Marine Invasive Non- Native Species The Manx Wildlife Trust has produced a photographic identification guide describing (with images) twenty marine invasive non- native species (INNS), including shrimps, limpets, mussels, crabs, seaweeds, clams and barnacles. It can be downloaded here [pdf]: http://www.manxwt.org.uk/sites/default/files/files/marine_invasive_idguide_sept2015.pdf More information about those twenty species is listed below: Wireweed (Sargassum muticum) Wireweed is a type of brown seaweed originating from the Pacific Ocean. This plant is found all around the Island, both intertidally and subtidally. Wireweed was first introduced to the UK in 1973 on the Isle of Wight and first identified on the Isle of Man in 2005 in Castletown. It typically grows on hard surfaces in rock pools and shallow waters of sheltered shores. Its distinctive features are its long wires of olive brown weed branches that hang from the stem like clothes from a washing line. Each branch is covered in small leaves and tiny round floats. The stems may form very long lengths, more than 1 meter in length. Wireweed grows quickly and produces many spores, so quickly that it outcompetes local species. It is also problematic in harbors, shallow waters and on beaches. The stems attach to large rocks and can continue to produce new branches each spring. The branches often detach and form large floating plant masses which interfere with recreational beach use, clog propellers and intakes and can foul oyster beds and fishermens nets. Once established, dense strands of wireweed are likely to reduce the flow of water and available nutrients, increase sedimentation and reduce the available light and space and therefore displacing native species. Green Sea Fingers (Codium fragile) Green Sea Fingers is a spongy green seaweed originating from the Pacific Ocean around Japan. The seaweed was first seen on the Isle of Man in 1960 in Scarlett and is now found in several locations around the Island. It typically grows in rock pools by attaching to exposed rocks on the lower shore in shallow and subtidal waters mainly in protected bays. On sandy bottom surfaces the seaweed attaches to bivalve shells, rocks and artificial surfaces. Its distinctive features are its green colour, felt- like texture with Y- shaped branching. Its fronds are cylindrical and spongy, usually forming in dense clumps with cylindrical holdfasts to the seabed. It may reach up to 70cm high, but typically extends to only 25cm. Various parts of the seaweed easily detach and drift in the current. These floating parts can be a nuisance to fisheries and shellfish aquaculture, causing fouling and clogging of equipment. It may also cause a nuisance to beach- goers due to its unpleasant smell when it rots. Green Sea Fingers tend to spread easily and therefore compete with native species for space leading to a reduction of native biodiversity. Oyster Thief (Colpomenia peregrina) Oyster Thief is brown seaweed that forms an air- filled sac originating from the Pacific coast of North America. It was first seen on the Island in 2006 in Port Erin and Peel. It has since been seen at Fort Island and Langness. It typically grows on rocks, shells (including oysters), and seaweeds in the mid- intertidal range down to the shallow subtidal range, especially in sheltered areas. Its distinctive features are its resemblance to a small air- filled bag which collapses when touched. Its thin- walled sphere is easy torn and only amounts to 1-7cm in diameter. Its colour varies from a greenish colour to a yellowish- brown or brownish- grey.
Many of its effects are still largely unknown. However due to its lack of predators and rapid reproduction it is known to outcompete native species. When the seaweed is undamaged it can fill with air and if attached to an oyster it can lift the oyster from the seabed, taking it away (hence the name oyster thief ) obviously negatively impacting aquaculture. Wakame (Undaria pinnatifida) Wakame is a large brown seaweed that originates from the North West Pacific around Japan, China, and Korea where it is cultivated for human consumption. It was sighted once on the Island in 2011 at Port Soderick, but this hasn t been confirmed. It is typically found attached to hard surfaces, both natural and man- made in the mid tide to shallow sublittoral tidal ranges. This species is predominantly marine. Its distinctive features are its golden- brown colour and large size of around 1-2m in length. It s frond is divided with a midrib with a lighter colored stripe and it has large reproductive frills just above the holdfast. This species is opportunistic, rapidly attaching to substrata forming a thick underwater canopy that outcompetes native species for space and light. Many of the effects are still unknown, but this species can potentially significantly change the ecosystem, especially in areas where native seaweeds are absent. They have the potential to disrupt aquaculture farms due to fouling which can restrict waterflow. Harpoon weed (Asparagopsis armata) Harpoon weed is red seaweed originating from Australia. It has been found on the Island in Castletown, Peel and the Point of Ayre. It is typically found attached to seaweeds and hard structures using its barbs in the low tidal areas down to shallow subtidal areas. The seaweed may also form floating rafts. Its distinctive features are its rosy, pink colour and distinctive barbed branches. It can grow up to 30cm in length. It typically grows in spherical or hemispherical masses of up to 1-3cm in diameter This species has a lack of predators and a rapid growth rate. It has the potential to outcompete native species due to its proliferation, however its impacts are still largely unknown. Pacific Oyster (Crassostrea gigas) The Pacific Oyster is a type of bivalve mollusc originating from Japan and North- East Asia that was purposefully imported for aquaculture in the UK. This bivalve is currently recorded on the walls of Ramsey harbour. It is generally found growing on the lower intertidal shore on hard substrates and can be found in harbours and marinas. Its distinctive features are its rough frilly oval shell that varies from an off- white colour to bluish grey that may have dark purple patches. It averages a length of 10cm; however they can grow up to 30 cm in length. Escapes from aquaculture farms have managed to form localised populations. The bivalve is highly adaptable, has rapid growth, and is resistant to high turbidity. These characteristics allow it to create dense reefs by cementing their shells together. This can alter the environment outcompeting and smothering native species. However, so far this has not been an issue on the Island. The sharp edges of the shells may also pose a threat to your toes! Australian barnacle (Austrominius modestus) (previously Elminius modestus)
The Australian barnacle, also known as Darwin s Barnacle, is a small barnacle. As indicated by its name it originates from Australia. It can be found at various locations around the island including Ramsey, Castletown, Port St Mary, Langness, Douglas and Laxey. It can be found growing on hard surfaces, such as rock and shell, and even man- made structures - more commonly in the mid- shore and may extend to the shallow sublittoral. The barnacle s distinctive features are its white colour and low conical body made of 4 outer shell plates, compared to our native species which have six plates. It has a small size, with a diameter between 5-10mm. The young are greyish white and adults tend to be a dull greyish- brown and eroded. It is a fast- growing species with a high reproductive rate which gives it a competitive advantage over slower growing native species. It is also adaptable to varying salinity levels, turbidity, low temperatures and even pollution. The Australian barnacle can dominate hard spaces and displace native species. They can also be a nuisance by fouling vessels and aquaculture equipment. Soft Shell Clam (Mya arenaria) The Soft Shell Clam is a bivalve that buries itself in the mud, originating from the Pacific. It is currently only recorded in Port Erin Bay. The soft shell clam can be found living in soft sediments in the intertidal and shallow sublittoral zones in bays and estuaries. Its distinctive features are its chalky white colour and oval, elongated shell that is gaping at both ends. The exterior of the shell is rough with uneven concentric rings. It can reach 15cm in length. From the surface, its burrow hole leaves a characteristic key- hole shaped opening in the sediment. Soft shell clams have a high adaptability to a variety of environments and can form large populations which can displace and dominate native species. They often die in situ forming large death- assemblages which may become a new habitat in itself. They can also be fouling pests on hulls of ships and aquaculture infrastructure. Leathery sea squirt (Styela clava) The leathery sea squirt is a brown solitary sea squirt originating from the North- West Pacific around Japan, Korea, and Northern China. It is currently found on the island on Octopus reef, off Douglas. It can be found attached to solid surfaces in low wave energy environments such as, harbours and marinas as well as natural surfaces. Its distinctive features are its elongated club- shaped body with a leathery appearance, and a rumpled or knobbly surface. Towards the top it has two tube- like siphons that are close together with dark brown stripes inside. Its body is commonly 8-12cm in length, but it can grow up to 20cm long. This sea squirt is highly adaptable to changes in temperature and salinity. Its ability to adapt and rapidly spread allows it to form large populations that can displace and dominate native species. The sea squirt has been found to grow to populations as large as 500-1500 individuals per square meter. It can also cause the decline of native populations through preying on the larvae of the native species. The sea squirt is also a fowling pest on ship hulls, fishing equipment, and oyster beds. Due to its large size the sea squirt can serve as a substrate for other fouling species, compounding the issue. Orange tipped sea squirt (Corella eumyota) The orange tipped sea squirt is a solitary sea squirt originating from the Southern Hemisphere (precise location unknown). It has been found in Douglas harbour in 2013, but has not been
seen since. It can be found attached to hard surfaces, both man- made and natural often, but not exclusively found in marinas and harbours. Its distinctive features are, when an adult, its transparent body with orange tipped siphons. It also has a distinctive C or U - shaped gut, rather than the typical S - shape. It lays flat, growing to 2-4cm in length. It is solitary, but highly gregarious (growing in loosely organized communities) forming large clumps which can clog underwater machinery and may compete with and smother local wildlife. Bryozoan (Bugula simplex) Bugula simplex is one of several bryozoans (small colonial organisms), this one originating from the western Atlantic. It is suspected that this bushy bryozoan has been identified in Manx waters. However, this is yet to be confirmed. It is predominantly found inhabiting the subtidal region in harbours and marinas. Its distinguishing features are its small erect, funnel shaped tufts forming colonies. The colonies are made up of multi- series of branches that are light brown in colour. The branches are narrow at the base and branch out at the top reaching up to 3cm in height. It is generally found during the summer months and often does not survive winter. Its impacts include fouling of underwater structures and competing with native species for resources. Bryozoan (Schizporella japonica) Schizporella japonica is one of several bryozoans (small colonial organisms), this one originating from Japan. It was first identified in 2014 on pontoons in Douglas harbour. It can be found encrusting rocks, algae and shells, as well as man- made structures. Its distinctive features include its orange/red colour and roughly rectangular shape. This bryozoan forms colonies of zooids (animals that bud off each other) forming encrusting mats. The colonies can be up to 20cm in diameter. This bryozoan is a common fouling organism attaching to underwater structures such as docks, hulls of ships, and shellfish. This has implications for additional cleaning costs for shellfish aquaculture and competes with native species for resources. Red seaweed (Antithamnionella ternifolia) The origin of the red seaweed is unclear, but it is likely to be from the Southern Hemisphere. It was first sited on the Island in 1905 in Port Erin. However, there have not been any recent sightings reported. It can be found growing on all types of substrata including seaweeds, rocks, rope, and other man- made underwater structures. Its distinctive features are its red- brown whorled shape. This species has a rapid growth rate and can grow in various environments across a wide range of temperatures. Its effects on the environment are unknown, but it is known to be a fouling organism. Hook weed (Bonnemaisonia hamifera) This red algae originate from the North West Pacific Ocean, likely Japan. It was first identified on the Island in 1956 in Port Erin. However, no recent sightings have been observed. It can be found on the lower shore into the shallow subtidal range attached to rocks and other hard substrata, sometimes man- made structures.
Its distinctive features are its red coloured hook- shaped branches that can grow in dense tufts up to 35cm in length. Its impacts are generally unknown, but it may smother or compete with other native algae and seagrasses. Carpet sea squirt (Didemnium vexillum) The Carpet sea squirt is one species of many sea squirts thought to originate from the North West Pacific, likely Japan. This species has been found in nine marines in Great Britain and in various locations around the world, but it has not yet been found on the Island. It has been found in shallow marinas on artificial substrates as well as on natural cobble or gravel seabeds, in tide pools near the shore, seagrass beds and on bivalve aquaculture installations. Its distinctive features are its firm smooth texture with either a veined or marble appearance. It varies in colour from white to cream to orange/brown. The carpet sea squirt is a fast growing species that forms extensive sheets or mats (2-5mm in thickness) that can smother native species and underwater structures. It also has potential impacts on the shellfish industry by fouling the farms and equipment. This species is registered as a high alert species by the Great Britain Non- Native Species Secretariat (GB NNSS). It has cost hundreds of thousands of pounds to remove and subsequently control in UK harbours. Chinese Mitten Crab (Eriocheir sinensis) The Chinese Mitten Crab is a small migrating crab originating from South East Asia. It is established in various rivers in the UK and Europe, but it is currently not found on the island. This can be found living in estuaries and rivers, but breeds in sea water. Its distinctive features are its dense fur on its claw, resembling mittens, and hexagonal body up to 8cm wide of an olive- green or brown colour. Its legs are long and hairy - twice the length of its body. Its hard square- shaped carapace (upper hard shell) distinguishes it from other crabs. The Chinese Mitten Crab can cause damage to riverbanks by burrowing and are likely to displace and compete with native benthic (bottom- dwelling) invertebrates of both freshwater and marine systems through predation and competition for space. It is also known to be a carrier of diseases. Economic impacts are difficult to estimate, but may be costly due to repairing flood defences, and land reclamation from burrowing. They also damage fishing nets and can clog up industrial water intake filters. This species is registered as a high alert species by the Great Britain Non- Native Species Secretariat (GB NNSS). Killer Shrimp (Dikerogammarus villosus) The Killer Shrimp is an aggressive freshwater shrimp (hence its name), originating from Eastern Europe. However, it is currently not yet found on the island. It can be found in still or flowing water amongst hard substrates and vegetation. Its distinctive features are its large curled, semitransparent body, up to 3cm long. Its tail has distinctive cones. It has two pair s antennae and relatively large and powerful mandibles. The Killer Shrimp can adapt to a wide variety of temperatures, salinity, and oxygen levels. This species kills and outcompetes native species, potentially significantly altering the local environment. The presence of this species could possibly affect the quality and distribution of fisheries either through altering the environment or through carrying diseases. Japanese Skeleton Shrimp (Caprella mutica)
The Japanese Skeleton Shrimp is an aggressive shrimp originating from North East Asia, from the Japanese Sea. It has not yet been found on the Island, but it is rapidly invading other areas of the UK. They tend to be found in harbours and marinas. Its distinctive features include its slender cylindrical body, large in size, growing up to 49mm in length. This species ranges from orange to red in colouration. Male shrimp have large spines on the 3 rd and 7 th body segments. Female shrimp have orange spots on the brood pouch and are much smaller than males. Japanese Skeleton Shrimp are known to show aggressive behaviour, and may outcompete native species; however their full impacts are still unknown. In the summer months their prevalence tends to clog nets and water intake systems. Slipper limpet (Crepidula fornicata) The Slipper limpet is a marine gastropod (snail) originating from North America, ranging from Canada along the East Coast of the United States to the Caribbean, but has spread to various regions of the UK. However, it has yet to reach Manx shores. They can be found attached to solid surfaces, such as stones and shells, in sediment located in low intertidal or shallow coastal waters. Its distinctive features include its smooth toenail- shaped shell often white or cream coloured with orange/pink blotches. The shells are often forming stacks, up to 5cm long, with the oldest shell at the bottom. Slipper limpets out compete local species for space and food. Their high tolerance of a variety of environmental conditions allows them to easily spread and often occur in large numbers. Their attachment to native species of mussels and mobile species may slow that species growth or reduce their chances of survival. In high densities Slipper limpets have also been shown to reduce water flow and increase siltation through faeces production. Slipper limpets can be major pests in oyster and mussel beds leading to additional cleaning costs from fouling. Zebra mussel (Dreissena polymorpha) The Zebra mussel is a freshwater mussel that can tolerate brackish water. It originates from Russia, has spread to various parts of the UK, but has not yet been identified in Manx waters. They can be found in slow moving brackish water, such as lakes, rivers and brackish lagoons. They are often attached to hard surfaces such as rocks and docks. Its distinctive features include the light and dark bands of colours, which give the Zebra mussel its name. The shell can be up to 3-5cm long with a distinctive D - shape. This species has a high reproductive rate allowing it to spread widely and rapidly. Zebra mussels can be a nuisance by clogging pipe work and underwater equipment and fouling ship hulls. They are also known to out compete native species. For example this species consumes a lot of algae, which may affect the native population of some fish. Their sharp edges may also cause injuries to bathers. Zebra mussels are also known to bioaccumulate pollution which may poison animals further up the food chain.