Parvicardium (Cerastobyssum) hauniense (Petersen & Russel 1971), Copenhagen cockle (Molluscs)

 Compiled by: Fritz Gosselck, Germany

 1. Description / Ecological demands / Autecology

The cockle lives on vascular plants and algae in shallow, macrophyte rich, not exposed inlets like lagoons and large bays. It climbs on the plants using its foot and byssus threads. Preference to certain plant species is not known. Copenhagen cockle tolerates salinities between 7 and 16 psu (stenohaline brackishwater species). The tolerance of temperture variability lies between 0° C and -25°C. The length is up to 10 mm (in Danish lagoons), in German only up to 8 mm. Lifespan 1 to 1½ years. Reproduction from April/May and June/July. Often abundant, up to 10.000 ind./m² in areas of high productivity.

2. Distribution

P. hauniense occurs in the Baltic Sea from the Belt Sea up to the Aland Islands. Populations are known from the Puck Bay (Poland), in the Curonian lagoon (Lithuania), and from the coast of Skane to Gothland. The main distribution area is in Danish and German inlets of the Belt Sea and the Pomeranian Bodden. The species inhabits sheltered inlets and is rare on exposed coasts.

3. Importance

Parvicardium hauniense is endemic to the Baltic Sea. It is a characteristic species of the shallow, brackish-water inlets of the Baltic Sea.

4. Status of threat

P. hauniense is red-listed in the German part of the Baltic Sea as “potentiell gefährdet” (rare). The species is classified as vulnerable in Sweden.

5. Threat factors

Reasons for threat are the habitats loss (eegrass meadows and other submerged vascular plants), reclaiming of shallow areas, change of salinity and exposition due to coastal construction, and eutrophication. The habitats have been reduced to about one third during the past 100 years.

6. Conservation measures needed

Protection of the submerged macrophyte meadows in shallow bays and nearshore areas from eutrophication and coastal construction enhances populations of Copenhagen cockle.