Short Snouted Seahorse (Hippocampus hippocampus) and the Spiny Seahorse (Hippocampus guttulatus)

There are two species of seahorse in UK waters: the Short Snouted (above left) and the Spiny (above right, which is also known as the Long Snouted Seahorse). They can both grow to a maximum length (or height) of around 15 cm to 17 cm and live in shallow, inshore waters in the warmer months of the year amongst rocks, mud, seaweeds and seagrass which they cling to with their prehensile tails.

The main difference between the two species is, unsurprisingly, the length of the snout, although the Spiny Seahorse can be further distinguished by the presence of longer spines on the back, just above the dorsal fin and especially on the head. Both species of seahorse can change colour to match their surroundings or when they are doing a courtship dance. Seahorses feed mainly on very small marine crustaceans. Both seahorse species have a wide distribution around the UK and are found all around the British Isles and Ireland up into the Shetland Isles.

Seahorses are often taken by predatory fish and have to rely on camouflage to avoid detection as they are poor swimmers, with only their small dorsal fin undulating at 35 to 70 beats per second to provide them with weak forward propulsion. Seahorses have an unusual breeding pattern; males vie with each other for a mate and once a pair bond is formed with the female they reinforce this daily to maintain it with an elaborate courtship dance.

By pairing up in this way in the cooler temperate waters around the UK it keeps them together for the breeding season which runs from early April to October. However recent research by The Seahorse Trust has shown they may even be breeding during the winter in deeper water, after a long migration out of the shallows which protects them from strong winter storms. The female passes eggs on to the male through an ovipositor, who then self-fertilises them within his own body. The eggs grow and hatch within the male who then gives birth to live young that are completely independent from the moment of birth.

While breeding populations of seahorses have been found in the Thames and Plymouth Sound; in other areas where they are present such as Studland Bay in Dorset threats such as drilling for oil and overuse of anchors threaten their future and in recent years the populations have declined rapidly. For this reason, there is much concern over the long-term stability of UK seahorse populations. The IUCN (International Union for the Conservation of Nature) does not have enough data on seahorse numbers to make an accurate assessment of their numbers and class them as Data Deficient.

In 2008 The Seahorse Trust managed to get both native seahorse species protected under the Wildlife and Countryside Act meaning that it is an offence to kill, injure, capture or possess seahorses in British waters. In addition to this seahorses are now protected under CITES (Convention on International Trade in Endangered Species).

Seahorse Sightings and The Seahorse Trust

If you see a seahorse please report it to The Seahorse Trust which runs the National Seahorse Database (they would love to hear of seahorses from all around the world, so please send them all in).

You can find a reporting form by clicking here and can e-mail it with any pictures to theseahorsetrust@gmail.com. Please include contact details in case they need more information.