Reviving Sydney’s seahorse haven: SIMS’ record-breaking release of endangered White’s seahorses (Hippocampus whitei) 

On July 18th, The Sydney Institute of Marine Science (SIMS) set the world record for the number of seahorses released into the ocean when 384 juvenile White’s seahorses were rehomed into Chowder Bay’s recently installed ‘seahorse hotels’. This milestone came after the brood was born from three pregnant males and raised for 6 months in the Ian Potter Research Aquarium at SIMS. 

The White’s seahorse, or Sydney seahorse, is native to Sydney Harbour and is one of two seahorse species to be listed as endangered globally following significant population declines that are primarily due to habitat degradation.  

Image Credit – Tom Burd

Enter The Sydney Seahorse Project, a collaboration between SIMS, The University of Technology Sydney (UTS), and the New South Wales Department of Primary Industries, which aims to conserve the endangered White’s seahorse.  

The brood of seahorses has been deemed “super seahorses” by experts Dr. David Harasti and Professor David Booth who believe this herd to be the most likely to succeed in the wild yet.  

The endurance of the critters can be largely attributed to the work of UTS PhD student and Project Manager, Mitchell Brennan, who raised the adorable ‘fry’ from birth for 6 months, optimising their husbandry and feeding the insatiable creatures three times a day!  

The successful project and unparalleled achievement received media attention worldwide, including coverage by the BBC, USA Today and Reuters to name a few.  

To see one of these super seahorses, just head down the the beautiful Chowder Bay for a SCUBA dive or snorkel. The released juvenile seahorses are identifiable by their visual implant elastomer tag, effectively a fluorescent tattoo, that can be seen in the presence of UV light. Citizen scientists are encouraged to keep an eye out for these baby seahorses and submit photographs to the Sydney Seahorse Project on iNaturalist, aiding in the collection of invaluable information and allowing researchers to monitor the survival, growth and reproductive success of the new locals. 

A bit of a tip for those wanting a closer look, many of them were rehomed along the netting on the southern side of the swimming pool. Mitch has done several recent dives to survey the released seahorses and is seeing about 100 seahorses on average in a 90-minute SCUBA dive. Several of the SIMS team went out snorkelling in the bay in the week of August 1st and were also able to see plenty of seahorses (and a few of their natural predators the cuttlefish).  

The Sydney Seahorse Project, and its collaborators, will continue to take positive action for the conservation of the endangered White’s seahorse, including the continuation of the captive-breeding and conservation stocking program at SIMS’ aquarium, habitat provision through seahorse hotel installation, the restoration and protection of critically important natural habitats, and the on-going development of scientific methods. 

The Sydney Seahorse Project aims to provide the necessary framework for White’s seahorse population recovery and long-term species persistence.