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Undersea ‘Hotels’ Deployed to Help Sydney’s Endangered Seahorses

Captive breeding and microhabitats may help restore White’s seahorse whose population plummeted 90 percent in the last decade

An endangered White's seahorse. (University of Technology Sydney)
smithsonianmag.com

Life in Sydney Harbor has not been kind to Hippocampus whitei, or White’s seahorse. Boat anchors, sedimentation, pollution and devastating storms in the area have destroyed the animal’s habitat.

That’s why the SEA LIFE Sydney Aquarium, University of Technology Sydney and various Australian government agencies are setting up a chain of so-called seahorse “hotels” to help restore the species.

Harriet Tatham at ABC Radio Sydney reports that the seahorses’ population in Sydney Harbor decreased by 90 percent over the last decade, leading to its listing as an endangered species in 2017. Now, researchers are hoping that by establishing the “hotels” around the harbor, they will be able to release captive bred seahorses and restock the seahorse stable.

According to a university press release, the project kicked off last month. Aquarium staff collected breeding pairs of the seahorses from Sydney Harbor, including some pregnant male seahorses. The staff has witnessed six births, during which dozens of baby seahorses about the size of a grain of rice emerge from their birth pouch. The goal is to raise the juvenile seahorses until they are large and strong enough to survive in the harbor.

A big part of that survival will be the seahorse hotels. Sabrina Imbler at Atlas Obscura reports that the hotel concept is the brainchild of marine biologist David Harasti of Australia’s Port Stephens Fisheries Institute. While diving in the harbor, he noticed that the surviving populations of White's seahorses congregated around abandoned crab traps and nets used to keep sharks out. So he designed a “hotel” made of chicken wire for the seahorses, deploying 18 of them in early 2018. By year’s end, he counted 65 White’s seahorses that called his hotels home.

“Everyone loved the seahorse hotels,” he tells Imbler. “It was a real, ‘If you build it, they will come’ situation.”

The seahorses, however, aren’t attracted to chicken wire, per se. Harasti says corals, sponges and algae begin to grow on the box-like scaffolding, which attracts the little marine animals the seahorses prey upon. The hope is after the hotels rust away, they will leave behind miniature coral mounds that will be long-term habitat for the seahorses.

Last year, after the hotels had been deployed for six months, Harasti told Ben Millington and Nancy Notzon at ABC Newcastle that the seahorses were bonding with the hotels.

“Each time we survey a hotel there are adults on there, there are juveniles and we're finding they're very territorial, so we tag the seahorses and we find the same animals from three or four months ago still living on them which is great,” Harasti says.

Currently, Harasti and his team are building a new batch of hotels that they will deploy next year along with the captive-bred seahorses. While the hotels appear to be a successful, he says the team is optimistic but cautious about the breeding program.

“When you raise something in captivity, they behave very differently to how they behave in the wild,” he tells Tatham. “When we release these animals, there’s not somebody giving them food every day or keeping them safe. They will be surrounded by fish and octopus that will predate on them, so we’re hopeful that they’ll adapt to being back in the wild but we’re not sure if this is going to work.”

Biologist Robbie McCracken of SEA LIFE Sydney Aquarium tells Imbler the seahorses should be big enough to release into the wild in April or May 2020. The researchers will tag the creatures with three neon spots injected under their skin that will allow long-term monitoring.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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