Hippocampus histrix 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Syngnathiformes Syngnathidae

Scientific Name: Hippocampus histrix Kaup, 1856
Common Name(s):
English Thorny Seahorse, Longspine seahorse, Spiny Seahorse
French Cheval de mer, Hippocampe, Hippocampe hérissé
Taxonomic Source(s): Kaup, J.J. 1856. Catalogue of Lophobranchiate Fish in the Collection of the British Museum. London, UK.
Taxonomic Notes: The wide geographic range of H. histrix (from east Africa to Japan) warrants further investigation, as Song and Mabuchi (2014) suggest that the genetic distance between Indian and Pacific populations is 6.6–6.7% (CO1) and this is also suggested by BOLD (2016) which indicates a 6.13% distinction between specimens from Mozambique/India versus Vietnam/Japan (648bp CO1). This high degree of divergence indicates the presence of at least one cryptic species across the range. There are no genetic data currently available for H. jayakari, which is morphologically very similar to but replaces H. histrix in the Red Sea and Arabian Gulf (Lourie et al. 2016).

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2cd+4cd ver 3.1
Year Published: 2017
Date Assessed: 2017-01-26
Assessor(s): Pollom, R.
Reviewer(s): Ralph, G.
Contributor(s): Wiswedel, S.
Hippocampus histrix is a widespread coastal seahorse species that occurs throughout much of the Indo-West Pacific from East Africa to Hawai'i and French Polynesia.  The species inhabits sponges, weedy rocky reefs, soft corals, and seagrass beds. It is threatened by overexploitation through small-scale targeted fisheries and as bycatch in trawl fisheries, and as a result of habitat loss from destructive fishing practices, coastal development, and pollution. Levels of exploitation obtained through fisher interviews indicate localised declines of Hippocampus spp. in the late 1990s and early 2000s, though few quantified estimates of declines are available. As these declines were reported from several parts of its range, it is suspected that the species had undergone a decline of at least 30% or more within a 10 year window. The primary threats to this species have not ceased, and some may be accelerating. It is suspected that these threats are likely contributing to further declines, and thus the previous estimate of decline is still applicable. No further studies on population size or trends, or on threats to the species have been undertaken since the previous assessment. Therefore Hippocampus histrix is assessed as Vulnerable under criterion A2cd+4cd.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Hippocampus histrix is widespread in the Indo-Pacific, occuring from southeastern Africa and Madagascar to Japan, Hawai'i, and French Polynesia (Lourie et al. 2016). It appears to be replaced in the Arabian and Red Seas by Hippocampus jayakari, although further taxonomic work is needed there (Lourie et al. 2016). The species inhabits waters to 82 m depth (Myers 1999), usually in 15 - 40 m (Allen and Erdmann 2012).
Countries occurrence:
Australia (New South Wales, Queensland); China; French Polynesia; India (Kerala, Tamil Nadu); Indonesia; Japan (Honshu); Korea, Republic of; Madagascar; Malaysia (Peninsular Malaysia); Mauritius; Micronesia, Federated States of ; Mozambique; New Caledonia; Papua New Guinea; Philippines; Réunion; Samoa; Seychelles; South Africa; Taiwan, Province of China; Tanzania, United Republic of; Tonga; United States (Hawaiian Is.); Viet Nam
FAO Marine Fishing Areas:
Indian Ocean – western; Indian Ocean – eastern; Pacific – western central; Pacific – eastern central; Pacific – northwest
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):UnknownEstimated extent of occurrence (EOO) - km2:
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):Unknown
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:Unknown
Lower depth limit (metres):82
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:To date there have been no dedicated surveys or population estimates for Hippocampus histrix. There is little information on population size or trends, but the species is inferred to be declining based on data from fisher interviews and from habitat loss and degradation. 

In parts of its range fishers and traders have reported declines in the availability and/or size of seahorses. For example, in 1998 and 1999 in Malaysia and Thailand, surveys of both fishers and traders reported declines in the availability of seahorses including H. histrix of 68 +/-24% over 12 years, although a minority of fishers reported stability (Perry et al. 2010)There are also reports of severe general seahorse declines since the 1970s in the Philippines (O'Donnell et al. 2010). In East Africa, surveys of fishers and traders in 2000 documented declines over the previous 20 years in seahorse availability and size, which included H. histrix (McPherson and Vincent 2004). These declines based on fisher interviews are complicated to accurately quantify, but it can be surmised that they are occurring.

General seahorse population declines within the range of H. histrix are suspected as a result of habitat degradation and declines in seagrasses (Marcus et al. 2007, Short et al. 2011), and mortality from intense trawling bycatch (Giles et al. 2006, Perry et al. 2010) - and indeed these threats are known to occur throughout this species' range (FAO 2001, Perry et al. 2010). 

Since declines are reported for several disparate parts of its range, it is suspected that these declines are occurring globally for H. histrix. It is conservatively suspected that the rate of decline has been at least 30% for the past 10 years and that this decline is expected to continue into the future. This decline rate is lower than that reported by most fishers.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:UnknownPopulation severely fragmented:Unknown
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:UnknownAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:Hippocampus histrix is found at depths between 10 and 40 m but may also be found deeper than this (Lourie 2016). This species is found on a variety of substrates including sponges, weedy rocky reefs, soft corals, and seagrass beds (Lourie et al. 2004, Kuiter 2000, Lourie 2016).

Little is known about feeding, but this species likely consumes small benthic and/or planktonic crustaceans such as harpacticoid and cyclopoid copepods, gammarid shrimps, and mysids (Woods et al. 2002, Kendrick and Hyndes 2005, Kitsos et al. 2008, Yip et al. 2015, Valladares et al. 2016). 

Seahorses including H. histrix are ovoviviparous and the males give birth to live young (Foster and Vincent 2004). The species reaches a maximum size of 17 cm, has a gestation period of 12-14 days, and matures at around 10 cm (Masuda et al. 1984).

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) - all traits which make seahorses vulnerable to exploitation. There are however some traits, such as small body size, fast growth and high fecundity that may make seahorses more resilient to exploitation (Morgan 2007). However a specialised life-history coupled with a dependence on 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).
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):2
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: Hippocampus histrix is one of the six seahorse species most often reported to CITES as being traded internationally (Evanson et al. 2011). This species is traded both live, for the aquarium trade as well as dry, for use in traditional medicine.

Trade in this species has been reported from countries throughout its range including from as early as 1996 in Malaysia and Thailand (Perry et al. 2010), Kenya and Tanzania (McPherson and Vincent 2004) and Vietnam (Meeuwig et al. 2006). Since the implementation of the listing of all seahorse species on CITES Appendix II in 2004, there have been reports of approximately 200 thousand individuals traded annually between 2004 and 2010 and (Evanson et al. 2011, UNEP-WCMC 2012a). Given that a large proportion of the trade reported to CITES is only reported to the genus level, it is possible this volume underestimates the true extent of trade in this species (Evanson et al. 2011). In the CITES Trade Database, international trade in this species has been reported from many countries throughout its range including, China, Hong Kong SAR, Indonesia, New Caledonia, Philippines, Thailand and Taiwan (UNEP-WCMC 2012a).  In 2010, this species was selected by the CITES Animals Committee for the Review of Significant Trade following COP15 due to large amounts of potentially unregulated international trade (UNEP-WCMC 2012b). 

Although it was originally suspected that this species was only rarely traded live for the aquarium trade (Lourie et al. 2004),  large volumes of trade in live specimens have subsequently been reported to CITES, primarily consisting of wild-caught specimens originating in Indonesia (Evanson et al. 2011, UNEP-WCMC 2012a).

When looking at trade in H. histrix, it is important to note that this species name is often used as a label for any spiny seahorse from the Indo-Pacific and therefore may contain specimens of other species (Lourie et al. 2004).

Threats [top]

Major Threat(s): The major threat to Hippocampus histrix is over-exploitation. This species is caught in both targeted fisheries and as bycatch in other non-selective fisheries, particularly shrimp trawls (McPherson and Vincent 2004, Meeuwig et al. 2006, Perry et al. 2010). H. histrix has been reported in international trade since the mid 1990s and even at this stage, interviews with fishers and traders reported declines in the availability of seahorses (McPherson and Vincent 2004, Perry et al. 2010). Although daily catch rates on individual vessels are quite low, the cumulative impact of the Indo-Pacific trawl fleet leaves little doubt that byactach is affecting populations of this species (Vincent et al. 2011, Lawson et al. 2017). 
This species' coastal seagrass and coral habitats are threatened throughout its range by eutrophication, sedimentation, coastal construction, dredging, destructive fishing practices such as trawling and dynamite use, and climate change (Carpenter et al. 2008, Normile et al. 2016, Short et al. 2011).

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

Conservation Actions [top]

Conservation Actions: All Hippocampus species are listed under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). This species likely occurs in many marine protected areas given its extensive range. 
Hippocampus histrix has been listed as Data Deficient in the Vietnamese Red Data Book.

Citation: Pollom, R. 2017. Hippocampus histrix. The IUCN Red List of Threatened Species 2017: e.T10070A54905206. . Downloaded on 18 January 2018.
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