The short-snouted seahorses have been found at three locations. Pic by Dan Sprawson/ZSL
Colonies of rare seahorses are living and breeding in the River Thames, conservationists have revealed.
The short-snouted variety are endangered and normally live around the Canary Islands and Italy.
Experts at London Zoo said the species had been found at Dagenham in east London and Tilbury and Southend in Essex, over the last 18 months.
The revelation coincided with new laws which came into force on Sunday to give the creatures protected status.
The seahorses, or Hippocampus hippocampus, are now protected under the Wildlife and Countryside Act 1981.
They are usually found in shallow muddy waters, estuaries or seagrass beds and conservationists said their presence in the Thames is another good sign that the water quality of the river was improving.
Alison Shaw, from London Zoo, said: "These amazing creatures have been found in the Thames on a number of occasions in the last 18 months during our regular wildlife monitoring work.
"It demonstrates that the Thames is becoming a sustainable bio-diverse habitat for aquatic life.
"It is not clear how endangered short-snouted seahorses are because there is little data known, particularly in the UK, so every scrap of information is valuable.
"Now they are protected conservationists are more relaxed about telling the world they are there."
Both the short-snouted and long-snouted seahorse are kept and bred in the aquarium at London Zoo in Regents Park.
Aquarists are studying their life history and behaviour so their wild habitats and requirements can be protected.