Advances in the ecology, biogeography and conservation of seahorses (genus Hippocampus)

Seahorses (genus Hippocampus) form a group of over 30 species of enigmatic and charismatic marine fish that are attracting increasing global concern for their threatened status. Particular issues include the overexploitation of seahorses in target and bycatch fisheries and their utilization for traditional Chinese medicines. Seahorses are also thought to be highly vulnerable to habitat loss and deterioration throughout their circumglobal range in temperate and tropical shallow seas. A suite of unusual biological characteristics, including male pregnancy, has not only stimulated research attention but also contributed to the seahorses’ apparently vulnerable nature. Key areas of advancement in recent years, as reviewed here, include the application of genetic tools to confirm the monogamous behaviour of many species both within and between breeding events, to elucidate their challenging taxonomy, to gain insight into their evolution, biogeography and origins, and to identify which species are being traded internationally. Efforts to conserve seahorses have included both ‘top-down’ and ‘bottom-up’ approaches, which together have highlighted the need for international regulation of seahorse exploitation and demonstrated that seahorses can stimulate local and regional action in protecting not only seahorses themselves but also a range of threatened habitats in which they live. Updating and extending the global assessment of individual seahorse species on the IUCN Red List of Threatened Species is urgently needed (currently only eight species have been fully assessed), as are a renewed survey of the global seahorse trade and further studies to assess how best to protect seahorses within marine reserves.