BIOTIC Species Information for Mytilus edulis
|Researched by||Lizzie Tyler||Data supplied by||University of Sheffield|
|Refereed by||This information is not refereed.|
|Scientific name||Mytilus edulis||Common name||Common mussel|
|MCS Code||W1695||Recent Synonyms||None|
|Additional Information||Mytilus edulis and Mytilus galloprovincialis often occur in the same location in the northern range of Mytilus galloprovincialis. As they both show great variation in shell shape due to environmental conditions (Seed, 1968, 1992), they are often difficult to distinguish. In addition, they may hybridize. However, in Mytilus galloprovincialis:
|Taxonomy References||Fish & Fish, 1996, Hayward & Ryland, 1990, Hayward et al., 1996, Tebble, 1976, Gosling, 1992(c), Bayne, 1976b, Clay, 1967(d), Gosling, 1992(a), Seed, 1992, Seed, 1995, Seed, 1968,|
||Feeding method||Passive suspension feeder
Active suspension feeder
|Typical food types||Bacteria, phytoplankton, detritus, and dissolved organic matter (DOM).||Habit||Attached|
|Bioturbator||Not relevant||Flexibility||None (< 10 degrees)|
|Height||Insufficient information||Growth Rate||See additional information.|
|Adult dispersal potential||<10m||Dependency||Independent|
|General Biology Additional Information||Mytilus edulis is one of the most extensively studied marine organisms. Therefore, this review is based on comprehensive reviews by Gosling (ed.) (1992a), Bayne, (1976b), Newell (1989), and Holt et al. (1998). Where appropriate the original source references in these reviews are given.
Mytilus edulis is gregarious, and at high densities forms dense beds of one or more (up to 5 or 6) layers, with individuals bound together by byssus threads. Young mussels colonize spaces within the bed increasing the spatial complexity, and the bed provides numerous niches for other organisms (see importance). Overcrowding results in mortality as underlying mussels are starved or suffocated by the accumulation of silt, faeces and pseudofaeces, especially in rapidly growing populations (Richardson & Seed, 1990). Death of underlying individuals may detach the mussel bed from the substratum, leaving the bed vulnerable to tidal scour and wave action (Seed & Suchanek, 1992).
Several factors contribute to mortality and the dynamics of Mytilus edulis populations, including temperature, desiccation, storms and wave action, siltation and biodeposits, intra- and interspecific competition, and predation. But predation is the single most important source of mortality.
Many predators target specific sizes of mussels and, therefore, influence population size structure. The vulnerability of mussels decreases as they grow, since they can grow larger than their predators preferred size. Mytilus sp. may be preyed upon by neogastropods such as Nucella lapillus, starfish such as Asterias rubens, the sea urchin Strongylocentrotus droebachiensis, crabs such as Carcinus maenas and Cancer pagurus, fish such as Platichthys flesus (plaice), Pleuronectes platessa (flounder) and Limanda limanda (dab), and birds such as oystercatcher, eider, scooter, sandpiper, knot, turnstone, gulls and crows (Seed & Suchanek, 1992; Seed, 1993). Important predators are listed below.
Fouling organisms, e.g. barnacles and seaweeds, may also increase mussel mortality by increasing weight and drag, resulting in an increased risk of removal by wave action and tidal scour. Fouling organisms may also restrict feeding currents and lower the fitness of individual mussels. However, Mytilus edulis is able to sweep its prehensile foot over the dorsal part of the shell (Thiesen, 1972, Seed & Suchanek, 1992). Fouling by ascidians may be a problem in rope-cultured mussels (Seed & Suchanek, 1992).
Diseases and parasites
Mytilus edulis is a filter feeding organism, which collects algae, detritus and organic material for food but also filters out other contaminants in the process. Shumway (1992) noted that mussels are likely to serve as vectors for any water-borne disease or contaminant. Mussels have been reported to accumulate faecal and pathogenic bacteria and viruses, and toxins from toxic algal blooms (see Shumway, 1992 for review). Bacteria may be removed or significantly reduced by depuration (removing contaminated mussels into clean water), although outbreaks of diseases have resulted from poor depuration and viruses may not be removed by depuration. Recent improvements in waste water treatment and shellfish water quality regulations may reduce the risk of bacterial and viral contamination. Shellfish should also be thoroughly cooked, not 'quick steamed', to ensure destruction of viruses (Shumway, 1992). The accumulation of toxins from toxic algal blooms may result in paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP) or amnesic shellfish poisoning (ASP). These toxins are not destroyed by cooking. Shumway (1992) suggested that mussels should only be collected from areas routinely monitored by public health agencies, or obtained from approved sources and never harvested from waters contaminated with raw sewerage.
|Biology References||Fish & Fish, 1996, Hayward & Ryland, 1990, Hayward et al., 1996, Tebble, 1976, Gosling, 1992(c), Bayne, 1976b, Seed & Suchanek, 1992, Gosling, 1992(b), Bayne et al., 1976, Dare, 1976, Dare, 1982(b), Raffaelli et al., 1990, Craeymeersch et al., 1986, Marsh, 1986, Richardson & Seed, 1990, Bower, 1992, Bower & McGladdery, 1996, Shumway, 1992, Holt et al., 1998, Baird, 1966, Meire & Ervynck, 1986, Thiesen, 1972, Clay, 1967(d), Gosling, 1992(a), Gray et al., 1997, Carter & Seed, 1998, Seed, 1968, Thompson et al., 2000, Seed 1993, Seed, 1969a, Ambariyanto & Seed, 1991, Hayward & Ryland, 1990, Heidi Tillin, unpub data, Julie Bremner, unpub data,|
|Distribution and Habitat|
|Distribution in Britain & Ireland||Very common all around the coast of the British Isles, with large commercial beds in the Wash, Morecambe Bay, Conway Bay and the estuaries of south-west England, north Wales, and west Scotland.|
|Global distribution||Occurs from the White Sea, south to southern France in the N.E. Atlantic. In the W. Atlantic it extends from the Canadian Maritimes south to North Carolina. It occurs on the coasts of Chile, Argentina, the Falkland Islands and the Kerguelen Isles.|
|Biogeographic range||Not researched||Depth range|
|Migratory||Non-migratory / Resident|
|Distribution Additional Information||Global distribution
Previous records of Mytilus edulis on north African coasts, and in the Mediterranean were probably Mytilus galloprovincialis and Mytilus edulis is absent from the Pacific coast of North America (Gosling, 1992c; Seed, 1992). Previous records of Mytilus edulis from the Pacific coast of North America were probably Mytilus trossulus and/or Mytilus galloprovincialis (Seed, 1992; Seed pers comm.). Mytilus edulis has been reported from Iceland (Varvio et al., 1988). Mytilus edulis occurs on the east and west coasts of South America, and the Falkland Islands (Seed, 1992). Records of mussels form the Kerguelen Islands may be Mytilus edulis (MacDonald et al., 1992; Gosling, 1992c; Seed, 1992).
Factors affecting zonation
The lower limit of distribution is strongly influenced by predation, primarily from starfish but also dog whelks and crabs. For example, on the east coast of England, the starfish Asterias rubens and the dog whelk Nucella lapillus eliminate mussels from the lower intertidal (Seed, 1969). In Ireland, however, the lower limit is probably controlled by the crabs Carcinus sp. and Liocarcinus sp., the dog whelk Nucella lapillus and the starfish Marthasterias glacialis (Kitching & Ebling, 1967).
Daly & Mathieson (1977) reported that the lower limit of Mytilus edulis populations at Bound Rock, USA, was determined by burial or abrasion by shifting sands. Burial or abrasion is probably an additional controlling factor on British coasts where mobile sediment, such as sand, cobbles or boulders, occur (Holt et al., 1998).
Subtidal populations often occur on sea mounts, dock pilings and offshore oil platforms, where they grow to a large size, probably due to the lack of predators (Seed & Suchanek, 1992).
Large to very large boulders
Artificial (e.g. metal/wood/concrete)
Crevices / fissures
|Physiographic preferences||Open coast
Strait / sound
Ria / Voe
Enclosed coast / Embayment
|Biological zone||Upper Eulittoral
|Wave exposure||Very Exposed
|Tidal stream strength/Water flow||Strong (3-6 kn)
Moderately Strong (1-3 kn)
Weak (<1 kn)
|Salinity||Reduced (18-30 psu)
Variable (18-40 psu)
Full (30-40 psu)
|Habitat Preferences Additional Information|
|Distribution References||Fish & Fish, 1996, Hayward & Ryland, 1990, Hayward et al., 1996, Tebble, 1976, Gosling, 1992(c), Varvio et al., 1988, MacDonald et al., 1992, Bayne, 1976b, Seed & Suchanek, 1992, Williams, 1970, Bourget, 1983, Almada-Villela et al., 1982, Seed, 1969b, Kitching & Ebling, 1967, Holt et al., 1998, Daly & Mathieson, 1977, Suchanek, 1978, Almada-Villela, 1984, Clay, 1967(d), Gosling, 1992(a), Seed, 1992, Seed, 1995, Gray et al., 1997, Carter & Seed, 1998, Suchanek, 1985, Hayward & Ryland, 1990,|
|Reproductive Season||April to September||Reproductive Location||Water column|
|Reproductive frequency||Annual protracted||Regeneration potential||No|
|Life span||21-50 years||Age at reproductive maturity||1-2 years|
|Generation time||1-2 years||Fecundity|
|Egg/propagule size||75 µm diameter||Fertilization type||External|
|Reproduction Preferences Additional Information||Life span
Longevity is dependant on locality and habitat. On the lower shore, few individuals probably survive more than 2-3 years due to intense predation, whereas high shore populations are composed of numerous year classes (Seed, 1969b). Specimens have been reported to reach 18-24 years of age (Thiesen, 1973). Mortality is size dependant and can be high, e.g. Dare (1976) reported annual mortalities of 74% in 25mm mussels and 98% in 50 mm mussels in Morecambe Bay, England.
Spawning is protracted in many populations, with a peak of spawning in spring and summer. For example, in north east England, resting gonads begin to develop from October to November, gametogenesis occurring throughout winter so that gonads are ripe in early spring. A partial spawning in spring is followed by rapid gametogenesis, gonads ripening by early summer, resulting in a less intensive secondary spawning in summer to late August or September (Seed, 1969a). Mantle tissues store nutrient reserves between August and October, ready for gametogenesis in winter when food is scarce (Seed & Suchanek, 1992). Larvae spawned in spring can take advantage of the phytoplankton bloom. The secondary spawning, is opportunistic, depending on favourable environmental conditions and food availability. Gametogenesis and spawning varies with geographic location, e.g. southern populations often spawn before more northern populations (Seed & Suchanek, 1992). Reproductive strategies in Mytilus edulis probably vary depending on environmental conditions (Newell et al., 1982).
Fertilization is external. Fertilization can occur successfully between 5 -22°C and at salinities of 15 -40psu (Bayne, 1965; Lutz & Kennish, 1992). Fertilized eggs are 60-90µm in diameter (Lutz & Kennish, 1992).
Fecundity and reproductive effort increase with age and size, young mussels diverting energy to rapid growth rather than reproduction. Reproductive output is influenced by temperature, food availability and tidal exposure and can therefore vary from year to year. An individual female (ca 7mm) can produce 7-8 million eggs, while larger individuals may produce as many as 40 million eggs (Thompson, 1979).
In optimal conditions larval development may be complete in less than 20 days but growth and metamorphosis in the plankton between spring and early summer, at ca. 10 °C, usually takes 1 month. However, it is not unusual for planktonic life to extend beyond 2 months in the absence of suitable substrata or optimal conditions (Bayne, 1965; Bayne, 1976a). Pediveligers can delay metamorphosis for up to 40 days at 10 °C (Lutz & Kennish, 1992) or for up to 6 months in some cases (Lane et al., 1985). The duration of the delay is mainly determined by temperature, with longer delays at low temperature (Strathmann, 1987). Larvae become less selective of substrata the longer metamorphosis is delayed.
In many populations Mytilus edulis exhibits a two stage settlement, the pediveliger settling on filamentous substrates and then moving on to suitable adult substrata by bysso-pelagic drifting. However, McGrath et al. (1988) and King et al. (1990) found little evidence of bysso-pelagic drifting in populations in Norwegian fjords or the Baltic, and pediveligers settled directly into adult beds.
Pediveligers typically settle at ca. 260 µm (McGrath et al., 1988) but can delay metamorphosis until ca. 350 µm. Pediveligers can delay settlement for up to 7 weeks (Holt et al., 1998). Pediveligers test the substrata using their sensory foot. Settling pediveligers prefer discontinuities in the substrata (Chipperfield, 1953), and reportedly tend to avoid adults (Lane et al., 1985).
Primary settlement tends to occur on filamentous substrata, such as, bryozoans, hydroids, filamentous algae such as Polysiphonia sp., Corallina sp. and Mastocarpus sp., or the byssus threads of previously settled adults. Primary settlement may allow the pediveligers to avoid competition for food with adults or being inhaled by suspension feeding adults. Post-larvae may remain on their primary attachment until 1-2mm in size (sometimes larger), and many late post-larvae over-winter on algae, moving to adult substrata in spring, although many will leave the algae earlier due to winter storms or death of the algae (Seed & Suchanek, 1992). Newly settled mussels are termed 'spat'.
Dispersal is dependant on the duration of planktonic life. Maintenance of their position in the water column by active swimming ensures that larvae can be potentially dispersed over great distances by currents. In addition, post-larvae can become bysso-pelagic up to 2-2.5 mm in size, which may take ca. 2 months to achieve, during which time they may be transported significant distances by currents.
Recruitment is dependant on larval supply and settlement, together with larval and post-settlement mortality. Jørgensen (1981) estimated that larvae suffered a daily mortality of 13% in the Isefjord, Denmark. Lutz & Kennish (1992) suggested that larval mortality was approximately 99%. Larval mortality is probably due to adverse environmental conditions, especially temperature, inadequate food supply (fluctuations in phytoplankton populations), inhalation by suspension feeding adult mytillids, difficulty in finding suitable substrata and predation (Lutz & Kennish, 1992). First winter mortality in the Exe estuary averaged 68%, adults suffering 39% mortality after spawning and 24% due to bird predation (McGrorty, et al., 1990). Beukema (1992) reported recruitment failure in Mytilus edulis populations in the Wadden Sea after mild winters, which was thought to be due to a resultant increase in the number of small crabs or flatfish on the flats. Recruitment in many Mytilus sp. populations is sporadic, with unpredictable pulses of recruitment, possibly from the pool of young mussels on filamentous algae (Seed & Suchanek, 1992). Mytilus sp. is highly gregarious and final settlement often occurs around or in between individual mussels of established populations. Competition with surrounding adults may suppress growth of the young mussels settling within the mussel bed, due to competition for food and space, until larger mussels are lost (Seed & Suchanek, 1992).
Persistent mussels beds can be maintained by relatively low levels of recruitment. McGrorty et al., (1990) reported that adult populations were largely unaffected by large variations in spatfall between 1976-1983 in the Exe estuary.
|Reproduction References||Hayward et al., 1996, Bayne, 1965, Lutz & Kennish, 1992, Bayne, 1983, Hrs-Brenko & Calabrese, 1969, Bayne, 1976b, Jørgensen, 1981, Chipperfield, 1953, Lane et al., 1985, McGrath et al., 1988, Sprung, 1984, Thorson, 1950, Seed, 1976, King et al., 1990, Seed & Suchanek, 1992, Mackie, 1984, Newell et al.,1982, Thompson, 1979, Thiesen, 1973, Dare, 1976, Holt et al., 1998, Strathman, 1987, McGrorty et al., 1990, Beukema, 1992, Widdows, 1991, Beaumont & Budd, 1982, Beaumont & Budd, 1984, Clay, 1967(d), Gosling, 1992(a), Gray et al., 1997, Seed, 1969a, Bayne, 1976a, Eckert, 2003, Heidi Tillin, unpub data, Julie Bremner, unpub data,|