Determining seahorse species distributions and conservation status from anecdotal information and in-water surveys

Background/Question/Methods

Seahorses are heavily traded on the global market, with millions of animals exported annually, but are vulnerable to overexploitation. According to official trade records, Vietnam ranks among the top ten exporters of seahorses worldwide. Basic biological information is needed to manage seahorse trade and assess the status of wild populations. However, seahorses are rare, cryptic and patchily distributed, and thus data-poor. Through this project, seahorse distribution and habitat preferences were documented to inform in-country conservation and management. Underwater surveys were conducted off the central and south coasts of Vietnam at 23 sites. Because seahorses are not always detected through in-water surveys, 57 fishers and other local stakeholders were interviewed to determine seahorse occurrence, species caught, seahorse habitats and catch rates.  

Results/Conclusions

Seahorses were scarce in the underwater surveys, and only found at two locations. Still, from interview responses, seahorses are widely distributed off Vietnam. Along the central and southern coast, seahorses were commonly caught in bottom trawls, with 96% of fishers estimating that seahorse populations have declined 40-90% over the past decade. Local researchers also encountered seahorses at islands off Vietnam’s northern coast. The most common species from surveys and in landings was Hippocampus spinosissimus, a species of concern in trade. Hippocampus spinosissimus, H. trimaculatus, H. kuda and H. mohnikei were all found in soft-bottom habitats. From landings, H. kelloggi and H. histrix were found in deeper waters, usually caught by trawlers operating far offshore. Our findings indicate that immediate action is needed to protect seahorses and their habitats, especially at Phu Quoc, which hosted the highest abundance of seahorses in our surveys, but where targeted fishing pressure from bottom trawling and compressor diving was also intense. There are already substantial efforts to study coastal areas off Vietnam, through research trawls, large-scale surveys, local monitoring programs, and citizen science, which can provide vital information on data-scarce species.