protection under the Wildlife Conservation Act 1950; and the Abrolhos Dwarf Bearded Dragon (Pogona minor minima), a Houtman Abrolhos endemic that is listed as a Priority 4 species by the Department of Environment and Conservation. Morelia spilota imbricata is a non-venomous Snake found in southern regions of Western Australia. The Wildlife Conservation Act 1950 is an act of the Western Australian Parliament that provides the statute relating to conservation of flora and fauna Pogona minor minima is an Agamid lizard found only on islands at Houtman Abrolhos, and commonly named for this location the Abrohlos Bearded The Department of Environment and Conservation is a department of the Government of Western Australia that is responsible for implementing the state's conservation and environment ^[35] For a full list of species, see list of reptiles of the Houtman Abrolhos. The Houtman Abrolhos, an island chain off the coast of Western Australia, is recognised as containing 24 terrestrial reptile species plus the marine Green Turtle

Amphibians

Specimens of the Pobblebonk (Limnodynastes dorsalis) and the Turtle Frog (Myobatrachus gouldii) were collected from the Houtman Abrolhos during the Percy Sladen Trust Expedition of 1913 and 1915, but no amphibians have been recorded on the islands since that time. Myobatrachus gouldii, the turtle frog is an Western Australian Frog, and the only species in the genus Myobatrachus ^[43]

Marine flora

Algae

260 species of benthic algae have been recorded at the Houtman Abrolhos. The benthic zone is the ecological region at the lowest level of a Body of water such as an Ocean or a Lake, including the sediment surface and some sub-surface Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms This figure is comprised of 178 species of red algae (Rhodophyta), 50 species of brown algae (Phaeophyta) and 32 species of green algae (Chlorophyta). The red algae (Rhodophyta ˌroʊdəˈfaɪtə roʊˈdɒfɨtə from Greek: ῥόδον (rhodon = rose + φυτόν (phyton = plant thus red plant are The Phaeophyceae or brown algae, (singular alga is a large group of mostly marine multicellular Algae including many Seaweeds of colder The green algae (singular green alga) are the large group of Algae from which the Embryophytes (higher plants emerged Both temperate and tropical species are present, in many cases near the northern or southern extent of their range. ^[45] For a full list, see list of algae of the Houtman Abrolhos. The marine waters of the Houtman Abrolhos, an island chain off the coast of Western Australia, have been recorded as containing 260 species of Benthic Algae

Seagrass

Only ten species of seagrass have been recorded at the Houtman Abrolhos. Seven of these are temperate species at or near the northern limit of their range; the other three have a tropical distribution. That there are so few tropical species may be due to periods of low sea temperatures, or the small areas of suitable habitat at the Abrolhos; alternatively it may be that more collecting effort is needed in habitats that suit tropical species. The seagrass species recorded at the Houtman Abrolhos islands are:^[46]

Amphibolis antarctica Amphibolis griffithii Halophila decipiens Halophila ovalis

Posidonia angustifolia Posidonia australis Posidonia coriacea

Posidonia sinuosa Syringodium isoetifolium Thalassodendron pachyrhizum

Marine fauna

Fish

At last count, a total of 389 species of fish have been recorded from the Houtman Abrolhos. Amphibolis antarctica, commonly known as Sea Nymph, is a Seagrass found in coastal waters of southern and western Australia Amphibolis griffithii is a Seagrass found in waters along the southwestern coasts of Western Australia Halophila ovalis is a Seagrass in the family Hydrocharitaceae, a common name is paddle weed. Posidonia australis is a species of Seagrass that occurs in the southern waters of Australia. The moon wrasse, Thalassoma lunare, is a Wrasse of the Labridae family found in the Indo-Pacific oceans at depths of between 16 species occur in very large numbers; in decreasing order of abundance, these are:^[47]

• Pomacentrus milleri (Miller's Damsel)
• Scarus schlegeli (Schlegel's Parrotfish)
• Stethojulis strigiventer (Stripebelly Wrasse)
• Coris auricularis (Western King Wrasse)
• Kyphosus cornelii (Western Buffalo Bream)
• Choerodon rubescens (Baldchin Groper)
• Chromis westaustralis (West Australian Puller)
• Thalassoma lutescens (Green Moon Wrasse)
• Scarus ghobban (Blue-barred Orange Parrotfish)
• Abudefduf sexfasciatus (Scissortail Sergeant)
• Thalassoma lunare (Moon Wrasse)
• Stegastes obreptus (Western Gregory)
• Halichoeres brownfieldi (Brownfield's Wrasse)
• Amblygobius phalaena (White-barred Goby)
• Asterropteryx semipunctatus (Starry Goby)
• Anampses geographicus (Scribbled Wrasse)

Commercially important species include Pagrus auratus (Pink Snapper), Choerodon rubescens (Baldchin Groper), Glaucosoma hebraicum (Westralian Dhufish) and Plectropomus leopardus (Coral Trout). UserPolbot. -->The baldchin groper or baldchin tuskfish ( Choerodon rubescens) is a species of Fish The Scissortail sergeant or Striptailed damselfish ( Abudefduf sexfasciatus, family Pomacentridae) is a large Damselfish. The moon wrasse, Thalassoma lunare, is a Wrasse of the Labridae family found in the Indo-Pacific oceans at depths of between The Australasian snapper or squirefish, Pagrus auratus is a species of Porgie found in coastal waters of New Zealand and southern Australia UserPolbot. -->The coral trout, leopard coral grouper, or leopard coral trout ( Plectropomus leopardus ^[48] For a complete list of fish species recorded at the Houtman Abrolhos, see list of fishes of the Houtman Abrolhos. The marine waters of the Houtman Abrolhos, an island chain off the coast of Western Australia, are unusual in containing a mix of tropical subtropical and warm-temperate fish

About two thirds of the total number of species are tropical in distribution, the remainder being subtropical or warm-temperate. This ratio also holds for the most abundant species, eleven of the sixteen species being tropical. ^[47] On the other hand, over 70% of tropical species occur in extremely low numbers, so low in fact that they are thought not to maintain breeding populations at the Abrolhos; rather, populations are maintained by larvae carried to the islands by the Leeuwin Current from populations further north. In Roman mythology, the larvae or lemures (singular lemur) were the spectres or spirits of the dead they were the malignant version of the ^[49]

Marine mammals

The Houtman Abrolhos maintains a breeding population of Australian Sea Lions (Neophoca cinerea), probably numbering between 75 and 100. The Australian Sea Lion ( Neophoca cinerea) is a species of Sea lion that breeds only on the south and west coasts of Australia. Historical data suggests numbers were previously much higher;^[50] for example, in 1727 survivors of the Zeewyk shipwreck killed over 150 sea lions in the Southern Group alone. This has led to a 1727 population estimate of between 290 and 580 animals for the entire Houtman Abrolhos. Populations apparently fell dramatically between the 1840s and the 1880s, largely due to extensive commercial sealing in the area. Sealing redirects here for other uses see Sealing (disambiguation. In addition to direct killing of the animals, it is likely that much of the mangrove habitat on the islands was cleared as fuel for trypots, and this may have affected the survival of young pups. Mangroves (generally are Trees and Shrubs that grow in saline coastal habitats in the Tropics and Subtropics. A try pot is a large pot used to remove and render the oil from Blubber obtained from Cetaceans Pinnipeds and also to extract oil from Penguins Populations are thought to have been fairly stable for the last fifty years, although the lack of genetic diversity in the smaller population remains of concern, as does climate change. Climate change is any long-term significant change in the “average weather” that a given region experiences ^[51]

Sea lions come ashore to rest on leeward beaches throughout the island chain, but only a small number of these "haulout sites" are used for breeding. Breeding has been observed on Serventy Island, Gilbert Island, Alexander Island, Suomi Island, Keru Island, Square Island, Stick Island, Gibson Island, Gun Island, Morley Island and Wooded Island. Alexander Island is one of the five largest Islands in the Easter Group of the Houtman Abrolhos. Gun Island is one of the larger Islands in the Pelsaert Group of the Houtman Abrolhos. All but the last three of these are considered current breeding sites, and are therefore considered by the Department of Fisheries to have a high conservation value. ^[35]

Little information is available on other marine mammals at the Abrolhos, as no direct research on this subject has been undertaken. Sightings of the Humpback Whale (Megaptera novaeangliae) are common between April and October, when the whales are migrating. The humpback whale ( Megaptera novaeangliae) is a Baleen Whale. Other marine mammals sometimes sighted at the islands include Pygmy Bryde's Whale (Balaenoptera edeni), Bottlenose Dolphin (Tursiops aduncus) and Striped Dolphin (Stenella coeruleoalba). Bryde’s Whales are the least-known and in many ways the most unusual of the Rorquals They are small by rorqual standards&mdashno more than about 25 tonnes&mdashprefer tropical The Bottlenose Dolphin is one of the most common and well-known Dolphins. The Striped Dolphin ( Stenella coeruleoalba) is an extensively studied Dolphin that is found in temperate and tropical waters of all the world's oceans ^[48]

Marine reptiles

The Green Turtle (Chelonia mydas) and the Loggerhead Turtle (Caretta caretta) both live in the waters off the Houtman Abrolhos, albeit in low numbers. "Chelonia" redirects here It is also the name of the Superorder uniting turtles tortoises and terrapins ( Testudines) with the "proto-turtle" The Loggerhead Sea Turtle ( Caretta caretta) is a Sea turtle and the only member of the genus Caretta. Neither species breeds in the area, as water temperatures are too low. ^[48]

Coral

The Houtman Abrolhos is unusual in having a luxuriant and diverse living coral reef at such a high latitude. 194 species in 50 genera have been recorded there,^[52] all but two of which are tropical. This is a surprisingly high coral diversity, considering the high latitude of the reef, and the relatively low diversity of other biota. ^[52] For a full list, see list of corals of the Houtman Abrolhos. The marine waters of the Houtman Abrolhos, an island chain off the coast of Western Australia, have been recorded as containing 194 species of Coral in 50 genera

The coral reef community at the Houtman Abrolhos is unusual in having tropical coral growing alongside and in direct competition with, temperate seaweed. Seaweed is a loose colloquial term encompassing macroscopic Multicellular, benthic marine Algae. As a result of this competition for light, space and nutrients, coral at the Houtman Abrolhos tends to grow more slowly and die younger than is usual. Reef production is to a large extent due to the production of carbon by coralline algae rather than by coral. Coralline algae are Red algae in the Family Corallinaceae of the order Corallinales.

Crustaceans

The most notable species of crustacean at the Houtman Abrolhos is the Western Rock Lobster (Panulirus cygnus). The western rock lobster or western crayfish, Panulirus cygnus, is a Spiny lobster found off the west coast of Australia and Hillarys Boat Harbour is a Marina and tourist precinct located in Hillarys, north of Perth Western Australia and on the Indian Ocean. Perth is the capital and largest city of the Australian state of Western Australia. Structure of crustaceans As Arthropods crustaceans have a stiff Exoskeleton, which must be shed to allow the animal to grow ( Ecdysis or molting The western rock lobster or western crayfish, Panulirus cygnus, is a Spiny lobster found off the west coast of Australia and 44 species of crab and 9 species of amphipod were recorded there by the Percy Sladen Trust Expedition of 1916. Crabs are decapod Crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (βραχύ / brachy Amphipoda (amphipods are an order of animals that includes over 7000 described Species of Shrimp -like Crustaceans ranging from 1 mm to 140 mm

Molluscs

492 species of marine mollusc have been recorded from the shallow waters of the Houtman Abrolhos. Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 These are predominantly gastropods (346 species, 70%) and bivalves (124, 25%); the remaining 5% of species consist of cephalopods (14 species), chitons (5 species) and scaphopods (3 species). The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails Bivalves are Molluscs belonging to the class Bivalvia. They have two-part shells and typically both valves are symmetrical along the hinge line The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Chitons are small to large primitive marine Mollusks in the class Polyplacophora. The tusk shells or scaphopods are a class of marine Mollusks which vary in size from very small to medium sized About two thirds of the species have a tropical distribution, temperate species account for 20%, and the remaining 11% are endemic to Western Australia. ^[53]

The Southern Saucer Scallop (Amusium balloti) is the only commercially important species. This occurs in sheltered areas of medium-fine sand in deep water to the north-east of the reefs; it is usually the dominant species there. ^[54]

Echinoderms

Houtman Abrolhos has an extremely high diversity of echinoderms, with 172 species having been recorded there. Echinoderms (Phylum Echinodermata) are a phylum of marine Animals (including Sea stars) 63% of these are tropical species, 14% are temperate, and 22% are endemic to Western Australia. None is endemic to the Houtman Abrolhos. ^[55] Published surveys have not included observations of the crown-of-thorns starfish (Ananthaster planci), but individuals have occasionally been observed there. The crown-of-thorns starfish ( Acanthaster planci) is a Starfish with thorn-like spines sprouting all over its body for protection ^[48] For a complete list of species, see list of echinoderms of the Houtman Abrolhos. The marine waters of the Houtman Abrolhos, an island chain off the coast of Western Australia, has been recorded as containing 172 species of Echinoderm in ?? genera

Other invertebrates

The sponges of the Houtman Abrolhos are poorly studied, although 109 species of demosponge have been collected there. The Demospongiae are the largest class in the Phylum Porifera. In the most recent survey, 77 species were collected, of which around half are probably new to science. Only two locations were surveyed in this study, however, so this figure is likely to represent only a small proportion of the total sponge fauna of the Houtman Abrolhos; the islands are therefore thought to harbour an extremely rich diversity of sponges. A preliminary assessment suggested that there were more temperate species than tropical, which stands in marked contrast to most other groups. ^[56]

The marine worms identified at the Houtman Abrolhos include 22 species of the polychaete family Terebellidae,^[57] and 16 species of the family oligochaete family Tubificidae. Any Worm that lives in a marine environment is considered a marine worm. The Polychaeta or polychaetes are a class of Annelid worms generally marine Terebellidae is a family of Polychaete worms They are surface Deposit feeders catching falling particles with numerous elongate prostomial tentacles For the plant Genus from the sunflower family ( Asteraceae) see Oligochaeta (plant. ^[58] For a list of species, see list of worms of the Houtman Abrolhos. The Marine worms identified at the Houtman Abrolhos comprise 22 species of the Polychaete family Terebellidae, and 16 species of the family Oligochaete

A total of 38 hydroid species have been collected at the Houtman Abrolhos. Hydroid may refer to Marine Biology Colonial plant-like animals closely related to jellyfish with stinging cells any member of the invertebrate order Hydroida (class 34 of these are leptothecates, the remainder being anthoathecates. 92% of the species attach to temperate algae, the others to coral rubble. ^[59] For a list of species, see list of hydroids of the Houtman Abrolhos. A total of 38 Hydroid species have been collected at the Houtman Abrolhos

Human uses

Fishing

The Houtman Abrolhos serves as a major resource for the local fishing industry.

Western rock lobster

It is the centre of the Western Rock Lobster fishery, the largest single-species fishery in Western Australia. The western rock lobster or western crayfish, Panulirus cygnus, is a Spiny lobster found off the west coast of Australia and

Saucer scallops

After Shark Bay, the Houtman Abrolhos supports Western Australia's second largest saucer scallop fishery. ^[60][32] This fishery is managed under the Abrolhos Islands and Mid West Trawl Limited Entry Fishery Notice 1993. Only 17 licences have been issued, and no more will be made available, as the saucer scallop is considered fully exploited. Licensees are constrained to operate only during scallop season, which generally runs from 1 April to 30 June, and are also subject to restrictions on gear design, boat size and crew numbers. ^[61]

Scallop fishers mainly operate east of the Houtman Abrolhos and between the island groups, in waters deeper than 30 metres. Activity is targeted at sheltered areas of bare sand, where scallops tend to settle. Catches vary greatly from year to year; from 2001 to 2003, for example, the total annual catch totalled 1182 tons, 195 tons and 5840 tons (whole weight) respectively. This variability is apparently related to the strength of the Leeuwin Current, as strong current is correlated with low scallop recruitment. ^[61]

The total value of the fishery in 2003 was AU$19. 6 million, although this figure includes a small prawn fishery operating out of Port Gregory. Most of the catch is frozen and exported to Asia. ^[61]

Finfish

The Houtman Abrolhos is the site and some wetlining activity.

Aquaculture

The Department of Fisheries have issued a number of licences to cultivate black-lip pearl oysters in the Abrolhos. The first recipient of a license was Abrolhos Pearls in 1996. ^[62] By 2000, another license had been issued and four more applications had been received. ^[60] A year later, there were 1,000 ha licensed for the culture of pearl oysters in the Abrolhos, of which about 21% was actually in use, carrying over 210,000 shell. ^[63] Six licences had been issued by 2002,^[48] and by 2007 that number had grown to eight. ^[32]

95% of the pearl aquaculture is carried out in the Pelsaert Group. A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk. Aquaculture is the farming of freshwater and saltwater organisms including Molluscs Crustaceans and aquatic plants Most licenses are over areas of sand, but some areas contain small amounts of coral reef. ^[48] The colour of the pearls produced is quite different to that of Pacific black pearls, and this is considered a potential marketing tool. ^[63]

In addition to pearl aquaculture, a pilot sea cage finfish farm was licensed in 2004, although as of 2007 the license had not been exercised. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Interest has also been expressed in the culture of live rock and coral for the aquarium industry. " Live rock " is rock from the ocean that has been introduced into a Saltwater aquarium, which confers to the closed marine system multiple benefits desired by the salt An aquarium (plural aquariums or aquaria) is a Vivarium consisting of at least one transparent side in which Water -dwelling Plants ^[32] The Department of Fisheries has identified a number of species as having potential for aquaculture in the Abrolhos, including the Shark Bay pearl oyster (Pinctata albina), the maxima clam (Tridacna maxima), rock oysters (Saccostrea sp. The maxima clam ( Tridacna maxima) also known as the small giant clam, is a species of Clam found throughout the Indo-Pacific. Rock oysters are Oysters of the genus Saccostrea. The best known species of rock oyster is the Sydney rock oyster ( Saccostrea glomerata ), the saucer scallop (Amusium balloti), the western rock lobster, and a number of species of finfish, most of which are filter feeders. Filter feeders (also known as suspension feeders) are Animals that feed by straining suspended matter and food particles from water typically by passing the water ^[60]

Mineral exploration

Petroleum exploration wells were drilled in Abrolhos waters in the 1960s and 1970s, but were capped and abandoned. Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum Geologists for Hydrocarbon deposits beneath the Earth's surface The Abrolhos was amongst the areas released for further exploration in 2002.

Recreation

The Abrolhos provides some of the best snorkeling, diving and deep sea fishing in the world, along with some of Australia's most significant historical sights, such as the shipwreck of the Batavia. Snorkeling ( British spelling: snorkelling) is the practice of Swimming at the surface of a body of water while equipped with a Diving mask, a Diving off a deck into the Great South Bay of Long Islandjpg|thumb|A man dives into the Great South Bay of Long Island. A shipwreck can refer to a wrecked ship or to the event that caused the wreck such as the striking of something that causes the ship to sink the stranding of the ship on rocks Mutiny on the Batavia Departure On 29 October 1628, the newly built Batavia, commissioned by the Dutch East India Company

Nowadays, many of the islets are used by fishermen. Although an important tourist destination, the tourists are not allowed to stay overnight.

Cultural references

The majority of cultural references to the Houtman Abrolhos relate to the islands' shipwrecks, particularly the Batavia. The events surrounding the loss of the Batavia is one of the most celebrated episodes in Australian popular history; in the words of Henrietta Drake-Brockman:

"In Australia, poets and schoolboys, artists and historians, have been inspired for half a century by the tragedy of an ancient shipwreck, a disaster that piled horror upon horror yet revealed so much of human fortitude as to invite comparison with the epic tales of Greece. "^[16]

The story has spawn a massive body of literature, both fiction and non-fiction,^[16] as well as numerous works in other media.

Other shipwrecks, notably the Zeewijk, have also become the subject of books and other works. Shipwrecks aside, however, cultural references to the Houtman Abrolhos are rare. By far the best known book on the Houtman Abrolhos itself is Malcolm Uren's Sailormen's ghosts: The Abrolhos islands in three hundred years of romance, history, and adventure. First published in 1940, this book saw numerous editions published in the 1940s, and was even republished in 1980 as a "West Australian classic". In it, Uren tells both the history of the islands and the story of his own visit to the islands. ^[64]

Other books include William Bede Christie's 1909 Christmas on the briny: the innocents abroad, or, a holiday trip to the Abrolhos islands, and Alison Louise Wright's 1998 Abrolhos Islands Conversations. The latter, a book of interviews and portraits of the people of the Abrolhos, won the Special Award in the 1999 Western Australian Premier's Book Awards. The Western Australian Premier's Book Awards is an award for books and scripts written by Western Australians or about Western Australia ^[65]

The islands featured in the first episode of Surfing the Menu, an eight-part food and travel series produced for the ABC in 2003. The Australian Broadcasting Corporation, commonly abbreviated to the 'ABC' is Australia's national public broadcaster. ^[66], and the following year were featured on Getaway, Australia's longest-running and most popular holiday and travel television programme. Getaway is Australia 's longest-running and most popular holiday and travel Television programme ^[67] They were the subject of a motion picture entitled Eye opener, published by The Film Centre WA in 1981, and of a piece of classical music entitled Abrolhos: A ceremonial overture, written by William Stewart in 1988 under commission to the Geraldton Town Council.

References

Further reading

• Collins, Lindsay. (1991) The Abrolhos coral reefs - history and present management. Curtin gazette, Mar 1991, p. 5-11
• Myra Stanbury et al. (2000)Abrolhos Islands archaeological sites : interim report, Fremantle, W. A. Australian National Centre of Excellence for Maritime Archaeology. Special publication no. 5. ISBN 1-876465-12-3

See also

• Batavia (ship)

Mutiny on the Batavia Departure On 29 October 1628, the newly built Batavia, commissioned by the Dutch East India Company

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