Scientists have released 380 Seahorses into Sydney harbour to boost their population numbers. The White’s seahorse, Hippocampus whitei, used to be a common sight in Sydney’s waters, the Syngnathids often seen holding onto swimming enclosure nets and crab pots.
But the Sydney population halved between 2008 and 2015 while the population in New South Wales’ north coast fell by as much as 95%. In 2017 the species was IUCN red-listed as endangered, the major cause being habitat loss, so The Sydney Seahorse Project, a collaboration between the Sydney Institute of Marine Science, the University of Technology Sydney, and the New South Wales (NSW) Department of Primary Industries stepped in to help the struggling species.
Three pregnant males
Earlier this year, the Sydney Institute of Marine Science captured three pregnant males and raised their fry in captivity to improve their chances of survival. The 380 juveniles were released with tags that will enable researchers to monitor their growth and reproductive success in the wild. They’ve also been given eight seahorse hotels – cages made from biodegradable metal, to offer some more anchor points for the fish in the harbour.
The seahorse hotels are designed to mimic crab traps and were placed in the water at least a month before the fish, to encourage algae, sponges, and biofouling. It is hoped that they will encrust over the next few years, the metal structure degrading, but leaving a semi-natural habitat for the seahorses as well as benefitting the wider ecosystem.
Results from a previous project in Chowder Bay, Mosman, not far from Sydney Harbour revealed that 20% of the released seahorses were still using the hotels a year later and that 10% of them were pregnant.
Image credits Sylke Rohrlach from Sydney, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons. And Sydney SeaLife.
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