Sydney Harbour's endangered seahorse population has been boosted after 100 captivity-raised baby White's seahorses were released in a North Shore tidal pool.

Clontarf will be home to the seahorses, which were raised and released by SEA LIFE Sydney Aquarium.

Key points:

· One hundred endangered White's seahorse have been released in a Clontarf tidal pool as part of a speical breeding program

· The species was listed as endangered in 2020 and suffered die-offs after recent floods

· Around 380 of the seahorses were released at Chowder Bay in July this year

SEA LIFE regional curator Laura Simmons says it's an important step in helping the seahorse, whose numbers have been declining. 

"Their numbers have decreased and declined quite a bit over the past 20 years," Ms Simmons told ABC Radio Sydney.

"They're only found in Australia — nowhere else in the world." 

 

Habitat loss has been a key driver of the White's seahorse decline.(Supplied: Northern Beaches Council)

Swimmers at the tidal pool may be able to see the seahorses clinging to the swimming net, which has become part of the seahorse "hotel".

Upgrades to the pool were finished in May this year and six months later became part of the conservation project. 

Northern Beaches Council encourages swimmers to admire the seahorses when at Clontarf but not to touch, catch or harm them. 

'Success rate there'

The release is the latest conservation project to lift the number of White's seahorses in their native habitat between Sydney and Port Stephens on the State's Mid North Coast.

 

The seahorses were bred in captivity at SEA LIFE Sydney Aquarium.(Supplied: Northern Beaches Council)

SEA LIFE released 300 White's seahorses at Port Stephens in May this year, taking the total number of White's seahorses released this year by the aquarium to 400. 

Ms Simmons says the Clontarf release is the sixth since the pilot program began in 2019, including at Chowder Bay in Sydney Harbour, Botany Bay and Little Manly Beach.

The project has seen pregnant male seahorses at the sites since their release, indicating some success, Ms Simmons said.

"We know there has been a survivability and a success rate there," Ms Simmons said. 

In July, 380 seahorses bred in captivity at the Sydney Institute of Marine Science (SIMS) were released at Chowder Bay, further south in Sydney Harbour.

 

Marine scientists at SIMS released 380 seahorses at Chowder Bay earlier in the year.(Credit: Jayne Jenkins )

Both SEA LIFE and SIMS have been releasing the seahorses, coordinating with the NSW Department of Primary Industries. 

More releases on the horizon

Another release at Port Stephens is expected to happen early next year, while further releases are planned at Balmoral in the middle of the year.

There are also plans to set up seahorse hotels at the ye-to-be-constructed Kamay ferry wharf at La Perouse

Ms Simmons says the aim is to get the White's seahorse off the endangered animals list, where it has been since 2020. 

"We really want to reverse that trend and get them re-established," Ms Simmons said.

"They're our seahorses, this is an Australian icon."