Seahorses are a unique group of sea fishes
Seahorses are very unlike your typical fish be it a Salmon, Trout, Cod or Goldfish. In body shape they are worlds away from flatfish like Plaice or Sole. They are unique in that they appear to stand upright with a head and neck like those of a horse.
Seahorses are poor swimmers. Their tails are able to grasp and to hold, so they use them to anchor themselves to seaweeds and seagrasses while they feed by sucking in any small prey items that happen to stray within their reach either floating in the water or crawling on the bottom. Their lives are mainly sedentary, and their diet consists mainly of small crustaceans, fish eggs and plankton.
Natural selection over a very long period of time has resulted in seahorses having excellent camouflage. Those that stood out from their surroundings fell victim to predators; those that blended in survived and lived to breed and pass on the genes that gave them the natural advantage.
In addition to their sitting and waiting lifestyle and camouflage, many of the 45 or so species found worldwide have bony armour and spines rather than scales to further deter predators from eating them. Seahorses are classified with their closely related pipefishes that are similarly armoured, but are much more numerous and are far more common.
We have only one, possibly two, species of seahorse in Ireland: the Short-snouted Seahorse and the Spiny Seahorse. Both average about 12cm long and both are regarded as being very rare with limited information about their distribution ranges. Since they are largely sedentary they do not disperse far from where they are born. However, storms do spread them around.
As its name tells us, the Short-snouted Seahorse has a short snout, ‘short’ being defined as less than one-third the length of its head. And its short snout is upturned. It also has a knob-like spine above each eye. It is found in shallow, inshore waters including muddy estuaries and rocky seashores. There are only seven records of it from counties Dublin, Waterford, Cork, Clare and Antrim.
The Spiny Seahorse is slightly bigger and has a longer, straighter snout, lots of long spines and a mane of spines down its neck and back. Its home range is the Mediterranean, but it is believed to disperse northwards to our shores. While some books record it as being present in Ireland, Biodiversity Ireland maps show no records for it.