Houtman Abrolhos

thumb|Aerial photograph of [[Rat Island (Houtman Abrolhos)|Rat Island (Easter Group), 2006]]

The Houtman Abrolhos (often called the Abrolhos Islands) is a chain of 122 islands and associated coral reefs in the Indian Ocean off the west coast of Australia about west of Geraldton, Western Australia. 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 the centre of Western Australia's largest single-species fishery, the western rock lobster fishery. It has a small seasonal population of fishermen, and a limited number of tourists are permitted for day trips, but most of the land area is off-limits as a conservation habitat. It is the site of numerous shipwrecks, the most famous being two Dutch ships: , which was wrecked in 1629 (followed by massacre of over 100 survivors by mutineers), and , wrecked in 1727.

The islands are an unincorporated area with no municipal government, subject to direct administration of the Government of Western Australia. In July 2019, the Houtman Abrolhos was declared a national park by the state government.

Geography

thumb|Aerial photograph of the southern half of North Island, looking westwards and showing the seasonal fishing camp

The Houtman Abrolhos archipelago is in the Indian Ocean off the west coast of Australia, about west of Geraldton in the state of Western Australia. Its 122 islands and associated coral reefs comprise three island groups, the Wallabi Group, Easter Group and Pelsaert Group.

The most northerly group, the Wallabi Group, consists of an island clump about by , and also takes in the outlying North Island to the north-west. The main islands of the Wallabi Group are North Island, West Wallabi Island, East Wallabi Island and Beacon Island. The group is best known for the shipwreck of Batavia on Morning Reef near Beacon Island in 1629, and the subsequent mutiny and massacre that took place among the survivors. Other wrecks include Ocean Queen, wrecked on the Half Moon Reef in 1842; Ben Ledi, wrecked off Pelsaert Island in 1879; Windsor, wrecked on the Half Moon Reef in 1908.; and possibly Ridderschap van Holland in 1694 and Aagtekerke in 1727.

Governance

The islands are a part of Western Australia. They are part of the Electoral district of Geraldton, and the City of Greater Geraldton. In July 2019, the Houtman Abrolhos was declared a national park by the Western Australian Government.

In early November 2022, the government published its three-part plan to manage the site in the following 10 years, based on research and community consultation carried out after the preceding two years. Some critics thought that the plan did not encourage land-based tourism to the archipelago enough. A spokesperson for Western Australia's Department of Primary Industries and Regional Development said that their top priority is preservation of the wildlife on the islands.

History

Aboriginal people visited the islands during the Holocene, as indicated by the discovery on Beacon Island of a flaked stone artefact made from Eocene fossiliferous chert.

Discovery by Europeans

thumb|Detail from [[Pierre Desceliers' 1550 world map, purportedly showing the north west coast of Australia, with an island labelled "Arenes" at the position of the Houtman Abrolhos.]]

thumb|The island labelled "Arenes".

thumb|[[Hessel Gerritszoon's 1627 "Caert van't Landt van d'Eendracht" contains the first use of the name Houtman's Abrolhos in print.]]

thumb|Detail of "Caert van't Landt van d'Eendracht", showing features labelled "Fr. Houtman's abrolhos"

According to the surviving historical record, the first sighting of the Houtman Abrolhos by Europeans was in 1619, sailing the Dutch VOC ships Dordrecht and Amsterdam, only three years after Dirk Hartog made the first authenticated sighting by a European of what is now Western Australia, and only 13 years after the first authenticated European voyage to Australia by the Duyfken, in 1606. Discovery of the islands was credited to Frederick de Houtman, Captain-General of Dordrecht, as it was Houtman who later wrote about the discovery in a letter to the directors of the Dutch East India Company:

The word is Portuguese, making the Houtman Abrolhos one of only two Australian places with a Portuguese name, the other being Pedra Branca in Tasmania. The noun means , and originally designated the spiny fruit of the bindii plant (Tribulus terrestris). Etymologically it is a contraction of the Portuguese expression (; that is, to protect yourself). As a technical term this phytonym was later applied to caltrops (chevaux de frise), i.e. "spiked obstructions", and Portuguese sailors used the word to refer to offshore reefs.

Houtman thus named the islands using a Portuguese loanword that was current in the Dutch marine terminology of the time. 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. That position is supported by the fact that Houtman was familiar with the Abrolhos Archipelago, having sailed through it in 1598. 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, becoming, by Houtman's time, a Dutch loan word for offshore reefs. Additionally, Frederick De Houtman had at least some grasp of Portuguese, having been sent by Amsterdam merchants to Lisbon from 15921594 with his brother Cornelis to learn about the Portuguese route to the Indies. Frederick also appears to have been a keen linguist, having published the first-known Dutch-Malay and Dutch-Malagasy dictionaries in 1603. He appears to have been fluent-enough in Portuguese that he might have used an evocative Portuguese word if it described the area better than any Dutch word did.

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. 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 those maps.

The primary piece of evidence used to support the claim of Portuguese priority is the 16th century Dieppe maps, some of which are alleged to show the west coast of Australia, including an island at the position of the Houtman Abrolhos. That island is unlabelled on most of the Dieppe maps but, on Pierre Desceliers' 1550 map, it is labelled Arenes. In 1895, George Collingridge suggested that Arenes was a corruption of Abrolhos, but that was mocked by Heeres in 1898, and, according to Battye, "this suggestion can scarcely be regarded seriously. It certainly does not in any way add to the merit of the Portuguese claim".

thumb|left|Houtman Abrolhos labelled 'Houtman Rocks' on Western Australia state map for 1897

Setting aside the Portuguese claims, the Houtman Abrolhos first appear on a map in 1622, on a little-known portolan by Hessel Gerritsz. They are first named in print in Gerritsz' 1627 map Caert van't Landt van d'Eendracht, where they bear the label Fr. Houtman's abrolhos. On a map produced by Gerritsz the following year, they are labelled Houtman's Abrolhos.

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

Wreck of Batavia

thumb|A 1647 engraving showing the Beacon Island massacre of survivors of the shipwreck

In 1629, some of the islands were the scene of an infamous shipwreck and mutiny. The Dutch ship , under the command of Francisco Pelsaert, ran aground on her maiden voyage to the port of Batavia, the capital of the Dutch East Indies. Pelsaert and some of his crew set off in an open boat to Batavia (now Jakarta) to get help. A group of the crew who remained on some of the islets terrorised and killed many of the other crew and passengers, including women and children. When Pelsaert returned, a number of the culprits were executed.

Wreck of Zeewijk

The was the last of the four Dutch East Indiamen to be wrecked on the west coast of Australia. Due to 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 7:30 pm on 9 June 1727. 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. Later, the men landed ten chests of money, containing 315,836 guilders and weighing a total of . Later during the 19th century many islets were used by men collecting guano.

A lease to mine rock phosphate on the islands was obtained by Charles Broadhurst in 1884. After surveying the area he constructed a plant, stone jetty and tramways on Rat Island, a number of buildings on Rat, Gun and Pelsaert islands and had over 40 Malay workers mining and processing the phosphate for export. Over was shipped between 1884 and 1896.

Tenure, governance and management

The islands are a part of the Division of Durack in the federal House of Representatives and the electoral district of Geraldton in the Western Australian Legislative Council. 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, while others were more recently formed from coral rubble and are made of limestone under a layer of sand, cemented coral rubble and shingle.

Oceanography

Bathymetry

The Houtman Abrolhos lies in the Indian Ocean about 60 kilometres (40 mi) off the coast of Western Australia, near the edge of Australia's continental shelf. 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 west 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 islands of each island group arise from a single carbonate platform, so the waters within an island group are mostly shallow. The channels between groups are deep, so no impediment to the exchange of offshore and inshore waters. so the Abrolhos can experience currents from any direction, even when the Leeuwin Current is flowing strongly. 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.

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. This province is defined as the area of shelf where tropical waters intergrade into temperate, thus supporting both tropical and temperate biota. In addition, this area contains the highest concentration of west coast endemics.

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.

Flora

thumb|[[Nitraria billardierei (nitre bush), pictured here in Adelaide, South Australia, is the most widely distributed plant species in the Houtman Abrolhos]]

The vascular flora of the Houtman Abrolhos has been thoroughly surveyed, and species lists have been published for 119 islands. As of 2001, these lists totalled 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. The remaining priority species are Chthonocephalus tomentellus, which is rated Priority Two under the Department of Environment and Conservation's Declared Rare and Priority Flora List; Calocephalus aervoides and Galium migrans, both Priority Three; and Lepidium puberulum, Priority Four.

Ninety-five 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. This weed was recorded on the islands as early as 1970. Efforts to eradicate it began in 1990; Other noxious weeds include Opuntia stricta (prickly pear),

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 and have been identified by BirdLife International as an Important Bird Area (IBA). 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. 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. In addition, they contain important breeding areas for the Pacific reef heron, Pacific gull, bridled tern, white-bellied sea eagle and osprey. although R. fuscipes has not been collected on East Wallabi Island since August 1967, and is probably extinct there. The tammar wallaby was seen on West Wallabi Island by survivors of the Batavia shipwreck, and recorded by Francisco Pelsart in his 1629 Ongeluckige Voyagie. This represents the first recorded sighting of a macropod by Europeans, and probably also the first sighting of an Australian mammal. Tammar wallabies were introduced to North Island from East Wallabi Island by fishermen, probably in the 1950s, but failed to establish themselves. 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. Research into the effectiveness of controlling population levels by the use of implanted contraceptives was begun in 2005, but in July 2007 the research was discontinued and the population culled instead.

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. In 1995 the house mouse was reported as also present on Rat Island for many years before 1987, 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. 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. This relatively low biodiversity is apparently due to the homogeneity of habitat on the islands, which provide few distinct ecological niches. 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. For a full list, see list of algae of the Houtman Abrolhos.

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:

Amphibolis antarctica
Amphibolis griffithii
Halophila decipiens
Halophila ovalis
Posidonia angustifolia
Posidonia australis
Posidonia coriacea
Posidonia sinuosa
Syringodium isoetifolium
Thalassodendron pachyrhizum

Marine fauna

Fish

thumb|The [[moon wrasse, pictured here at the Great Barrier Reef, is one of the most abundant fish species at the Houtman Abrolhos]]

At last count, a total of 389 species of fish have been recorded from the Houtman Abrolhos. 16 species occur in very large numbers; in decreasing order of abundance, these are:

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 semipunctata (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).

Marine mammals

The Houtman Abrolhos maintains a breeding population of Australian sea lions (Neophoca cinerea), probably numbering between 75 and 100. Historical data suggests numbers were previously much higher; 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. 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. 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.

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. 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.

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), followed by southern rights (Eubalaena australis), are common between April and October, when the whales are migrating. Other marine mammals sometimes sighted at the islands include pygmy Bryde's whale (Balaenoptera edeni), orca (Orcinus orca), bottlenose dolphin (Tursiops aduncus), common dolphin (Delphinus delphis),

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. Neither species breeds in the area, as water temperatures are too low. 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.

Crustaceans

thumb|A juvenile [[western rock lobster at the Naturalist Marine Research Centre, Hillarys Boat Harbour, Perth]]

The most notable species of crustacean at the Houtman Abrolhos is the western rock lobster (Panulirus cygnus). 44 species of crab and 9 species of amphipod were recorded there by the Percy Sladen Trust Expedition of 1916.

Molluscs

492 species of marine mollusc have been recorded from the shallow waters of the Houtman Abrolhos. 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). About two-thirds of the species have a tropical distribution, temperate species account for 20%, and the remaining 11% are endemic to Western Australia. For a full list, see List of molluscs of the Houtman Abrolhos.

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.

Echinoderms

Houtman Abrolhos has an extremely high diversity of echinoderms, with 172 species having been recorded there. 63% of these are tropical species, 14% are temperate, and 22% are endemic to Western Australia. None is endemic to the Houtman Abrolhos. Published surveys have not included observations of the crown-of-thorns starfish (Ananthaster planci), but individuals have occasionally been observed there.

The marine worms identified at the Houtman Abrolhos include 22 species of the polychaete family Terebellidae, and 16 species of the family oligochaete family Tubificidae. For a list of species, see list of worms of the Houtman Abrolhos.

A total of 38 hydroid species have been collected at the Houtman Abrolhos. 34 of these are leptothecates, the remainder being anthoathecates. 92% of the species attach to temperate algae, the others to coral rubble. For a list of species, see list of hydroids of the Houtman Abrolhos.

Human uses

Fishing and tourism

Fresh water has always been a significant constraint on any permanent settlement. Aside from the early castaways noted above, the Islands have only had a small seasonal population of fishermen. The present fishermen all have permanent residence elsewhere, mainly in Geraldton, but their island shacks are used as a base during the season. For example, North Island has a seasonal camp for western rock lobster fishers, with individual moorings and simple dwellings. During lobster season, which runs from 15 March to 30 June, the island hosts up to 130 people. The camp is serviced by a carrier boat, the North Islander, which visits the island every three days, bringing supplies and taking out the catch and any domestic waste.

Tourists are not allowed to camp, and the conservation designation of the Island group forbids any real expansion in human occupation.

Western rock lobster

The islands are the centre of the western rock lobster fishery, the largest single-species fishery in Western Australia.

Saucer scallops

After Shark Bay, the Houtman Abrolhos supports Western Australia's second largest saucer scallop fishery. 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.

Scallop fishers mainly operate east of the Houtman Abrolhos and between the island groups, in waters deeper than . 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 (whole weight) respectively. This variability is apparently related to the strength of the Leeuwin Current, as strong current is correlated with low scallop recruitment. By 2000, another license had been issued and four more applications had been received. Six licences had been issued by 2002,

Other shipwrecks, notably Zeewijk (also spelled Zeewyk), have also become the subject of books and other works. Other cultural references to the Houtman Abrolhos are rare. By far the best known book on it 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.

Other books include William Bede Christie's 1909 Christmas on the briny: the innocents abroad, or, a holiday trip to the Abrolhos islands, Deborah Lisson's 1991 The Devil's Own, 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 islands featured in the first episode of Surfing the Menu, an eight-part food and travel series produced for the ABC in 2003, and the following year were featured on Getaway, Australia's longest-running and most popular holiday and travel television programme. 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.

In April 2019 the Houtman Abrolhos became the site of the failure of reportedly one of Australia's biggest drug smuggling operations, worth $73 million.

In 2020 a Western Australian man briefly established the Houtman Abrolhos Micro Nation, based on Uncle Margie Island. The self-declared 'prince' represented himself in the four-day trial in 2023 and relied on a bevy of pseudolegal claims to challenge the Department of Primary Industries & Regional Development (DPIRD).

Notes

References

General references

Markey, K. L., Abdo, D. A., Evans, S. N., Bosserelle, C. (2016). Keeping it Local: Dispersal Limitations of Coral Larvae to the High Latitude Coral Reefs of the Houtman Abrolhos Islands. PLos ONE 11(1).

External links

Abrolhos Islands Information Guide
Fisheries Western Australia – Exploring the Houtman Abrolhos Islands
Long Island Tourism Development, Abrolhos Islands