Hippocampus whitei 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Syngnathiformes Syngnathidae

Scientific Name: Hippocampus whitei Bleeker, 1855
Common Name(s):
English White's Seahorse, New Holland Seahorse, New Holland Seahorse, Sydney Seahorse
Hippocampus novaehollandae Steindachner, 1866
Hippocampus procerus Kuiter, 2001
Taxonomic Source(s): Kuiter, R.H. 2001. Revision of the Australian seahorses of the genus Hippocampus (Syngnathiformes: Syngnathidae) with descriptions of nine new species. Records of the Australian Museum 53: 293-340.

Assessment Information [top]

Red List Category & Criteria: Endangered A2bc ver 3.1
Year Published: 2017
Date Assessed: 2016-10-05
Assessor(s): Harasti, D. & Pollom, R.
Reviewer(s): Ralph, G.
Hippocampus whitei is a coastal seahorse that inhabits estuaries and areas with seagrasses, macroalgae, corals, sponges, and anthropogenic structures in some of the most densely populated areas in Australia. These areas are subject to a range of anthropogenic impacts, including coastal development, pollution, destructive boat anchoring, and sedimentation. Recently, there have been documented population declines at several locations across this species' range, primarily as a result of loss of important marine habitats such as soft corals and sponges. The population declines observed in two of the largest known concentrations of the species over one 6-year study (2009-2015) are reported as over 90% with some fluctuation. Population trends varied in other areas, ranging from stability to declines of 40%. These observed declines are corroborated by anecdotal evidence from other areas and by the ongoing observed decline in several important habitats. Although the numbers in several sites indicate that the species may reach thresholds for a Critically Endangered listing, subpopulations are stable in several marine reserves and the species is not likely declining as quickly in less populated parts of its range. It is suspected that across the species' range, declines of 50-70% have occurred in the past three generations (<10 years). Therefore, Hippocampus whitei is listed as Endangered under criterion A2bc.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Hippocampus whitei is thought to be endemic to southeastern Australia, from Sydney, New South Wales to southern Queensland (Lourie et al. 1999).
Countries occurrence:
Australia (New South Wales, Queensland)
FAO Marine Fishing Areas:
Pacific – southwest
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):12
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Information is available on population status for Hippocampus whitei from two estuaries where this species was found to be most abundant: Port Stephens and Port Jackson (Sydney Harbour) (Harasti et al. 2012). Resurveys of population abundance at both Port Stephens and Sydney Harbour have found declines in population abundance over the past decade.

Initial population declines were first noticed between 2010 and 2013 (Harasti 2014) in Port Stephens. Populations at the two largest known aggregation sites (the Pipeline and Seahorse Gardens, both in Port Stephens) were found to decline in abundance from 2006 to 2015. The Seahorse Gardens had a population estimate of ~370 (95% CIs: 239-612) mature animals in 2009, whilst resurveys of the site in 2015 provided a population abundance of only 10 animals (95% CIs: 10-12; or a 98% decline over if extrapolated over 10 years, Harasti 2016). Similarly, the Pipeline site was found to experience a large decline with initial estimates indicating a population abundance of ~260 animals in 2009, compared to only 45 animals in 2015 (a 95% decline if extrapolated over 10 years). Both locations saw some year-to-year fluctuations. The population abundance decline in Port Stephens was correlated with significant declines in the preferred habitats of seahorses. Both soft coral and sponge habitats were found to significantly decline at both these sites from 2009 to 2015 (Harasti 2016). Populations of H. whitei were relatively stable at two other sites in the region.

Populations in Sydney Harbour were also found to decline at the one location where population abundance had been collected. The protective swimming enclosure in Manly Harbour (referred to as Manly Net) was initially surveyed for Hippocampus whitei in 2007-2008 as part of a study assessing the impacts of council net cleaning on seahorse populations (Harasti et al. 2010). The adult population size on the Manly net from May 2007 to February 2008 was estimated at 315 (95% CI 304-326). This net was resurveyed from November 2014 to April 2015, and it was found that the population had declined by approximately 40% with a population abundance estimate of 176 (165-189)(or 56% if extrapolated over 10 years, Harasti unpublished data).

Also, anecdotal information on Hippocampus whitei populations in Sydney Harbour indicates that there have been declines at various other locations within the Harbour. Resurveys of the Clifton Gardens net in February 2015 only recorded seven mature animals, compared to 70 animals being recorded in the last survey of the net in 2008 (a 98% decline if extrapolated to 10 years). Similarly, divers have reported low numbers of seahorses on nets at Balmoral and Neilsen Park when compared to dives in the early 2000s.

The status of H. whitei populations in the seven other estuaries is unknown. However, no large populations of H. whitei are known to occur in these estuaries, with only Sydney Harbour and Port Stephens known to have large populations (Harasti et al. 2012).

Even though the species is totally protected in Australia ensuring it is not taken from the wild, it’s likely that the decreasing population trend will continue in the future if habitat degradation and loss continue.

Overall, it is suspected that declines of at least 50-70% have occurred based on the data from the most populated portion of the species' range.
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 whitei is known to occur at depths to 12 m and is found utilising a wide range of habitat types including seagrasses, macroalgae, corals, sponges, and anthropogenic structures (Kuiter 2009, Harasti et al. 2014). In Port Stephens, it has been shown that juveniles prefer gorgonian habitats (Euplexaura sp.) whilst adults had a preference for both sponges and soft coral (Dendronephthya australis) habitats. They were also found occurring in Posidonia seagrass and juveniles also used Sargassum sp. and soft coral habitats (Carijoa sp. and D. australis) (Harasti et al. 2014a). They are known to show a preference for more complex habitats, as it is believed that this provides better protection and more food resources (Hellyer et al. 2011, Harasti et al. 2014a).

Burchmore et al. (1984) reported that the species consumes amphipods, but did not elaborate. Most seahorses feed on a variety of small crustaceans, including harpacticoid, caprellid, and cyclopoid copepods, gammarid amphipods, caridean shrimp, and mysids (Woods 2002, Kendrick and Hyndes 2005, Kitsos et al. 2008, Yip et al. 2014).

As is the case for other seahorses, Hippocampus whitei are ovoviviparous, and males brood the young in a pouch prior to giving live birth (Foster and Vincent 2004). They breed from October to April. Within this breeding season, they are site-faithful to a home range (averaging 8 m² for males, 12 m² for females: Vincent et al. 2005) and are faithful to a single mate (Vincent and Sadler 1995).

The species is known to display strong site fidelity with tagged males occurring on the same site for up to 56 months and females 49 months, whilst no seahorses were ever recorded moving between sites. The species is known not to move far, as the largest distance a tagged animal was found to travel was only 70 m. It has also been shown that individuals show strong fidelity to holdfasts such as sponges, with some individuals being recorded on the same holdfast for up to 17 months (Harasti et al. 2014a).

Within Sydney Harbour, seahorses are generally found on artificial habitats such as the protective swimming net enclosures and also on jetty pylons. Their use of these artificial habitats is most likely driven by a loss of natural habitats (such as seagrass, sponges and soft corals) within Sydney Harbour. Seagrass habitats within Sydney Harbour have been shown to decline (West et al. 2004) and anecdotal information suggests large declines in available soft coral and sponge habitats.

Growth parameters for Port Stephens were: females L∞ = 149.2 mm and K= 2.034 per year and males L∞ = 147.9 mm and K=2.520 per year compared to estimates from Sydney Harbour:  females L∞ = 139.8 mm and K= 1.285 per year and males L∞ = 141.6 mm and K=1.223 per year (Harasti et al. 2012).

Hippocampus whitei displays rapid growth, early maturity and reproduction (Harasti et al. 2012), indicating that it has the ability to develop large populations if conditions are appropriate, such as the availability of suitable habitat and few predators (Harasti et al. 2014b). However, the species has very limited chance for dispersal given that there is no pelagic stage for juveniles, with newborns generally settling in the area of birth and not travelling far (Harasti et al. 2014a). Even though the life-history parameters of H. whitei suggest it may be reasonably resilient, precaution should be taken in its future management as a result of its limited geographical distribution and increasing pressures from anthropogenic sources on its habitats.

Although generation length is unknown, the species is thought to be similar to other seahorses in having a generation length of approximately one year. Therefore declines are assessed over a 10-year period for this species, which is thought to be longer than three generation lengths.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):0-2
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: Seahorses in general are typically traded for use as curios, in aquariums, and in traditional medicines (Vincent et al. 2011). Given that Hippocampus whitei is protected across its range in Australia, there is no reported legal trade in this species. Although the species has been detected in the aquarium trade (Martin-Smith and Vincent 2006), there have been no permits issued in the past five years to allow collection of this species for aquaria. It's unknown whether there is any illegal take of the species. The small numbers caught in bycatch may be subsequently illegally traded, but this has not been documented and numbers do not pose a conservation threat.

Threats [top]

Major Threat(s): The major threat to Hippocampus whitei is loss of essential marine habitats across its range. This species is known to occur along some of the most heavily populated and impacted estuaries in Australia (NSW EPA 2012). As the species displays strong site fidelity and has specific habitat preferences (Vincent et al. 2005, Harasti et al. 2014a), the further loss of key habitats through anthropogenic effects would result in a negative effect on species abundance and distribution; as occurred in Port Stephens (Harasti 2016). Whilst the Port Stephens estuary was previously considered a ‘stronghold’ for populations of H. whitei, the recent population declines as a result of habitat loss indicates that its long-term conservation within the Port Stephens waterway is at risk if essential marine habitats continue to be lost.

Within Sydney Harbour, it has been shown that H. whitei are very susceptible to councils cleaning the nets as removal of epibiota caused a decrease in abundance and that the species showed significant avoidance of areas devoid of epibiotic growth (Harasti et al. 2010). Guidelines for cleaning of the nets to minimise harm to the seahorses were developed and provided to councils in 2009 (Harasti et al. 2010); however, councils rarely implement these guidelines.

Conservation Actions [top]

Conservation Actions: In addition to Hippocampus whitei being protected under the NSW Fisheries Management Act 1999, 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. 

Hippocampus whitei likely occurs in several marine protected areas, including Port Stephens - Great Lakes Marine Park. Dedicated population surveys and habitat monitoring are needed.

Citation: Harasti, D. & Pollom, R. 2017. Hippocampus whitei. The IUCN Red List of Threatened Species 2017: e.T10088A46721312. . Downloaded on 22 January 2018.
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