Juvenile endangered seahorses have been released again in man-made ‘seahorse hotels’

Juvenile endangered White’s Seahorses (Hippocampus whitei) have been released back into the wild this week at 15 ‘seahorse hotels’ in Botany Bay, Sydney.

This is the third successful release of seahorses bred and raised by experts from SEA LIFE Sydney Aquarium, in a three-year ongoing collaboration to help recover the species’ declining population.

Seahorses are actually poor swimmers and instead wrap their tails around seagrass and corals to stop themselves from being carried away by currents.

But much of their habitat across the Australian east coast was destroyed between 2010 and 2013, so researchers have been helping conserve these seahorses by rehousing them in man-made structures aptly named ‘seahorse hotels.’

“It means the world to the team at SEA LIFE Sydney Aquarium, to lead the charge, collaborating with such highly esteemed experts and to be able to contribute towards the recovery of a species that really needs our help, in our own backyard,” says Daniel Sokolnikoff, Aquarist and Seahorse Expert at SEA LIFE Sydney Aquarium and leading the Sydney Seahorse Breeding Project.

“We have taken some really exciting steps over the last three years and will continue to do so for years to come.”

The collaboration between industry experts includes the Gamay Rangers and the Sydney Institute of Marine Science – with scientists from the University of New South Wales (UNSW), the University of Technology Sydney (UTS) and industry experts from the NSW Department of Primary Industries (DPI) Fisheries and the Gamay Rangers.

This species, which is also known as the ‘Sydney Seahorse,’ has been in dramatic population decline over the past decade and is now Australia’s only threatened seahorse species.

In September 2021, aquarists at SEA LIFE Sydney Aquarium paired up breeding adults for the third time and babies were born and raided from October.

Then, in July 2022 the juveniles were tagged for future monitoring by injecting coloured elastomer fish tags in a unique pattern just under their skin – allowing them to be identified individually.

“Today was another milestone of success in the conservation stocking program,” says Dr David Harasti, Senior Marine Scientist with DPI Fisheries, who has over a decade of experience working with seahorses and will oversee the release and follow-up.

“The conservation actions being implemented in this large collaborative project, such as the restocking and the deployment of artificial seahorse hotels, are helping ensure this endangered seahorse is given every chance to recover.”

The artificial seahorse hotels are made of net and steel which algae, sponges, and corals can grow on over time to create a home for the endangered seahorses. Then the metal frame will eventually erode, leaving behind the natural habitat that grew around it.

A simple box design has been used for the past two years, but this year two new designs are being trialed to see whether different structures and materials are preferred. This includes a fun design that resembles a house (fitting for a seahorse hotel), and a “Nautilus shell” design with curves meant to mimic nature – developed by Dr Kate Dunn and her team of researchers from UNSW’s Built Environment Design Futures Lab.

Because the seahorses are individually tagged, diving surveys will determine whether there has been migration from one hotel design to another.

But the seahorse hotels are also getting a bit of landscaping… or should we say sea-scaping?

Professor Adriana Vergés and her team of researchers at UNSW and the Sydney Institute of Marine Science have also been planting Posidonia seagrass with the hotels.

Posidonia is the seahorses’ preferred natural habitat and also an endangered species, so these efforts are helping to conserve more than just one species.

“We are hoping that by combining the use of seahorse hotels with the restoration of Posidonia we are giving seahorses the best chance of recovery, while we also work on the recovery of their natural habitats,” says Professor Vergés.