In what habitats can we expect to meet seahorses on our coasts? The answer is quite simple: mostly where you never go! These animals are not quite common on beautiful sea fan walls or on deep wrecks. Even if the data collected in Hippo-ATLAS show a certain variety in their habitat, seahorses dwell mainly on muddy sandy shallow bottoms, where the water is not often clear…The biggest French populations of seahorses are to be found in lagoons such as Arcachon Bay and Hossegor Lake for the Atlantic, and Thau lagoon for the Mediterranean. But they can also be met here and there, almost everywhere along European and Mediterranean coasts. ...
Long-snouted seahorses (Hippocampus guttulatus) may be found in quite different habitats: in shallow waters on algae covered rocks on the French coast between Cerbère and Port-Vendres; on sandy bottoms in Cymodocea seagrass in Corsica or Giglio islands; on sandy slopes or at the bottom of shallow walls in Marseille ; in eelgrass (Zostera marina) in Brittany where they seem to be more easily spotted at night...
Short-snouted seahorses (Hippocampus hippocampus) dwell mainly on shallow sedimentary bottoms, sometimes even slightly muddy in the Mediterranean. In the Atlantic Ocean French coasts, they may also be found on sandy bottoms with shell fragments or in scattered eelgrass fields.
Some Hippo-ATLAS ecological results
Mineral environment : kind of substrate (results on 15/09/2011)
Short-snouted seahorses are found mainly on soft substrate (mud, sand, occasionally dead shells), sometimes with pebble or stones. Long-snouted seahorses live in more varied habitats, even on hard substrates such as rock or coralligenous rock in about one third of the encounters.
Living environment : bottom organisms (results on 15/09/2011)
The first obvious conclusion of the Hippo-ATLAS survey is that seahorses do not live uniquely in seagrass (less than one third of encounters are in seagrass [herbier]).
One can also observe differences between species. Short-snouted seahorses are most often found on totally bare soft substrate, and in places occupied by filter feeders such as sponges and sea squirts or detritus feeders such as brittlestars. Long-snouted seahorses are usually observed close to marine plants (mainly algae), and rarely on bare bottoms.
Depth repartition (results on 15/09/2011)
Short-snouted seahorses were met mainly in medium depths from 2 to 9 meters. Even if they were also mostly encountered shallower than 10 meters., long-snouted seahorses were recorded from very shallow waters down to more than 30 meters deep.