• Citizen Science with the Seahorse Project

    Steve Hippocampus guttulatus copyVolunteering as a research diver means showing that you really care about the marine environment and are taking an active role to protect it. Not content to simply be led around in a "PADI shoal" like all the average dive tourists, you want to get an in depth understanding of marine ecology and make your diving count.

    Gathering underwater data takes considerable diver hours and researchers are turning to divers, as citizen scientists, to provide the information that they need. With underwater digital cameras increasing in quality and becoming cheaper, it is easy to gather photo data that is very useful to marine researchers - once you know what you're looking for.

    Gaye Rosier has been leading volunteer divers as citizen scientists on the Costa Brava since 1999, gathering data on Posidonia oceanica and key species data for the Silmar Project since 2009.

    Now she is devoting herself to studying European seahorses via her Seahorse Project during their peak breeding season, July and August. She will be accepting just a handful of experienced divers to join her as self-funded research assistants in the Seahorse Project.

    Gaye has already built up a photo-base of over 50 individual seahorses that she can recognise by their unique facial patterns. Getting clear macro photos, without the use of flash, whilst hovering inches above the sea bed requires Divemaster level buoyancy skills. Seahorses are easily stressed and data must be obtained without creating any disturbance. Taking part in the Seahorse Project offers a unique opportunity for research assistants to refine their buoyancy skills and improve their underwater photography whilst looking into the private lives of these mythical creatures.

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    Some of the seahorses living on the Costa Brava

    These seahorses may all look pretty similar to you, but Gaye Rosier knows each one as an individual by their distinctive facial patterns. They each have a name and, during the 2015 research season Gaye´s volunteer research assistants had the pleasure of choosing the name whenever they discovered a new individual. We now have seahorses named after volunteer divers, their family members, and even their pets!

    Gaye has been scuba diving the Costa Brava for the past 16 years, researching and photographing the amazing abundance of marine life, some of which can be viewed on this site. Now that she has retired as marine research coordinator with Kenna Eco Diving, Gaye will be devoting her personal diving time to a breeding colony of European seahorses that she has been researching for the past two years. Already she has catalogued over 50 individual seahorses, both Hippocampus hippocampus and Hippocampus guttulatus, via her Seahorse Project.

    "Opportunities to scuba dive and see wild seahorses are very few and far between, and I feel blessed to be able to closely study them." says Gaye, who has spent 4 hours underwater in one day in order to film rare cross-mating between the two different species.

    Gaye is a member of the Seahorse Alliance, comprised of European seahorse researchers. She shares her data with The Seahorse Trust and Project Seahorse via their iSeahorse trends monitoring system. In fact, Gaye and her team were the first iSeahorse trends monitoring group to have submitted a full year's worth of data.

    Melon, Hippocampus guttulatus

  • L’Escala’s Hidden Treasure - Posidonia Oceanica

    When you go for a stroll along the beach at Cala Montgó or Riells, do you ever wonder about the piles of brown leaves washed up on the sand? They are the dead leaves of the underwater plant Posidonia oceanica, named after the Greek god of the sea, Poseidon, which are shed each winter. Left to remain on the beach the mounds of leaves can sustain a complex invertebrate food web, protect the shoreline from erosion, and deliver sand in the form of carbonate and silica shells.

    As a true plant that evolved on land and returned to the sea millions of years ago, Posidonia oceanica has roots, stem, and leaves (between 20 and 80 cms in length), and is capable of bearing flowers and fruits with seeds (called “sea olives”). At the base of each plant is a rhizome, which is actually a modification of the stem. The hairy remains of old, degrading leaf sheaths found around the rhizomes can also be found as conspicuous balls of fibres washed onto the beaches, known as egagropili.

    Dried Posidonia oceanica leaves were traditionally used in Mediterranean countries as packing material to transport fragile items of glassware and pottery, and also to ship fresh fish from the coast to cities. As parasites are less successful in Posidonia leaves than in straw, they were utilised in stables, as roof insulation, and as a filling material for pillows and mattresses to prevent respiratory infections. Further medicinal uses included the alleviation of skin diseases and leg pain caused by varicose veins.

    Posidonia oceanica is unique to the Mediterranean sea where it grows in beds that cover between 25,000 and 50,000 km² of coastal areas, corresponding to 25% of the sea bottom at depths between 0 and 40 meters. Posidonia oceanica has been called “the lungs of the Mediterranean” due to the large amount of oxygen that it provides to coastal waters, producing oxygen at an average rate of 5110 liters/m²/per year. It also absorbs carbon dioxide, storing carbon at an average rate of 83 g C/m² per year and helping to alleviate the effects of climate change.

    The plants of Posidonia oceanica grow very slowly, at a rate of only 1 to 6 centimeters per year, but over thousands of years they form meadows that support a wide variety of species. Gaining its energy from the process of photosynthesis, Posidonia oceanica needs transparent waters. For this reason, the presence of large, dense meadows is a clear sign of the quality of local waters.

    In fact, Posidonia meadows are excellent indicators of environmental quality as they can only grow in clean unpolluted waters. Despite legislation* protecting this important species, it is threatened by pollution, coastal development, the presence of fish farms, bottom-trawling and boat anchoring. Studies show that 46% of the underwater meadows in the Mediterranean have experienced some reduction in range, density and/or coverage, and 20% have severely regressed since the 1970s. Of Spanish meadows, 60% are found to be declining at a rate of 5% per year.

    A cartographic survey of the 595 km coast of Catalunya in 2002 found that the Tarragona area had 2483 hectares (ha) of Posidonia oceanica, the Barcelona region had 1275 ha, and the Girona coast only 302 ha. Near L’Escala the Posidonia oceanica beds in Cala Montgó and around Illa Mateua are responsible for attracting hundreds of scuba divers and snorkellers every summer, who come for the clear waters and the abundance of marine life associated with the meadows.

    The leaves and rhizomes of Posidonia plants increase the surface available to sessile species and offer shelter to mobile species, sustaining a diverse community in which more than 700 different species have been identified. A complex community lives on the leaves of Posidonia oceanica, composed of large quantities of micro- and macro-algae, hydroids and briozoa. These provide food for a wide variety of molluscs, crustacea and fish.

    Among the Echinoderms, Sea urchins are common. They are able to digest the tough lignin of Posidonia oceanica leaves . There are also delicate Feather stars (photo: Antedon Mediterranea) and Brittle stars. The most abundant Echinoderms are Sea cucumbers which play an important ecological role in filtering the sediment. Among them, Holothuria tubulosa predominates. Many species of worms (Polychaeta) are found living in the substrate within the Posidonia meadows and sponges are encountered around the rhizomes.

    Posidonia beds are especially valuable as nursery grounds for several commercial species such as anchovy, sardinella and bream which find food and shelter in the meadows during their juvenile stage. The most common resident species are Gobies (Gobius spp.), Wrasse (Labrus merula, L. viridis, Symphodus spp., Coris julis), and Sea bream (Diplodus spp,). There are also species living within the leaf canopy, like the Seagrass clingfish (Opeatogenys gracilis), the Seagrass pipefish (Syngnathus typhle). European seahorsea (Hippocampus hippocampusand Hippocampus guttulatus)depend on the seagrass for shelter and camouflage, and are the subject of Gaye´s Seahorse Project, which she began in 2013.

    Blotched picarel (Spicara maena) take on a brilliant irridescent blue colouration during the mating season, when they build and defend nests within the Posidonia beds. Damselfish (Chromis chromis) also lay eggs within the Posidonia beds, but it is their young that have an irridescent blue coloration, which changes to brown as they mature.

    The Cow bream (Sarpa salpa) is the only species of fish able to digest Posidonia leaves thanks to a bacteria in the gut. Huge shoals graze on the seagrass meadows each summer, just like herds of cows!

    Within the rhizome substrate, some sessile species are only found in healthy Posidonia oceanica beds. This is true of the the large fan mussel Pinna nobilis, which, due to their filter feeding habits, longevity and slow growth, are good indicators of water quality and mechanical stability within the meadows. Unfortunately most of the remaining large and ancient examples of Pinna Nobilis in Cala Montgó were destroyed during the severe storm on 26th December 2009 along with an estimated 25% of the Posidonia oceanica meadow. Pinna nobilis is a protected species, but like Posidonia it is also vulnerable to damage from the number of pleasure boats anchoring in Cala Montgó each summer.

    Gaye Rosier has been carrying out research into Posidonia oceanica for the past 16 years. Since 2009 she has also been a voluntary coordinator for the Silmar Project researching two L’Escala research stations, located in Cala Montgó and near Illa Mateua. She scuba dives at these locations to monitor the health of the Posidonia oceanica beds and to gather data on indicator species that show how the ecosystem is coping with the impacts upon it. Volunteer divers from all over the world have been coming to L’Escala during spring and summer to help Gaye with this marine conservation activity.

    “One of the most destructive things we see affecting the Posidonia meadows in Cala Montgó is pleasure boat anchoring. Posidonia plants grow very slowly and an anchor can destroy decades of growth in seconds” said Gaye. 

    The Cala Montgó transect now lies within the Parc Natural del Montgri, les Illes Medes i el Baix Ter and Gaynor and her team of volunteers will be assessing the improvements as protective regulations come into force, the most important of which should be a strict regulation of anchoring activity.

    So the next time that you see piles of brown leaves on the beach, remember! It is thanks to the presence of Posidonia oceanica that Escalencs can benefit from the transparent waters and abundant marine life that attracts so many beach tourists to the lovely sea-side town of L’Escala.

    *Posidonia oceanica meadows are protected at the European level, under the European Union’s Habitats Directive as a priority habitat (Dir. 92/43/CEE 21/05/92 and 97/62/CE 27/10/1997) and as a species (Bern Convention, Annex 1). Bottom-trawling is expressly forbidden on seagrass meadows (Fishing regulation 1626/94). At the national and regional levels, Posidonia oceanica meadows are protected in Spain (RD 7/12/1995, BOE nº310) and in Catalonia (Spain, Orden 91.210.098 DOGC nº 1479 12/08/1991), where all seagrass species are protected.

    In the strictly protected area of Illas Medas, 54 moorings have been installed and free anchoring has been banned since 1994. The costs of installation and management are largely covered by a small fee of €3.5 per mooring user.

  • Photography

    The issues around photographing seahorses in the natural marine environment

  • Research Assistants

    Opportunities to scuba dive with, and closely study, wild seahorses are very few and far between. The participation of a very small number of experienced divers who are able to join the Seahorse Project as research assistants on a self-funding internship basis are welcomed.

  • Seahorse Conservation Status

    Hippocampus guttulatus female seahorseUnfortunately, there´s a huge human appetite for these animals and they are sold as souvenirs, and sometimes even snacks, round the world. They are used mainly for medicinal purposes in China, Japan and Korea, as they are believed to treat asthma, sexual dysfunctions, pain, and other ailments. Although there is no scientic proof of the effectiveness of such treatment, the demand for seahorses has exploded in the past few decades, mirroring China´s economic growth.

    Fisheries all over the world supply this demand, with seahorses that are either targeted directly, or captured unintentionally (as bycatch) in bottom-trawl fisheries. By 2001, at least 25 million seahorses were traded by 77 countries – more than 70 tonnes!

    Seahorses are also popular in aquariums (selling for €100 – 500 each). Thankfully they are now being successfully bred in captivity by the leading authority in Spain – Miquel Planas, University of Santiago de Compostela - who has spent a decade of the research to achieve a 90% success (survival) rate.

    The Convention on the International Trade of Endangered Species (CITES) lists all seahorse species on its Appendix II, recognising that they may become threatened with extinction unless trade is closely controlled. In order to trade seahorses internationally, countries who have signed the CITES agreement must control and monitor exports, granting export permits only where it is clear that trade does not threaten wild seahorse populations. Nevertheless, illegal harvesting and trade occurs, and several countries have opted out of the CITES agreement.

    In January 2010, 25,000 seahorses were seized from a warehouse in Peru, which belonged to a Chinese citizen who had planned to export them to Japan via Hong Kong. Only a month later in Panama, 20,000 seahorses were discovered hidden inside the stomach of a fish from Peru. In Hong Kong seahorses sell for 550 USD/lb.

    Victor

    Recent research comparing seahorse numbers in no-take fishing zones and adjacent areas suggests that such measures do not benefit seahorses. In fact the population of seahorses was found to be lower in the no-take zones correlated with a higher number of seahorse predators. A better way to protect seahorses is via preserving their habitats.

    They commonly live in seagrass beds, mangroves, and coral reefs in coastal shallow waters, which are all highly sensitive to pollution, climate change and other human impacts. For example, the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 destroyed seagrass beds, driving down populations of an already-threatened pygmy seahorse species that inhabits the area. In the Med the seagrass Posidonia oceanica is listed as a protected species but is still declining due to human impacts.

    Current research, combined with customs and trade records, shows that seahorse populations have undergone rapid declines. The Ria Formosa lagoon in Portugal was an area that became famous for its European seahorse population. However, after several years of study, these seahorses almost totally disappeared and no-one is sure exactly why (although illegal fishing is suspected).

    There are still many unanswered questions, as seahorses are very difficult to study in the wild. They are listed in the IUCN Red List as Data Deficient and organisations such as iSeahorse and the Seahorse Trust encourage divers to report their sightings to their databases. 

    During the Seahorse Project 2014 research season, 28 individuals were found, about half of these were spotted regularly, others only a few times. A photo base has been built up (without using flash photography so as not to stress these sensitive creatures) in order to recognise individuals and be able to monitor their movements from year to year.

  • Seahorse News

    Latest news on research into European seahorses on the Costa Brava

  • Seahorse Project

    The Seahorse Project is the ongoing study of a breeding population of European seahorses developed on the Costa Brava by Gaye Rosier.

  • Seahorse Project - July 2015 Update

    Beauty 29.7.15Many of the seahorses that research volunteers were monitoring last summer have returned to to breed again this summer. Danny and Queenie are still a couple, and Danny has had at least one pregnancy so far. They have adopted a different territory within the Seahorse City area this year. Eagle-eyed volunteer research divers have also spotted several new individuals, and had the honor of choosing their names.

    A strange finding was a black female Hippocampus hippocampus that we've named Beauty. Normally they are well camouflaged to blend in with the algae or dead Posidonia oceanica roots. The black female was vulnerable as she really stood out against the sand and algae and could be spotted by a tourist or predator. She was also missing her right eye, making her doubly vulnerable to being eaten by the many octopus living there! We expected to find her easily when we returned for a second survey dive, but she had disappeared.

    According to The Seahorse Trust, with which we form part of The Seahorse Alliance, the dark colouration was dues to stress. No wonder after losing an eye, although the injury did not look very recent. Seahorses are very susceptible to stress, and carry dormant viruses that can mulitply and cause the death of the animal if stress is prolonged. This is why we do not use flash when photographing them. Let's hope that she has hidden herself away successfully and we are able to find her again, and monitor her throughout the summer.

  • Seahorse Project - May 2015 Update

    White Eyes 8.7.15 compOur conservation research season has started and a seahorse survey dive in a secret location on the Costa Brava, Spain, this month revealed the first returner to the Seahorse City research area. She is a Hippocampus guttulatus named "White Eyes". Located about 25 meters from where she was living last summer, she was alone and the male thought to be her mate, "Mike", was not seen on this ocassion.

    Algae is beginning to develop to provide the cover that seahorses require when feeding outside the relative safety of the Posidonia oceanica seagrass meadow. However, the lovely weather has brought many tourist boats that are anchoring in and around this area, causing considerable disturbance. In fact, apart from a few large features, it was very difficult to recognise the specific spots where last summer's 28 individual seahorses were living and being monitored. 

    The seahorses' preferred food source – mysis shrimps - is now in evidence, but not as plentiful yet as during the height of summer. The unusually high April/May temperatures are warming the Mediterranen sea quicker than last year, which will reinforce the increasing daylight hours effect upon the seahorses' egg production and the length of gestation. This should result in a bumper year for seahorse reproduction at Seahorse City!

    An article on the Seahorse Project has been published here with a video of "Mr Itchy" showing his comical scratching behaviour last summer. Fortunately he survived the parasite attack and stopped scratching.

    Volunteer research divers who join for at least three weeks are able to take part in the Seahorse Project research.

  • Seahorse Project - September 2015 Update

    What an amazing summer we have had researching European seahorses at Seahorse City!
    Our total count in the seahorse photobase is now 54 individuals identified, with 26 of those being new discoveries this season. 5 Hippocampus hippocampus and 11 Hippocampus guttulatus returned to our study area to breed, one pair for the third year running. Of the new seahorses found this year, 16 were H. guttulatus females.

    Volunteer research divers at Seahorse City have set several records this summer in terms of the numbers of seahorses found per survey and also the unusual nature of some individuals or behaviour observed:

    • First black seahorse
    • First one-eyed seahorse
    • First inter-species mating filmed*
    • First data on breeding cycles
    • First data on synchronised breeding between two pairs living 45 meters apart
    • Smallest individual
    • Smallest pregnant male

    *That was a big surprise as there is little known about this phenomenon and also because the pair were known from 2014 when they were definately not a couple.

    Our one-eyed seahorse, Beauty, is doing well and is seen regularly. However, she is not alone. Another one-eyed individual was found, and named Jack. He has been breeding with Blondie, who was first seen in 2014, and we were able to monitor two of his pregnancies and also film them mating. Quite a few eggs were lost, as he is smaller than her, as you can see in this photo by volunteer Jasmine Corbett, but during the peak breeding season they were mating every 16 days!

    Blondie and Jack matingOne-eyed Jack has a normal colouration and I recently found another black individual, who I named Zebra due to his whitish stripes, that has both eyes. Therefore, Beauty is probably naturally black, rather than changing due to stress, which is good.

    We have continued to share our data with The Seahorse Trust (as a member of the Seahorse Alliance) and with Project Seahorse. Both organisations have been impressed with the quantity and quality of our observations as citizen scientists. In fact, the Seahorse Project is the only seahorse research group to contribute a whole year of data to the Project Seahorse world-wide database using their Trends Toolkit.

    Although many volunteers have been marine biology students enjoying affordable work experience, regular divers with good buoyancy skills and a keen eye have been just as successful in spotting seahorses.

    For example, Chris, from Belgium, spotted the tiniest male - who turned out to be the smallest found to be pregnant. Another great example is Louise, who found a seahorse in a totally different location whilst surveying bryozoans for our Silmar Project research. 

    Volunteers who find a new seahorse are rewarded by choosing its name. We now have seahorses named after most of our volunteers, their relatives, and even a beloved pet!

    If you would like to name a seahorse and receive a photo of it, you can Sponsor a Seahorse. All contributions will help us to continue the Seahorse Project research into the future. Contact This email address is being protected from spambots. You need JavaScript enabled to view it. for information

  • Seahorse Project research by citizen scientists

    Hippocampus guttulatus. Copyright Gaye Rosier, Kenna Eco Diving, SpainOpportunities to scuba dive with, and closely study, wild seahorses are very few and far between. In fact, Gaye searched for seahorses on the Costa Brava for 15 years before discovering a location where both species of European seahorses, Hippocampus hippocampus and Hippocampus guttulatus, return to breed every summer. 

    Many volunteer divers and marine biology students have taken part in the Seahorse Project over the past three years. From 2016 Gaye will be concentrating on the July - August peak breeding season and accepting only a very small number of self-funding research assistants to join her for this unique fieldwork experience.

    European Seahorses, Hippocampus hippocampus and Hippocampus guttulatus, living in the Mediterranean Sea have their preferred coastal habitats in Posidonia oceanica meadows. However, these seagrass meadows are being destroyed by coastal development and tourism in so many places. Even where seahorses still exist they are difficult to spot: they are small and able to camouflage themselves exceedingly well, changing colour to blend in with their environment.

    Seahorses are amazing, cryptic creatures, unlike other fish. They don't have scales but skin covering bony plates, often with many frilly appendages that serve to increase their camouflage. The jaws are united together in a pipe snout, with a small toothless mouth. The family name Syngnathidae means "fused jaw". They feed on tiny Mysis shrimp and zooplankton, prey which are easily digestable as they have no stomach and cannot store food. An adult eats 65 to 70 shrimps per day while baby seahorses need to eat 3000 planktonic shrimps per day!

    The seahorse´s typical horse-like head allows a greater range of movement than their pipefish cousins. The head is very mobile, with  muscles in the neck which can be tensed and quickly released to catch passing prey. This evolutionary development, called pivot-feeding, gives seahorses a feeding advantage in terms of speed and stealth. There´s a great slow-mo video of pivot-feeding in action on YouTube.

    Compared with the typical fish anatomy seahorses hardly look like fish at all, the difference is striking. Pelvic fins are missing, anal and caudal fins are very small or missing. The prehensile tail is long and can withstand considerable crushing, for example from a turtle's jaws, due to being articulated. During swimming, propulsion is given by dorsal fin movement, with the participation of the pectoral fins beating 35 to 70 times per second.Generally seahorses prefer to remain stationary, the tail gripping a holdfast of seagrass or algae, where they can be well hidden from predators whilst feeding.

    Seahorse love Copyright gaye Rosier, Kenna Eco Diving, SpainThe Seahorse Project has been researching the size of territory utilised by individuals and mating pairs, we have found that paired males keep to a small area of just a couple of square meters while their female partners have a larger, overlapping territory of around 10 square meters. Females visit their mates each morning for a greeting/bonding session.

    Gaye was surprised to find that Danny, pictured above, who was pregnant five times during June to October 2014, could reliaby be located within his small territory almost every time she surveyed. It was a different story with unattached females. They travelled around a lot, presumably looking for a mate, with Topsey moving almost 100 meters from her original position over the course of two weeks. In 2014 volunteers studied 28 individual seahorses and in 2015 the number rose to over 50 catalogued into Gaye Rosier´s photo-base.

    The seahorse reproductive system is unique: during mating females pass their eggs, via their ovipositor, to the male breeding pouch, the marsupium. Here the eggs are fertilized by the male and provided with oxygen and nourishment during their development. After 2 to 4 weeks, depending on the number of hours of daylight and sea temperature, the male gives birth to hundreds of baby seahorses. Birthing usually occurs at night, to avoid predators, as the young are released to form part of the zooplankton for several weeks. In the wild less that 1% survive this stage. Those that do, then settle down into the relative safety of a holdfast in the seagrass and by six months of age they can begin reproducing. 

  • Seahorses and flash photography

    Worldwide, seahorses (genus Hippocampus) populations and their relatives in the family Syngnathidae (pipefishes, seadragons and pipehorses) are threatened by degradation of their estuarine, seagrass, mangrove and coral habitats (Olden et al. 2007), incidental capture in fishing gear (bycatch) (Vincent 1996), and overexploitation for use in traditional medicines and in the aquarium trade (Salin et al. 2005).

    As a result all species of seahorse are on Appendix II of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES 2002), which restricts their international trade.

    Seahorses have a number of traits that make them vulnerable to overexploitation including low mobility, small home range, pair bonding behaviour and extended parental care. They also live in coastal habitats that are increasingly facing human impacts leading to their destruction.

    In particular, Hippocampus guttulatus Cuvier, 1829 and Hippocampus hippocampus Linnaeus, 1758 (two European species of seahorses) are also listed under OSPAR, European CITES (Curd 2009), the Bern Convention and the Barcelona Convention (Abdul Malak et al. 2011) and protected by the UK Wildlife and Countryside Act of 2008 (DEFRA 2008). However, as few data are available across most of their geographic range, neither species can be reliably classified in terms of global level risk according to IUCN categories, and they are listed as "data deficient" (DD).

    Although they are not closely related, genetically, both European seahorse species have similar life history traits with low mobility, small home ranges, low fecundity, lengthy parental care and mate fidelity. Seahorses produce pelagic young which can live in the plankton for up to eight weeks before settling in their adult habitat. Very few survive to this stage and little is known about individual populations of seahorses.

    H. guttulatus (the spiny or long snouted seahorse) shows a marked preference for habitats with algae or seagrass coverage, but it is frequently found on the edges of seagrass habitat and it is believed there is a trade-off between the shelter of the seagrass and the availability of prey in more open water with better water exchange (OSPAR, 2009a). H. guttulatus inhabits shallow waters during summer months (as little as 1.5m depth) but migrates to deeper waters in winter, a journey which can take several weeks due to their ineffective fins.

    Pixie, Hippocampus hippocampus, Copyright Gaye Rosier Photo taken by Gaye Rosier, Seahorse Project, without flash by adjusting camera settings to allow in more light.

    H. hippocampus has a much less selective habitat preference than H. guttulatus and can be found on artificial structures. H.hippocampus generally inhabits deeper water than H. guttulatus (preferring minimum water depths of 10 m) but is believed to undertake a similar migration journey to deeper water over winter (OSPAR, 2009b).

    Many species of seahorse are highly territorial with small home ranges and high levels of site fidelity (Garrick-Maidment et al. 2010). The size of home ranges appears to be smaller for males.

    Seahorses are enigmatic species, with a crypto-benthic nature (live near the seabed and hide or are camouflaged) and unique characteristics where the male has a brood pouch and "gives birth" to the young. They are ofter found in easily accessible, shallow, near shore habitats, for example seagrass, and as a result they are a popular subject for professional and recreational underwater photography.

    Photography is also being increasingly used to to identify individual seahorses as each has a unique pattern and set of projections on its skin. Photographs of seahorses, collated from both recreational divers and focused surveys can be used in conjunction with pattern matching software to assess populations and movements of these species (Goffredo et al. 2004).

    However, using flash photography with seahorses is a contentious issue. Using the precautionary principle, it is best to avoid using a flash so as not to risk impairing, even temporarily, the visual acuity upon which a seahorse's survival depends.

    Seahorses are believed to have a well developed acute visual system (Lee & O’Brien 2011). They are generally considered diurnal feeders (i.e. feed during the day), relying heavily on their vision to locate and capture prey.

    Vision is thought to play an important role in crypsis (ability to avoid observation or detection) for seahorses (which can change skin colour and texture to match their surroundings) as well as in locating mates (Foster & Vincent 2004). In addition, vision is likely to play an important role in sexual selection and mating, for receiving visual ‘cues’ such as animal size, morphology and colour changes (Rosenqvist & Berglund 2011). Any damage to seahorse vision therefore has the potential to negatively impact their survival or reproductive potential.

    Studies have shown that the visual systems of seahorses, like most fish, have evolved specific adaptations that can be related to the depth and colour of water in which they live, and to specific visual tasks such as predator avoidance and food acquisition (Bone et al. 1996).

    Both European species are believed to be diurnal. In comparison with a human retina, the seahorse retina receives approximately ten times more illumination when exposed to an identical light source. Flash use at night or in low light conditions (twilight) would likely result in temporary visual impairment of any species due to the slow light adaptation response, and may modify behaviour or induce a stress response (MMO 2014).

    Many seahorses pair-bond, if not for life, then on a seasonal basis, and it has been demonstrated that the seahorse reinforces its pair bonds by daily greeting (Vincent 1995). Disorientation or a behavioural response to a flash in terms of moving away from their current location may therefore disrupt pair bonding.

    References:

    Abdul Malak D., Livingstone S.R., Pollard D., Polidoro B.A., Cuttelod A., Bariche M., Bilecenoglu M., Carpenter K.E., Collette B.B., Francour P., Goren M., Hichem Kara M., Massut ı E., Papaconstantinou C., Tunesi L. (2011) Overview of the Conservation Status of the Marine Fishes of the Mediterranean Sea. IUCN, Gland, Switzerland and Malaga, Spain: vii + 61 pp. ISBN: 978-2-8317-1307-6.
    Bone, Q., Marshall, N.B., Blaxter, J.H.S. (1996). Biology of Fishes, Vol. Chapman and Hall, London.
    CITES. (2002) Conservation of seahorses and other members of the family Syngnathidae. Twelfth Meeting of the Conference of the Parties, Santiago, Chile. Available at: http://www.cites.org/eng/cop/12/doc/index.shtml.
    Curd A. (2009) Background document for the short-snouted seahorse Hippocampus hippocampus. OSPAR Commission, Biodiversity Series.
    DEFRA. (2008) UK Wildlife and Countryside Act of 2008. Available at: http://www.legislation.gov.uk/uksi/2008.
    Foster, S.J., Vincent, A.C.J. (2004). Life history and ecology of seahorses: implications for conservation and management. Journal of Fish Biology 65:1-61.
    Garrick-Maidment, N., Trewhella, S., Hatcher, J., Collins, K., Mallinson, J. (2010). Seahorse tagging project, Studland Bay, Dorset, UK. Marine Biodiversity Records 3.
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