A Cruise through the Reefs and Islands of the Kimberley Coast

Northern Suburbs Branch, 20 March 2024

NSB member Don Poynton stepped in as our guest speaker in March when the scheduled speaker was unavailable. Don’s presentation was based on a cruise he had undertaken to some of the reefs and islands of the Kimberley coast in 2023.

He introduced each area by briefly mentioning the maritime history and origin of the name of each reef or island.

Ashmore Reef covers an area of almost 600 sq km and includes three low-lying tropical islands. Although lying closer to Indonesia than Australia, it is reputed to be the best-studied of the Kimberley cays with around 255 coral species, over 700 fish species and at least 15 species of birds breeding on the islands, including tropic birds, boobies, terns, and frigatebirds. Club founder Dom Serventy visited one of the islands in 1949 and photographed young Lesser Frigatebirds on their nests.

Scott Reef has been the site of trepang fishing by Indonesian fishermen for at least a couple of centuries. Captain Peter Heywood of HMS Vulcan was the first European to report the reef in 1801. Heywood was one of the mutineers on the Bounty who survived the wreck of the Pandora on the Great Barrier Reef and later, due to family connections, escaped severe punishment and rejoined the Navy.

Scott Reef Image by Don Poynton

Scott Reef was extensively affected by coral bleaching in 1998 and 2016. The warm water killed approximately 80% of corals in 1998, but the reef recovered in the subsequent decades. Don was particularly intrigued by the Christmas Tree Worms.

Adele Island is a sandy island covered in a grassland of Saltwater Couch (Sporobolus virginicus) and Long-leafed Spinifex (Spinifex longifolius), two species also found on our metropolitan beaches. The island has the largest population of seabirds of all the Kimberley islands; up to 8500 breeding pairs of Brown Boobies, 5700 breeding pairs of Lesser Frigatebirds, 5500 individual Grey-tailed Tattlers and 4100 Red-necked Stints have been recorded. It is the only island where Red-footed Boobies and Great Frigatebirds breed.

Koolan Island was an unexpected stop due to a medi-vac. The island is one of about 800 islands in the Buccaneer Archipelago. These islands and the adjacent mainland consist predominantly of Precambrian sandstone over 1.8 billion years old. The islands were formed much more recently by rising sea levels that drowned the coastline. Koolan Island and the nearby Cockatoo Island have been mined for their iron-rich hematite ore.

Montgomery Reef is the world’s largest inshore reef, covering approximately 400 sq. km. Red crustose coralline algae in the form of Rhodoliths are the predominant reef-building organisms.

In 1986, rats were eradicated from the A-class Lacepede Islands Nature Reserve, 30km offshore from the Dampier Peninsula, allowing the recolonization of the islands by nesting seabirds, including up to 18,000 breeding pairs of Brown Boobies, possibly the largest colony in the world. 30,000 Roseate Terns were recorded on West Island in 2010. The beaches are Western Australia’s most important breeding habitat for Green Turtles.

Rowley Shoals Marine Park includes Clerke Reef, Bedwell Island, and Imperieuse Reef. Due to its clear water and marine biodiversity, it is considered a premium dive location in Western Australia.

Don Poynton