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Underwater Mosman

Marine Species

Sydney has better marine life than any other city on the planet, and Mosman is home of the Striped Anglerfish, one of Sydney’s greatest secrets.

Mosman is in an area referred to as the ‘gold zone’ for marine creatures, with more weird and wonderful animals here than anywhere else in Sydney.

Check out the new interactive site Underwater Mosman and explore the unique marine environment of Mosman via fisheye cam!

Our Marine Species

marine moray marine nudibranch marine seahorse

Left to right: Seive-patterned Moray (Gymnothorax cribroris), Nudibranch (Glossodoris atromarginata), White’s Seahorse (Hippocampus whitei). Photographed in Mosman by Iain Gray.

Mosman’s coastal and marine environment is home to numerous species, including various sea birds, sea grasses, rays, octopus, sea horses and several species of fish.


Seagrass beds grow in Harbour waters near Mosman providing habitat for a variety of marine life. Seagrass meadows also trap and stabilise sediments, helping to improve water clarity.

Seagrasses can be destroyed by stormwater run-off carrying excess nutrients and sediments as well as by anchor chains, boat propellers, discarded fishing lines, construction of jetties and seawalls, dredging and land reclamation. Such pressures have contributed to a decline in seagrass populations near urban areas.

Sea grass beds are important habitats protected by legislation so if boating be especially careful to avoid damaging them when anchoring.

White's Seahorse (Hippocampus whitei) photographed in Mosman by Iain Gray.
White's Seahorse (Hippocampus whitei) photographed in Mosman by Iain Gray.


Waters surrounding Mosman are home to over 500 tiny seahorses from two species, White’s Seahorse (Hippocampus whitei) and Big Belly Seahorse (Hippocampus abdominalis).

Big Belly Seahorse is also found in New Zealand, while White’s seahorse is endemic to (only found in) Australia.

The seahorses grow to around 18-20cm long and live amongst seagrass and algae beds. They are almost invisible in the small clumps of marine vegetation as they are very well camouflaged in murky shades of mottled yellow, orange, brown, grey and black.

Fortunately they are protected under NSW legislation. It is illegal to harm or move seahorses in NSW, and many are under close surveillance. Scientists and SCUBA divers are monitoring the numbers of seahorses at Mosman and at Manly.

Find out more at the Australian Museum Fish Site – White's Seahorse and Big Belly Seahorse .

Marine Mammals

Photo by Trish Franklin © The Oceania Project /
Photo by Trish Franklin © The Oceania Project /

Australian waters contain over 45 different species of whales, porpoises and dolphins. Australia boasts 10 large whales, 20 smaller whales, 14 dolphins and 1 porpoise.

‘Cetacean’ is the scientific name (of the Order Cetacea) that describes whales, dolphins and porpoises.

Whales have been seen near Mosman during their migratory season, a delight for whale watchers.

Regulations apply to whale watching.

Vessels must be at least 100m away from a whale or 50m away from a dolphin and when calves are present, vessels must remain at least 300m from a whale or 150m from a dolphin.

Swimmers must be at least 30m from a whale. Information about whale watching and regulations for giving whales space can be found at Wild About Whales .

Any marine mammal incidents and/or sightings should be reported to ORRCA . Contact the hotline 24 hours 7 days a week on 9415 3333.

Gamarada: Mosman’s Whale
Mosman’s adopted Humpback Whale. Photo by Trish Franklin.
The humpback whale mother adopted by Mosman. Photo by Trish Franklin © The Oceania Project /

Mosman Council has adopted a mother humpback whale in support of the Humpback Whale Migration Icon Project.

Mosman’s whale has been named ‘Gamarada’ by Mosman Reconciliation.

Gamarada (pronounced Gamada) comes from the Sydney Aboriginal language and means friend.

Our whale friend Gamarada and her calves are at risk from numerous threats.

Whales and Threats to Whales

Five whale species, the humpback, blue, fin, sei and southern right, have been listed as threatened species by the Australian Government. Recovery Plans have been created for these species. The Recovery Plan outlines the threats to the species and actions required to halt the decease in the number of the species.

Threats to whales include marine pollution such as plastic bags, fishing nets and line and cigarette butts. Whales, as well as seals, turtles and sea birds can mistake plastic waste for food or become entangled in it causing pain and death. In every square mile of ocean it is estimated that there are over 46,000 pieces of plastic. Litter is washed into the sea from waterways or blown from the land, so it is important to dispose of rubbish appropriately so that it does not end up in the ocean killing marine life.

Fishing nets can become lost at sea, floating through the oceans for years continually trapping and killing marine animals such as dolphins and dugongs. These nets are often referred to as ghost nets. Meanwhile overfishing and illegal fishing depletes the ocean of fish stocks in the food webs of marine ecosystems.

Whaling is of particular concern to many due to the inhumane practices that inflict cruelty upon whales and the fact that whaling is unnecessarily threatening whale populations. Australia stoppped whaling in 1979 and has since sought a permanent ban on commercial and ‘scientific’ whaling. As whales are migratory species, their protection requires international cooperation. The Australia Government aims to achieve whale conservation through the International Whaling Commission (IWC). Click here for a fact sheet on the IWC. For more information go to the Australian Government Department of the Environment .

What You Can Do
Learn more and keep up to date with these whale websites!


SharkSmart offers advice on how to reduce the risk of shark attack and aims to inform the public about sharks, their habitat and nature.

Sharks are a natural part of healthy oceanic and estuarine environments. When people enter open water, they are entering the shark’s domain. A better awareness and understanding of sharks and their behaviour can help those who wish to enjoy the world class waterways of New South Wales.

Sydney Harbour Ecology

Biscuit Sea Star (Tosia australis) photographed in Mosman by Iain Gray.
Biscuit Sea Star (Tosia australis) photographed in Mosman by Iain Gray.

Australia’s Marine Ecology

Australia’s stunning coastlines are the envy of the world with over 3 million international visitors a year.

Australian waters contain:

  • 43 different species of whales, porpoises and dolphins
  • Over 4 000 fish species – 20% of all species recorded worldwide
  • Giant kelp forests up to 30 metres high!
  • 80 to 90% of our marine species are not found anywhere else in the world!

Biological material from the ocean is used for numerous benefits, including pharmaceuticals. In addition to marine biotechnology, other marine based industries may also develop further such as alternative energy sources.

What about other coastal and marine issues?