Taxonomic notes: Section empty

Present in shallow coastal waters from the North Sea, down the European coast and into the Mediterranean Sea. The geographic range extends down the Atlantic African coast as far as Senegal, including the Atlantic Ocean islands of the Azores, Madeira and Canaries (Lourie et al. 2004). Exact locations of populations are unknown, but it is expected that seahorses occur at low densities along the coastline (L. Woodall pers. obs).

Generally seahorse density is patchy (Foster and Vincent 2004) and at most locations they are rare, but can be abundant locally (Curtis and Vincent 2005, Woodall 2009). Where data are available, seahorse populations appear to be declining (Foster and Vincent 2004, Vincent et al. 2011). 

There is no global estimate of Hippocampus hippocampus population size and no global assessment of population trends. However there are two locations where long-term datasets are available.

In the Ria Formosa, Portugal, H. hippocampus exhibited a 73% decrease (I. Caldwell, Project Seahorse, pers. comm.) between 2002 and 2008. More recent surveys at this location reveal that the population size is possibly increasing again (M. Correia pers. comm.) No cause for the population change has been confirmed, but benthic macrofauna changes recorded in the area have been shown as a result of anthropogenic stressors (Gamito 2008) and this could be related to the declines in seahorses.  

In the Arcachon Basin (France), interviews suggest that the population distribution is very patchy, but to date no trend has been established due to lack of consistent data collection (Grima 2011).

Anecdotal evidence is available in other locations, however exhaustive surveys and systematic data collection did not occur at these sites. In Mar Menor (Spain), Voiotias (Greece) and the Canary Islands, the population size of H. hippocampus has fluctuated greatly each year (anecdotal evidence compiled by L. Woodall. Project Seahorse). In other coastal sites populations have both decreased (Badalona, Spain- J. Ortiz, in. litt.; Malaga, Spain- P. Cabrera, in. litt.) and increased (La Herradura, Spain- P. Cabrera in. litt.).

No estimates of population trends are available outside of European waters, but trade research presently being carried out in West Africa may elucidate the situation.

Hippocampus hippocampus are mostly found inhabiting small home ranges in shallow coastal waters, lagoon systems and estuaries at depths of one to 55 m (Curtis and Vincent 2005, Garrick-Maidment and Jones 2004, Woodall 2009), but there may be seasonal migration to deeper waters (Boisseau 1967, Garrick-Maidment 2007, Garrick-Maidment and Jones 2004). Adult H. hippocampus use varied habitats of all sediment types, and in addition are often observed on artificial structures using them as holdfasts (Curtis and Vincent 2005, Franco et al. 2006, Garrick-Maidment and Jones 2004, Woodall 2009). 

In the Ria Formosa adult H. hippocampus are associated with habitats of low complexity, including sand and shell fragments (Curtis and Vincent 2005). However this species is seen in different habitats in other locations (Garrick-Maidment and Jones 2004, Woodall 2009). As an ambush predator H. hippocampus has a wide dietary range, which mainly comprises Amphipoda, Anmura, and Mysidacae and (Kitsos et al. 2008) and thus is associated with highly productive habitats.

Hippocampus hippocampus are seasonal breeders, breeding from April to October (Foster and Vincent 2004). Mating is temperature limited and gestation period is around a month (Boisseau 1967). Juvenile H. hippocampus (<87 mm) are rarely observed during surveys (Curtis and Vincent 2006, Woodall 2009). They spend the first weeks of life as plankton, but nothing more is known about them until recruitment at 62mm (Curtis and Vincent 2005). 

Hippocampus hippocampus adults have low dispersal and limited migration. This reduces their ability to colonize new areas, recolonize old ones, and in addition reduces their ability to move when habitat become unfavourable  (J. Curtis pers. comm. 2012). Most seahorses are monogamous, at least within a breeding season (Foster and Vincent 2004). This may reduce their reproductive potential if their partner was removed from the population (e.g., caught). However H. hippocampus matures at an early age, has rapid growth rates, and a short generation time, which suggests that it has reasonable potential to recover rapidly after direct (e.g. exploitation) and indirect (e.g., by-catch and habitat damage) effects of disturbance cease, but may be vulnerable to extended periods of poor recruitment (J. Curtis pers. comm. 2012).

No specific targeted fishery is known in Europe for H. hippocampus. There are exploited populations in Africa but the intensity is unknown (Senegal; J. Lam pers. comm.). In fishing, the whole animal is removed and all trade is in wild populations. The trend of exploitation is unknown.

International trade should be recorded, as H. hippocampus is listed on CITES Appendix II, however this species is often misidentified and were recorded as other species in at least one shipment (L. Woodall pers. obs.). There are very few records of trade exports from the species native range in the CITES Trade Database (UNEP-WCMC 2012a). Other records are exports from the indo-pacific region and are thus either misidentifications or re-exports for which no initial export certificate was granted (UNEP-WCMC 2012a). Seahorses of other species are used for traditional medicines, aquarium display and curiosities.

In Europe H. hippocampus are sold as curiosities and good-luck charms when caught as by-catch, (France, Portugal and Spain; L. Woodall, pers. obs.) and are collected occasionally under permits for display in local public aquariums (Portugal and France; L. Woodall pers. obs.). It is unlikely that these activities threaten the species globally unless large volumes of trade are uncovered in Africa.

The major continuing threat to Hippocampus hippocampus is assumed to be similar to that for Hippocampus guttulatus, which is habitat degradation and disturbance through direct anthropogenic activities such as coastal developments and the effect of fishing gear (e.g. trawls and dredges) (Caldwell and Vincent 2012). As it is a shallow coastal species it is extremely susceptible to anthropogenic activities. Habitat degradation through climate change continues across H. hippocampus geographic range, and H. hippocampus, like other small coastal fish, is also threatened by pollution from shore side run-off and ships (Islam and Tanaka 2004).

In addition H. hippocampus is taken in parts of its range as accidental bycatch from fisheries are sold as curiosities or into the live aquarium fish trade (see 'Use and trade').

• 5.4.4 Unintentional effects: (large scale) [harvest]
• 5.4.3 Unintentional effects: (subsistence/small scale) [harvest]
• 11.1 Habitat shifting & alteration

The entire genus Hippocampus was listed in Appendix II of CITES in November 2002 with implementation of the listing in 2004. 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. This species is also listed under OSPAR, European CITES (Curd 2009), the Bern Convention and the Barcelona Convention (Abdul Malak et al. 2011).

Regionally, it is listed as Near Threatened in the Mediterranean (Abdul Malak et al. 2011) and Data Deficient in Croatia (Jardas et al. 2007). Hippocampus hippocampus is protected by the UK Wildlife and Countryside Act of 2008 (DEFRA 2008) and is a UK Biodiversity Action Plan priority species (JNCC 2010).

Further research on this species biology, ecology, habitat, abundance and distribution is needed. Long-term monitoring is required for this species across its geographic range focusing on population trends, harvest level trend and habitat trends.

• 2.3 Habitat & natural process restoration
• 1.2 Resource & habitat protection
• 2.1 Site/area management
• 5.2 Policies and regulations
• 4.2 Training
• 1.1 Site/area protection
• 4.3 Awareness & communications

Hippocampus hippocampus retains its 2003 classification of Data Deficient.

There is some evidence for a large (73%) decrease in population census size from one location (Ria Formosa, Portugal) (Curtis & Vincent 2005, Caldwell and Vincent 2012), but a lack of reliable survey data in many parts of this species' range means that no consistent trends have been observed across the species' range. Thus, based on a lack of data the extinction risk of this species cannot be reliably categorised on a global level.

Urgent population assessments and long term monitoring programs across its geographic range are required to assess the extinction risk of this species. In addition there is, at present, no no data as to the extent populations are exploited in Africa. Current research ongoing in West Africa will hopefully elucidate this situation.

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