Hippocampus denise 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Syngnathiformes Syngnathidae

Scientific Name: Hippocampus denise Lourie & Randall, 2003
Common Name(s):
English Denise's Pygmy Seahorse
Taxonomic Source(s): Lourie, S.A. and Randall, J.E. 2003. A new pygmy seahorse, Hippocampus denise (Teleostei: Syngnathidae), from the Indo-Pacific. Zoological Studies 42(2): 284-291.

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2017
Date Assessed: 2015-10-08
Assessor(s): Kuo, T.-C. & Pollom, R.
Reviewer(s): Smith, R. & Ralph, G.

Hippocampus denise is a coastal seahorse species that inhabits coral reefs, and specifically gorgonian corals. The species may be threatened by coral reef habitat degradation and loss as a result of coastal development and pollution, destructive fishing practices such as bottom trawling and the use of dynamite, ocean acidification, and the effects of climate change including rising sea temperatures. Further research is needed in order to determine population size, trends in abundance, and the effects of climate change and coral habitat loss on this species. Therefore H. denise is listed as Data Deficient.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Hippocampus denise inhabits the the western Pacific Ocean (Lourie and Randall 2003). Specimens have been observed in Australia (Nishikawa et al. 2011, Foster et al. 2012), Thailand, Malaysia, the Philippines, Indonesia, Vanuatu, Palau, Solomon Islands, and Micronesia (Lourie and Randall 2003, iSeahorse 2015).
Countries occurrence:
Indonesia (Bali, Jawa, Kalimantan, Lesser Sunda Is., Maluku, Papua, Sulawesi); Malaysia; Micronesia, Federated States of ; Palau; Philippines; Solomon Islands; Thailand; Vanuatu
FAO Marine Fishing Areas:
Pacific – western central
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):100
Upper depth limit (metres):7
Range Map:Click here to open the map viewer and explore range.

Population [top]


The global population size for H. denise has not yet been estimated. The only population survey to date was in southeast Sulawesi, Indonesia, and found that the density of H. denise in the area to be 0.0059 (±0.001) seahorses/m² (Smith 2010).  The density was the lowest for an unexploited seahorse population yet recorded.  Further research is needed in order to determine population size and trends in abundance.

Current Population Trend:Unknown
Additional data:
Continuing decline of mature individuals:Unknown
Extreme fluctuations:UnknownPopulation severely fragmented:Unknown
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:UnknownAll individuals in one subpopulation:Unknown

Habitat and Ecology [top]

Habitat and Ecology:Hippocampus denise is one of the smallest seahorse species, measuring less than 2 cm in height (Lourie and Randall 2003).

It inhabits gorgonian corals including Annella reticulata, Muricella spp., Echinogorgia spp., Verrucella spp., Acanthogorgia spp., Melithaea spp., Villogorgia spp., and Ellisella spp. at depths of 10-100 m (Lourie and Randall 2003, Smith 2010, Smith et al. 2012).  After juveniles settle on gorgonians, they do not move between host corals and remain in small mixed-sex groups.

The species is mostly monogamous, although polyandry has also been observed (Smith 2010).  Males carry the eggs in a brood pouch on their trunk, and they give birth to 6-16 live young (Smith and Tibbetts 2008).
Continuing decline in area, extent and/or quality of habitat:Unknown
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: There are no records of trade in Hippocampus denise. Although the species is likely attractive for the aquarium trade, they are notoriously hard to find and do not do well in captivity.

Threats [top]

Major Threat(s):

Hippocampus denise is under threat as a result of  anthropogenic destruction and degradation of their coral reef habitat. This includes destructive fishing practices (e.g., the use of dynamite and cyanide), sedimentation from poor land use practices, pollution (Smith 2010, Lim et al. 2011), extreme temperature events, and ocean acidification (Thresher et al. 2011). The scope and severity of these threats has not yet been assessed.

Conservation Actions [top]

Conservation Actions: The entire genus Hippocampus was listed in Appendix II of CITES in 2004. The species occurs in more than one protected area. Addressing destructive fishing practices and mitigating climate change would be the most effective interventions for conserving this species.

Citation: Kuo, T.-C. & Pollom, R. 2017. Hippocampus denise. The IUCN Red List of Threatened Species 2017: e.T41716A54909161. . Downloaded on 21 September 2018.
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