Taxonomic notes: The 1996 and 2000 IUCN Red Lists included H. planifrons and H. takakurae. These are now considered to be synonyms of H. trimaculatus (Lourie et al. 2004).

This species' range encompasses much of the Eastern Indian Ocean and the Western Pacific. It extends from the West coast of India and Sri Lanka northeast to Japan, Sakhalin Island and southeastern Russia and south throughout Southeast Asia to the eastern Australian coast (Lourie et al. 2004). Lourie et al. (2009) also report a single record of the species from Tahiti, however no specimens have been encountered between there and the islands near Australia.

Hippocampus trimaculatus is most often found at depths greater than 10m with a maximum reported depth for this species being 100m (Lourie et al. 2004).  This species utilizes soft substrates such as sand and mud as well as macro algae and soft corals (Nguyen and Do 1996, Choo and Liew 2003, Lourie et al. 2004). As these are similar habitats to where shrimp trawling often occurs (FAO 2008), this makes H. trimaculatus especially susceptible to exploitation as bycatch in the tropical shrimp trawl fishery. Shrimp trawling is also known to be causing a decline in the quality of these habitats (FAO 2008), which is suspected to effect H. trimaculatus. Although the habitat preferences of this species have not been studied in detail, anecdotal evidence suggests that, at least in Malaysia, this species prefers sandy and muddy substrates similar to those inhabited by tropical shrimp (Lim, in. litt. 2012).

All seahorse species have vital parental care, and many species studied to date have high site fidelity (Perante et al. 2002, Foster and Vincent 2004), highly structured social behaviour (Vincent and Sadler 1995), and relatively sparse distributions (Lourie et al. 1999) -  traits that make seahorses especially vulnerable to over-exploitation. Seahorses also have some traits, such as small body size, fast growth and high fecundity, that may confer resilience to exploitation pressures (Morgan 2007). However a specialized life-history coupled with a dependence on relatively shallow habitats that are subject to extremely high fishing pressure, and the fact that seahorses do not move very much and are thus easily captured, means they are very vulnerable to over-exploitation. The importance of life history parameters in determining response to exploitation has been demonstrated for a number of species, including seahorses (Jennings et al. 1998, Foster and Vincent 2004).

While detailed population numbers for Hippocampus trimaculatus remain unknown, analysis of international trade data shows that this is one of the species most often reported as being traded internationally, indicating heavy and widespread exploitation globally (UNEP-WCMC 2012a; Foster et al. 2014). Also, local surveys throughout this species' range indicate that there are declines in the availability and size of seahorses (Giles et al. 2006 - 30-60% declines over 2-5 years in Vietnam; Perry et al. 2010 - declines of 68+/-24% over 12.5 years in Malaysia and Thailand). In Hong Kong traders reported that local seahorses common 30 years ago were rarely found in 2000, with the decrease in availability attributed to habitat destruction and pollution (B. Kwan, unpublished data).These declines, coupled with the known extensive trade, can be used to infer that there have been declines of at least 30%  have occurred in the past and that these declines are expected to continue into the future. 

All Hippocampus species are listed under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This means that countries who are signatories to CITES are subject to regulations on the export of seahorses. Trade surveys and data reported to CITES indicate that Hippocampus trimaculatus is one of the species most reported as being traded internationally with volumes in excess of  1 million individuals traded annually between 2004 and 2010 (UNEP-WCMC 2012a; Foster et al. 2014). Although the implementation of the CITES listing of seahorses only took place in 2004, trade in this species has been reported throughout its range from as early as the mid 1990's (Salin et al. 2005, Giles et al. 2006, Perry et al. 2010, Murugan et al. 2011, UNEP-WCMC 2012b). There have also been reports of continued trade in countries where trade is banned and under-reported, indicating that current estimates of exploitation may be underestimated (Salin et al. 2005, Murugan et al. 2011, UNEP-WCMC 2012b).

Since the vast majority of all seahorses entering the trade are appear to be sourced from bycatch in shrimp trawl fisheries (Salin et al. 2005, Giles et al. 2006, Perry et al. 2010, Murugan et al. 2011) and the fact that there is no evidence for a decline in the effort of these fisheries (FAO 2008), it is unlikely that the pressure on these populations will cease in the near future. 

The majority of Hippocampus trimaculatus reported in trade are traded dry for the traditional medicine trade (Salin et al. 2005, Gile et al. 2006, Foster et al. 2014). This speciesis also traded live, for the aquarium trade, but the volumes are low (UNEP-WCMC 2012a; Foster et al. 2014). The overall volume of trade in this species is very large and as a result H. trimaculatus was selected for the CITES Review of Significant Trade following COP 15 of CITES (UNEP-WCMC 2012b).

This species is relatively large and pale with smooth skin, all of which are known to be desirable traits in the traditional medicine trade (Vincent 1996) and may help to explain why it is so prevalent in trade. Indeed, since the implementation of the listing of all Hippocampus species on Appendix II of CITES in 2004, Hippocampus trimaculatus has been one of the top two species most reported to CITES as being traded internationally with an average of 1.8 million individuals reported in trade annualy between 2004 and 2011 (Foster et al. 2014).

The Australian populations of this species were moved under the Environment Protection and Biodiversity Conservation Act 1999, so export permits are now required. There is currently a national ban on the capture and trade of seahorses in the Philippines as per The Philippine Fisheries Code of 1998: Republic Act No. 8550. Other countries such as Cambodia, China and Sri Lanka have also reported bans on trade in seahorses generally (UNEP-WCMC 2012b) but it is unclear if these have yet been implemented. Since 2001, all seahorses have been listed under Schedule 1 of the Indian Wildlife Protection Act, which bans trade in these species (Indian Ministry of Environments and Forests 2001).

The primary threat to Hippocampus trimaculatus is bycatch in incidental and target fisheries throughout its range including Malaysia and Thailand (Choo and Liew 2003, Perry et al. 2010), Vietnam (Giles et al. 2005, Meeuwig et al. 2006) and India (Salin et al. 2005, Murugan et al. 2011). These fisheries, specifically shrimp and other trawl fisheries, are known to cause substantial damage to the habitats in which they occur (FAO 2001, FAO 2008). 

Although the majority of seahorses are caught as bycatch, there are some small fisheries that target seahorses (Giles et al. 2005, Salin et al. 2005, Perry et al. 2010), which are presumably driven by the demand for seahorses in traditional medicine and the aquarium trade.

Seahorses life history and ecological traits may increase their susceptibility to these threats (see Habitats and Ecology).

• 5.4.6 Motivation Unknown/Unrecorded
• 5.4.4 Unintentional effects: (large scale) [harvest]
• 5.4.3 Unintentional effects: (subsistence/small scale) [harvest]
• 5.4.1 Intentional use: (subsistence/small scale) [harvest]

All Hippocampus species are listed under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This means that countries who are signatories to CITES are subject to regulations on the export of seahorses. Countries are required to provide permits for all exports of seahorses and are meant to provide evidence that these exports are not detrimental to wild populations. However a lack of basic information on distribution, habitat and abundance means many CITES Authorities cannot assess sustainability of their seahorse exploitation and meet their obligations to the Convention.  The challenge is particularly large in that most seahorses entering trade are caught incidentally as bycatch and thus imposing export quotas would achieve next to nothing for wild populations. 

CITES has recommended a minimum size limit of 10 cm height for all seahorse specimens in trade (CITES Decision 12.54). This limit represents a compromise between the best biological information available at the time of listing and perceived socioeconomic feasibility.  But we urgently need information on wild populations to assess their conservation status and take conservation action, as well as refine management recommendations.  For example, evidence on variation in the spatial and temporal abundance of seahorses would enable areas of high seahorse density to be identified, as the basis for considering area restrictions on nonselective fishing gear that obtains Hippocampus species as bycatch.  An understanding of the technical and logistical feasibility of returning to the sea live seahorses taken as bycatch in various types of fishing gear would provide the basis for considering the feasibility of minimum size limits and/or other output controls. Establishing monitoring program of landings of seahorses at representative sites, taking into account different gear types and means of extraction and recording catch and effort metrics would allow us to assess population conservation status and development management recommendations for various fishery types.

• 3.1.1 Harvest management
• 3.1.2 Trade management
• 4.2 Training
• 4.3 Awareness & communications

Hippocampus trimaculatus is listed as Vulnerable (VU A2d+4d) based on suspected declines of at least 30% caused by incidental capture, targeted catch and habitat degradation. While there is little information on changes in population numbers of the species, there is indirect evidence to suggest that declines have taken place and are continuing. This listing is consistent with the precautionary approach of the IUCN. 

The primary threat to Hippocampus trimaculatus is bycatch in the multiple fisheries throughout its range and these fisheries are also known to cause damage to this species' habitat. This is one of the most traded species in the international seahorse trade (Evanson et al. 2011, UNEP-WCMC 2012a) and due to its large size and smooth/pale complexion it is much desired in the traditional Chinese medicine market (Vincent 1996).

Local surveys throughout this species' range indicate that there are declines in the availability and size of seahorses (Giles et al. 2006, Perry et al. 2010). These declines coupled with the extensive trade can be used to infer that there have been declines of at least 30% over the past 10 to 15 years and that these declines are expected to continue into the future.

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