Red List habitat classification > RL - Marine habitats > RLNEA - Atlantic > NEAA5.65 Neopycnodonte cochlear beds on exposed and tide-swept circalittoral rocks and cobbles

Neopycnodonte cochlear beds on exposed and tide-swept circalittoral rocks and cobbles

Quick facts

Red List habitat type code NEAA5.65
Threat status
Europe Data Deficient
EU Data Deficient
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


This habitat occurs in the circalittoral zone on both hard and mixed substrates. It has been recorded in exposed and tide-swept sites at depths of 60 - 150m in the Faial-Pico channel and the Formigas Bank in the Azores and in deeper waters on the upper slope of the Bay of Biscay between 200-500m. Sessile macrofauna is dominated by the oyster Neopycnodonte cochlear and the clam Chama circinata.  Some variance has been observed in the abundance of the two species although in shallower zones it may be exclusively Neopycnodonte . On hard substrates the two species growing together may build up to form a calcareous bioherm. The habitat has also been observed on mixed carbonate-volcanoclastic sediment plains where the two species form cobble to small-boulder sized clumps. N. cochlear is able to create thick mantles, serving as hard substrate for other species including foraminifera, bryozoan, ascidians, coral and sponges.

Indicators of quality:

Both biotic and abiotic indicators have been used to describe marine habitat quality. These include: the presence of characteristic species as well as those which are sensitive to the pressures the habitat may face; water quality parameters; levels of exposure to particular pressure, and more integrated indices which describe habitat structure and function, such as trophic index, or successional stages of development in habitats that have a natural cycle of change over time.

The overall quality and continued occurrence of this habitat is dependent on the presence of the predominate structural species, the oyster Neopycnodonte cochlear and the clam Chama circinata species which create the biogenic structural complexity on which the associated species depend. The density and the maintenance of viable populations of these species are therefore likely to be a key indicator of habitat quality, together with the visual evidence of presence or absence of physical damage.

Characteristic species
For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

This habitat has a widespread distribution (EOO >50,000 km2 ) and although not reported to occur in many locations (AOO <50) it is unlikely that the available data cover its full distribution. Because of the lack of information on area and any trends in quantity and quality expert opinion is this habitat should be considered Data Deficient for both the EU 28 and EU 28+.
Red List Category Red List Criteria
Data Deficient -
Red List Category Red List Criteria
Data Deficient -

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Biological resource use other than agriculture & forestry
    • Fishing and harvesting aquatic resources
    • Professional active fishing
    • Benthic or demersal trawling
    • Benthic dredging
  • Pollution
    • Marine water pollution
  • Natural System modifications
    • Siltation rate changes, dumping, depositing of dredged deposits

Habitat restoration potential

There is insufficient information to determine the recovery capacity of this habitat although shallow water oyster species are generally fast growing and relatively short lived (less than 20 years).

Trends in extent

Average current trend in quantity

Unknown Unknown
EU28 EU28+

Trends in quality

Average current trend in quality

Unknown Unknown
EU28 EU28+

Conservation and management needs

Conservation measures which prevent damage to the seabed where this habitat occurs will be beneficial. These include regulation of demersal fisheries, establishment of Marine Protected Areas (with regulation or prohibition of demersal fisheries) and measures to maintain water quality.

List of conservation and management needs

  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
  • Measures related to spatial planning
    • Other marine-related measures
    • Establish protected areas/sites
  • Measures related to hunting, taking and fishing and species management
    • Regulation/Management of fishery in marine and brackish systems


For each habitat a distribution map was produced from a wide variety of sources indicating known and potential occurrences of the habitat in 10x10 km grids within Europe. Occurrences in grid cells were given in two classes: actual distribution from relatively reliable sources (surveys, expert knowledge), and potential distribution based on models or less reliable indicators. Please download the fact sheet to see the map.

Geographic occurrence and trends

Seas Present or presence uncertain Current area of habitat (Km2) Recent trend in quantity (last 50 years) Recent trend in quality (last 50 years)
Macaronesia Present Unknown Unknown Unknown
Bay of Biscay and the Iberian Coast

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 430,484 > 18 Unknown These values are likely underestimated.
EU28+ > 18 Unknown These values are likely underestimated.
AOO = the area occupied by a habitat measured in number of 10x10 km grid cells.
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).

Characteristic species

The full list of characteristic species and genus are available above from the Summary. The species available in the EUNIS database are shown here.
Invertebrates Centrostephanus longispinus
Invertebrates Hydroides azoricus
Invertebrates Neopycnodonte cochlear
Invertebrates Spirobranchus polytrema
Species scientific name English common name Species group
Centrostephanus longispinus Invertebrates
Hydroides azoricus Invertebrates
Neopycnodonte cochlear Invertebrates
Spirobranchus polytrema Invertebrates

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
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