Biodiversity & Conservation

Mytilus edulis and piddocks on eulittoral firm clay


<i>%Mytilus edulis%</i> and piddocks on eulittoral firm clay
Distribution map

LR.MLR.MytPid recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Recorded distribution in Britain and Ireland

The biotope is recorded in the River Blackwater in Essex, the Swale in Kent and in Morecambe Bay, Lancashire.

Habitat preferences

Temperature range preferences - Data deficient

Water clarity preferences - Medium clarity / Medium turbidity
Low clarity / High turbidity

Limiting Nutrients - Data deficient

Other preferences - Clay

Additional information

This biotope occurs in predominantly turbid waters which are vital for the suspension feeders, the dominant trophic group. The three piddock species are likely to be fairly specific with regard to substratum preferences. Petricola pholadiformis, for example, requires a fairly soft but firm and stable sediment in which to live and in Britain, its upper limit is usually determined by a change in substratum (Duval, 1963a), namely a lack of appropriate substrata. Richter & Sarnthein (1976) looked at the re-colonization of different sediments by various molluscs on suspended platforms in Kiel Bay, Germany. They found that Barnea candida was restricted to clay, and occasionally fine sand, and that substrate type was certainly the most important factor for this species, in contrast to depth that was the primary factor for all other piddock species. No information was found concerning the factors influencing the lower limits of their distribution.

The upper limit of mussel beds is often clear cut (see Lewis, 1964) and determined by physical factors such as temperature and desiccation, which may be synergistic, i.e. sudden mass mortalities at the upper limit of intertidal mussel beds are often associated with prolonged periods of unusually high temperatures and desiccation stress (Seed & Suchanek, 1992).

The lower limit of distribution is strongly influenced by predation, primarily from starfish but also dogwhelks and crabs. Tsuchiya & Nishihira (1985, 1986) noted that increase sediment or silt build up within the mussel bed matrix, reduced the available space within the matrix, changing species composition, presumably in favour of infaunal invertebrates, and reduced species richness.

The high silt deposition environment is also favourable for deposit feeders which may include the ragworm Hediste diversicolor and mud shrimps Corophium spp.

This review can be cited as follows:

Marshall, C.E. 2008. Mytilus edulis and piddocks on eulittoral firm clay. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 28/11/2015]. Available from: <>