Abstract:

Background & Aims: Seahorses (Hippocampus spp.) are well-known fishes from the family Syngnathidae, mainly due to their unique external morphology and reproductive strategy of male pregnancy. All Hippocampus species, listed in CITES Appendix II in 2002, are under trade regulations internationally. All Hippocampus species (wild populations only) inhabiting in China’s waters were listed as Category II of the National Key Protected Wild Animals in 2021. Through literature review, we (i) updated the species list of seahorses occurring in China’s waters, (ii) summarized their distribution regions, habitat and breeding features, and (iii) presented their threatened categories and threats. Our goal is to inform effective conservation measures for seahorse wild populations in China.

Review findings: In this paper, we reviewed and summarized seahorse species diversity, distributions, habitat uses, reproductive features, threatened categories, and threat factors from various reference sources, including online databases (Fishbase, The Fish Database of Taiwan, GBIF, WoRMS, IUCN), peer-reviewed papers, reports, theses, as well as informative Chinese ichthyographies. A total of 16 seahorse species were recorded in China’s waters, including 5 pygmy seahorses that are no more than 30 mm in body height. Among these, Japanese seahorses (H. mohnikei) were distributed most widely, across China’s all four seas. Crowned seahorses (H. coronatus) were only found in the Bo Hai, while Barbour’s seahorses (H. barbouri), Beibu Bay seahorses (H. casscsio, a new species found in 2016), and Tiger tail seahorses (H. comes) were only found in the South China Sea. Six species were only found in the coastal waters of Taiwan Province. Southern China, including Taiwan, Hainan, Guangdong, Fujian, and Guangxi, has high seahorse species diversity. The habitat uses of seahorses in China’s waters are very diverse, including coral and rocky reefs, seagrass and seaweed beds, muddy and sandy bottoms, gravels, and mangrove meadows. Some species have special requirements for their habitats. According to IUCN, 8 seahorse species were listed as Vulnerable (VU), 2 species were listed as Least Concern (LC), 5 species were listed as Data Deficient (DD), and 1 species was Not Evaluated (NE). The main threats to seahorses are bycatch and habitat destruction.

Recommendations: Seahorses are a special taxonomic group of fishes with high vulnerability, and we propose five recommendations for urgent conservations of seahorses in China. First, the significance of seahorses as flagship species in marine biodiversity conservation should be realized and we need to use them to raise marine-conservation awareness of the general public. Establishing marine protected areas for seahorses and their habitats, and applying other effective area-based conservation measures (OECMs) might also be taken into account. Second, it is known that non-selective fishing gears such as bottom trawling have high seahorse bycatch volume, and the dredge net operations can damage seaweed beds where seahorses inhabit. Therefore, any solution for reducing bycatch, increasing survival rates of seahorses after releasing, protecting habitats and innovating fishing gears are welcome. Third, identifying the key habitats of different seahorse species in China’s waters is very important for establishing protected areas and fisheries spatial management. Currently, such data are very limited. Some key areas we synthesized in this study require national-wide surveys to validate before planning for marine reserves and OECMs of seahorses in China. Fourth, seahorse trade regulation and enforcement should be strengthened, and the management of seahorse utilization should be regulated properly. To this end, techniques to distinguishing wild populations from farmed seahorses should be established as soon as possible before the expansion of seahorse aquaculture.

Key words: seahorse, species diversity, protected animals, distribution, habitat