Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: How many species live in The Houtman Abrolhos reef?
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,[60] 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.[60] For a full list, see list of corals of the Houtman Abrolhos.
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. Nominally located at ,[2] it lies about eighty kilometres (50mi) west of Geraldton, Western Australia.[3] 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. 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 conservation habitat. It is 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.
This list of molluscs of the Houtman Abrolhos includes 492 species of marine molluscs which have been recorded from the waters of the Houtman Abrolhos, an island group in the Indian Ocean off the coast of Western Australia.
23 terrestrial reptile species are known to occur on the islands of the Houtman Abrolhos.[50] This relatively low biodiversity is apparently due to the homogeneity of habitat on the islands, which provide few distinct ecological niches.[51] 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.[42] For a full list of species, see list of reptiles of the Houtman Abrolhos.
184 species in 42 genera of hermatypic corals have been recorded from the Houtman Abrolhos:
In addition to the hermatypic corals, the Houtman Abrolhos contains ten species in eight genera of ahermatypic coral.
North Island is the northernmost island in the Houtman Abrolhos, a coral reef archipelago in the Indian Ocean off the coast of Mid West Western Australia. Located about 14 km (9 mi) from the nearest island group, it is one of the largest islands in the Houtman Abrolhos, and one of the few to support dune systems. It has relatively diverse flora dominated by chenopod shrubs and fauna that includes the introduced tammar wallaby, around seven species of reptile, and about 15 resident bird species.
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:[53]
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.[55]
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. This extremely high diversity has been attributed to a combination of factors, namely: the position of the Houtman Abrolhos within a biotone between temperate and tropical waters; the wide variety of habitats; and the Leeuwin Current, which both transports tropical species southwards, and keeps the reef warm enough for them to survive. This is a list of echinoderms of the Houtman Abrolhos:
Published surveys have not included observations of the crown-of-thorns starfish ("Ananthaster planci"), and this species is therefore not listed above. However, individuals have occasionally been observed at 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.[31]
A area of reef immediately south of North Island is designated a Reef Observation Area (ROA). Fishing is prohibited in this area, except for the use of lobster pots. One of four ROAs in the Houtman Abrolhos, these protected areas are intended to help conserve species of territorial fish that are fished elsewhere, and to provide divers with the opportunity to observe large populations that are not frightened by their approach.
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.[64] Published surveys have not included observations of the crown-of-thorns starfish (Ananthaster planci), but individuals have occasionally been observed there.[55] 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, are unusual in containing a mix of tropical, subtropical and warm-temperate fish species. This mix is largely due to the Leeuwin Current, which brings warm tropical water to the Houtman Abrolhos, especially in winter. Tropical species are the most abundant, eleven of the sixteen most abundant species being tropical fishes. However, there are also a large number of tropical species with populations so small that they are thought not to maintain populations be breeding at the Houtman Abrolhos.
The coral reef community at the Houtman Abrolhos is unusual in having tropical coral growing alongside and in direct competition with, temperate seaweed. 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.[61]
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).
Commercially important species include Pagrus auratus (pink snapper), Choerodon rubescens (baldchin groper), Glaucosoma hebraicum (westralian dhufish) and Plectropomus leopardus (coral trout).[55] For a complete list of fish species recorded at the Houtman Abrolhos, see List of fishes 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 ("Chelonia mydas") which is often observed in large numbers near shore. This is a list of reptiles of the Houtman Abrolhos:
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.[62] For a full list, see List of molluscs 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. 35 of them (92%) attach to temperate algae; the remaining, the others to coral rock. This is a list of hydroids 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. This figure comprises 178 species of red algae (Rhodophyta), 50 species of brown algae (Phaeophyta) and 32 species of green algae (Chlorophyta). Both temperate and tropical species occur there. 
This is a list of algae of the Houtman Abrolhos:
The range of the species is along the coast of Western Australia, from Hamelin Bay to the North West Cape, and at islands such as the Houtman Abrolhos. The larvae of the species develop in the meadows of seagrasses of Western Australia, migrating out from these toward the deeper ocean and coral reefs such as the Abrolhos Islands.
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.
The Houtman Abrolhos is home to around 100 species of bird; for a complete list, see list of birds of the Houtman Abrolhos. Six species are land birds, and three are shore birds. The remainder, the vast majority, are seabirds. 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.[39]
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. This is a surprisingly high coral diversity, considering the high latitude of the reef, and the relatively low diversity of other biota. This is a list of corals of the Houtman Abrolhos:
260 species of benthic algae have been recorded at the Houtman Abrolhos. This figure comprises 178 species of red algae (Rhodophyta), 50 species of brown algae (Phaeophyta) and 32 species of green algae (Chlorophyta). Both temperate and tropical species are present, in many cases near the northern or southern extent of their range.[52] For a full list, see list of algae of the Houtman Abrolhos.