Short description of Solidobalanus fallax, A barnacle

Although similar to Balanus crenatus this species tends to be smaller but relatively taller up to 12 mm in diameter. Shell colour variable from almost entirely white with pink tinges, to reddish purple patches. The scutum is coloured and shows strong growth ridges. Shells have solid walls without pores. 

Impact summary: Solidobalanus fallax, A barnacle

Can infest pink sea fan (Eunicella verrucosa) colonies and may foul fish farming cages and other aquaculture structures.

Habitat summary: Solidobalanus fallax, A barnacle

This barnacle does not settle on rocks, but primarily lives attached to biological substrata including macroalgae, sea-fans, mollusc shells and crabs.  It also settles on plastic bags, nets ropes and lobster pots. It occurs subtidally, from seven to 220 metres depth.

Overview table

Environment	Marine
Species status	Non-Native
Native range	Northern Europe, Southwestern Europe, Northern Africa, West Tropical Africa
Functional type	Filter-feeder
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	English Channel
Date of first record	1988

Origin

Native to North and West Africa, from Angola to Morocco and Algeria.

First Record

First reported from the English Channel in 1994, growing attached to queen scallop shells. However, it is difficult to distinguish from related species so may have been present but misidentified for some time.  Barnacles attached to hydroids in Cornwall which were collected during the 1980s and later re-examined were found to be S. fallax.

Pathway and Method

Not known but may have arrived attached to floating plastic debris.  The recent records may be evidence of a range extension rather than introductions of a non-native species. 

Species Status

This species is becoming common along west European coasts from southern Spain and Portugal round to the southern bight of the North Sea.  Its range expansion has been reported to occur at a rate of 49 km per year. 

Dispersal Mechanisms

Plastic debris in the sea provides a vector for dispersal of attached barnacles.  Planktonic larvae are dispersed by wind driven and tidal currents.

Reproduction

Little is known about reproduction in this species.  Brooding individuals have been recorded in British waters in May, and juveniles found in October and November.  It is thought that larval development and settlement may occur until December.  Larval development includes six naupliar and one cyprid stage.  Development to the cyprid stage is reported to take eight days at 25 °C.

Known Predators/Herbivores

Worms, whelks, fish, birds, crabs, some sea slugs and starfish are amongst the wide range of animals to prey upon acorn barnacles. 

Resistant Stages

None known.

Habitat Occupied in GB

Lives attached to biological and plastic substrata including sea fans, mollusc shells, crabs and plastic objects; does not settle on rocks.  It occurs subtidally from seven to over 200 metres depth. 

In GB it is common in Devon and Cornwall and also found in Dorset, several regions of Wales and Lundy Island. 

Environmental Impact

The settlement of this species on the pink sea fan may adversely affect the condition of this UK Biodiversity Action Plan species which is also listed in GB for protection under Schedule 5 of the Wildlife and Countryside Act 1981.

Health and Social Impact

None known.

Economic Impact

This species may have the potential to become a serious pest of fish cages and other sea-farming structures in the south of Britain and Western Europe.  Economic losses may occur through cleaning costs and loss of utility.

Identification

Southward, A.J. (1995) Occurrence in the English Channel of a warm-water cirripede, Solidobalanus fallax. Journal of the Marine Biological Association of the United Kingdom, 75, 199-210.

Southward, A.J., Hiscock, K., Kerckhof, F., Moyse, J. & Elfimov, A.S. (2004) Habitat and distribution of the warm-water barnacle Solidobalanus fallax (Crustacea: Cirripedia).  Journal of the Marine Biological Association of the United Kingdom, 84, 1169-1177.

Biology, ecology, spread, vectors

Korn, O.M. & Elfimov, A.S. (1999) Larval development of a warm-water immigrant barnacle, Solidonalanus fallax (Cirripedia: Archaeobalanidae) reared in the laboratory.  Journal of the Marine Biological Association of the United Kingdom, 79, 1039-1044.

Management and impact

Sorte, C.J.B., Williams, S.L. & Carlton, J.T. (2010) Marine range shifts and species introductions: comparative spread rates and community impacts.  Global Ecology and Biogeography, 19, 303-316.

General

Southward, A.J. (1995) Occurrence in the English Channel of a warm-water cirripede, Solidobalanus fallax. Journal of the Marine Biological Association of the United Kingdom, 75, 199-210.