Amorous seahorses: Underwater love at London Zoo

Conservationists encourage animals to mate by supplying the fishy couples with their own private tanks

Sometimes all a seahorse needs is a little privacy. Conservationists have discovered that the secret to the fish's mating success lies in creating private "honeymoon suites" for breeding.

Seahorses are a protected species in the UK, and London Zoo is managing to boost populations of native short- and long-snouted varieties by providing couples with their own private tanks. This technique has allowed the institution to give more than 300 seahorses to breeding and research projects across Europe.

The zoo's work in breeding the declining fish has been taking place in a hidden warehouse behind the public aquarium since 1996. Now, for the first time, the public can watch the conservationists in action at a special exhibit, which opened yesterday.

Brian Zimmerman, curator of the aquarium at London Zoo, said: "We noticed when we kept the seahorses in bigger groups, a pair would start a courtship dance, and another male – or sometimes a female – would try to muscle in and disrupt their ability to complete courtship."

"Now we put a mixture of males and females in a larger courtship tank, then, when we observe a couple pairing off, we give them their own individual tanks. It's their honeymoon suite."

Seahorses give very clear indications of their chosen partner before they actually mate. At first light in the spring they will perform an elaborate flirtation, entwining tails, twirling each other round in a dance and promenading along the bottom of the tank. When their keepers observe this behaviour the fish are quickly removed to their own private breeding tank.

To keep more of the offspring, known as fry, alive, London Zoo has also pioneered the use of spherical tanks with a current running through them to replicate ocean life. After birth, they are immediately removed, allowing their parents to get on with making a new batch. The fry are later moved into the mixed tanks, where they can select a mate.

Seahorses often mate for life, so once paired off, they can be kept in the same tank indefinitely. It is the males that carry the eggs to gestation, after the females deposit them in their brood pouch.

Conservationists believe seahorse populations are dwindling rapidly. The zoo's work is part of Project Seahorse, a worldwide breeding and conservation programme which it has been involved with since 1996.

Dr Heather Koldewey, field conservation manager of Project Seahorse, who travels the world to boost populations of the endangered fish, said: "Seahorses provide a focus for us to address some of the ocean's major threats – getting it right for seahorses will mean we have helped most marine life... Every year, millions of seahorses are stripped from the sea by shrimp trawlers as their nets rake the bottom; they are overfished by small-scale or subsistence fishers; their inshore coastal habitats are subject to pollution, dredging, mining, blasting, farming, and other human damage."

Scientists from around the world will meet in Faro, Portugal, next month to discuss what many believe is a grave situation for seahorses across the planet.

Dad's left holding the babies as mum's out dancing with the girls!

* Unlike most other animals, pregnancy is left to the men. Male seahorses have a brood pouch into which the female deposits up to 1,500 eggs. Though more than 1,000 can be born at once, fewer than 0.5 per cent of infants survive adulthood in the wild.

* Many seahorses are monogamous and mate for life – but they still like to flirt, and not necessarily with the opposite sex: both males and females are happy to twine tails and do a bit of synchronised swimming with fish of either gender.

* Seahorses are rather weak swimmers and often die of exhaustion in stormy seas. They propel themselves using a fin on their back that flutters up to 35 times per second.

* They anchor themselves by curling their tails around sea grasses and corals.

* Seahorses may be tiny but they have a big appetite; they graze continually and are able to consume 3,000 or more brine shrimp a day.

* Coastal habitat depletion, pollution and harvesting have made several species vulnerable to extinction.