BIOTIC Species Information for Fucus serratus
Researched byAngus Jackson Data supplied byMarLIN
Refereed byDr Graham Scott
Scientific nameFucus serratus Common nameToothed wrack
MCS CodeZR382 Recent SynonymsNone

PhylumChromophycota Subphylum
Superclass ClassPhaeophyceae
Subclass OrderFucales
Suborder FamilyFucaceae
GenusFucus Speciesserratus

Additional InformationAlso known as serrated or saw wrack. Ripe male plants can be distinguished by their orange colour.
Taxonomy References Howson & Picton, 1997, Hayward et al., 1996, Dickinson, 1963, Williams, 1996, Knight & Parke, 1950,
General Biology
Growth formShrub
Feeding methodPhotoautotroph
Mobility/MovementPermanent attachment
Environmental positionEpifloral
Typical food typesNot relevant HabitAttached
BioturbatorNot relevant FlexibilityHigh (>45 degrees)
FragilityIntermediate SizeLarge(>50cm)
HeightUsually up to 70 cm Growth Rate0.2-0.1 cm / day
Adult dispersal potentialNone DependencyIndependent
General Biology Additional InformationDuring most of the year plant densities range between 10-14/0.25 square metres. When recruitment is occurring then densities may rise to 18-22/0.25 square metres. Surface cover by this species may reach over 95 percent during the summer. This decreases and becomes more patchy during winter and autumn. Fucus serratus typically grows up to 70 cm but has been recorded at over 2 m in length in very sheltered environments. Growth rate refers to maximal growth rate under optimal conditions. Growth rate varies considerably depending on environmental conditions. Growth rate ranges from 4-12 cm per annum. There are two size classes: germlings less than 10 cm (30-40 percent of the population); and adult plants greater than 40 cm. The germlings developing from eggs are initially microscopic and become visible to the naked eye after about two weeks. There is no clear mode in between but individuals of intermediate size are always present. Fucus serratus supports a wide variety of epiphytes with over 90 species having been recorded. Growth of microalgae on the frond surface can cause shading and reduced photosynthesis, anoxia at the frond surface and may interfere with reproduction. Mobile herbivores may benefit Fucus serratus through removal of this algal film. Other dominant macrofaunal species found on Fucus serratus include Lacuna pallidula, Littorina mariae, Amphithoe rubricata, Idotea granulosa and epiflora include Rhydomenia palmata and Elachista fucicola.
Biology References Creed et al., 1997, Brenchley et al., 1997, Seed & O'Connor, 1981, Lüning, 1990, Williams, 1996, Knight & Parke, 1950,
Distribution and Habitat
Distribution in Britain & IrelandAll British and Irish coasts.
Global distributionNorthern Portugal and the Atlantic coast of France; British Isles, North Sea coasts and into the western Baltic; Scandinavia up to Novaya Zemlya; Iceland and the Gulf of St. Lawrence in the western north Atlantic.
Biogeographic rangeNot researched Depth rangeNot relevant
MigratoryNon-migratory / Resident   
Distribution Additional InformationDepth in metres is considered not relevant because the species is intertidal. More exposed coasts have a lower proportion of adult individuals in the population. In more sheltered areas Fucus serratus may grow on substrata such as cobbles.

Substratum preferencesBedrock
Large to very large boulders
Small boulders
Physiographic preferencesOpen coast
Ria / Voe
Biological zone Wave exposureModerately Exposed
Very Sheltered
Extremely Sheltered
Tidal stream strength/Water flowStrong (3-6 kn)
Moderately Strong (1-3 kn)
Weak (<1 kn)
Very Weak (negligible)
SalinityReduced (18-30 psu)
Full (30-40 psu)
Variable (18-40 psu)
Habitat Preferences Additional Information
Distribution References Hayward et al., 1996, Williams, 1996, Knight & Parke, 1950,
Reproduction/Life History
Reproductive typeGonochoristic
Developmental mechanismInsufficient information
Reproductive SeasonMay to November Reproductive LocationWater column
Reproductive frequencyAnnual protracted Regeneration potential No
Life span3-5 years Age at reproductive maturityInsufficient information
Generation timeInsufficient information FecunditySee additional information
Egg/propagule sizeInsufficient information Fertilization typeExternal
Larval/Juvenile dispersal potential>10km Larval settlement period
Duration of larval stageInsufficient information   
Reproduction Preferences Additional InformationDickinson, (1963) notes that fruiting fronds can be found almost throughout the year with fertile plants most in evidence during the winter months. However, most other work suggests that reproduction commences in late spring/early summer and continues through summer and autumn, peaking in August - October. Eggs and sperm are released into the water and fertilisation occurs in the water column. The eggs produce a sperm attractant called fucoserratin that is active within 0.5mm. The zygote then develops into a minute plant that can then settle onto the substratum. Post reproductive fronds are shed contributing to loss of surface cover. Many plants may be lost during winter due to storms and heavy wave action. Germlings have a high mortality, up to 83 % being recorded lost in 77 days on the Isle of Man. Reproduction occurs earlier and growth is faster on sheltered shores. Egg release is protracted. The largest number of receptacles recorded from a single plant is over 4,600. Eggs are broadcast into the water column to be carried by the current to settle and develop wherever they fall. Eggs attach firmly to the substratum within a few hours. Many eggs are eaten by browsing molluscs.
Reproduction References Dickinson, 1963, Brenchley et al., 1997, Johnston, 1977, Williams, 1996, Knight & Parke, 1950,
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