While Sydney was under COVID-19 lockdown, a group of aquarium-bred White’s seahorses was released into Sydney’s harbor.

While Sydney was under COVID-19 lockdown, a group of aquarium-bred White’s seahorses, also known as Sydney seahorses, was released into Sydney Harbor as part of a conservation project. Monitoring the ongoing program is master’s research student Brooke ‘Bee’ Kyle. We spoke with Bee about the Sydney seahorse program and her lifelong love of seahorses.

Q: What sparked your interest in seahorses?

I started my degree in Bay of Plenty, New Zealand where we have Hippocampus abdominalis, one of the largest species of seahorse in the world. After that project I fell in love with seahorses; they are the most incredible sea creatures, with such character and personality. I then moved on to work at SEA LIFE Kelly Tarlton’s Aquarium in Auckland while researching the Hippocampus kuda, a tropical yellow seahorse. I loved working with them.

Q: When did you first get involved in this breeding program?

Seahorse expert Amanda Vincent, who runs an organization called Project Seahorse, put me in touch with my now supervisor, David Harasti. I moved over from New Zealand just before the end of the breeding program, got to tag the juveniles alongside my supervisor and was part of the release of the juvenile White’s seahorse into the wild. I am now monitoring them and collecting data on how they are doing in the wild.

Q: What are the key factors to the success of this project?

There are a few key factors to this project being a success: their survival and growth rates, brood pairings, and reproduction. I am hoping to see a survival rate greater than 20 percent. Another aspect is reproduction — if there’s a low survival rate but they are breeding and giving birth to live young that would be a huge success, as it is adding to the wild population. Another thing I’m hoping for is to see our aquarium-raised juveniles pair up with wild seahorses. To see aquarium-raised juveniles able to integrate into the wild population would be a huge success.

Q: What do we know about populations in Sydney historically? When did the decline become significant?

“White’s seahorse (Hippocampus whitei) is one of four species that occupy New South Wales’ waters. They are endemic to the east coast of Australia, occurring commonly in Sydney Harbor, which gives them their other common name — the Sydney seahorse. The species is fairly common around Sydney and well known to the local dive community, although it has now been classified as endangered due to recent decline.

The exact size of the seahorse population here is unknown historically, but we do know that populations have declined in in Port Stephens and Port Jackson in the last decade. The main reason their population has declined is the loss of habitat across their limited range in eastern Australia. They occur within coastal estuaries, areas often damaged by development and pollution.

In Port Stephens, an area well-known for Hippocampus whitei sightings, over 90 percent of the soft coral and sponge habitats have been lost. Coastal estuaries are subject to man-made degradation, such as the installation of wharfs, moorings, anchors and pollution, as well as things like habitat coverage from sand movement.

Something that I find so beautiful and interesting about this particular species is that the White’s seahorse is monogamous, pairing for life. Each seahorse couple will find each other every breeding season and remain a couple unless one of them dies. They’ve been shown to even stick by one another even if the other is sick or injured.

The Sydney seahorse collaboration

The White’s Seahorses recovery project is led by SEA LIFE Sydney Aquarium in collaboration with the NSW Department of Primary Industries (DPI) Fisheries and the University of Technology Sydney (UTS).

The project aims to breed, raise and release the White’s seahorses, and monitor their success in helping reverse the decline of this endangered species, with four key stages of this project now complete:

  1. Collect

Planning for this project started in August 2019 and kicked off in October 2019. The SEA LIFE Sydney Aquarium team, assisted by experts from DPI Fisheries and UTS, collected breeding pairs from Sydney Harbor, including some pregnant males.

  1. Breed

The seahorses were placed in a custom-built seahorse breeding facility at the Aquarium, and dozens of White’s seahorses were successfully bred on site and on display to visitors.

  1. Prepare hotels

In March 2020, nine seahorse hotels were placed underwater in Clifton Gardens, Mosman in preparation to become homes for the juvenile seahorses being raised at the aquarium.

  1. Tag and release

The final stage involved the juveniles being carefully tagged for future monitoring before release into their seahorse hotels in Clifton Gardens. The seahorses were injected just under their skin with a colored elastomer fish tag in a unique pattern, allowing researchers to identify individuals.

Seahorse hotels

Before the White’s seahorses were released, artificial habitat was created for them in Chowder Bay. Inspired by crab traps, seahorse hotels were trialed in Port Stephens in 2018 and 2019 and were found to be very successful in attracting seahorses, which led to mating and breeding.

The seahorse hotels start as artificial habitats that grow into natural habitats once they are placed in the marine environment. Over time, encrusting corals, sponges, and algae colonize these structures, providing protection from predators and a steady supply of food. The ‘hotels’ are completely biodegradable, so the artificial structures will slowly collapse over time under the weight of the marine growth, leaving a new natural habitat behind.

SEA LIFE Trust’s ‘Ocean Youth’ helped with the seahorse hotel construction, along with Seadragon Diving Co. and Sydney-based Indigenous Sea Rangers with support from DPI’s Marine Estate Management Strategy (MEMS).

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