BIOTIC Species Information for Pecten maximus
|Researched by||Charlotte Marshall & Emily Wilson||Data supplied by||MarLIN|
|Refereed by||Andy Beaumont|
|Scientific name||Pecten maximus||Common name||Great scallop|
|MCS Code||W1771||Recent Synonyms||None|
|Additional Information||Also known as the King scallop, Giant scallop, escallop and Coquille St. Jacques.|
|Taxonomy References||Howson & Picton, 1997, Fish & Fish, 1996, Tebble, 1976,|
||Feeding method||Active suspension feeder
|Typical food types||Seston including phytoplankton, especially single celled algae, particulate organic matter (POM), bacteria and other micro-organisms (Fegley et al., 1992; Reitan et al., 2002).||Habit||Free living|
|Bioturbator||Flexibility||None (< 10 degrees)|
|Height||Insufficient information||Growth Rate||See additional text|
|Adult dispersal potential||100-1000m||Dependency||Independent|
|General Biology Additional Information||
Pecten maximus normally lies recessed into slight hollows (recesses) in the seabed (Mason, 1983). Recessing is achieved through a series of powerful adductions (valve closures) where water is ejected from the mantle cavity and lifts the shell at an angle to the seabed so that subsequent water jets blow a hollow into the sediment (Brand, 1991).
Size and growth
Embedded among the bases of the sensory tentacles around the edge of the mantle are numerous tiny eyes (Mason, 1983). The eyes are a blue green colour no more than ca 1.5 mm in diameter. The eyes bear a superficial resemblance to the camera eyes of vertebrates and have a highly specialized retina (Wilkens, 1991). Light has both inhibitory and excitatory effects and scallops will swim, orient themselves or close their shell in response to shadows or movement (Wilkens, 1991).
|Biology References||Fish & Fish, 1996, Ansell et al., 1991, Mason, 1983, Minchin, 2003, Laing, 2002, Campbell et al., 2001, Thomas & Gruffydd, 1971, Mason, 1957, Bradshaw et al., 2001, Brand, 1991, Ansell et al., 1991, Fegley et al., 1992, Reitan et al., 2002, Shumway, 1991, Beaumont et al, 1985,|
|Distribution and Habitat|
|Distribution in Britain & Ireland||Recorded around most coasts of Britain and Ireland, with only scattered records from the east coast of Great Britain.|
|Global distribution||Pecten maximus occurs along the European Atlantic coast from northern Norway, south to the Iberian peninsula and has also been reported off West Africa, the Azores, Canary Islands and Madeira.|
|Biogeographic range||Not researched||Depth range||10-110 m|
|Migratory||Non-migratory / Resident|
|Distribution Additional Information||Factors affecting distribution
Water flow and wave exposure
The areas with highest abundance and the fastest growth rates of scallops are usually in areas with little mud (Brand, 1991). Gruffydd (1974) found that the maximum shell size of Pecten maximus from the north Irish Sea was significantly negatively correlated with increasing mud content in the sediment.
Aggregation and population subdivision
|Substratum preferences||Coarse clean sand
Gravel / shingle
Fine clean sand
|Physiographic preferences||Offshore seabed
Enclosed coast / Embayment
|Biological zone||Lower Infralittoral
|Tidal stream strength/Water flow||Moderately Strong (1-3 kn)
Weak (<1 kn)
|Salinity||Full (30-40 psu)
|Habitat Preferences Additional Information|
|Distribution References||Ansell et al., 1991, Mason, 1983, Gibson, 1956, Tebble, 1976, Brand, 1991, Ansell et al., 1991, Beaumont & Zouros, 1991, Gruffydd, 1974, Picton & Costello, 1998, JNCC, 1999, NBN, 2002, Beaumont, 2005, Wilding et al., 1998, Wilding et al., 1999,|
|Reproductive type||Permanent hermaphrodite
|Reproductive Season||April to September||Reproductive Location||Water column|
|Reproductive frequency||Annual protracted||Regeneration potential||No|
|Life span||11-20 years||Age at reproductive maturity||2-3 years|
|Generation time||3-5 years||Fecundity||15-21 million oocytes for a 3yr old|
|Egg/propagule size||Insufficient information||Fertilization type||External|
|Reproduction Preferences Additional Information||Reach first maturity at 2 years and full maturity at 3-5 years.
Mason (1983) reported a scallop with 18 growth rings although he stated that beyond the ninth or tenth ring, they are hard to distinguish and so attract some uncertainty in terms of age. Minchin (2003) states that the maximum age for Pecten maximus is about 22 years. In reality however, especially in heavily fished areas, the average age / size is reduced and those caught commercially rarely exceed 16 cm (Minchin, 2003). The rate of natural mortality is low at 10-15 % for adult Pecten maximus (Rees & Dare, 1993).
The gametogenic cycle is highly variable and the timing of spawning may be influenced by both internal and external factors such as age and temperature respectively (Barber & Blake, 1991). Ansell et al. (1991) provide an excellent review of work done by several authors on populations of Pecten maximus in the Bay of Brest and the Bay of St Brieuc in France including work involving the transplantation of some individuals into different populations. They noted that differences in spawning cycles between populations reflect not only differences in their responses to local environmental variables but are also a consequence of genetic adaptation.
In general, mature scallops spawn over the summer months from April or May to September. Estimates of gamete emission range from 15 - 21 million oocytes per emission for a three year old (Le Pennec et al., 2003). A bi-modal spawning pattern has been reported by several authors in different areas. In Manx waters for instance, Mason (1983) found most of the adults spawned partially in the 'spring spawning' in April or May and then more fully in an 'autumn spawning' event in late August. He also found that the virgins (scallops that have not spawned previously) and juveniles (those between their first and second spawns) only had one major spawning in autumn. Spawning is followed by a period of recovery of the gonad before the next spawn. Gibson (1956) found a similar bi-modal spawning in Bere Island sound (Ireland) but here the spring spawn was reported to be the most significant of the two. In the same study (Gibson, 1956), the Bantry Bay area scallops matured up to six weeks earlier than the Connemara area further north.
Fertilization is external and either sperm or eggs can be exuded first (Mason, 1983).
Dispersal potential in Pecten maximus is high given that the length of the pelagic larval stage exceeds one month. In addition, Beaumont & Barnes (1992) have observed 'byssus drifting' in vitro which would provide a possible mechanism for the secondary dispersal of post-larval stages (spat). Some spat were observed to detach from the byssus thread and the subsequent production of a long and fine drifting thread slowed the decent of the spat thereby increasing the potential for dispersal (Beaumont & Barnes, 1992). Thouzeau & Lehay (1988, cited in Le Pennec et al., 2003) determined that Pecten maximus larvae could travel 10-40 km in 18 days due to tidal currents. However, Sinclair et al. (1985) hypothesized that using vertical migrations, larvae may be able to maintain their location within the confined of the scallop bed and that many aggregations are self-sustaining. Wilding et al. (1999) found that Pecten maximus from Mulroy Bay were genetically distinct to other populations. This genetic isolation is thought to arise as a result of the enclosed nature of Mulroy Bay which probably means that the population is sustained through self-recruitment (Beaumont, 2005).
See General (larval) information for details of larval development and settlement.
|Reproduction References||Fish & Fish, 1996, Beaumont & Budd, 1982, Ansell et al., 1991, Mason, 1983, Gibson, 1956, Ansell et al., 1991, Barber & Blake, 1991, Beaumont & Budd, 1983, Beaumont, 2005, Wilding et al., 1998, Wilding et al., 1999, Beaumont & Barnes, 1992,|