BIOTIC Species Information for Pecten maximus
Researched byCharlotte Marshall & Emily Wilson Data supplied byMarLIN
Refereed byAndy Beaumont
Reproduction/Life History
Reproductive typePermanent hermaphrodite
Developmental mechanismPlanktotrophic
Reproductive SeasonApril to September Reproductive LocationWater column
Reproductive frequencyAnnual protracted Regeneration potential No
Life span11-20 years Age at reproductive maturity2-3 years
Generation time3-5 years Fecundity15-21 million oocytes for a 3yr old
Egg/propagule sizeInsufficient information Fertilization typeExternal
Larval/Juvenile dispersal potential>10km Larval settlement periodInsufficient information
Duration of larval stage11-30 days   
Reproduction Preferences Additional InformationReach first maturity at 2 years and full maturity at 3-5 years.
Life Span
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,
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