Hammerhead Sharks in Australia: Where to See Them

Spring on the NSW mid-north coast brings a particular kind of anticipation. Divers hang off the pinnacle at [Fish Rock](https://scubadownunder.com/dive-sites/fish-rock-cave) with their eyes on the open water rather than the reef, waiting for a row of odd silhouettes to sharpen at the edge of visibility: wide, flat heads, tall dorsal fins, twenty or thirty sharks moving as one. When it happens, it is one of the great sights in Australian diving.

Hammerhead sharks are instantly recognisable, yet still only partly understood. Australia has four species, two of them listed as threatened in NSW, and the places where divers see them reliably are few, seasonal and at the mercy of water clarity.

## Which hammerheads live in Australian waters?

Fishes of Australia lists four members of the hammerhead family (Sphyrnidae) in Australian waters. Ranges and sizes below come from the FRDC's shark report cards.

- **Scalloped hammerhead** (*Sphyrna lewini*): found in NSW, Queensland, the Northern Territory and Western Australia, with a maximum reported length of about 3.5 m. The front of the head has a central indentation and smaller notches along its edge, giving the "scalloped" look (Florida Museum). - **Great hammerhead** (*Sphyrna mokarran*): from Sydney across the tropics to Mandurah in Western Australia. The largest of the family, reaching 5.5-6.1 m, although about 4 m is more usual for a mature adult. Its head is nearly straight across the front with a shallow central notch, and its first dorsal fin is very tall and sickle-shaped (Florida Museum). - **Smooth hammerhead** (*Sphyrna zygaena*): the species that reaches furthest south, ranging from the Coral Sea through NSW, Victoria, South Australia and Tasmania to Western Australia, and growing to 3.7-4 m. NSW fisheries managers say most hammerheads caught by fishers in NSW are likely to be this species. - **Winghead shark** (*Eusphyra blochii*): a smaller (to 1.86 m) northern species from Gladstone to the Monte Bello Islands that favours river mouths. Its head can be nearly half the length of its body.

The schools divers seek out on the east coast are scalloped hammerheads.

## What the hammer is for

The flattened, widened head is called the cephalofoil, and researchers have tested several ideas about what it does.

**A wider search sweep.** Kajiura and Holland (2002) compared juvenile scalloped hammerheads with sandbar sharks hunting prey-like electric fields. The hammerheads were no more sensitive, but their heads let them sample a much wider strip of seabed and pivot sharply onto a target, which may help them find and catch prey.

**Better depth perception.** McComb, Tricas and Kajiura (2009) measured the overlap between the two eyes' fields of view. Scalloped hammerheads had 34 degrees of overlap in front of the head and winghead sharks 48 degrees, compared with 10-11 degrees in lemon and blacknose sharks. The hammerheads also swung their heads more while swimming, which offsets a blind spot directly in front.

**An efficient sideways cruise.** Payne and colleagues (2016) found tagged great hammerheads spend up to 90% of their time swimming rolled 50-75 degrees onto their side, using the tall dorsal fin to generate lift. That posture cuts drag, and the energy cost of travel, by around 10%.

Adult scalloped hammerheads eat mostly bony fish, with crustaceans and squid or octopus making up most of the rest (NSW Fisheries Scientific Committee). Great hammerheads are known to prefer stingrays and other rays when they can find them (Florida Museum).

## Why scalloped hammerheads school

The NSW Fisheries Scientific Committee notes that scalloped hammerheads sometimes form dense aggregations and large migratory schools. By day, adults gather around seamounts and pups in shallow inshore waters, and these non-feeding daytime groups disperse at night to hunt. Mature females mostly live offshore and move onto the continental shelf to mate and give birth. The FRDC adds that Australia's population is thought to be mostly males and juveniles, with adult females possibly spending more time in Indonesian waters, and that the schooling habit makes the species more vulnerable to fishing.

Why they gather at particular Australian sites is still an open question. The Important Shark and Ray Area (ISRA) assessment for Fish Rock suggests the aggregations may coincide with seasonal upwellings as the East Australian Current strengthens, and divers have reported hammerheads there feeding on yellowtail kingfish, bonito and mackerel tuna.

## Where and when to see hammerheads in Australia

**Fish Rock, South West Rocks, NSW.** Fish Rock's ISRA listing is based partly on its hammerheads. Seasonal aggregations have been recorded since 2005, usually from mid-October to mid-January, with near-daily sightings in season since 2015 and an apparent shift to a September-December season since about 2022. Divers have counted anywhere from 2 to more than 100 sharks depending on water clarity, usually mid-water at the edge of what they can see. The same site is also a resting area for [grey nurse sharks](https://scubadownunder.com/blog/the-grey-nurse-shark-the-gentle-giant-of-australias-reefs), so a good day can deliver both.

**Solitary Islands, off Coffs Harbour, NSW.** The Solitary Islands ISRA records scalloped hammerhead aggregations every spring and summer from 2016 to 2025, peaking in November. Divers typically see 5-30 sharks at a time. These sightings depend on clear water of 20 m or more, because the sharks are usually timid and keep to the edge of visibility.

**[Osprey Reef](https://scubadownunder.com/dive-sites/osprey-reef), Coral Sea.** Parks Australia notes that in the cooler months scalloped hammerheads aggregate off the reef walls at this isolated seamount, which is reached by liveaboard and suited to experienced divers.

More broadly, the NSW Fisheries Scientific Committee records scalloped hammerheads in NSW waters from at least November to June.

## Are hammerhead sharks dangerous?

The record says hammerheads pose a low risk, but not zero. The International Shark Attack File lists 18 confirmed unprovoked bites worldwide attributed to hammerheads, none of them fatal, from records going back to 1580. ISAF also notes that hammerheads are easy to identify, so incidents involving them nearly always name the right species. In Australia, Taronga reports that over 90% of shark bites are attributed to [white sharks](https://scubadownunder.com/blog/great-white-sharks-in-australia), [bull sharks](https://scubadownunder.com/blog/bull-sharks-the-oceans-nomadic-apex-predator), tiger sharks, [wobbegongs](https://scubadownunder.com/blog/wobbegong-the-camouflaged-carpet-shark-of-australia) and other whaler sharks.

Respect still matters. The Florida Museum notes that scalloped hammerheads have occasionally shown threat postures when closely approached by divers, and that the great hammerhead's size alone warrants caution. In practice, the scalloped hammerheads at Australian aggregation sites are usually timid and keep to the edge of visibility (ISRA). Hold your position in the blue, keep your fins still, follow your guide's plan and let the school come past rather than chasing it.

## Conservation: a family in trouble

The **scalloped hammerhead** is listed as Conservation Dependent under the EPBC Act. On 1 February 2018 the federal environment minister added it to the threatened species list in that category, which allows continued commercial harvest in line with EPBC Act requirements. A 2019 review commissioned by conservation groups notes that the Threatened Species Scientific Committee found the species eligible for Endangered listing, but recommended Conservation Dependent based on management commitments from Queensland and the Northern Territory. Globally, the IUCN lists it as Critically Endangered, and an Australian IUCN assessment rates it Endangered. Queensland shark control data showed declines of 67-84% from 1966 to the early 1990s (FRDC).

The **great hammerhead** is Critically Endangered globally and assessed as Endangered in Australia, but it is not listed under the EPBC Act. The **smooth hammerhead** is listed as Vulnerable globally and Near Threatened in Australia; hammerhead catch rates in the NSW shark control program, made up mostly of smooth hammerheads, fell by about 85% between 1973 and 2008.

In NSW, the scalloped hammerhead is listed as Endangered and the great hammerhead as Vulnerable under the Fisheries Management Act 1994. Both are totally protected and cannot be taken by recreational or commercial fishers.

## Sources

- [Fishes of Australia: Hammerhead Sharks, Sphyrnidae](https://fishesofaustralia.net.au/home/family/23) - [FRDC: Scalloped Hammerhead report card (2023)](https://fish.gov.au/docs/SharkReport/2023_FRDC_Sphyrna_lewini_Final.pdf) - [DCCEEW: EPBC Act listed sharks and rays](https://www.dcceew.gov.au/environment/marine/marine-species/sharks-and-rays/epbc-act-listed) - [Federal Register of Legislation: Great Barrier Reef Marine Park Amendment (Hammerhead Shark) Regulations 2018, explanatory statement](https://legislation.gov.au/F2018L00191/asmade/2018-03-05/es/original/pdf) - [NSW DPIRD: Hammerhead Sharks in NSW, Frequently Asked Questions](https://www.dpird.nsw.gov.au/fishing/threatened-species/hammerhead-sharks-faq) - [Parks Australia: Osprey Reef, Coral Sea Marine Park](https://australianmarineparks.gov.au/parks/coral-sea-marine-park/explore-coral-sea-marine-park/osprey-reef/) - [ISRA factsheet: Fish Rock and Green Island](https://sharkrayareas.org/wp-content/uploads/isra-factsheets/8Australia-Southeast-Indian-Ocean/Fish-Rock-and-Green-Island-8Australia-Southeast-Indian-Ocean.pdf) - [ISRA factsheet: Solitary Islands](https://sharkrayareas.org/wp-content/uploads/isra-factsheets/8Australia-Southeast-Indian-Ocean/Solitary-Islands-8Australia-Southeast-Indian-Ocean.pdf) - [Kajiura & Holland (2002): Electroreception in juvenile scalloped hammerhead and sandbar sharks](https://doi.org/10.1242/jeb.205.23.3609) - [Payne et al. (2016): Great hammerhead sharks swim on their side to reduce transport costs](https://doi.org/10.1038/ncomms12289) - [McComb, Tricas & Kajiura (2009): Enhanced visual fields in hammerhead sharks](https://www.fau.edu/science/documents/mtk09.pdf) - [International Shark Attack File: Species implicated in attacks](https://www.floridamuseum.ufl.edu/shark-attacks/factors/species-implicated/)

Header photo: A scalloped hammerhead shark (Sphyrna lewini) in open water off Costa Rica, showing the notched, scalloped front edge of the cephalofoil. by Kris-Mikael Krister, [CC BY 2.0, via Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Scalloped_hammerhead_shark_(Sphyrna_lewini)_Costa_Rica.jpg).