Feasibility study of detecting local seahorse and pipefish species in the coastal area of Hong Kong by environmental DNA (eDNA)

Funded by: Marine Conservation Enhancement Fund

Global Syngnathidae populations are being threatened due to habitat destructions, pollution from human activities and bycatches using non-selective fishing methods. In order to conserve and protect these threatened species populations and their habitat, it is important to provide precise and scientific survey results for the Government to develop conservation management plans. A traditional way to survey the Syngnathidae species is through underwater visual observations by divers. This method is time-consuming and requires subsequent morphological identification of specimens based on taxonomic expertise, and also likely to be overlooked because they are small with camouflage and live in a low clarity environment. With the help of eDNA methods, the local Syngnathidae populations in all parts of Hong Kong can be systematically and comprehensively investigated in a way that is fast, safe, and without habitat disturbances. This study will be the first substantial investigation on the local Syngnathidae populations using eDNA methods in Hong Kong, and the results obtained will also facilitate nearby regions such as China and southeastern Asia.

Research objectives

To conduct a comprehensive and systemic survey of Syngnathidae in Hong Kong by eDNA methods and underwater visual survey.
To develop an eDNA method specific for the yellow seahorse.

About Yellow Seahorse Hippocampus kuda

Yellow seahorses are commonly found in waters up to 7 meters deep in the eastern part of Hong Kong.
It was a common species in Hong Kong several decades ago but has become increasingly rare due to overfishing for traditional medicine, habitat destruction, and marine pollution.
It has been listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) since 2004 (www.cites.org).
It is classified as “Vulnerable” in the IUCN Red List of Threatened Species (www.iucnredlist.org).

What is environmental DNA (eDNA)?

When organisms inhabit or pass through a place, their DNA will be scattered in the surrounding environment through shed skin cells, excrement, secretions, etc. Environmental DNA (eDNA) refers to DNA collected directly from environmental samples such as soil, seawater, sediment, or air.

Why do we use eDNA to investigate pipefish and seahorses?

Previous pipefish and seahorse surveys mainly focused on the eastern waters of Hong Kong, and data in the southern and western areas remains limited.
Due to the low visibility of Hong Kong’s seawater, divers may easily overlook the small cryptic seahorses and pipefish.
Closely related seahorse and pipefish species share similar appearances, requiring a certain level of expertise to accurately identify the species.
Underwater visual surveys can be invasive, as divers and their equipment may disturb marine organisms and cause habitat destruction.
eDNA has been considered a non-destructive and cost-effective tool that can provide sensitive, accurate, unbiased, and high-resolution ecological data.

Research Methods

We collected water samples from 12 study sites distributed in the eastern, southern, and western waters of Hong Kong. Then we identified pipefish and seahorse species in the samples by eDNA methods.
We conducted aquarium experiments in Simon F.S. Li Marine Science Laboratory (MSL) at the Chinese University of Hong Kong to evaluate the effectiveness of eDNA methods.

Visiting these seahorses in Ocean Park Hong Kong!

The Coral Academy research team obtained an import permit under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and legally purchased the artificially bred yellow seahorses from Australia, and raised them in the laboratory for the research.
Since these yellow seahorses used are not from Hong Kong, they cannot be released directly into the wild after the experiment to avoid polluting the local ecology.
The Coral Academy eventually donated all the yellow seahorses to the Ocean Park Hong Kong for display and educational purposes. Under the careful care of Ocean Park caregivers, they have been settled in Ocean Park and are ready to meet everyone at the Grand Aquarium! Welcome everyone to visit them in the Park and learn more about the information of yellow seahorses and the eDNA technology.