Pioneering Hong Kong scheme to track 2 species of horseshoe crabs launched

“Young horseshoe crabs’ habitat – mudflats – has been destroyed,” he added. “Adult crabs are often found to have been entangled in marine debris, such as abandoned nets, leading to their deaths.”

The foundation said it had also installed an underwater acoustic telemetry system – four receivers with a total area of 3 sq km (1.15 square miles) – to monitor the crabs’ activities, such as their locations and ranges, as well as environmental information, including water temperature and salinity.

Chuk explained that the crabs were hard to observe in the wild because they migrated to deeper waters when they reached maturity and only returned to beaches to spawn.

The first group released were two tri-spine horseshoe crabs and two mangrove ones. The tri-spine variety is considered endangered because of habitat loss and overfishing.

The creatures, which predate dinosaurs, are relatives of spiders and scorpions, and are widely regarded as living fossils as their appearance has remained largely unchanged over the past 475 million years.

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Hundreds of thousands of the crabs are harvested every year for their blood, which the pharmaceutical industry uses to check for contamination caused by bacteria in vaccine and drug samples.

Kevin Laurie, a horseshoe crab expert and a foundation partner, said Hong Kong also lost “a large percentage” of its horseshoe crab population during the development of Hong Kong International Airport on Chek Lap Kok island and because of commercial fishing in the 1980s.

“I’ve spoken to people in the 1970s who used to see hundreds of tri-spine horseshoe crabs on the beaches in Chek Lap Kok. But now, all gone,” he said.

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Cheung Siu-gin, an associate professor of chemistry at the City University of Hong Kong who advised on the scheme, said the study would help scientists understand the crabs’ behaviour, such as where they laid their eggs, foraged and spent the winters, so that society could protect them properly.

Laurie said the project would give a “whole new insight” into the lives of the crabs.

“Speaking to the government, you have to give them facts,” Laurie said.

“You can’t say ‘I think’or ‘in my opinion’ – with a project like this, you can give them the facts.”