The Abrolhos is home to a diverse and unique range of temperate and tropical marine and terrestrial species, due to its southern geographical location (28 to 29° S) and the influence of the warm-flowing Leeuwin Current.
The islands support a number of conservation-significant species, including several seabird and migratory shorebird species and the Australian sea lion. The FHPA supports the southernmost coral reef system in the Indian Ocean and one of the highest latitude coral reef systems in the world.
To help protect the natural values of the Abrolhos, please view the Houtman Abrolhos Islands protection video and the island protection brochure.
Aquatic organisms
More than 380 species of finfish have been reported in the Abrolhos FHPA, and include demersal (bottom dwelling) species, pelagic (water column) species and nearshore species. Some of the common types of finfish include gropers, dhufish, snappers, emperors, coral trout, samson fish, mackerel, tuna, sharks and rays. Nearshore finfish species include buff bream, herring, trevallies, garfish, longtom and barracuda. Smaller colourful reef fish add to the beauty of the coral reefs such as damselfish, butterflyfish, cardinalfish, wrasse, porcupine fish and parrotfish. Seahorses and pipefish can be seen residing in seagrass and macroalgae habitats.
The Abrolhos FHPA plays a vital role as a major habitat for the spawning stock of western rock lobster. Eggs and larvae from the Abrolhos FHPA and the deep-water refuges further north along Big Bank are thought to be distributed by ocean currents along the west coast. Other crustaceans found in sand habitat include western king and coral prawns and crabs.
Over 490 mollusc species have been recorded in the Abrolhos FHPA. Molluscs include octopus, cuttlefish and squid, saucer scallops, oysters and clams, and gastropods.
More than 170 echinoderm species have been identified in the Abrolhos FHPA, including sea cucumbers, featherstars, sea stars, brittlestars and sea urchins.
Aquatic habitats
The coral fauna of the Abrolhos FHPA is diverse for a high-latitude reef system, with over 180 species discovered so far. The FHPA is home to the Octocorals, including fleshy soft corals - gorgonian (sea whip) corals, organ pipe corals, sea fans and sea pens. The hard (Scleractinids) corals are reef builders and include branching, encrusting, plate corals and brain corals, with the Abrolhos FHPA recognised for its high percentage of branching Acropora species.
Sea anemone (Actinarid) communities are common including the bubble tip anemone which is home to the Clark’s anemone fish. Sea sponges can also be found attached to rocky substrate, either by a holdfast or an encrusting mass. Tunicates (ascidians) known as sea squirts can also be found attached to rocky substrate.
Around 295 species of marine plants have been recorded in the Abrolhos FHPA including a mixture of species from both tropical and temperate origins. Brown, red and green macroalgae species mix with tropical coral communities in a unique display of marine biodiversity.
Seagrasses are flowering plants and are generally located in protected, shallow sand and silt habitats up to 15 m in depth. The predominant species of seagrasses occurring in the Abrolhos FHPA include Posidonia australis, Amphibolis sp. and Halophila sp.
Mangroves are coastal plants which live in the upper intertidal zone. A single mangrove species, the grey mangrove (Avicennia marina), occurs at the Abrolhos. The grey mangrove provides an important source of nutrients for marine food chains, in addition to habitat for terrestrial and marine animals, including the Australian sea lion and the lesser noddy at the Abrolhos. Mangroves also protect the Abrolhos shoreline from storm damage and erosion. Extensive stretches of mangroves can be seen on Pelsaert Island, Wooded Island and Morley Island.
A number of Reef Observation Areas have been created in the FHPA to conserve and protect fish, fish breeding areas, and aquatic habitats and ecosystems.
Mammals
The Abrolhos Islands mark the northern-most habitat and breeding location of the Australian sea lion. Australian sea lions feed on fish, lobster, octopus and occasionally sea birds. They can dive to depths of up to 150 m in search of their prey. Often, they can be seen resting on sandy beaches throughout the islands.
The main whale species that pass through the Abrolhos are humpback and southern right whales. Sightings of humpback whales are between April and October each year, during their annual northward breeding migration and return journey to Antarctica.
Dolphins are present at the Abrolhos all year round. The most common species is the bottlenose dolphin, but other species include striped and common dolphins.
The main land mammal living on the islands is the tammar wallaby. The population on West Wallabi Island is of particular biodiversity importance.
Seabirds and shorebirds
The Abrolhos is one of the most significant seabird nesting areas in the eastern Indian Ocean. A total of 95 bird species have been recorded as residents or visitors to the islands and more than two million birds breed on the islands and small rocky atolls. Schools of pelagic baitfish in the waters of the Abrolhos FHPA provide an important food source. The mixture of species is unique, as subtropical and tropical species, and littoral and oceanic foragers, share the breeding islands.
Conservation significant birds include the Abrolhos painted buttonquail, the Australian lesser noddy, the common noddy, wedge-tailed shearwater, little shearwater, roseate tern, fairy tern, and sooty tern.
Reptiles
Turtles are regularly observed in the Abrolhos FHPA. Resident green turtles forage in and around the reefs. Sea snakes are not residents in the Abrolhos FHPA, but during strong winter storms they may be transported south from Shark Bay and other northern areas.
There are 26 terrestrial reptile species living on the islands. The Houtman Abrolhos spiny-tailed skink and the Abrolhos dwarf bearded dragon are both endemic to the Abrolhos and of conservation significance. There is also a large population of carpet pythons on West Wallabi Island.
Native flora
The islands support a variety of plant species and communities, which are utilised by a diverse range of fauna. All native terrestrial flora at the Abrolhos is protected under the Biodiversity Conservation Act. A number of vegetation communities at the Abrolhos are also recognised as being of conservation significance including mangrove communities, shrubland, coastal saltmarsh, salt lake and saltbush flats.