The Houtman Abrolhos Islands are low-lying, barely-there, windswept islands, which are little hidden gems and a bundle of raw nature at its fullest. The islands are of high biodiversity, cultural and historical conservation value and support thriving fishing industries and offer a multifaceted tourism experience. They are isolated and remote. They emerge out of deep, clear offshore waters and are fringed by hazardous coral reefs, which give rise to their name "keep your eyes open."
The Houtman Abrolhos Islands (the Islands) are located between sixty to eighty kilometres west of Geraldton, Western Australia in the Indian Ocean. Over 122 islands and associated coral reefs are located on three shallow platforms -the Southern Group, Easter Group and Wallabi Group, which includes North Island. The three platforms are separated by two 40 m deep channels. The island system stretches over 100 km and is located near the edge of the continental shelf, where the southwards flowing Leeuwin Current flows and eddies.
The islands are seasonally bathed by the tropical, warm Leeuwin Current. Its flow rate is strongest from March to October and varies between years, influencing regional sea surface temperatures, productivity and climate. At the Islands temperate and tropical marine communities meet. The coral reefs are the southernmost in the Indian Ocean, which co-exist with temperate algae systems, seagrass meadows and sponge gardens. It is an underwater wonderland with tropical, temperate and endemic species, including over 389 species of finfish, 492 species of mollusc and 172 species of echinoderms. It an important breeding site for the Baldchin Groper during the summer months, and they cannot be fished from 1 November to 31 January, whilst the West coast demersal finfish closure extends from 15 October to 15 December and includes the islands (and Baldchin Gropers).
Here, endangered Australian Sea lions swim in coral reefs at the northernmost extent of their breeding range. Similarly, the Little Shearwater is also at the northern limit of its breeding range and such species are likely to be impacted by climate change. Some tropical finfish species started to arrive at the islands during the 2011 marine heat wave, when coral bleaching was evident. Some seabirds such as the Sooty Tern and Common Noddy have already undergone a southwards range extension, potentially in response to our changing climate.
It is one of Australia's most important seabird breeding sites, as large number of birds depend on the islands and "nearby" marine systems, some for reproduction, other for over-wintering. Seasonally, eight species of tern, of which one - the Lesser Noddy is endemic, three species of tube-nosed burrow nesting birds and two species of gull breed here. Surface nesting birds often have cryptic nests and eggs susceptible to trampling. In the windy, summer months Pelseart Island alone is used as a breeding site by an estimated 246,000 Sooty Terns, 130,000 Common Noddies, 75,000 Wedge-tailed Shearwaters, 34,870 threatened Lesser Noddies, 1000 Crested Terns and other seabirds, including the threatened Fairy Tern. Some surface nesting terns will shift breeding sites based on an annual resource assessment.
In sandy areas on West Wallabi Island, over a million Wedge-tailed Shearwaters dig burrows to raise their young in summer and autumn and support an unusually high concentration of White-bellied Sea eagles. Whilst in winter and spring Little Shearwaters and White-faced Storm Petrels dig burrows in sandy areas to breed underground. These burrow nesting species are "invisible" during the day (but often noisy at night) and are susceptible to inadvertent trampling and burrow collapse by visitors to sandy central parts of islands. Many seabirds are also disorientated by bright lights -which can be shielded or their use minimised during the breeding season, near flight paths or when fledglings depart (April for Wedge tailed shearwaters). Many islands also support a resident pair of Ospreys, which forage in the shallows, which along with other territorial, residents such as the White bellied Sea eagle and Pacific Gull may be impacted by visitors in their territories.
The central islands are older islands of continental origin and have been separated by rising seawater from the mainland around 10,000 years ago. They are floristically diverse and support isolated continental flora and fauna, including the threatened Tammar Wallaby, Abrolhos Painted Button Quail, Spiny tailed Skink, Abrolhos Island Dwarf bearded Dragon and a diversity of reptiles. Only one Eucalyptus species found at the islands - Eucalyptus oraria growing only on East Wallabi Island. Tidal pools exist on some islands, surrounded by Samphire or saltmarsh a threatened ecological community and occasionally Mangrove systems. Green algae are harvested from these ponds by the threatened Lesser Noddies to build nests in Mangroves on Pelseart, Wooded and Morley Island. Like most seabirds they are seasonally sensitive to visitor disturbance, but if carefully managed at selected visitor managed sites may offer a memorable tourism experience.
The islands are of economic and cultural significance. It is the A-zone of the western rock lobster fishery (or crayfish) Western Australia's largest single-species fishery, and other fisheries include wild caught fin-fish, scallops and aquaculture. Aquaculture is expanding from filter feeding pearls and corals to an emerging caged fin-fish industry in the new Mid West Aquaculture zone (2,200 and 800 ha) between the Southern and Easter Group. Cray fishing families have self-made camps and other infrastructure on approximately 20 islands, usually those with the best boat access and anchorages. These sites are leased, managed by body corporates and are excluded from the Houtman Abrolhos Islands National Park. It was declared on 25 July 2019 and focuses only on islands, or section of islands, above the high tide mark not managed by body corporates. Tourism has always been part of the islands and is growing and changing its emphasis from fishing to a focus on nature-based tourism and maritime history.
The islands have a rich maritime history and diverse economic past. The reefs are dotted with shipwrecks, including the Batavia which grounded on Morning Reef on 4 June1629 and a tragic story unfolded on Batavia's Grave yard or Beacon Island, which can be traced in the Wallabi Group. Whilst the Zeewijk ran aground on Halfmoon Reef in the southern Group and survived on once abundant sea lions. They were followed by sealers and whalers who decimated populations. Numerous Islands have been mined for guano - including Pelseart, Middle, Rat, Pigeon and West Wallabi Island. Some islands recovered, whilst Rat Island remained silent and largely devoid of seabird colonies until the Conservation Council WA Rat Island Recovery Project removed mice. Currently, Tammar Wallabies are being culled on North Islands, where they were introduced by fishing families. They overgrazed the vegetation and potentially led to a local extinction of the endangered Abrolhos Painted Button Quail on North Island.
A major change in user patterns is expected to arise from a shift from hard working (and playing) fishing families to visitors focused on leisure and natured-based experiences, which want to engage with the natural wonders and history. Prior to the introduction of the quota system for the "cray" fishery - the islands were virtually deserted during the windy, summer months when the majority of seabirds breed. Visitor numbers will only increase with promotion of the islands and its maritime history including the Batavia- as an attraction.