Biodiversity & Conservation

Sea pens and burrowing megafauna in circalittoral soft mud



Image Mark Davies - Pennatula phosphorea and Turritella communis in muddy sediment. Image width ca XX cm.
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Distribution map

SS.SMu.CFiMu.SpnMeg recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Marine natural heritage importance

Listed under EC Habitats Directive
UK Biodiversity Action Plan
National importance Not available
Habitat Directive feature (Annex 1) Large shallow inlets and bays

Biotope importance

  • The opening of the burrows of Callianassa subterranea (and other burrowing shrimps) provide temporary refuge for fish such as the black goby Gobius niger and occasional errant polychaetes, particularly polynoid worms, inhabit the burrows (Nickell & Atkinson, 1995).
  • Nephrops norvegicus is known to be eaten by a variety of bottom-feeding fish including haddock, cod, skate and dogfish (Jones et al., 2000). In some areas, up to 80% of cod stomachs are found to contain Nephrops. Burrowing shrimps and echiuran worms are also found in the stomachs of bottom feeding fish.
  • If present in high numbers Amphiura filiformis provides an important link between the benthic and pelagic environments because it seems to be important in the diets of many fish and invertebrate predators including dab Limanda limanda, haddock Melanogrammus aeglefinus and Norwegian lobster Nephrops norvegicus (Baden et al., 1990). These predators do not generally consume the entire brittle star but crop only the arms, which are later regenerated. An energy budget estimated for the Amphiura filiformis population of Galway Bay suggested that arm regeneration contributed significantly to the total annual production of this species (O'Connor et al., 1986).


  • Nephrops norvegicus is the only species within the biotope that is of any commercial importance. Nephrops fisheries are of major economic importance and the species is fished throughout most of the geographic range of the biotopes in which it occurs including CMU.SpMeg. This includes both shallow, semi-enclosed sea loch areas, and open-coast grounds in deeper water such as the Irish and North Seas. In British waters the Nephrops fishery has grown rapidly since its inception in the 1950s. Nephrops is now one of the most valuable shellfish resources in the north-eastern Atlantic (Hughes, 1998b). None of the other species in the biotope are collected or harvested.
  • Thalassinidean shrimps such as Callianassa subterranea can be a pest of oyster fisheries. Oyster survival and growth is affected indirectly through sediment disturbance. As the shrimps burrow through the mud constructing their extensive burrows, sediment compaction is reduced to the point that oysters growing directly on the benthos sink into the unconsolidated mud and settling larvae and spat are particularly vulnerable (Feldman et al., 2000).

Additional information icon Additional information

EC Habitats Directive: Sea pen faunal communities can be found in some very sheltered examples of Annex 1 type Large shallow inlets and bays, and in Scandinavian fjords. UK Biodiversity Action Plan: Mud in deep water (Habitat Action Plan).

This review can be cited as follows:

Hill, J.M. 2004. Sea pens and burrowing megafauna in circalittoral soft mud. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 29/11/2015]. Available from: <>