The low-crowned seahorse (Hippocampus trimaculatus) can exist in a variety of colours and patterns, ranging from golden orange to sandy coloured, with some individuals being completely black. It may also have dark spots on the first, fourth and seventh trunk rings. These spots are less visible on the darker individuals and are also more common in the male than the female. A number of low-crowned seahorses are striped with brown and white, in a zebra-like pattern. Some specimens found in Australia also have distinctive split spots on their first and fourth trunk rings. These trunk rings are visible as ridges around a seahorses’ body and are formed from skin being stretched over a series of bony plates, which are jointed in the tail (2).
The low-crowned seahorse (Hippocampus trimaculatus) has a distinctive low coronet, which is the bony projection or ‘crown’ on the top of a seahorse's head and coronet isvisible as five small points. It is also has sharp, hook-like cheek and eye spines and a narrow head (2).
As with all species of seahorses, it is the male low-crowned seahorse that becomes pregnant, and sexual maturity is reached when the brood pouch of the male is fully developed. The female seahorse places the eggs inside the male’s brood pouch, where he fertilises, protects and nourishes them. The low-crowned seahorse has a year-round breeding season, with a peak in Reproduction around March to May and also October. The gestation period averages 16 days with the maximum brood size reported to be 1783 eggs (5). The eggs have an average diameter of one millimetre with the length of the seahorses at birth averaging six millimetres (2).
Adult seahorses are very adept at camouflaging themselves in their surroundings, decreasing the likelihood of being preyed upon (2). The habitat of the low-crowned seahorse often contains octocorals or seaweeds which it uses to anchor itself to the sea floor with the use of its prehensile tail (4).
A marine species, the low-crowned seahorse is normally found at depths of around 10 metres; however, it has also been reported to have been found at a depth of 100 metres. The low-crowned seahorse can also be found in mangrove swamps and estuaries (4). This species is also found around shallow reefs with octocorals (coral lacking a stony skeleton) that have either a gravel or sandy bottom, and can also be found in deeper waters that have muddy bottom (2).
Surveys conducted from 2000 to 2001 suggest that the population across the entire range of the low-crowned seahorse is in decline. In the Philippines, fishers reported declines of between 50% and 95% in the number of seahorses caught from 1980 to 1997 (1). The main threat to this species is trading in the traditional Chinese medicine market, and it is one of the most widely traded seahorse species (approximately 35% of all seahorses traded). These seahorses are also caught and traded live for aquariums and curiosities (1).
The low-crowned seahorse is particularly at risk from intense fishing as it has a sparse distribution, low reproductive rates and reluctance to move from a site. Fishing techniques using bottom trawlers also pick up this species in the nets as bycatch. Its habitat is also under threat of destruction due to human activities (6).
In 1996 Project Seahorse produced documentation on the seahorse trade and consumption, this led to changes in the management regulation in Hong Kong, the European Union and Australia (2). In 1998 the low-crowned seahorse was placed under the Australia Wildlife Protection Act, requiring all exports of this species to have a permit, which are only given for approved management plans and captive bred individuals (1). In India they are protected under the Wildlife (Protection) Act of 1972 which bans the trade and capture of this species. It is also listed as Vulnerable in the Vietnam National Red Data book (1).
Project Seahorse has also so far set up 34 fishing sanctuaries in the Philippines where fishing is prohibited, improving the number and diversity of fish species present (7). Since 2002 all seahorse species are listed in CITES Appendix II which aims to ensure that trade across borders does not threaten the survival of the species or populations in question (2).
IUCN Red List (November, 2011) http://www.iucnredlist.org/
Lourie, S.A., Foster, S.J., Cooper, E.W.T. and Vincent, A.C.J. (2004) A Guide to the Identification of Seahorses. Project Seahorse and TRAFFIC North America. University of British Columbia and World Wildlife Fund, Washington D.C. Available at http://seahorse.fisheries.ubc.ca/Seahorses/IDguide.html
Sheng, J., Lin, Q., Chen, Q., Shen, L and Lu, J. (2007) Effect of starvation on the initiation of feeding, growth and survival rate of juvenile seahorses, Hippocampus trimaculatus leach and Hippocampus kuda bleeker. Aquaculture, 271: 469-478.
Nguyen, V.L. and Do, H.H., (1996) Biological Parameters of Two Exploited Seahorse Species in a Vietnamese Fishery. Proceedings of the 1st International Conference in Marine Conservation, Hong Kong.
Murugan A., Dhanya S., Sreepada R.A., Rajagopal S. and Balasubramanian T. (2009) Breeding and mass-scale rearing of three spotted seahorse, Hippocampus trimaculatus leach under captive conditions. Aquaculture, 290(1): 87-96.
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