Invasion History

First Non-native North American Tidal Record: 1885
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1885

General Invasion History:

Balanus trigonus was described using specimens from the Pacific (Indonesia, Colombia, Peru, Australia, and New Zealand) (Darwin 1854). This species appears to have a broad native distribution in the Pacific and Indian Oceans, including Australia and Japan, southern California (north to Monterey Bay), Peru, the Red Sea, and the southern tip of Africa. It may be introduced to New Zealand where it has a limited range (Cranfield et al. 1998), although it was reported from there by Darwin (1854).

Balanus trigonus is introduced in the Atlantic Basin (Carlton et al. 2011), where it was first recorded in Brazil in 1867. It is found on both sides of the Atlantic and throughout the Mediterranean. In the Western Atlantic, it occurs from North Carolina to Argentina, and in the Eastern Atlantic it is known from the Azores to South Africa. It seems to have colonized the warmer, more saline parts of the Atlantic long before reaching the East and Gulf coasts of the United States (US). It was found on a ship returning from the West Indies in 1877 (Pilsbry, 1916; US National Museum of Natural History 2012). This barnacle generally prefers subtidal habitats in warm-temperate to tropical waters (Werner 1967; Utinomi 1970; Southward 1975; Laguna 1985).

North American Invasion History:

Invasion History on the East Coast:

In U.S. waters, Balanus trigonus was found on the hull of ships arriving at Cape Cod in 1877 and 1879 (Zullo 1992; USNM 51541 and 21550, U.S. National Museum of Natural History 2012), but it was not found until 1961 on the Atlantic coast, in Biscayne Bay, Florida (Moore and McPherson 1963). In 1963 it was collected near Cape Lookout, North Carolina, at, or near, the northern limit of its range (Ross et al. 1964). This barnacle is now widespread from Florida to North Carolina (Werner 1967; Zullo and Lang 1978; Williams et al. 1984; Crickenberger and Sotka 2009).

Invasion History on the Gulf Coast:

In 1885, Balanus trigonus was collected off the Florida Coast in the Gulf of Mexico (Henry pers. comm., cited by Werner 1967). Currently its known range in the Gulf is from the southern tip of Florida, through Louisiana and Texas (Gittings 1985) to Tamaulipas, Mexico (Celis et al. 2007). Most records are from clear, high-salinity waters, including offshore oil platforms (Gittings et al. 1986). Carlton et al. (2011) correct and expand the chronology of Atlantic collections reported by Werner (1967) and Zullo (1992), and provide a detailed discussion of its history in the Western Atlantic. 

Invasion History Elsewhere in the World:

Balanus trigonus was first recorded in the Atlantic from Florianopolis, Brazil in 1864 (Carlton et al., 2011). It now ranges from North Carolina (35° N) and the Azores (38° N) south to Rio Grande do Sul, Brazil (27° S) and False Bay, South Africa (34° S) (Zullo 1992; US National Museum of Natural History 2012). In the Eastern Atlantic, it was first found on the West African Coast, Madeira, and the Azores between 1887 and 1909 (Zullo 1992). In the Mediterranean, as far as we are aware, the earliest dated record is from Sicily in 1927 (Zullo 1992). One empty specimen of B. trigonus was found on a buoy in Belgian waters in 1997-1998 (Kerckhof and Cattrijsse 2001).

While B. trigonus is native to Korea and southern Japan (Utinomi 1970; Kim 1992), it appears to be sporadically introduced by shipping to the northern Sea of Japan, where it has not become established (Zvyagintsev 2003). It has been listed as introduced to New Zealand (1960, Cranfield et al. 1998). Cranfield et al. (1998) give the first date of occurrence as 1960, and do not mention Darwin’s New Zealand specimens, or other early collections (Darwin 1854; Jennings 1917, cited by Foster 1967). Its distribution is limited to the region around Auckland (Foster 1967). Dromgoole and Foster (1983) considered it a species of 'uncertain native status'.


Balanus trigonus is a small to medium-size barnacle, ranging from conical to nearly-cylindrical in shape and reaching up to 25 mm in diameter. Its shell is composed of six overlapping plates, which are folded with wide longitudinal spaces (radii) which narrow at the top, and with transverse striations around a roughly triangular central opening (orifice). The shell has narrow white longitudinal ribs, and is colored or mottled with colored or mottled with purplish pink. . Inside the orifice are two large valves covering the appendages of the animal. Each valve is composed of two parts, the scutum and the tergum. The scutum is distinguished by one to six longitudinal rows of pits. Balanus trigonus can be distinguished by the scutum, which has one to six longitudinal rows of pits (Darwin 1854). The tergum is externally smooth and flat, with 'scarcely a trace of a longitudinal furrow' (Darwin 1854). The spur of the tergum is broad, being one-third to one-half of the width (Darwin 1854; Pilsbry 1916; Foster 1967; Werner 1967). Larval stages are illustrated by Barker (1976) and Lang (1979).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Maxillopoda
Subclass:   Thecostraca
Infraclass:   Cirripedia
Superorder:   Thoracica
Order:   Sessilia
Suborder:   Balanomorpha
Superfamily:   Balanoidea
Family:   Balanidae
Genus:   Balanus
Species:   trigonus


Potentially Misidentified Species



Balanus trigonus prefers saline (26-40 ppt), subtidal habitats in warm-temperate, subtropical and tropical seas (Werner 1967). This species, like many other barnacles, is hermaphroditic, but is capable of cross-fertilization. The fertilized eggs are brooded in the mantle cavity, sometimes for several months, and are released as nauplius larvae with three pairs of appendages (Barnes 1983). Balanus trigonus in culture produced broods of 1,000 to 35,000 eggs, averaging ~13,000 eggs (El-Komy and Kajihara 1991)..The nauplii feed in the plankton and go through five successive molts, spending at least 4 -11 days in the water column before molting into a non-feeding cypris stage, covered with a pair of chitinous shells (Barker 1976). Cyprids swim, investigating suitable surfaces and then settle, secreting a shell, and molting into the first juvenile barnacle stage (Barnes 1983). Juvenile and adult barnacles are filter feeders, sweeping the water with their long bristled appendages, and gathering phytoplankton, zooplankton, and detritus (Barnes 1983). Balanus trigonus grows on a wide range of hard surfaces, including mangroves, rocks, oysters, crabs, pilings, docks and ship hulls (Werner 1967; Zullo 1992).


Phytoplankton, zooplankton

Trophic Status:

Suspension Feeder



General HabitatRockyNone
General HabitatMarinas & DocksNone
General HabitatMangrovesNone
General HabitatOyster ReefNone
General HabitatCoarse Woody DebrisNone
General HabitatVessel HullNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone

Tolerances and Life History Parameters

Maximum Temperature (ºC)3750% of adults survived 20 h in water at 37ºC.(Ritz and Foster 1968)
Minimum Salinity (‰)22Lowest tested (Thiyagarajan et al. 2003)
Maximum Salinity (‰)40Typical Red Sea salinity.
Minimum Reproductive Temperature18Lowest tested (Thiyagarajan et al. 2003).
Maximum Reproductive Temperature28Highest tested (Thiyagarajan et al. 2003).
Minimum Reproductive Salinity22Lowest Tested(Thiyagarajan et al. 2003).
Maximum Reproductive Salinity40Typical Red Sea salinity.
Minimum Duration4.528 C (Thiyagarajan et al. 2003).
Maximum Duration1520 C, Barker 1976
Minimum Width (mm)25Maximum adult size (Darwin 1854)
Broad Temperature RangeNoneWarm temperate-Tropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Economic Impacts 

Shipping- We have not found specific reports of economic impacts for Balanus trigonus in North American waters. However, it is common in subtropical waters, frequently reported from ship hulls, and contributes to barnacle fouling of ships and harbor structures (Utinomi 1970; Moore et al. 1974; Zullo 1992).

Ecological Impacts

Fouling communities including B. trigonus were studied in North Carolina, off Cape Lookout. This barnacle was the most common species on fouling plates, together with the octocoral, Titanideum frauenfeldii. However, there was no evidence of spatial competition, since much space remained unoccupied. Balanus trigonus suffered considerable mortality from sea urchin (Arbacia punctulata) predation and sediment scour (Williams et al. 1984). These studies did not indicate unique impacts resulting from this barnacle’s invasion. However, B. trigonus is a potential competitor with other fouling organisms in suitable habitats.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-4a None 0 Native Estab
NWP-3b None 0 Native Estab
NWP-3a None 0 Native Estab
NWP-2 None 0 Native Estab
EAS-I None 0 Native Estab
EAS-III None 0 Native Estab
EAS-II None 0 Native Estab
EAS-VIII None 0 Native Estab
AUS-I None 0 Native Estab
AUS-II None 0 Native Estab
AUS-XIV None 0 Native Estab
AUS-XII None 0 Native Estab
AUS-XIX None 0 Native Estab
SP-I None 0 Native Estab
AUS-XI None 0 Native Estab
AUS-X None 0 Native Estab
AUS-VIII None 0 Native Estab
NZ-IV None 1854 Crypto Estab
AUS-III None 0 Native Estab
AUS-IV None 0 Native Estab
AUS-VI None 0 Native Estab
AUS-VII None 0 Native Estab
AUS-V None 0 Native Estab
EAS-VII None 0 Native Estab
EAS-VI None 0 Native Estab
CIO-IV None 0 Native Estab
CIO-V None 0 Native Estab
CIO-III None 0 Native Estab
CIO-II None 0 Native Estab
CIO-I None 0 Native Estab
IP-1 None 0 Native Estab
OM None 0 Native Estab
AG-1 None 0 Native Estab
AG-5 None 0 Native Estab
AG-3 None 0 Native Estab
AG-4 None 0 Native Estab
AG-2 None 0 Native Estab
GAden Gulf of Aden 0 Native Estab
RS-1 None 0 Native Estab
AUS-XIII None 0 Native Estab
EA-II None 0 Native Estab
RS-2 None 0 Native Estab
RS-3 None 0 Native Estab
EA-III None 0 Native Estab
EA-IV None 0 Native Estab
WA-V None 0 Native Estab
SP-XXI None 0 Native Estab
WA-IV None 1905 Def Estab
WA-II None 1897 Def Estab
WA-III None 1992 Def Estab
WA-I None 1897 Def Estab
NEA-VI None 1887 Def Estab
MED-IV None 1927 Def Estab
NEA-V None 0 Def Estab
MED-I None 0 Def Estab
MED-II None 1979 Def Estab
MED-III None 1969 Def Estab
MED-V None 1935 Def Estab
MED-VI None 1998 Def Estab
SA-II None 1867 Def Estab
SA-III None 1994 Def Estab
SA-IV None 1992 Def Estab
CAR-VI None 1992 Def Estab
CAR-III None 1939 Def Estab
CAR-II None 1975 Def Estab
CAR-IV None 1877 Def Estab
CAR-I Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida 1885 Def Estab
MED-VII None 1977 Def Estab
CAR-V None 1992 Def Estab
CAR-VII Cape Hatteras to Mid-East Florida 1963 Def Estab
NEP-VI Pt. Conception to Southern Baja California 0 Native Estab
NEP-VII None 0 Native Estab
NEP-VIII None 0 Native Estab
NEP-IX None 0 Native Estab
SEP-H None 0 Native Estab
SEP-I None 0 Native Estab
NEA-II None 1990 Def Unk
S190 Indian River 1966 Def Estab
G070 Tampa Bay 2000 Def Estab
G130 Pensacola Bay 2002 Def Estab
S180 St. Johns River 2001 Def Estab
S020 Pamlico Sound 1963 Def Estab
S030 Bogue Sound 1977 Def Estab
S120 Savannah River 1983 Def Estab
S090 Stono/North Edisto Rivers 1977 Def Estab
S076 _CDA_S076 (South Carolina Coastal) 1977 Def Estab
S080 Charleston Harbor 1977 Def Estab
S140 St. Catherines/Sapelo Sounds 1977 Def Estab
S175 _CDA_S175 (Nassau) 1977 Def Estab
S183 _CDA_S183 (Daytona-St. Augustine) 1966 Def Estab
S196 _CDA_S196 (Cape Canaveral) 1966 Def Estab
S200 Biscayne Bay 1961 Def Estab
S206 _CDA_S206 (Vero Beach) 1966 Def Estab
G050 Charlotte Harbor 1885 Def Estab
G020 South Ten Thousand Islands 1982 Def Estab
G045 _CDA_G045 (Big Cypress Swamp) 1982 Def Estab
G056 _CDA_G056 (Sarasota Bay) 1981 Def Estab
P050 San Pedro Bay 0 Native Estab
G090 Apalachee Bay 1964 Def Estab
G240 Calcasieu Lake 1982 Def Estab
G300 Aransas Bay 1984 Def Estab
G330 Lower Laguna Madre 1984 Def Estab
P062 _CDA_P062 (Calleguas) 0 Native Estab
P065 _CDA_P065 (Santa Barbara Channel) 0 Native Estab
P064 _CDA_P064 (Ventura) 0 Native Estab
SEP-Z None 0 Native Estab
NWP-4b None 0 Native Estab
P040 Newport Bay 0 Native Estab
PAN_PAC Panama Pacific Coast 0 Native Estab
PAN_CAR Panama Caribbean Coast 1939 Def Estab
SP-IX None 0 Native Estab
SP-XVI None 0 Native Estab
SEP-C None 1853 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


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