Spencer Gulf
The Spencer Gulf is the westernmost and larger of two large inlets on the southern coast of Australia, in the state of South Australia, facing the Great Australian Bight. It spans from the Cape Catastrophe and Eyre Peninsula in the west to Cape Spencer and Yorke Peninsula in the east.
The largest towns on the gulf are Port Lincoln, Whyalla, Port Pirie, and Port Augusta. Smaller towns on the gulf include Tumby Bay, Port Neill, Arno Bay, Cowell, Port Germein, Port Broughton, Wallaroo, Port Hughes, Port Victoria, Port Rickaby, Point Turton, and Corny Point.
History
The first recorded exploration of the gulf was that of Matthew Flinders in February 1802. Flinders navigated inland from the present location of Port Augusta to within of the termination of the water body.The gulf was named Spencer's Gulph by Flinders on 20 March 1802, after George John Spencer, the 2nd Earl Spencer. The Baudin expedition visited the gulf after Flinders with Nicholas Baudin giving it the name Golfe Bonaparte and Louis de Freycinet using the name Golfe de la Melomanie on the expedition's published charts.
By the 1830s, the natural harbour of Port Lincoln had become the site of an unofficial settlement, due in part to its convenience as a base for whaling vessels – which had long operated in the Great Australian Bight. Prior to the selection of Adelaide, some consideration was given to Port Lincoln as the potential site of a capital city.
Geography and topography
The Gulf is wide at its mouth and long. The western shore of the gulf is the Eyre Peninsula, while the eastern side is the Yorke Peninsula, which separates it from the smaller Gulf St Vincent. Its entrance was defined by Matthew Flinders in 1802 as a line from Cape Catastrophe on Eyre Peninsula to Cape Spencer on Yorke Peninsula. At the time of Flinders' exploration the gulf was noted to extend inland from a point near the Port Augusta crossing. This so-called extension of the gulf consists of a land depression and occasional watercourse known as the Pirie–Torrens corridor, and the inland waterbody Lake Torrens.The northern end of the gulf is spanned by the Joy Baluch AM Bridge between Port Augusta and Port Augusta West and further north by Yorkey Crossing.
Informal names for subdivisions of the gulf waters are sometimes used. "Northern Spencer Gulf" refers to waters north of Wallaroo and Arno Bay, while "Southern Spencer Gulf" refers to waters south of that line, extending to the mouth of the gulf. "Upper Spencer Gulf" includes the waters north of Port Pirie, and includes the three towns sometimes referred to as the Iron Triangle: Whyalla, Port Augusta and Port Pirie. Its boundary lacks precise definition.
Wildlife
The land surrounding the gulf, consisting of the Eyre and Yorke Peninsulas, is the Eyre Yorke Block bioregion. This was originally wooded shrubland but has now mainly been cleared for agriculture. The arid Gawler bioregion extends to the Spencer Gulf on the north-west. Many of South Australia's iconic marine species can be found on the shores and in the waters of Spencer Gulf.Marine species
The rocky inshore reef along the coast near Port Bonython and Point Lowly is a breeding ground for the Northern Spencer Gulf population of Australian giant cuttlefish. They are a favorite food of local bottlenose dolphins, who have developed sophisticated techniques for safely eating these creatures. The Upper Spencer Gulf is also known for its snapper and Yellowtail kingfish fishing. Great white sharks are sometimes seen in Spencer Gulf by fishermen, and shark cage diving and surface tours operate out of Port Lincoln.A relic population of tiger pipefish, a subtropical species is range limited to Northern Spencer Gulf.
Marine mammals
Visiting southern right whales and humpback whales enter Spencer Gulf from June through to October, and can be seen as far north as Point Lowly and Port Augusta. New Zealand fur seals and Australian sea lions can be found in southern Spencer Gulf, with significant breeding colonies located at Dangerous Reef and in the Sir Joseph Banks Group. Occasional sightings occurring in Northern Spencer Gulf. Bottlenose dolphins can be seen in the gulf's waters year-round.Seabirds
Breeding colonies of little penguins exist on islands in Spencer Gulf. The northernmost colonies are located at Lipson Island and Wardang Island. In 2004, the Wardang Island colony's population was approximately 8,000 penguins. Cape Barren geese and several species of cormorants also breed on islands in Spencer Gulf.Islands
Spencer Gulf contains a number of inshore and offshore islands. These include :- Curlew Island
- Weeroona Island
- Shag Island
- Entrance Island
- Bird Islands
- Lipson Island
- Tumby Island
- Wardang Island & the Goose Island group
- The Sir Joseph Banks Group
- Louth Island & Rabbit Island
- Boston Island
- Grantham Island and Bicker Isles
- Donington Island, Carcase Rock, Owen Island, Taylor Island, Grindal Island, Little Island, Lewis Island, Smith Island, Hopkins Island and Thistle Island.
- Middle Island, South Island and Royston Island
- Gambier Islands including Wedge Island
Port development proposals
Due to its proximity to many identified mineral deposits in South Australia's Far North, Eyre Peninsula and Braemar regions, there are multiple new port and harbour developments proposed for the region.These include new or expanded facilities at :
- Port Bonython - Port Bonython Bulk Commodities Export Facility - Spencer Gulf Port Link
- Port Playford - Iron ore transshipment port proposed to be constructed on the site of the former Playford A Power Station, south of Port Augusta
- Whyalla - Inner harbour expansion - Arrium
- Port Pirie - Possible expansion for trans-shipment of iron ore from the Braemar region
- Lucky Bay - Lucky Bay Common User Export Facility - SeaSA
- Myponie Point - Possible port location for Braemar region mineral exports
- Cape Hardy - Iron Road Limited
- Lipson Cove - Port Spencer - Centrex Metals The port could be completed in 2023.
Seawater desalination plants
In 2022, the government of South Australia announced the Northern Water Supply Project, which as of 2023, is considering a business case for establishing a large seawater desalination plant in the upper Spencer Gulf. If constructed, water will be supplied for use to the Olympic Dam and Carapateena copper mines in the state's far north. It is also intended to supply water for a prospective hydrogen export industry. An environmental impact statement for the project is anticipated mid-2024., one reverse osmosis and one thermal seawater desalination plant draw water from Spencer Gulf. Several others are planned. All currently or will produce water primarily or exclusively for industrial use. They are:
| Location | Company | Production capacity | Purpose | Status |
| Whyalla | Arrium | 1.6 | Whyalla Steelworks industrial supply | Commissioned 2011, operating |
| Port Augusta | Sundrop Farms | 3 | Growing vegetables | Operational in October 2016 |
| Point Lowly | BHP | 100 | Olympic Dam mine mineral processing | Approved 2011, not constructed |
| Upper Spencer Gulf | SA Water | 94.9 | Olympic Dam mine, Carapateena mine, hydrogen production | Northern Water Supply Project business case under development in 2023 |
| Lipson Cove | Centrex Metals | 5-20 | For iron ore slurry pipeline | Proposed 2013, not constructed |
| Myponie Point | Braemar Alliance | 20-50 | For iron ore slurry pipeline | Concept stage |
Spencer Gulf in film & video
The Spencer Gulf region, its wildlife and its development are the subjects of a documentary film in production entitled Cuttlefish Country.Protected areas
Reserves declared by the South Australian government
Aquatic Reserves
Spencer Gulf contains four aquatic reserves.Blanche Harbour-Douglas Bank Aquatic Reserve which is located in west side of Spencer
Gulf, north of Whyalla, was declared in 1980 'for fisheries management, protection of its mangrove-seagrass communities and associated fish nursery areas.'
Goose Island Aquatic Reserve which is located at Goose Island on the east side of Spencer Gulf near Port Victoria was d eclared in 1971 to provide 'a conservation area where teaching institutions may conduct classes and scientific research on marine biology and ecology and to protect the habitat of the seal colony situated on White Rocks.'
Whyalla - Cowleds Landing Aquatic Reserve which is located on the west side of Spencer Gulf, just south of Whyalla, was declared in 1980 to 'protect the mangrove-seagrass communities and associated fish nursery areas.'
Yatala Harbour Upper Spencer Gulf Aquatic Reserve which is located in Yatala Harbour on the east side of Spencer Gulf, north of Port Pirie, was declared in 1980 for 'the protection of its mangrove-seagrass communities and associated fish nursery areas.'
Marine Parks
Spencer Gulf contains five marine parks, each with its own outer boundary and internal zoning. Fishing is prohibited with Sanctuary Zones, and detailed maps and GPS coordinates for the parks are available from the Government of South Australia's Department of Environment, Water & Natural Resources.The marine parks within Spencer Gulf are :
- Upper Spencer Gulf Marine Park
- Franklin Harbor Marine Park
- Eastern Spencer Gulf Marine Park
- Sir Joseph Banks Group Marine Park
- Southern Spencer Gulf Marine Park
Cuttlefish Coast Sanctuary Zone
Within the sanctuary, the largest and densest breeding aggregation of cuttlefish in the world occurs annually from May to August, with intense competition between male cuttlefish leading to complex behaviours and spectacular massed displays of colour and shapeshifting. The cuttlefish in this area face several threats, including vulnerability to the impact of commercial fishing. These risks are being managed by the South Australian Government through protection in a marine protection area and fishing bans. Other possible risks are pollution from industrial sites or plastic pollution being washed in on the tide.
In August 2025, the state and federal governments provided funding of almost $700,000 to install a bubble curtain to protect the giant cuttlefish in the Upper Spencer Gulf during their breeding season from the harmful algal bloom that began on the Fleurieu Peninsula in March, and had not yet dissipated. The curtain would protect approximately 50,000 to 80,000 eggs and hatchlings. However, the bloom had not reached the Upper Spencer Gulf by October 2025.