Report invasive species & other threats

A spongy green seaweed from Japan. First seen at Scarlett in 1960 and now at several locations around the Island.

ID features: Grows to around 25cm; Felt-like texture; Fronds are cylindrical and spongy; Forms dense clumps.

Issues: Competes with native species for space and is a potential nuisance to fisheries and aquaculture.

Habitats: It grows in rock pools and attaches to exposed rocks on the lower shore.

Further species information can be found here.

A brown seaweed that forms an air-filled sac. First seen on the Island in Port Erin and Peel in 2006. It has also been seen at Fort Island and Langness. It originates from the Pacific.

ID features: Thin-walled sphere, easily torn; Usually 1-7cm in diameter.

Issues:  Reproduces rapidly, out competes native species and is a potential nuisance for aquaculture.

Habitat: Grows on rocks, shells (including oysters) and seaweeds, in the mid intertidal down to the shallow subtidal, especially in sheltered areas.

Further species information can be found here.

This large brown seaweed originates from the NW Pacific and has currently only been sighted here once in 2011 at Port Soderick.

ID features: Large golden brown seaweed, 1-2m in length; Divided frond with midrib; Large reproductive frills just above the holdfast.

Issues: Covers underwater structures and out competes native species for space, and potentially changes the ecosystem.

Habitat: Attaches to hard surfaces, both natural and man-made, from mid tide to shallow sublittoral. Predominantly marine.

Further species information can be found here.

This red seaweed originated from Australia and has been found at Castletown, Peel and the Point of Ayre.

ID features: Distinctive barbed branches; Up to 30cm in length; Rosy, pink in colour.
Issues: Unknown.

Habitat: Attaches to seaweeds and hard structures using its barbs, but may form rafts. Found from low intertidal areas down to shallow subtidal areas.

Further species information can be found here.

A type of bivalve mollusc from Asia used in aquaculture in the UK. Currently only recorded on Ramsey harbour walls.

ID features: Frilly oval shell with an average length of 10cm; Shell may have dark purple patches.

Issues:  It out competes and can smother local species, although so far this is not an issue on the Island.

Habitats:  Grows on the lower intertidal shore on hard substrates and can be found in harbours and marinas.

Further species information can be found here.

A small barnacle which is native to Australia. It can be found at various locations around the Island, including Ramsey, Castletown, Port St Mary, Langness, Douglas and Laxey.

ID features: 5-10mm in diameter; White in colour with only 4 outer shell plates and a low conical body; Tolerant of a wide range of salinities.

Issues:  Can dominate hard surfaces and displace native species and can be a nuisance as a fouling organism.

Habitat:  Grows on hard surfaces such as rock and shell but also man-made structures.

Further species information can be found here.

A brown solitary sea squirt that originates from Korea. Currently only found on Octopus reef, off Douglas.

ID features: Up to 20cm long; Leathery appearance, rumpled or knobbly surface; The siphons are close together, with dark brown
stripes inside.

Issues: Large populations can displace and dominate native species and can be a fouling pest on hulls and aquaculture infrastructure.

Habitat: Attaches to solid surfaces in harbours and marinas as well as natural surfaces.

Further species information can be found here.

A solitary sea squirt which has bright orange tips. It has been found in Douglas harbour in 2013 but not since then. It originates from the Southern Hemisphere.

ID features: 2 – 4cm long; Orange tipped siphon in adults; Transparent body; Distinctive C/U-shaped gut rather than an S-shape.

Issues: Can clog underwater machinery and can smother local wildlife.

Habitat: Attaches to solid surfaces, both man-made and natural.

Further species information can be found here.

It is suspected that this bushy bryozoan has been identified in Manx waters. However this is yet to be confirmed. It originates from the western Atlantic.

ID features: Forms small erect, funnel shaped tufts; Light brown in colour; Multi-serial branches.

Issues: Fouling of underwater structures and competes with native species for resources.

Habitat:  Predominantly found in harbours and marinas.

Further species information can be found here.

A small colonial bryozoan first identified on pontoons in Douglas harbour in 2014. Originates from Japan.

ID features: Forms encrusting mats; Orange/red in colour; Forms colonies up to 20cm in diameter.

Issues: Fouling of underwater structures and shellfish, which has implications for additional cleaning costs for shellfish aquaculture and competes with native species for resources.

Habitats: Will encrust rocks, algae and shells, as well as man-made structures.

Further species information can be found here.

A rapid growing red, brown whorled seaweed identified back in 1905 in Port Erin. However, there have been no recent sightings reported. Its origin is unclear but likely to be from the Southern Hemisphere.

Habitat: It grows on all types of substrata including seaweeds, rocks, rope and other man-made underwater structures.

Further species information can be found here.

This red algae was first identified back in 1956 in Port Erin, however, no recent sightings have been observed. Originates from the NW Pacific Ocean.

ID features: It has hookshaped branches and can grow to 35cm in length.

Habitat: It can be found on the lower shore into the shallow subtidal. Its impacts are unknown.

Further species information can be found here.

A fast growing extensive sheet or mat-forming sea squirt, not yet found on the Island.

ID features: It has a firm, smooth texture with a varied colour range, from white to cream to orange/brown. It can have a veined or marbled appearance.

Issues and habitat: It attaches to hard substrates where it can smother native species and underwater structures.

Further species information can be found here.

A brown crab which lives in freshwater but breeds in sea water. Originally from SE Asia and as yet not found on the Island.

ID features: It has dense fur on its claws like mittens and a hexagonal body up to 8cm wide. Its legs are long and hairy.

Issues: It can cause damage to riverbanks by burrowing and feeds on a wide range of native prey items and competes with native species.

Habitat: It is found in estuaries and rivers.

Further species information can be found here.

An aggressive freshwater shrimp found in brackish water, originating from Eastern Europe. Not found on the Island yet.

ID features: It is larger than our native shrimps, up to 3cm with a tail with distinctive cones. It can tolerate poor quality water.

Issues: It kills and outcompetes native species .

Habitats: It can be found in still or flowing water amongst hard substrates and vegetation.

Further species information can be found.

An aggressive shrimp originally from SE Asia, which is rapidly invading part of the UK. It has not been found on the Island yet.

ID features: It can grow up to 49mm in length. It has large spines on the 3rd and 7th body segments in males. The female has orange spots on the broad pouch.

Issues: They can clog nets and outcompete native species.

Habitats:They tend to be found in harbours and marinas.

Further species information can be found here.

Originally from the US and has yet to reach Manx shores.

ID features: The shell is toenail shaped, up to 5cm long, white or cream coloured with orange/pink blotches. Often forming stacks with the oldest shell at the bottom.

Issues: They out compete local species and can be major pests in oyster and mussel beds.

Habitats: They attach to solid surfaces in sediment in low intertidal or shallow coastal waters.

Further species information can be found here.

It originates from Russia but has not been identified in Manx waters.

ID features: The shell can be up to 3cm long with a distinctive D shape. Light and dark bands of colour give it its name.

Issues: They can clog pipework and underwater equipment and outcompete our native species.

Habitats: They are found in slow moving brackish water such as docks.

Further species information can be found here.