Toothed wrack (Fucus serratus)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Chromista · Phylum: Ochrophyta · Class: Phaeophyceae · Order: Fucales · Family: Fucaceae · Genus: Fucus.

Accepted name: Fucus serratus · Authority: Linnaeus, 1753 · Taxonomic status: accepted · AphiaID: 145546.

Synonyms and superseded combinations recorded for this taxon: Fucus serratus f. abbreviatus Kjellman, 1883; Fucus serratus f. angustus Kjellman, 1883; Fucus serratus f. arcticus (J.Agardh) Kjellman, 1880; Fucus serratus f. elongatus Kjellman, 1890; Fucus serratus f. grandifrons Kjellman, 1883; Fucus serratus f. laciniatus Kjellman, 1890; Fucus serratus var. angustifolius Stackhouse, 1816; Fucus serratus var. arcticus J.Agardh, 1868; Fucus serratus var. integer Turner, 1809; Fucus serratus var. integerrimus C.Agardh, 1820; Fucus serratus var. lacinatus Greville, 1890; Fucus serratus var. latifolius Turner, 1809; Halidrys serrata (Linnaeus) Stackhouse, 1809; Virsodes serratum (Linnaeus) Kuntze.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=145546 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Fucus serratus. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 70 cm · Habitat zone: sessile · Vulnerability index: 48 of 100.

SeaLifeBase notes: It is found on stony substrates (Ref. 95730).

Source: SeaLifeBase species summary (SpecCode 115508) — https://www.sealifebase.se/summary/Fucus-serratus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

51,873 georeferenced occurrence records for Fucus serratus are published through GBIF from 25 countries or marine areas. The map above plots 167 distinct locations from a sample of 3,000 records, omitting 196 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: United Kingdom of Great Britain and Northern Ireland (20,561); Norway (10,456); Sweden (9,318); France (4,464); Canada (2,328).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 3196437) — https://www.gbif.org/occurrence/search?taxon_key=3196437&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=145546 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Description and natural history (Wikipedia)

Fucus serratus is a robust alga, olive-brown in colour and similar to Fucus vesiculosus and Fucus spiralis. The species is one of many algae that are multicellular. It grows from a discoid holdfast up to 180 cm long.

The fronds are flat, about 2 cm wide, bifurcating, and up to 1 m long including a short stipe. It branches irregularly and dichotomously. The flattened blade has a distinct midrib and is readily distinguished from related taxa by the serrated edge of the fronds.

It does not have air vesicles, such as are found in F. vesiculosus, nor is it spirally twisted like F. spiralis. Male and female receptacles are on different plants. The lamina shows cryptostomata – small cavities which produce colourless hairs.

The reproductive bodies form in conceptacles sunken in receptacles towards the tips on the branches. In these conceptacles oogonia and antheridia are produced and after meiosis the oogonia and antheridia are released. Fertilisation follows and the zygote develops, settles and grows directly into the diploid sporophyte plant. The fertilization in the Fucus serratus would be associated with egg activation.

Distribution

Fucus serratus is found along the Atlantic coast of Europe from Svalbard to Portugal, in the Canary Islands. It was introduced to the shores north-east America over 140 years ago, is presence described first at Pictou Harbour in the late 1860s by George Upham Hay and Alexander Howard McKay, its introduction to Iceland and the Faroe Islands could date back to the Vikings, within the last 1000 years and was first noted in a phycological survey in 1900.

Ecology

Fucus serratus grows very well on slow draining shores where it may occupy up to a third of the area of the entire seashore. It often dominates the rocky parts of the lower shore, exposed or immersed in rock pools, on all but the most exposed shores. "...the littoral zone is characterised especially by such Phaeophyta (brown algae) as Pelvetia, Ascophyllum, Egregia, Fucus and Laminaria, particularly when the shore is rocky". It is considered an invasive species in the Canadian Maritimes, particularly on Prince Edward Island, Nova Scotia and the Northern coastline of New Brunswick. In Northern Europe and Iceland it is known to hybridize with Fucus distichus.

Uses

Fucus serratus is used in Ireland and France for the production of cosmetics and for thalassotherapy. In the Western Isles of Scotland, it is harvested for use as a liquid fertiliser. Since the organism contains triacylglycerols and fatty acids.

Source: Wikipedia: Fucus serratus — https://en.wikipedia.org/wiki/Fucus_serratus (CC BY-SA 4.0). Accessed 2026-09-25.