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Tide-swept channels
Tide-swept channels occur where the constricted coastline acts as a funnel. They are found at the entrances to fjords, lochs and lagoons, between individual islands, and between islands and the mainland. The plentiful supply of food brought in on each tide supports rich and varied communities of marine life.
Tide-swept channel © JNCC
Many of the animals that live here, including soft corals, sea firs, sponges, anemones, and mussels are strongly anchored to the seabed. Common starfish, brittlestars, edible crabs, whelks and topshells are also found here.
Tide-swept rocky shores that emerge between the tides support seaweeds such as kelp and sea oak, which grow to great lengths in the currents. Smaller red and brown seaweeds also occur, and animals in these plant-dominated communities include limpets, barnacles, shore crabs, whelks and winkles.
Where the seabed is of coarse gravel, it is constantly moving and difficult to inhabit. Even here there are animals, such as sea cucumbers, worms and burrowing anemones.
The marine life in tide-swept channels can be affected by construction of bridges and causeways that disrupt the water flow. Edible species such as mussels may occur in large numbers, making them attractive to fisheries. Crabs, on the other hand, may be safer in tide-swept channels as the conditions make pot or creel fishing difficult.
A potential threat to the marine life of tidal channels arises from the growing interest in tidal power. The possible effects are largely unknown, but have the potential to be serious where a large number of tidal current devices are installed.
Brief description of European distribution
Tide-swept channels occur in Norwegian fjords, Scottish and Irish lochs and islands, the Pembrokeshire islands and the Menai Strait in North Wales. They also occur at the entrances of drowned river valleys in south-west England including the Dart, Tamar and Fal.
Maerl beds are also closely identified with tide-swept channels in the south-west (the Fal estuary) and the north of the British Isles (Orkney).
Conservation status / need
UKBAP Priority Habitat
Listed in Annex 1 of the Habitats Directive: Reefs, and large shallow bays and inlets.
Further information sources
Priority habitat descriptions
(PDF 1.5Mb) (UKBAP)
Very tide-swept faunal communities (JNCC)
Interesting fact
Between islands, the influence of strong tidal streams may be felt to a depth of 30 metres.
