Invasion History

First Non-native North American Tidal Record: 1975
First Non-native West Coast Tidal Record: 1975
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Fucus spiralis (Spiral Rockweed) is a brown seaweed, growing in the upper-mid-intertidal of rocky shores of the North Atlantic. In the North Atlantic, it occurs from the Canary Islands to Iceland, southern Norway and the Faroe Islands, and New York to the southern Gulf of St. Lawrence (Taylor 1957; Coyer et al. 2006; Van Patten 2006; Guiry and Guiry 2016). In 1959 –1973, F. spiralis was collected in a number of sites on the West Coast from the San Juan Islands, Washington, to the Aleutian Islands, Alaska (Norris and Conway 1974). Many of these locations are remote and distant from ports, although introductions in dry ballast from whaling and sealing ships cannot be ruled out. Natural dispersal from the Atlantic to the Pacific is unlikely, since the prevailing movement for fucoid seaweeds and other taxa is from the Pacific to the Atlantic. Fucus spiralis probably evolved from a Pacific ancestor, so the northeast Pacific populations could represent a remnant of pre-glacial populations (Coyer et al. 2006). We consider these populations cryptogenic. Recent appearance (1994) in Tomales and Humboldt Bays, California, is clearly an introduction (Hughey 1995; Miller et al. 2011; Humboldt State University Herbarium 2016).

North American Invasion History:

Invasion History on the West Coast:

Fucus spiralis was first collected on the West Coast of North America in Clayoquot Sound, on the western side of Vancouver Island in 1959. It was subsequently collected in many locations around Vancouver Island, the San Juan Islands, Washington, and in Alaska, Sitka Sound, and in the Aleutians, Attu and Unimak Island (Norris and Conway 1974). Many of these locations are distant from ports, although they may have been visited by whaler and sealers. Coyer et al. (2006) consider the possibility of an anthropogenic introduction from the Atlantic, and also the persistence of a remnant ancestral Pacific population. They consider natural dispersal from the Atlantic to be less likely (Coyer et al. 2006).

In 1994, Jeffery Hughey found Fucus spiralis growing on rocks and logs in the upper intertidal in Tomales Bay. He also cited reports from Humboldt Bay. A specimen from Humboldt Bay, collected in 1994, is displayed online (Humboldt University Herbarium 2016). Possible vectors of transport include dry ballast, hull fouling, or transport with transplanted oysters from Washington or British Columbia. Fucus spiralis occasionally occurs in saltmarshes, so transport with baitworms, packed in seaweed (Ascophyllym nodosum) from Maine or the Maritime Provinces might be possible.


Fucus spiralis is a brown seaweed of marine rocky intertidal zones. The thallus is formed of flat, strap-like blades, rising from a small disc-shaped holdfast. They are occasionally twisted and branching somewhat regularly, and dichotomously. The blades have a strong midribs, and end in long, pointed, swollen fleshy reproductive areas called receptacles. Fucus spiralis lacks the inflated air-bladders typical of F. vesiculosus. The thallus is typically 150 to 300 mm long, but occasionally reach 600 mm. The color is olive-green to brown, and occasionally reddish-brown (Taylor 1957; Van Patten 2006).


Taxonomic Tree

Kingdom:   Plantae
Phylum:   Phaeophycophyta
Class:   Phaeophyceae
Order:   Fucales
Family:   Fucaceae
Genus:   Fucus
Species:   spiralis


Fucus vesiculosus var. spiralis ((Linnaeus) Roth, 1800)
Halidrys spiralis ((Linnaeus) Stackhouse, 1809)
Fucus sherardii f. spiralis (Areschoug, 1868)
Fucus platycarpus f. spiralis ((Linnaeus) Thuret, 1878)
Fucus spiralis f. borealis (Kjellman, 1883)
Fucus areschougii (Kjellman 1890, 1890)
Fucus vesiculosus f. spiralis ((Linnaeus) Batters, 1890)
Fucus platycarpus var. spiralis ((Linnaeus) Rosenvinge, 1897)
Fucus spiralis f. nanus ((Kjellman) Batters, 1902)
Fucus spiralis var. nanus ((Stackhouse) Batters, 1902)
Fucus spiralis f. arenicola (Hamel, 1939)

Potentially Misidentified Species

Fucus distichus
Fucus distichus is a circumboreal species, formerly recognized as a group of separate species or varieties, including a Northern Atlantic F. evanescens, and a North Pacific F. gardneri, with numerous subspecies and varieties (Taylor 1957; Abbott and Hollenberg 1976; Guiry and Guiry 2016). Genetic studies indicate that F. distichus is a species of Northeastern Pacific origin, which has colonized the Northwest Pacific, and the Atlantic (through the Arctic Ocean), in a series of natural expansions during the Pleistocene (Coyer et al. 2011).



Fucus spiralis is a brown seaweed of marine rocky intertidal zones. The tips of the branches of the thallus are swollen reproductive structures, called receptacles. The interior of the receptacle includes cavities called conceptacles. F. spiralis is hermaphroditic, and its conceptacles produce both eggs and sperm. When a fucoid seaweed is exposed at low tide, shrinkage of the frond causes extrusion of slime, and prepares the conceptacle for release of the gametes on the incoming tide (Taylor 1957; Bold and Wynne 1978).

Fucus spiralis tends to grow in the upper-mid-intertidal, above the zones dominated by F. vesiculosus and Ascophyllum nodosum on the East Coast of North America (Taylor 1957; Van Patten 2006) and Fucus distichus (=F. gardneri) on the West Coast (Norris and Conway 1974; Hughey 1995). It has been found growing in saltmarshes in Massachusetts and Iceland (Taylor 1957; Coyer et al. 2006). In Tomales Bay, F. spiralis was growing on rocks and logs, mostly above F. distichus, but also intermixed with it (Hughey 1995). In this habitat, it tolerates long periods of air exposure, and a wide range of air temperatures. It may be limited by high water temperatures. At a site in Portugal, it was found at maximum temperatures up to 20.5 °C (Carraio et al. 2009), and probably is exposed to temperatures of 24–25 °C in Long Island Sound. It has not been reported from strongly brackish water, but at the mouth of the Lima estuary in Portugal, it occurs at a range of 12–36 PSU (Carraio et al. 2009).

Trophic Status:

Primary Producer



General HabitatRockyNone
General HabitatSalt-brackish marshNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeHigh IntertidalNone
Tidal RangeLow IntertidalNone
Tidal RangeMid IntertidalNone
Vertical HabitatEpibenthicNone

Life History

Tolerances and Life History Parameters

Minimum Temperature (ºC)-2Based on geographical range
Maximum Temperature (ºC)20.5Field water temperature, Portugal (Carraio et al. 2009). Water temperatures of 30 and 35 C were lethal, while growth was normal at 20 C (Stormgren 1977). Intermediate temperatures (25 C) were not tested.
Minimum Salinity (‰)12.1Field, Cabedelo-Mouth of Lima river estuary, Portugal (Carraio et al. 2009)
Maximum Salinity (‰)36Field, Cabo do Mundo-coastal zone, Portugal (Carraio et al. 2009)
Minimum Length (mm)200Van Patten 2006
Maximum Length (mm)600Van Patten 2006
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity Range12


General Impacts

No impacts have been reported for Fucus spiralis (Spiral Rockweed) on the West Coast. However, fucoid seaweeds are a very important component of the intertidal habitats, providing shelter for other intertidal algae and invertebrates.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
P110 Tomales Bay 1994 Def Estab
NEP-V Northern California to Mid Channel Islands 1994 Def Estab
NEP-III Alaskan panhandle to N. of Puget Sound 1959 Crypto Estab
NEP-II Alaska south of the Aleutians to the Alaskan panhandle 1960 Crypto Estab
NA-ET3 Cape Cod to Cape Hatteras 0 Native Estab
NA-ET2 Bay of Fundy to Cape Cod 0 Native Estab
NA-ET1 Gulf of St. Lawrence to Bay of Fundy 0 Native Estab
NA-S3 None 0 Native Estab
AR-V None 0 Native Estab
B-I None 0 Native Estab
NEA-II None 0 Native Estab
NEA-III None 0 Native Estab
NEA-III None 0 Native Estab
NEA-IV None 0 Native Estab
NEA-V None 0 Native Estab
NEA-VI None 0 Native Estab
WA-I None 0 Native Estab
AR-IV None 0 Native Estab
NEP-IV Puget Sound to Northern California 1994 Def Estab
P130 Humboldt Bay 1994 Def Estab
P292 _CDA_P292 (San Juan Islands) 1973 Crypto Estab
P286 _CDA_P286 (Crescent-Hoko) 1972 Crypto Estab
P290 Puget Sound 2006 Crypto Estab
MED-II None 1987 Def Failed
P223 _CDA_P223 (Siltez-Yaquina) 1975 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Bold, Harold C.; Wynne, Michael J. (1978) Introduction to the Algae: Structure and Reproduction, Prentice-Hall, Englewood Cliffs, NJ. Pp. <missing location>

Cairrão, E.; Pereira, M. J.; Morgado, F.; Nogueira, A. J. A.; Guilhermino, L.; Soares, A. N. V. M. (2009) Phenotypic variation of Fucus ceranoides, F. spiralis and F. vesiculosus in a temperate coast (NW Portugal), Botanical Studies 50: 205-215

Coyer, James A.; Hoarau, Galice; Van Schaik, Jaap; Luijckx, Pepijn; Olsen, Jeanine L. (2011) Trans-Pacific and trans-Arctic pathways of the intertidal macroalga Fucus distichus L. reveal multiple glacial refugia and colonizations from the North Pacific to the North Atlantic, Journal of Phycology 38: 756-771

Coyer, James A.; Hoarau, Galice; Oudot-Le Secq, Marie-Pierre; Stam, Wytze T.; Olsen, Jeanine L. (2006) A mtDNA-based phylogeny of the brown algal genus Fucus (Heterokontophyta; Phaeophyta), Molecular Phylogenetics and Evolution 39: 209-222

Fernandez-Alvarez, Fernando Angel Machordom, Annie (2012) DNA barcoding reveals a cryptic nemertean invasion in Atlantic and Mediterranean waters, Helgoland Marine Research 67: 599-605
DOI 10.1007/s10152-013-0346-3

Guiry, M. D.; Guiry, G. M. 2004-2023 AlgaeBase. National University of Ireland Galway--

Hughey, Jeffery (1995) Noteworthy Collections: California: fucus spiralis, Madroño 42: 409

Humboldt State University 8/1/2016 HSC02010. Taxon: <em>Fucus spiralis</em> Linnaeus. <missing description>

Macroalgal Herbarium Consortium 2023 Macroalgal Herbarium Consortium Portal. <missing description>

Miller, Kathy Ann (2004) California's non-native seaweeds, Fremontia 32(1): 10-15

Miller, Kathy Ann; Aguilar-Rosas, Luis Ernesto; Pedroche, Francisco F. (2011) A review of non-native seaweeds from California, USA and Baja California, Mexico, Hidrobiológica 21(3): 365-379

Norris, R. E.; Conway, Elsie (1974) Fucus spiralis in the northeast Pacific, Syesis 7: 79-81

Oliveira, Otto M. P. and 24 authors (2016) Census of Cnidaria (Medusozoa) and Ctenophora from South American marine waters, Zootaxa 4194: 1-256

Taylor, William Randolph (1957) Marine Algae of the Northeastern Coast of North America, University of Michigan Press, Ann Arbor. Pp. <missing location>

Van Patten, Margaret Stewart (2006) Seaweeds of Long Island Sound, Connecticut Sea Grant, Groton. Pp. <missing location>