They are actually a type of fish related to the stickleback, but with their long horse-like snout, strange upright swimming style and delicate grasping tail, seahorses have fascinated us for centuries, spawning poems and seafaring legends.

Zoologists are warning that if we are not careful, those legends may be all we have left of these fascinating creatures unless we can find ways of halting an alarming decline in numbers.

Some populations are thought to have been cut by half in just five years, and one species in South Africa is now officially on the endangered list.

Habitat destruction

Humans are responsible for this decline in a number of ways - we are destroying their coastal habitats with holiday developments and pollution, leaving fewer and fewer places where they can lurk in the sea grass and pounce on their prey.

Seahorses are also being fished in huge numbers, mainly for their value in traditional Chinese medicine, where they are highly prized as treatment for asthma, lethargy and impotence.

At least 20 million of them are taken from the sea each year to meet this demand. Many hundreds of thousands more are turned into souvenirs for tourists or captured live for the international aquarium trade.

Project seahorse

An international programme known as Project Seahorse is being co-ordinated at London Zoo, where the warning is being made.

Curator Dr Heather Hall says a better understanding of the biology and ecology of the seahorse is imperative if action is to be taken to stem the decline.

Although the zoo has a successful seahorse breeding programme, aquarium keeper Brian Zimmerman warns that rearing the creatures is extremely difficult.

They need to feed constantly as they have no stomachs and will normally insist on live food. Unaware of this, many people buy seahorses at pet shops and watch helplessly as they starve to death within days.

Because most seahorses are not technically endangered, the trade is legal, and the project sees one of its aims as education, working with Chinese medicine practitioners to find alternatives to wild-caught seahorses. It also wants to persuade tourists that these beautiful creatures are much more attractive viewed live at an aquarium, rather than dead as a trinket sold in a market.