The short-snouted sea horse, Hippocampus hippocampus, is very young and only 5cm long. Its discovery is a sign that sea horses may be breeding in the river.

Hippcampus hippocampus sea horses grow up to 15cm long and are normally found in the Mediterranean and around the Canary Islands. Although they have been seen around the coast of Britain in the past, this is the first time one has been found so far upriver.

It is thought that this could be because the quality of the Thames water has improved.

Emma Barton, a fisheries officer at the Environment Agency, said the sighting was a “really exciting discovery.”

The young sea horse was measured and then returned to the water.

If a colony of sea horses is breeding in the Thames, it is good news for the river. A recent online river survey found that more than half of river users (such as anglers and cyclists) think that

Thames wildlife is under threat from dangers such as pollution.