Invasion History

First Non-native North American Tidal Record: 1982
First Non-native West Coast Tidal Record: 1993
First Non-native East/Gulf Coast Tidal Record: 1982

General Invasion History:

Since 1990, scientists in several parts of the world have observed the growth and spread of an unidentified species of Didemnum in the temperate marine waters of New Zealand, North America, and Europe. While there have been differing opinions on the identity of these different populations (Kott 2002; Kott 2004), some have suspected that it is a single species (Bullard et al. 2007). Recently, genetic and morphological studies have apparently resolved the great Didemnum species debate. The first description of this tunicate was by Kott (2002). Specimens from New Zealand were intensely reviewed and the study concluded that the correct name is D. vexillum (Lambert 2009; Stefaniak et al. 2009). Didemnum vexillum probably originated from the northwest Pacific, possibly Japan (Lambert 2009). Genetic analysis supports the native status of populations in eastern Japan. Further sampling in the northwest Pacific is needed to determine the full extent of the native range (Stefaniak et al. 2012). It has invaded the West and East Coasts of North America including Mexico, California, Alaska and New York, Massachusetts and Maine.

North American Invasion History:

Invasion History on the West Coast:

Didemnum vexillum was first reported from San Francisco Bay in 1993 and it seemed to be limited to the saltier (>26 ppt) parts of the bay (Cohen 2005; Cohen et al. 2005; Bullard et al. 2007; USGS Woods Hole Science Center 2008; Ruiz et al., unpublished data). North of San Francisco Bay, D. vexillum was found in Tomales Bay (CA) and Humboldt Bay (CA) in 2001, Bodega Harbor (CA) in 2003, Puget Sound (WA) in 2004, Okeover Inlet (British Columbia) in 2003 (Bullard et al. 2007) and Jervis Inlet (British Columbia; USGS Woods Hole Science Center 2008). In 2010, it was found in Sitka (AK), its northernmost site on the West Coast (Cohen et al. 2011). South of San Francisco Bay, D. vexillum was found in Half Moon Bay (CA) in 1997, Monterey Bay (CA) and Elkhorn Slough (CA) in 1998, Morro Bay (CA) in 2000, and Port San Luis (CA) in 2002 (Bullard et al. 2007). In 2007, it was found in Mission Bay (CA) (USGS Woods Hole Science Center 2008). In 2005, it was found fouling oysters (Crassostrea gigas) in Bahia San Quintin, Mexico (Rodriguez and Ibarra-Obando 2008).

On the West Coast, the sequence of occurrences suggests an introduction to San Francisco Bay, followed by dispersal from shipping and aquaculture to the north and south. However, fishermen in British Columbia claim that D. vexillum may have been present for more than a decade before its official discovery (USGS Woods Hole Science Center 2011).

Invasion History on the East Coast:

Didemnum vexillum was first reported in 1982 from the Damariscotta River estuary, Maine (Dijkstra and Nolan 2011). This occurrence has sometimes been attributed to experimental culture of Pacific Oysters (Crassostrea gigas) in the 1970s (Shatkin et al. 1997), but these oysters were hatchery-reared seed, and would not have be fouled with tunicates. Ship fouling from Europe, where fouled Pacific Oysters were planted and reared, is the most probable vector (James T. Carlton, personal communication). In 1996, D. vexillum was collected on Tillies Bank, MA. A few years later in 1998, it was collected on Stellwagen Bank and Georges Bank, MA where it has continued to spread in offshore waters (Bullard et al. 2007). By 1998, D. vexillum was present in the Cape Cod Canal (Sandwich, MA) and had been tentatively identified in photographs taken of floating docks from Woods Hole in 1998 (Bullard et al. 2007; USGS Woods Hole Science Center 2008). In 2000, it was collected in Eel Pond at Woods Hole, MA and was found along the southern side of the Cape and east to Orleans, MA (USGS Woods Hole Science Center 2008). Again in 2000, it was collected in Buzzards Bay, MA and Narragansett Bay, RI (MIT Sea Grant 2008; Osman and Whitlatch 2007, Bullard et al. 2007), as well as in eastern Long Island Sound, NY (Osman and Whitlatch 2007). In 2004, D. vexillum reached its current southern limit of Shinnecock Bay, NY (Bullard et al. 2007; USGS Woods Hole Science Center 2008). There may be a temperature and/or salinity threshold that complicates its spread to warmer (e.g. southern) and low salinity waters, given that its presence seems to be limited to the mouth of estuaries (e.g. Long Island Sound, NY and Narragansett Bay, RI). Currently, D. vexillum ranges from Parrsboro, Nova Scotia to Shinnecock Inlet, NY (Bullard et al. 2007; USGS Woods Hole Science Center 2008; Moore et al. 2014). In recent surveys (2006-2009), it was not found in New Brunswick waters, although it was found in Eastport, Maine, only 2 km from the border (Martin et al. 2011). However, in 2013 it was found on the Bay of Fundy, Nova Scotia (Moore et al. 2014). 

Invasion History Elsewhere in the World:

Northeast Atlantic: The earliest report of Didemnum vexillum from Europe was along the Dutch coastline in 1991. It remained relatively rare until 1996 when the population rapidly expanded, especially in the province of Zeeland, Netherlands (Gittenberger 2007). Subsequently, in 2001, D. vexillum was found growing on the face of a brick quay (wharf or reinforced bank) and overgrowing other invertebrates (barnacles, mussels, tunicates, etc.) in the Port of Le Havre, France. In 2002 it was found growing on ropes and overgrowing other invertebrates in Perros-Guirec, Brittany (USGS Woods Hole Science Center 2011). In 2005, it was found in Ireland’s Malahide Estuary attached to boats, pontoons, ropes, buoys, seaweed and mussels (Minchin and Sides 2006; USGS Woods Hole Science Center 2011). In 2008-2009, D. vexillum was found on the coast of Spain, in the towns of Santander, Baiona, Moana, Corme-Porto, and Gijon (El Nagar et al. 2010).

In 2010, D. vexillum was discovered growing in the Lagoon of Venice, at the head of the Adriatic Sea, the first record from the Mediterranean Sea (Tagliopietra et al. 2012). In 2012, it was found growing on oysters in Fangar Bay, in the Ebro Delta, on the Spanish Mediterranean coast. Genetic analysis suggested the likely source was oyster cultures on the French Atlantic Coast. This invasion suggests that D. vexillum has greater capacity, than previously thought, to invade warm waters (Ordonez et al. 2015).

Southwest Pacific: In October 2001, An unidentified species of Didemnum was discovered fouling mooring posts and boats in Whangamata Harbour, New Zealand. Patricia Kott described it as D. vexillum, and considered it a native species, previously unnoticed in New Zealand (Kott 2002). In December 2001, this organism was found overgrowing a barge in Shakespeare Harbour near Picton, New Zealand. In 2003, eradication of the fouling on the barges, recreational vessels, moorings, salmon cages and wharf pilings was attempted, using a variety of methods (Coutts and Forrest 2007). Fouled areas were wrapped in plastic and treated with chlorine, moorings were water-blasted, boats were cleaned and repainted with antifouling paints, the seabed was covered with fresh dredge spoil, and riprap was covered with Geotextile fabric and treated. However, some tunicates survived in joints in the riprap and eventually repopulated the area (Coutts and Forrest 2007).


Description

Didemnum vexillum is an aggressive and rapidly spreading colonial tunicate species forming extensive thin sheets which often overgrow rocks, shells, other sessile organisms (e.g. sponges, hydroids, oysters), and even itself ultimately forming large sponge-like masses. These masses often have long, flexible leaf or flag like projections that are cylindrical and branched. Large D. vexillum colonies may appear to be folding in on themselves and neighboring surfaces. Colonies are yellowish-cream in color with the yellow pigment observed in the gut, eggs, and embryos. The thorax of its zooids are white in color. Star shaped calcareous spicules are patchily distributed in the surface layer and in the cloacal cavity; patchiness increases closer to the tunic surface. Spicules are approximately 58 µm in diameter with 9-11 conical rays. The oral siphon is short with only six lobes. The atrial siphon is surrounded by large clumps of spicules around the opening. There are 8-9 stigmata in an anterior row of the oral cavity. The post-stomach gut forms a double loop in the abdomen. Zooids are about 1 mm long and are arranged along the common cloacal canals that extend through the colony. Didemnum vexillum has nine coils of vas deferens around the testis. Embryos are approximately 600 µm (with tail wrapped around body) and are incubated in the core of the tunic, and not within each zooid (Kott 2002, as D. vexillum, New Zealand).

Morphological identification criteria for Didemnum species, particularly in the USA, have not been re-evaluated since Van Name published his monograph in 1945. Since that time, there has been a turbulent taxonomic evolution in the identification of Didemnum species. The near simultaneous discovery of outbreaks of similar didemnids in New Zealand, the East and West Coast (North America), and Europe raised questions of whether a single or multiple species existed, and whether the outbreaks were true invasions or simply population booms of native species (Bullard et al. 2007). Kott (2002) named the New Zealand form D. vexillum, but found morphological differences in specimens from the northwest Atlantic (New Hampshire) and therefore named these as a separate species, D. vestum. Gretchen Lambert investigated the possibility that this species was conspecific with D. lahillei, described from Brittany in 1909. However, she found that the type material (physical representative specimen) was a mixture of several species (Lambert 2009). In 2005, others began a molecular (18S rDNA) study using the samples from New Hampshire, New Zealand and Japan, and found that all of the samples were the same species, for which D. vexillum was the valid name (Lambert 2009; Stefaniak et al. 2009). Genomic sampling of populations worldwide indicates high genetic diversity, but also genetic differentiation among populations. Of two major groups with different COI (Cytochrome oxidase I) groups, only one was widley introduced, with three major colonization events (Casso et al. 2018).


Taxonomy

Taxonomic Tree

Kingdom:   Animalia
Phylum:   Chordata
Subphylum:   Tunicata
Class:   Ascidiacea
Order:   Aplousobranchia
Family:   Didemnidae
Genus:   Didemnum
Species:   vexillum

Synonyms

Didemnum sp. A (Bullard et al., 2009)
Didemnum vestum (Kott, 2004)

Potentially Misidentified Species

Didemnum albidum
NW Atlantic native

Didemnum areolatum
NW Pacific native

Didemnum carnulentum
NE Pacific native

Didemnum maculosum
NE Atlantic native

Didemnum misakiense
NW Pacific native

Didemnum pacificum
NW Pacific native

Didemnum pardum
NW Pacific native

Ecology

General:

Life History- A colonial tunicate consists of many zooids, bearing most or all of the organs of a solitary tunicate, but modified to varying degrees for colonial life. Colonial tunicates of the family Didemnidae have small zooids, completely embedded in an encrusting and thin tunic. Each zooid has an oral siphon and an atrial aperture which opens to a shared cloacal chamber. Water is pumped into the oral siphon, through finely meshed ciliated gills on the pharynx, where phytoplankton and detritus is filtered, and passed on mucus strings to the stomach and intestines. Excess waste is expelled in the outgoing atrial water (Van Name 1945; Barnes 1983).

Colonial tunicates reproduce both asexually by budding and sexually from fertilized eggs that develop into larvae. Buds can form from the body wall of the zooids. Colonies vary in size ranging from small clusters of zooids to huge spreading masses. The zooids are hermaphroditic, which means both eggs and sperm are released into the atrial chamber. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but some species have a partial block to self-fertilization. Fertilized eggs are brooded within the tunic until they hatch into lecithotrophic (non-feeding, yolk-dependent) tadpole larvae. The larva has a muscular tail and a notochord, eyespots, and a set of adhesive papillae. The larvae are expelled upon hatching and swim briefly before settlement. Swimming periods are usually less than a day, but some larvae settle immediately after release or swim for longer periods if the water temperature is low. In experiments, 10% of larvae remained viable after a delay of 36 h. In field experiments, most settlement occured within 250 m of the parent population, but some settlement is possible at distances of 1 km or more (Fletcher et al. 2012). On settlement the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Van Name 1945; Barnes 1983).

Colonies of D. vexillum can also disperse by fragmentation and zooids are capable of reproduction while suspended in the water column. Fragments of colonies can remain suspended for up to three weeks, and can reattach to surfaces and grow. However, the apparent health of the colony declines, the longer it is suspended in the water column. The viability of fragments is a concern for attempts to control or eradicate this species (Morris and Carman 2012). Fragments will reattach on eelgrass and artificial surfaces at water temperatures of 6-10 °C, but at a lower rate than at summer temperatures (16-22 °C) (Carman et al. 2014). Exposure to high temperatures results in increased DNA methlylation, and decreased growth rates, which may 'buy survival time' as a stress resonse (Hawes et al. 2018). The rapid spread of D. vexillum may be due to the ability of genetically different colonies to fuse, forming rapidly growing ramets, forming transient chimeras, stretching and dispersing across a substrate, and later resegregating (Fidler et al. 2018).

In all part of its native and introduced range, D. vexillum is more frequently reported from anthropogenic stuctures than from natural surfaces, (Simkanin et al. 2012). Dock floats are especially favored habitats, probably because their motion provides rapid water exchange, and a fresh supply of food-laden water (Glasby 2001). Other colonized man-made structures include pilings, piers, aquaculture structures, and boat hulls (Carman et al. 2010; Davidson et al. 2010; Simkanin et al. 2012). Natural habitats include rocky reefs, gravel bottoms, bivalve colonies, seaweeds, and eelgrass (Valentine et al. 2007; Carman and Grunden 2010 Simkanin et al. 2012; Carman et al. 2016).

Food:

Phytoplankton, bacteria, detritus

Consumers:

Starfish, urchins

Trophic Status:

Suspension Feeder

SusFed

Habitats

General HabitatGrass BedNone
General HabitatCoarse Woody DebrisNone
General HabitatUnstructured BottomNone
General HabitatOyster ReefNone
General HabitatMarinas & DocksNone
General HabitatRockyNone
General HabitatBedrockNone
General HabitatVessel HullNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone


Tolerances and Life History Parameters

Minimum Temperature (ºC)-2Field data, Bullard et al. 2007
Maximum Temperature (ºC)24Field data, Bullard et al. 2007, reduced growth at 23 C, experimental data, McCarthy et al. 2007
Minimum Salinity (‰)19Field and laboratory data (Bullard et al. 2007; Gröner et al. 2011; Hawes et al. 2018). Growth and survival at medium (15-28 PSU) and low (10-26 PSU) sites was greatly reduced compared to a high-salinity site (26-30 PSU) in the Thames estuary, Connecticut (Bullard and Whitlach 2009; Auker 2019).
Maximum Salinity (‰)35Highest observed?
Minimum Reproductive Temperature14Onset of spring recruitment, but fall reproduction ceases at 9-11 C (Valentine et al. 2009). In New Zealand, recruitment was not detected when temperatures dropped below 12 C, but some larvae were present in the the tissues of colonies (Fletcher et al. 2013).
Maximum Reproductive Temperature20end of spring recruitment (Valentine et al. 2009)
Minimum Duration0Larvae can settle immediately on release (Fletcher et al. 2012)
Maximum Duration1.5 In experiments, 10% of larvae remained viable after a delay of 36 h (Fletcher et al. 2012)
Broad Temperature RangeNoneCold temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Didemnum vexillum is widely considered to be an invasive species with potentially important economic and ecological impacts. As a recent invader in many parts of the world, the extent of its impacts have only just begun to be studied. Didemnum vexillum is unique in that, unlike many marine invasive organisms, it is not only common in confined, disturbed, and polluted harbors and estuaries, but is also common in the more ‘pristine’ waters of Georges Bank (MA), British Columbia and New Zealand. Consequently, its invasions potentially have major implications on industries that take place in 'cleaner' waters, such as fisheries and aquaculture (Bullard et al. 2007; Valentine et al. 2007), and may impact natural ecosystems by significantly altering the local habitat (Bullard et al. 2007; Valentine et al. 2007).  

Economic Impacts

Fisheries: Economic impacts on 'wild' fisheries (e.g. bottom fishes, scallops, lobsters, mussels, etc.) are expected due to D. vexillum altering habitat and food resources on Georges Bank and elsewhere in the world (Bullard et al. 2007; Valentine et al. 2007). Didemnum vexillum is considered a major threat to New Zealand's mussel industry because of its demonstrated invasiveness on artificial structures, and its ability to over-grow and smother mussels (Coutts and Forrest 2007). To help save the shellfish industry in New Zealand, $650,000 NZ dollars were spent on eradication of D. vexillum (Coutts and Forrest 2007). However, the attempts to eradicate D. vexillum were unsuccessful and it was soon seen spreading to mussel farms in the region, resulting in significant crop losses (Coutts and Forrest 2007).

Shipping and Industry: Since New Zealand relies on sea-borne shipping for over 90% (by volume) of its international commerce (Hewitt et al., 2004), D. vexillum is considered a serious and persistent fouling pest to their commercial shipping industry and ports (Coutts and Forrest 2007).


Ecological Impacts

Competition: Rapid population explosions are known to reduce the abundance of previously established benthic species and cause significant changes in benthic community structure (Whitlatch et al. 1995; Bak et al. 1996; Lambert 2001; Castilla et al. 2004). Since D. vexillum can attach and encrust nearly every substrate it encounters, competition for resources (e.g. suitable attachment substrates, food, etc.) becomes a problem. In many locations, D. vexillum overgrows benthic biota, such as seaweeds, scallops, mussels, and other invertebrates (Bullard et al. 2007; Auker and Oviatt 2008; Gittenberger 2007; Valentine et al. 2007; Dijkstra and Harris 2009) which further exacerbates competition pressures. However, its competitiveness is partly related to environmental conditions. In laboratory and field conditions, D. vexillum was most competitive at sites with cooler temperatures (approx. 15-21°C), where it outgrew other tunicates, such as Botrylloides violaceus, Botryllus schlosseri, and Ascidiella aspersa (McCarthy et al. 2007). However, D. vexillum was less dominant on plates where other colonies of species had been established (Osman and Whitlatch 2007). In experiments at Eel Pond (Woods Hole), D. vexillum began to recruit later (October) than other species, however, it rapidly expanded its coverage on plates from October-December (Agius 2007). In Narragansett Bay (MA), D. vexillum dominated plates in the fall, and overgrew Blue Mussel (Mytilus edulis) recruits (Auker and Oviatt 2008). Didemnum vexillum was one of several invasive fouling species which showed increased growth (% coverage) at temperatures 3.5 and 4.5°C above the ambient temperature in Bodega Harbor (13.5°C), while the native Distaplia occidentalis showed reduced survival (Sorte et al. 2010).

In field experiments with a diversity of competitors and predators, D. vexillum was less successful in the presence of other species, suggesting that it is not a stronger competitor compared to other non-native colonial ascidians (e.g. Botrylloides violaceus, Botryllus schlosseri) (Stefaniak 2007). However, the ability of colonies to form tendrils for dispersal, to fuse, to form extensive colonies on pebble and cobble surfaces, and to resist grazing, due to calcareous spicules in the tunic, enable D. vexillum to form extensive colonies (Stefaniak 2017).

Habitat Change: Didemnum vexillum overgrows gravel, seaweeds, scallops, mussels, and other invertebrates thereby greatly altering the structure of the pre-existing habitat (Bullard et al. 2007; Auker and Oviatt 2008; Gittenberger 2007; Valentine et al. 2007). These D. vexillum mats are thought to reduce the amount of seabed surface suitable for larval settlement of other benthic species, such as sea scallops, on Georges Bank, MA. Additionally, these mats likely reduce the amount of suitable shelter available for juvenile fish and other prey organisms (Valentine et al. 2007). Sea Scallops overgrown by D. vexillum have reduced swimming speeds, and may be less able to escape predators (Dijkstra and Nolan 2011). By 2003-2006, colonial tunicates, including D. vexillum, replaced mussels (M. edulis) as the dominant species in fouling communities in Portsmouth Harbor, NH. (Dijkstra and Harris 2009). This is a major functional habitat change because while mussels provided a year-round substrate available to other organisms for settlement, tunicates, such as D. vexillum, are more resistant to secondary settlement by these other organisms. However, D. vexillum dies off seasonally and creates large areas of bare substrate available for colonization by other organisms (Dijkstra and Harris 2009). Of course this bare substrate is only available to those organisms with settlement periods that overlap with D. vexillum seasonal die offs, thereby excluding some benthic species from settlement opportunities.

Herbivory: Experiments by Byrne and  Stachowicz (2009) in Bodega Harbor (CA) indicate that D. vexillum has a lower filtration rate than the native Distaplia occidentalis. Similar results were obtained for other exotic/native pairs. It has been suggested that the cumulative effect of increased invasions in filter feeding fouling communities may increase seasonal consistency of filtration. This is probably due to spreading out of recruitment times of filter feeding organisms rather than increases in filtration rates.

Food/Prey: On Georges Bank (MA), Valentine et al. (2007) suggest that dense mats of D. vexillum colonies possibly form a physical barrier between fish and benthic prey resources, such as worms and bivalves. In Long Island Sound (NY),  predation studies by Osman and Whitlatch (2007) found that some predation did occur on D. vexillum recruits by the gastropod Mitrella lunata. Additionally, their study suggests that there was possibly a fish predator that preyed on their suspended uncaged D. vexillum treatments. However, Osman and Whitlatch (2007) state that the growth and dominance of juvenile and adult colonies of D. vexillum at Pine Island suggests that their abundance is not significantly reduced by predation.

Toxicity: Many species of Didemnum are chemically defended by a variety of compounds and for most species, including D. vexillum, this results in a lower surface pH (2-3) (Bullard et al. 2007).

Regional Impacts

NEA-IINoneEcological ImpactCompetition
Overgrowth of epibenthic flora and fauna, killing some species (Netherlands, Gittenberger 2007).
NEA-IINoneEcological ImpactHabitat Change
Overgrowth of epibenthic flora and fauna, killing some species (Netherlands, Gittenberger 2007).
NA-ET3Cape Cod to Cape HatterasEcological ImpactCompetition
Didemnum vexillum overgrows benthic fauna, including scallops, mussels, and other sessile species, on the Georges Bank (Valentine et al. 2007). On bare experimental plates in Fishers Island Sound, Connecticut, Didemnum was most competitive at sites with cooler temperatures, where it outgrew other tunicates, such as Botrylloides violaceus, Botryllus schlosseri, and Ascidiella aspera. However, Didemnum was less dominant on plates in which colonies of other species were already established (Osman and Whitlatch 2007). Invasion success of D. vexiullum in experimental fouling communities was dependent on the presence of large amounts of unoccupied space (Janiak et al. 2013). In experiments at Eel Pond, Woods Hole, Didemnum began to recruit later than other species, in October, and rapidly expanded its coverage on plates in October-December (Agius 2007). In Narragansett Bay, Didemnum dominated plates in the fall, and overgrew recruits of the Blue Mussel (Mytilus edulis) (Auker and Oviatt 2008).

In field experiments with a diversity of competitors and predators, Didemnum vexillum was less successful than when predators were excluded. However, the ability of colonies to form tendrils for dispersal, to fuse, to form extensive colonies on pebble and cobble surfaces, and to resist grazing, due to calcareous spicules in the tunic, enable D. vexillum to form extensive colonies in open areas (Stefaniak 2017).

On Georges Bank, the abundance of Didemnum vexillum had a negative asssociation with that of both juvenile and Sea Scallops (Placopecten magellanicus. Didemnnum vexillum was more abundant i areas open to trawling than in areas closed to fishing, indicating that it may be favored by disturbance (Kaplan et al. 2017)
NA-ET3Cape Cod to Cape HatterasEcological ImpactHabitat Change
Didemnum vexillum overgrows gravel and benthic fauna, including scallops, mussels, and other sessile species. The surface of D. vexillum appears to repel settlement of secondary fouling organisms, suggesting that large areas of D. vexillum may reduce the amount of seabed suitable for settlement of larvae of other benthic species, including sea scallops.  The mats of Didemnum sp. may also reduce the amount of suitable shelter available for juvenile fish and other organisms (Valentine et al. 2007).

On Georges Bank, the abundance of Didemnum vexillum had a negative asssociation with that of both juvenile and Sea Scallops (Placopecten magellanicus. Didemnum vexillum may inhibit the settling of Sea Scallops, because of the acidity of its tunic (Kaplan et al. 2017).
NA-ET3Cape Cod to Cape HatterasEcological ImpactFood/Prey
Dense mats of Didemnum vexillum colonies possibly form a barrier between fish and their benthic prey such as worms and bivalves, on the Georges Bank (Valentine et al. 2007). Some predation occurred on Didemnum, by the snail Astyris lunata and probably by fish on uncaged plates, but this tunicate appears less limited by predation than other tunicates, whose recruits are less likely to survive in open, deeper waters than Didemnum (Osman and Whitlatch 2007). Many benthic invertebrates on Georges Bank were positively associated with D. vexillum, and many of these invertebrates were important components of 5 important species of fishes (Winter Skate (Leucoraja ocellata), Little Skate (Leucoraja erinacea), Haddock (Melanogrammus aeglefinus), Winter Flounder (Pseudopleuronectes americanus), and Longhorn Sculpin (Myoxocephalus octodecemspinosus) (Smith et al. 2014).
NA-ET3Cape Cod to Cape HatterasEconomic ImpactFisheries
Economic impacts on 'wild' fisheries, such as bottom fishes, scallops and lobsters are expected due to habitat change and replacement of food resources. Didemnum vexillum was found fouling aquaculture gear at 11 sites, and cultured Bay Scallops (Argopecten irradians) at three sites, of 26 aquaculture sites surveyed on Marthas Vineyard (Carman et al. 2010). This tunicate was also reported at aquaculture sites in Rhode Island (Carman et al. 2010). On Georges Bank, a major concern was possible negative impacts on the commercially important Sea Scallop (Placopecten magellanicus). Experiments indicate that can negatively affect larval settlement (Morris et al. 2009) and escape responses of the scallops (Dijkstra et al. 2011; Kaplan et al. 2017). However, the commerically important fishes Haddock Melanogrammus aeglefinus and Winter Flounder (Pseudopleuronectes americanus) fed heavily on benthic invertebrates positively associated with D. vexillum (Smith et al. 2014).
M040Long Island SoundEcological ImpactCompetition
On bare experimental plates in Fishers Island Sound, Connecticut, Didemnum was most competitive at sites with cooler temperatures, where it outgrew other tunicates, such as Botrylloides violaceus, Botryllus schlosseri, and Ascidiella aspera. However, Didemnum was less dominant on plates in which colonies of other species were already established (Osman and Whitlatch 2007). Invasion success of D. vexillum in experimental fouling communities was dependent on the presence of large amounts of unoccupied space (Janiak et al. 2013). In field experiments with a diversity of competitors and predators, Didemnum vexillum was less successful than when competitors and predators were excluded. However, the ability of colonies to form tendrils for dispersal, to fuse, to form extensive colonies on pebble and cobble surfaces, and to resist grazing, due to calcareous spicules in the tunic, enable D. vexillum to form extensive colonies (Stefaniak 2017).
M040Long Island SoundEcological ImpactFood/Prey
Some predation occurred on Didemnum, by the snail Mitrella lunata and probably by fish on uncaged plates, but this tunicate appears less limited by predation than other tunicates, whose recruits are less likely to survive in open, deeper waters than Didemnum (Osman and Whitlatch 2007).
N195_CDA_N195 (Cape Cod)Ecological ImpactCompetition
In experiments at Eel Pond, Woods Hole, Didemnum began to recruit later than other species, in October, and rapidly expanded its coverage on plates in October-December (Agius 2007).
M020Narragansett BayEcological ImpactCompetition
In Narragansett Bay, Didemnum dominated plates in the fall, and overgrew recruits of the Blue Mussel (Mytilus edulis) (Auker and Oviatt 2008).
NEP-IIIAlaskan panhandle to N. of Puget SoundEconomic ImpactFisheries
Didemnum vexillum was found fouling shellfish cages and other aquaculture structures at Taylor Shellfish Farms, Quilcene, WA, and in Gallagher Cove, WA, Puget Sound and on oyster trays in Deep Bay, Baynes Sound, and mussel cages in Okeover Inlet, British Columbia (USGS Woods hole Science Center 2008). Switzer et al. (2011) tested chemical treatments (hydrated lime), mechanical treatments (manual scrubbing) and biological control (sea urchins. Strongylocentrotus droebachiensis, native) for cleaning fouled oysters. The mechanical and chemical treatments reduced fouling by Didemnum, but created free pace for botryllid tunicates to settle.
P290Puget SoundEconomic ImpactFisheries
Didemnum vexillum was found fouling shellfish cages and other aquaculture structures at Taylor Shellfish Farms, Quilcene, WA, and in Gallagher Cove, WA, Puget Sound (USGS Woods Hole Science Center 2008).
NZ-IVNoneEconomic ImpactFisheries
Didemnum vexillum is considered a major threat to New Zealand's mussel industry (Coutts and Forrest 2007). It was also found overgrowing salmon aquaculture cages (USGS Woods Hole Science Center 2008). As much as $650,000 NZ dollars were spent on an unsuccessful eradication attempt (Coutts and Forrest 2007).
NZ-IVNoneEconomic ImpactShipping/Boating
Didemnum vexillum is considered a serious fouling pest to recreational boating and commerical shipping. In New Zealand, attempts at eradicating and preventing the spread of Didemnum vexillum required costly cleaning of boats, pilngs, floats, etc.(Coutts and Forrest 2007).
NA-ET2Bay of Fundy to Cape CodEcological ImpactCompetition
In Portsmouth Harbor, by 2003-2006, colonial tunicates including D. vexillum replaced the mussel Mytilus edulis (1979-1982) as the dominant species in fouling communities (Dijkstra and Harris 2009).
NA-ET2Bay of Fundy to Cape CodEcological ImpactHabitat Change
In Portsmouth Harbor, by 2003-2006, colonial tunicates including D. vexillum replaced the mussel Mytilus edulis (1979-1982) as the dominant species in fouling communities (Dijkstra and Harris 2009). A major functional change is that while mussel shells provided a year-round structure on the substrate, available to settlement by other organisms, colonial tunicates are more resistant to secondary settlement, and die off seasonally, creating large areas of bare substrate which can be colonized by other organisms (Dijkstra and Harris 2009). Didemnum vexillum can make Sea Scallops (Placopecten magellanicus) more vulnerable to predators by fouling their shells and decreasing their swimming speed (Dijkstra and Nolan 2011). On Georges Bank, extensive cover of D. vexillum is negatively correlated iwth abundance of P. magellanicus, barncles, tube anemones, Cerianthus, to sea urchins (Strongylocentrotus droebachiensis). Didemnum vexillum is considered a major driver of biodiversity decline on Georges Bank. Its effects are strongest on areas disturbed (by trawling (Kaplan et al. 2017).
NEP-VNorthern California to Mid Channel IslandsEcological ImpactCompetition
Didemnum vexillum was one of several invasive fouling species which showed increased growth (% coverage) at temperatures 3.5 and 4.5⁰C above the ambient temperature in Bodega Harbor (13.5⁰C), while the native Distaplia occidentalis showed reduced survival (Sorte et al. 2010). Didemnum vexillum was one of a group of seven non-native species, most of which were rare or absent in 1970-1971, but were among the eight most abundant species in 2005-2009. Spawning periods and abundance of species in this group appeared to be favored by a 1⁰C increase in average temperatures at this site over a 30-year period (Sorte and Stachowicz 2011). Didemnum vexillum overgrowth had a modest effect on the growth of eelgrass (Zostera marina) blades in mesocosms filled with water from Tomales Bay (Long and Grosholz 2015).
P112_CDA_P112 (Bodega Bay)Ecological ImpactCompetition
Didemnum vexillum was one of several invasive fouling species which showed increased growth (% coverage) at temperatures 3.5 and 4.5⁰C above the ambient temperature in Bodega Harbor (13.5⁰C), while the native Distaplia occidentalis showed reduced survival (Sorte et al. 2010). Didemnum vexillum was one of a group of seven non-native species, most of which were rare or absent in 1970-1971, but were among the eight most abundant species in 2005-2009. Spawning periods and abundance of species in this group appeared to be favored by a 1⁰C increase in average temperatures at this site over a 30-year period (Sorte and Stachowicz 2011).
N195_CDA_N195 (Cape Cod)Economic ImpactFisheries
Didemnum vexillum was found fouling aquaculture gear at 11 sites, and cultured Bay Scallops (Argopecten irradians) at three sites, of 26 aquaculture sites surveyed on Marthas Vineyard (Carman et al. 2010). This tunicate was also reported at aquaculture sites in Rhode Island (Carman et al. 2010).
NA-ET2Bay of Fundy to Cape CodEconomic ImpactFisheries
Didemnum vexillum was reported fouling aquaculure sites in Maine (Carman et al. 2010; Bullard et al. 215).
N130Great BayEcological ImpactCompetition
In Portsmouth Harbor, by 2003-2006, colonial tunicates including D. vexillum replaced the mussel Mytilus edulis (1979-1982) as the dominant species in fouling communities (Dijkstra and Harris 2009).
N130Great BayEcological ImpactHabitat Change
In Portsmouth Harbor, by 2003-2006, colonial tunicates including D. vexillum replaced the mussel Mytilus edulis as the dominant species in fouling communities (Dijkstra and Harris 2009). A major functional change occured because while mussel shells provided structure, which other organisms can settle upon, colonial tunicates are more resistant to secondary settlement.  However, colonial tunicates die off seasonally, creating large areas of bare substrate which can be colonized by other organisms (Dijkstra and Harris 2009).
NEA-IINoneEconomic ImpactShipping/Boating
Because of potential economic and ecological impacts, eradication was attempted in Holyhead Harbour, Wales, in 2009, by enclosing floats in plastic bags, creating a stagnant environment. This was temporarily effective, but the regrowth of new colonies was seen by 2011 (Holt 2011). Fouling impacts fave been reported for the British Isles (Minchin et al. 2013).
N135_CDA_N135 (Piscataqua-Salmon Falls)Ecological ImpactFood/Prey
Increasing abundance of the introduced colonial tunicates Didemnum vexillum and Diplosoma listerianum has resulted in population growth of the native Bloodstar starfish Henricia sanguinolenta (Dijkstra et al. 2012).
N135_CDA_N135 (Piscataqua-Salmon Falls)Ecological ImpactTrophic Cascade
Increased abundance of the Bloodstar starfish (Henricia sanguinolenta), supported by growing populations of Didemnum vexillum and Diplosoma listerianum, has resulted in increased predation and near-disappearance of the cryptogenic sponge Halichondria panicea (Dijkstra et al. 2012).
NA-ET2Bay of Fundy to Cape CodEcological ImpactFood/Prey
Increasing abundance of the introduced colonial tunicates Didemnum vexillum and Diplosoma listerianum has resulted in population growth of the native Bloodstar starfish Henricia sanguinolenta (Dijkstra et al. 2012).
NA-ET2Bay of Fundy to Cape CodEcological ImpactTrophic Cascade
Increased abundance of the Bloodstar starfish (Henricia sanguinolenta), supported by growing populations of Didemnum vexillum and Diplosoma listerianum, has resulted in increased predation and near-disspapearance of the cryptogenic sponge Halichondria panicea (Dijkstra et al. 2012).
P290Puget SoundEcological ImpactHabitat Change
The introduced isopod Ianiropsis serricaudis occurred in high abundance with D. vexillum at Taylor Shellifish Frams, Puget Sound, but not found at other sites in the Sound (Cordell et al. 2012).
NEP-IIIAlaskan panhandle to N. of Puget SoundEcological ImpactHabitat Change
The introduced isopod Ianiropsis serricaudid occurred in high abundance with D. vexillum at Taylor Shellifish Frams, Puget Sound, but not found at other sites in the Sound (Cordell et al. 2012).
P110Tomales BayEcological ImpactCompetition
Didemnum vexillum overgrowth had a modest effect on the growth of eelgrass (Zostera marina blades in mesocosms filled with water from Tomales Bay (Long and Grosholz 2015).
P110Tomales BayEcological ImpactHabitat Change
Didemnum vexillum faciltated growth of invertebrates (polychaetes and tanaids) on eelgrass blades (Long and Grosholz 2015).
NEP-VNorthern California to Mid Channel IslandsEcological ImpactHabitat Change
Didemnum vexillum faciltated growth of invertebrates (polychaetes and tanaids) on eelgrass blades (Long and Grosholz 2015)
NEA-IIINoneEconomic ImpactFisheries
Fouling of cultured mussels by a variety of non-native tunicates was reported beginning in 2013, and was a serious problem by 2016 (Palanisamy et al. 2018).
N070Damariscotta RiverEconomic ImpactFisheries
Didemnum vexillum was reportedly fouling aquaculture sites in Maine (Carman et al. 2010; Bullard et al. 2015)

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NZ-IV None 2001 Def Estab
NA-ET2 Bay of Fundy to Cape Cod 1982 Def Estab
NA-ET3 Cape Cod to Cape Hatteras 2000 Def Estab
NEP-V Northern California to Mid Channel Islands 1993 Def Estab
NEP-IV Puget Sound to Northern California 2001 Def Estab
NEP-III Alaskan panhandle to N. of Puget Sound 2003 Def Estab
NEA-II None 1991 Def Estab
NEA-IV None 2002 Def Estab
M050 Great South Bay 2004 Def Estab
M040 Long Island Sound 2001 Def Estab
M020 Narragansett Bay 2000 Def Estab
N195 _CDA_N195 (Cape Cod) 2000 Def Estab
M010 Buzzards Bay 2000 Def Estab
N185 _CDA_N185 (Cape Cod) 2003 Def Estab
N180 Cape Cod Bay 2000 Def Estab
N170 Massachusetts Bay 2006 Def Estab
N130 Great Bay 2001 Def Estab
N070 Damariscotta River 1982 Def Estab
N060 Muscongus Bay 2002 Def Estab
N010 Passamaquoddy Bay 2005 Def Estab
NEP-VI Pt. Conception to Southern Baja California 2007 Def Estab
P030 Mission Bay 2007 Def Estab
P069 _CDA_P069 (Central Coastal) 2002 Def Estab
P070 Morro Bay 2000 Def Estab
P080 Monterey Bay 1998 Def Estab
P086 _CDA_P086 (San Francisco Coastal South) 1997 Def Estab
P090 San Francisco Bay 1993 Def Estab
P110 Tomales Bay 2001 Def Estab
P112 _CDA_P112 (Bodega Bay) 2003 Def Estab
P130 Humboldt Bay 2001 Def Estab
P290 Puget Sound 2004 Def Estab
P293 _CDA_P293 (Strait of Georgia) 2007 Def Estab
N036 _CDA_N036 (Maine Coastal) 2005 Def Estab
NEA-III None 2007 Def Estab
NWP-4b None 0 Native Estab
NWP-3b None 0 Native Estab
NEA-V None 2007 Def Estab
M023 _CDA_M023 (Narragansett) 2007 Def Estab
N135 _CDA_N135 (Piscataqua-Salmon Falls) 2003 Def Estab
P180 Umpqua River 2010 Def Estab
P170 Coos Bay 2010 Def Estab
M030 Gardiners Bay 2009 Def Estab
N165 _CDA_N165 (Charles) 2006 Def Estab
MED-VII None 2010 Def Estab
P100 Drakes Estero 2010 Def Estab
N100 Casco Bay 2010 Def Estab
N120 Wells Bay 2013 Def Estab
P062 _CDA_P062 (Calleguas) 2011 Def Estab
MED-II None 2012 Def Estab
NWP-4a None 2016 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
6947 USGS Woods Hole Science Center 2003-2007 2004 2004-12-03 Old Ponquogue Bridge Def 40.8448 -72.5006
6948 USGS Woods Hole Science Center 2010 2009 2009-11-17 521 East Lake Drive, Montauk Def 41.0614 -71.9222
6949 Osman and Whitlatch 2007 2000 2000-01-01 Avery Point, Groton Def 41.3154 -72.0634
6950 Carman et al. 2009 2007 2007-01-01 Block Island Def 41.1831 -71.5828
6951 MIT Sea Grant 2009 2009-01-01 Matunuck, Point Judith Marina Def 41.3732 -71.5367
6952 Auker and Oviatt 2008 2005 2005-01-01 South Pier, Prudence Island Def 41.5882 -71.3245
6953 Auker and Oviatt 2008 2005 2005-01-01 Fort Wetherill, Jamestown Def 41.4773 -71.3578
6954 MIT Sea Grant 2003-2007 2000 2000-01-01 Coasters Harbor Island, Newport Def 41.5107 -71.3270
6955 USGS Woods Hole Science Center 2003-2007 2002 2002-01-01 URI Dock, Graduate School of Oceanography Def 41.4883 -71.4250
6956 MIT Sea Grant 2003 2000 2000-01-01 Tripps Marina Def 41.5079 -71.0486
6957 MIT Sea Grant 2003 2000 2000-01-01 Massachusetts Maritime Academy, Bourne Def 41.7396 -70.6239
6958 USGS Woods Hole Science Center 2003-2007 2004 2004-01-01 West Falmouth Harbor Def 41.6057 -70.6495
6959 USGS Woods Hole Science Center 2003-2007 2000 2000-01-01 Woods Hole Def 41.5200 -70.6667
6960 MIT Sea Grant 2003-2007 2004 2004-01-01 Vineyard Haven Def 41.4668 -70.5911
6961 Osterville/MA/Cotuit Bay 2005 2005-01-01 Osterville Def 41.6284 -70.3870
6962 USGS Woods Hole Science Center 2003-2007 2003 2003-08-07 Chatham Def 41.6650 -69.9567
6964 USGS Woods Hole Science Center 2003-2007 2003 2003-01-01 Provincetown Def 42.0492 -70.1808
6965 MIT Sea Grant 2011 2008 2008-01-01 Sesuit Harbor Def 41.7557 -70.1550
6966 MIT Sea Grant 2003-2007 2000 2000-01-01 Sandwich Marina Def 41.7704 -70.5036
6968 USGS Woods Hole Science Center 2003-2007 2006 2006-01-01 off Cottage Park Road, Winthrop Def 42.3751 -70.9828
6969 MIT Sea Grant 2011 2008 2008-01-01 Winter Island Def 42.5293 -70.8689
6970 MIT Sea Grant 2011 2007 2007-01-01 Beverly Public Pier Def 42.5404 -70.8870
6971 MIT Sea Grant 2011 2006 2006-01-01 Straitsmouth Island, Rockport Def 42.6598 -70.5912
6972 Bullard et al. 2007 2003 2003-02-01 Duck Island, Isles of Shoals Def 43.0048 -70.6059
6973 Ruiz et al. unpublished data 2001 2001-01-01 Badger Island Marina, Kittery Def 43.0823 -70.7517
6974 USGS Woods Hole Science Center 2003-2007 2002 2002-01-01 Fort Point, Newcastle Def 43.0723 -70.7098
6975 USGS Woods Hole Science Center 2003-2007 1991 1991-01-01 Damariscotta Def 43.8947 -69.5878
6976 USGS Woods Hole Science Center 2003-2007 1982 1982-01-01 Damariscotta Def 43.8947 -69.5878
6977 MIT Sea Grant 2008 2008 2008-01-01 Boothbay Harbor Def 43.8465 -69.6348
6978 USGS Woods Hole Science Center 2003-2007 2002 2002-01-01 Bremen Long Island Def 43.9901 -69.3876
6983 Dijkstra et al. 2007 2005 2005-01-01 Winter Harbor Def 44.3645 -68.0811
6984 USGS Woods Hole Science Center 2003-2007 2005 2005-01-01 Cobscook Bay Def 44.9095 -67.0555
6985 Cohen et al. 2011 2010 2010-06-13 Sitka Def 57.0481 -135.3694
6986 USGS Woods Hole Science Center 2007 2004 2004-12-01 Nelson Island Def 49.7000 -124.0667
6988 USGS Woods Hole Science Center 2007 2004 2004-08-10 Christy Island Def 50.2900 -124.7242
6989 USGS Woods Hole Science Center 2007 2003 2003-01-01 Okeover Inlet, Straits of Georgia Def 49.0163 -124.6900
6990 Bellingham Herald 2007 2007 2007-01-01 Larrabee State Park, Bellingham Def 48.6584 -122.4766
6991 USGS Woods Hole Science Center 2007 2004 2004-01-01 Edmonds Underwater Park Def 47.8138 -122.3833
6993 USGS Woods Hole Science Center 2007 2006 2006-08-02 Des Moines Marina Def 47.3992 -122.3280
6994 USGS Woods Hole Science Center 2007 2004 2004-11-01 Taylor Shellfish Farms Def 47.1397 -122.9792
6995 USGS Nonindigenous Aquatic Species Program 2010 2010 2010-02-01 near Reedsport Def 43.6771 -124.1748
6996 USGS Nonindigenous Aquatic Species Program 2010 2010 2010-04-01 Charleston Boat Basin Def 43.3406 -124.3219
6997 Ruiz et al., unpublished data 2003 2003-01-01 Fields Landing Def 40.7246 -124.2151
6999 USGS Woods Hole Science Center 2007 2003 2003-01-01 Woodley Island Marina Def 40.8076 -124.1623
7000 Bullard et al. 2007 2003 2003-01-01 Bodega Harbor Def 38.3235 -123.0478
7001 de Rivera et al. 2005a 2004 2004-01-01 Porto Bodega Marina Def 38.3338 -123.0511
7004 Rivera et al. 2005a 2004 2004-01-01 Sacramento Landing Def 38.1496 -122.9064
7013 Cohen and Chapman 2005 2005 2005-11-27 San Mateo Bridge Pylon Def 37.6019 -122.2047
7014 USGS Woods Hole Science Center 2012 1998 1998-04-30 Moss Landing Def 36.8058 -121.7902
7016 Bullard et al. 2007 2002 2002-01-01 Port San Luis Def 35.1750 -120.7552
7017 USGS Woods Hole Science Center 2007 2007 2007-01-01 Mission Bay Def 32.7925 -117.2512
7018 Rodriguez and Ibarra-Obando 2008 2005 2005-01-01 Bahia San Quintin Def 30.4500 -116.0000
7019 USGS Woods Hole Marine Science Center 2008. 2007 2007-08-16 Misaki Marine Biological Station Native 35.1577 139.0102
7020 USGS Woods Hole Marine Science Center 2008 2007 2007-07-13 Asamushi Marine Biological Station Native 40.8917 140.8602
7023 USGS Woods Hole Marine Science Center 2008 2007 2007-05-30 Coastal Research Center, Otsuchi Native 39.3538 141.9188
7024 Kott 2002 2001 2001-10-01 Whangamata Harbor Def -37.1833 175.8833
7025 Kott 2002 2002 2002-05-01 Picton Def -42.2667 174.0000
7027 USGS Woods Hole Science Center 2008 2006 2006-02-25 Arapawa Island Def -41.1705 174.3198
7028 Gittenberger 2007 1991 1991-01-01 Lake Grevelingen Def 51.7142 4.0222
7029 Gittenberger et al. 2010 2008 2008-01-01 Terschelling Def 53.4000 5.3167
7030 USGS Woods Hole Science Center 2012 2002 2002-08-07 Le Havre Def 49.9997 0.1200
7031 Minchin and Sides 2006) 2005 2005-01-01 Malahide Estuary Def 53.4333 -6.1500
7033 Minchin and Sides 2006 2006 2006-01-01 Carlingford Lough Def 54.0333 -6.1833
7034 Griffith et al. 2009, Holt 2011 2008 2008-10-12 Holyhead Marina Def 53.3196 -4.6415
7035 Griffith et al. 2009 2005 2005-06-29 Darthaven Marina, Dartmouth Def 50.3529 -3.5774
7036 Marine Conservation Society UK 2010 2010-03-01 Cowes Def 50.7595 -1.3002
7037 Beveridge et al. 2011 2010 2010-01-25 Largs Def 55.7925 -4.8678
7038 USGS Woods Hole Science Center 2008 2007 2007-09-26 Parknahallagh Def 53.1800 -8.9517
7039 Woods Hole Science Center 2008 2008 2007-11-09 Murrisk Def 53.7905 -9.6170
7042 USGS Woods Hole Science Center 2002 2002 2002-08-02 Perros-Guerec Def 48.8153 -3.4366
7043 USGS Woods Hole Science Center 2005 2005 2005-08-25 Brest Def 48.3908 -4.4856
7044 Lambert 2009 2009 2009-01-01 La Rochelle Def 46.1667 -1.1500
7045 Lambert 2009 2007 2007-01-01 Pornic Def 47.1167 -2.1000
7046 Lambert 2009 2007 2007-01-01 Archachon Def 44.6594 -1.1675
7047 El Nagar et al. 2010 2009 2009-01-01 Santander Def 43.4280 -3.8080
7048 El Nagar et al. 2010 20098 2009-01-01 Gijón Def 43.5450 -5.6650
7049 El Nagar et al. 2010 2009 2009-01-01 Baiona Def 42.1210 -8.8470
7050 El Nagar et al. 2010 2009 2009-01-01 Moaña Def 42.2770 -8.7350
7051 El Nagar et al. 2010 2009 2009-01-01 Corme-Porto Def 43.2620 -8.9650
7858 Tagliapietra et al. 2012 2010 2010-09-23 Arsenal of Venice Def 45.4369 12.3539
7859 Tagliapietra et al. 2012 2012 2012-07-01 Certosa marina floating pontoon, Venice Def 45.4314 12.3678
7860 Tagliapietra et al. 2012 2012 2012-07-01 Lido Grando marina, Venice Def 45.4542 12.4336
7888 ICES WGITMO 2012 2011 2011-01-01 North Kent Coast Def 51.3706 1.1270
7983 Santa Rosa Press-Democrat 2012 2010 2010-01-01 Drake's Bay Oyster Farm Def 38.0474 -122.9422
30685 USGS Woods Hole Science Center 2007) 1993 1993-10-03 San Francisco Bay Def 37.8494 -122.3681
767369 Ruiz et al., 2015 2012 2012-08-22 Tomales-Marshall, Bodega Bay, California, USA Def 38.1514 -122.8888
767380 Ruiz et al., 2015 2012 2012-08-21 Tomales-Nick's Cove, Bodega Bay, California, USA Def 38.1980 -122.9222
767400 Ruiz et al., 2015 2012 2012-08-16 Tomales-SNPS, Bodega Bay, California, USA Def 38.1359 -122.8719
767412 Ruiz et al., 2015 2012 2012-08-17 Tomales- Shell Beach, Bodega Bay, California, USA Def 38.1163 -122.8713
767425 Ruiz et al., 2015 2013 2013-07-19 SeaWorld Marina, Mission Bay, CA, California, USA Def 32.7676 -117.2314
767461 Ruiz et al., 2015 2013 2013-07-29 Mission Bay Yacht Club, Mission Bay, CA, California, USA Def 32.7778 -117.2485
767527 Ruiz et al., 2015 2013 2013-08-03 Mission Bay Sport Center, Mission Bay, CA, California, USA Def 32.7857 -117.2495
767567 Ruiz et al., 2015 2013 2013-08-05 Paradise Point Resort, Mission Bay, CA, California, USA Def 32.7730 -117.2406
767581 Ruiz et al., 2015 2013 2013-08-30 201 Main, Morro Bay, CA, California, USA Def 35.3564 -120.8474
767592 Ruiz et al., 2015 2013 2013-08-27 City Harbor, Morro Bay, CA, California, USA Def 35.3709 -120.8582
767606 Ruiz et al., 2015 2013 2013-09-05 Launch Ramp, Morro Bay, CA, California, USA Def 35.3577 -120.8508
767614 Ruiz et al., 2015 2013 2013-08-29 Moorings, Morro Bay, CA, California, USA Def 35.3619 -120.8548
767627 Ruiz et al., 2015 2013 2013-08-31 Morro Bay Marina, Morro Bay, CA, California, USA Def 35.3641 -120.8532
767634 Ruiz et al., 2015 2013 2013-08-28 Sealion Dock, Morro Bay, CA, California, USA Def 35.3658 -120.8555
767645 Ruiz et al., 2015 2013 2013-09-03 State Park Marina, Morro Bay, CA, California, USA Def 35.3459 -120.8423
767657 Ruiz et al., 2015 2013 2013-09-04 Tidelands, Morro Bay, CA, California, USA Def 35.3602 -120.8521
767669 Ruiz et al., 2015 2013 2013-07-16 Naval Base Point Loma, San Diego Bay, CA, California, USA Def 32.6886 -117.2343
767682 Ruiz et al., 2015 2013 2013-07-17 Naval Station San Diego, San Diego Bay, CA, California, USA Def 32.6867 -117.1333
767708 Ruiz et al., 2015 2013 2013-07-25 Navy Ammo Dock, Pier Bravo, San Diego Bay, CA, California, USA Def 32.6939 -117.2276
767990 Ruiz et al., 2015 2012 2012-08-24 Richmond Marina Bay Yacht Harbor, San Francisco Bay, CA, California, USA Def 37.9134 -122.3523
768010 Ruiz et al., 2015 2012 2012-08-23 Sausalito Marine Harbor, San Francisco Bay, CA, California, USA Def 37.8609 -122.4853
768025 Ruiz et al., 2015 2012 2012-08-28 San Francisco Marina, San Francisco Bay, CA, California, USA Def 37.8071 -122.4341
768043 Ruiz et al., 2015 2012 2012-08-27 Port of San Francisco Pier 31, San Francisco Bay, CA, California, USA Def 37.8078 -122.4060
768066 Ruiz et al., 2015 2012 2012-09-11 Ballena Isle Marina, San Francisco Bay, CA, California, USA Def 37.7676 -122.2869
768089 Ruiz et al., 2015 2012 2012-08-30 Oyster Point Marina, San Francisco Bay, CA, California, USA Def 37.6633 -122.3817
768113 Ruiz et al., 2015 2012 2012-08-29 Coyote Point Marina, San Francisco Bay, CA, California, USA Def 37.5877 -122.3174
768135 Ruiz et al., 2015 2012 2012-09-04 Redwood City Marina, San Francisco Bay, CA, California, USA Def 37.5023 -122.2130
768179 Ruiz et al., 2015 2012 2012-09-05 Port of Oakland, San Francisco Bay, CA, California, USA Def 37.7987 -122.3228
768199 Ruiz et al., 2015 2012 2012-09-07 Jack London Square Marina, San Francisco Bay, CA, California, USA Def 37.7940 -122.2787
768237 Ruiz et al., 2015 2012 2012-09-13 San Leandro Marina, San Francisco Bay, CA, California, USA Def 37.6962 -122.1919
768301 Ruiz et al., 2015 2013 2013-08-20 Coyote Point Marina, San Francisco Bay, CA, California, USA Def 37.5877 -122.3163
768361 Ruiz et al., 2015 2013 2013-08-13 Oyster Point Marina, San Francisco Bay, CA, California, USA Def 37.6639 -122.3821
768405 Ruiz et al., 2015 2013 2013-08-19 Richmond Marina Bay Yacht Harbor, San Francisco Bay, CA, California, USA Def 37.9138 -122.3522
768422 Ruiz et al., 2015 2013 2013-08-12 San Francisco Marina, San Francisco Bay, CA, California, USA Def 37.8078 -122.4354
768435 Ruiz et al., 2015 2013 2013-08-21 San Leandro Marina, San Francisco Bay, CA, California, USA Def 37.6980 -122.1908
768453 Ruiz et al., 2015 2013 2013-08-16 Sausalito Marine Harbor, San Francisco Bay, CA, California, USA Def 37.8611 -122.4851

References

Abbott, Cathryn L.; Ebert, Daniel; Tabata, Amy; Therriault, Thomas W. (2011) Twelve microsatellite markers in the invasive tunicate, Didemnum vexillum, isolated from low genome coverage 454 pyrosequencing reads, Conservation Genetics Resources 3: 79-81

Abbott, Donald P.; Lambert, Charles C.; Lambert, Gretchen; Newberry, A. Todd (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon (4th Edtion), University of California Press, Berkeley, CA. Pp. 949-964

Agius, Brad P. (2007) Spatial and temporal effects of pre-seeding plates with invasive ascidians: Growth, recruitment and community composition., Journal of Experimental Marine Biology and Ecology 342: 30-39

Aldred, Nick; Clare, Anthony S. (2014) Mini-review: Impact and dynamics of surface fouling by solitary and compound ascidians, Biofouling 30(3): 259-270

Altman, Safra; Whitlatch, Robert B. (2007) Effects of small-scale disturbance on invasion success in marine communities., Journal of Experimental Marine Biology and Ecology 342: 15-29

Associated Press (12/2021) Lummi Nation declares disaster after invasive crab arrives, Seattle Times <missing volume>: <missing location>

Auker, Linda A.; Oviatt, Candace A. (2008) Factors influencing the recruitment and abundance of Didemnum in Narragansett Bay, Rhode Island., ICES Journal of Marine Science 65: 765-769

Auker, Linda A.; Oviatt, Candace A. (2007) Observations on the colonization of the invasive tunicate Didemnum sp., Rhode Island Naturalist 14(1): 1-2

Bak, R. P. M.; Lambrechts, D. Y. M.; Joenje, M.; Nieuwland, G.; Van Veghel, M. L. J. (1990) Long-term changes on coral reefs in booming populations of a competitive colonial ascidian., Marine Ecologiy Progress Series 133: 303-306

Baldwin, Andy; Leason, Diane (2016) Potential Ecological impacts of Emerald Ash Borer on Maryland's Eastern Shore, In: None(Eds.) None. , <missing place>. Pp. <missing location>

Bancila. Raluca I.; Skolka, Marius; Ivanova, Petya; Surugiu, Victor; Stefanova, Kremena; Todorova. Valentina; Zenetos, Argyro (2022) Alien species of the Romanian and Bulgarian Black Sea coast: state of knowledge, uncertainties, and needs for future research, Aquatic Invasions 17: Published online

Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Beveridge, C.; Cook, E.J.; Brunner, L.; MacLeod, A.; Black, K. ; Brown, C.; Manson, F.J. (2011) Initial reponse to the invasive carpet sea squirt, Didemnum vexillum, in Scotland., Scottish Natural Heritage Commissioned Report 413: 1-24

Bishop, John D. D.; Wood, Christine A.; Lévêque, Laurent; Yunnie, Anna L. E.; Viard, Frédérique (2015b) Repeated rapid assessment surveys reveal contrasting trends in occupancy of marinas by non-indigenous species on opposite sides of the western English Channel, Marine Pollution Bulletin 95: 699-706

Bishop, John D.D.; Wood, Christine A.; Yunnie, Anna L. E.; Griffiths, Carly A. (2015a) Unheralded arrivals: non-native sessile invertebrates in marinas on the English coast, Aquatic Invasions 10: 249-264

Bullard, S. G. and 15 authors. (2007) The colonial ascidian Didemnum sp. A: Current distribution, basic biology and potential threat to marine communities of the northeast and west coasts of North America., Journal of Experimental Marine Biology and Ecology 342: 99-108

Bullard, Stephan G.; Whitlatch, Robert B. (2009) In situ growth of the colonial ascidianDidemnum vexillum under different environmental conditions., Aquatic Invasions 4(1): 275-278

Byrnes, Jarrett; Stachowicz, John J. (2009) Short and long term consequences of increases in exotic species richness on water filtration by marine invertebrates, Ecology Letters 12: 830-841

California Department of Fish and Wildlife (2014) Introduced Aquatic Species in California Bays and Harbors, 2011 Survey, California Department of Fish and Wildlife, Sacramento CA. Pp. 1-36

Carman, M. R.; Morris, J. A.; Karney, R. C.; Grunden, D. W. (2010) An initial assessment of native and invasive tunicates in shellfish aquaculture of the North American east coast, Journal of Applied Ichthyology 26(Suppl. 2): 8-11

Carman, Mary R. and 13 authors (2016) Distribution and diversity of tunicates utilizing eelgrass as substrate in the western North Atlantic between 39° and 47° north latitude (New Jersey to Newfoundland), Management of Biological Invasions Published online: <missing location>

Carman, Mary R.; Allen, Hannah M.; Tyrrell, Megan C. (2009) Limited value of the common periwinkle snail Littorina littorea as a biological control for the invasive tunicate Didemnum vexillum., Aquatic Invasions 4(1): 291-294

Carman, Mary R.; Bullard, S.G.; Donnelly, J.P. (2007) Water quality, nitrogen pollution, and ascidian diversity in coastal waters of southern Massachusetts, USA., Journal of Experimental Marine Biology and Ecology 342: 175-178

Carman, Mary R.; Grunden, David W. (2010) First occurrence of the invasive tunicate Didemnum vexillum in eelgrass habitat, Aquatic Invasions 5(1): <missing location>

Carman, Mary R.; Grunden, David W.; Ewart, Danielle (2014) Coldwater reattachment of colonial tunicate Didemnum vexillum fragments to natural (eelgrass) and artificial (plastic) substrates in New England, Aquatic Invasions 9: in press

Carman, Mary R.; Hoagland, K. Elaine; Green-Beach, Emma; Grunden, David W. (2009) Tunicate faunas of two North Atlantic-New England islands: Martha’s Vineyard, Massachusetts and Block Island, Rhode Island., Aquatic Invasions 4(1): 65-70

Cheng, Brian S.; Blumenthal, Jeffrey; Chang, Andrew L.; Barley, Jordanna; Ferner, Matthew C.; Nielsen, Karina J. Ruiz , Gregory M. ; Zabin, Chela (2022) Severe introduced predator impacts despite attempted functional eradication, Biological Invasions 24: 725-739

9/24/12 Scientists look for ways to kill Sitka tunicate. http://www.kcaw.org/2012/09/24/scientists-look-for-ways-to-eradicate/

2005 Exotics Guide. San Francisco Estuary Institute, Oakland, CA, www.exoticsguide.org

Cohen, Andrew N. and 10 authors (2005) <missing title>, San Francisco Estuary Institute, Oakland CA. Pp. <missing location>

Cohen, Andrew N.; Chapman, John T. (2005) <missing title>, San Francisco Estuary Institute, San Francisco. Pp. <missing location>

Cohen, C. Sarah; McCann, Linda; Davis, Tammy; Shaw, Linda; Ruiz, Gregory (2011) Discovery and significance of the colonial tunicate Didemnum vexillum in Alaska, Aquatic Invasions 6: corrected proof

Cohen, Sarah; Ruiz, Greg; Zabin, Chela; Alroy, Karen; Wang, Verena (2008) <missing title>, National Sea Grant Program & Prince William Sound Regional Citizens’ Advisory Council, Valdez AK. Pp. 1-20

Colarusso, Phil; Nelson, Eric; Ayvazian, Suzanne; Carman, Mary R.; Chintala, Marty; Grabbert, Sinead; Grunden, David (2016) Quantifying the ecological impact of invasive tunicates to shallow coastal water systems, Management of Biological Invasions 7: 33-42

Cordell, Jeffery R.; Levy, Claire; Toft, Jason D. (2012) Ecological implications of invasive tunicates associated with artificial structures in Puget Sound, Washington, USA, Biological Invasions 15(6): 1303-1318

Coutts, Ashley D.M.; Forrest, Barrie M. (2007) Development and application of tools for incursion: Lessons learned from the management of pest Didemnum vexillum., Journal of Experimental Marine Biology and Ecology 342: 154-162

de Rivera, Catherine, and 27 authors (2005a) <missing title>, National Fish and Wildlife Foundation, Washington, D.C.. Pp. <missing location>

Denny, C. M. (2008) Development of a method to reduce the spread of the ascidian Didemnum vexillum with aquaculture transfers., ICES Journal of Marine Science 65: 805-810

Dias, P. Joana and 8 authors (2016) Investigating the cryptogenic status of the sea squirt Didemnum perlucidum (Tunicata, Ascidiacea) in Australia based on a molecular study of its global distribution, Aquaitc Invasions In press: <missing location>

Dias, P. Joana; Simpson,Tiffany; Hitchen, Yvette; Lukehurst, Sherralee; Snow, Michael; Kennington, W. Jason (2016) Isolation and characterization of 17 polymorphic microsatellite loci for the widespread ascidian Didemnum perlucidum (Tunicata, Ascidiacea), Management of Biological Invasions 7: in press

Dijkstra, Jennifer A.; Harris, Larry G. (2007) <missing title>, The New Hampshire Estuaries Project, Portsmouth, NH. Pp. 1-21

Dijkstra, Jennifer A.; Harris, Larry G. (2009) Maintenance of diversity altered by a shift in dominant species: implications for species coexistence, Marine Ecology Progress Series 387: 71-80

Dijkstra, Jennifer A.; Lambert, Walter J.; Harris, Larry G. (2012) Introduced species provide a novel temporal resource that facilitates native predator population growth, Biological Invasions published online: <missing location>

Dijkstra, Jennifer A.; Nolan, Riley (2011) Potential of the invasive colonial ascidian, Didemnum vexillum, to limit escape response of the sea scallop, Placopecten magellanicus, Aquatic Invasions 6(4): 451-456

Dijkstra, Jennifer A.; Westerman, Erica L.; Harris, Larry G. (2011) The effects of climate change on species composition, succession and phenology: a case study, Global Change Biology 17: 2360-2369

Dijkstra, Jennifer; Dutton, Anthony; Westerman, Erica; Harris, Larry (2008) Heart rate reflects osmotic stress levels in two introduced colonial ascidians Botryllus schlosseri and Botrylloides violaceus., Marine Biology 154: 805-811

Dijkstra, Jennifer; Harris, Larry G.; Westerman, Erica (2007) Distribution and long-term temporal patterns of four invasive colonial ascidians in the Gulf of Maine, Journal of Experimental Marine Biology and Ecology 342: 61-68

Dijkstra, Jennifer; Sherman,Hillary; Harris, Larry G. (2007) The role of colonial ascidians in altering biodiversity in marine fouling communities., Journal of Experimental Marine Biology and Ecology 342: 169171

El Nagar, Aliya; Huys, Rony; Bishop, John D. D. (2010) Widespread occurrence of the Southern Hemisphere ascidian Corella eumyota Traustedt, 1882 on the Atlantic coast of Iberia, Aquatic Invasions 5(2): 169-173

Faasse, Marco (2012) The exotic isopod Synidotea in the Netherlands and Europe, A Japanese or American invasion (Pancrustacea: Isopoda)?, Nederlandse Faunistiche Mededelingen 108: 103-106

Ferguson, Louis F.; Landry, Thomas; Therriault, Thomas W.; Davidson, Jeff (2016) Effectiveness of a neutral red viability protocol developed for two colonial tunicate species, Management of Biological Invasions 7: In press

Fletcher, Lauren M.; Forrest, Barrie M. (2011) Induced spawning and culture techniques for the invasive ascidian Didemnum vexillum (Kott, 2002), Aquatic Invasions 6(4): 457-464

Fletcher, Lauren M.; Forrest, Barrie M.; Atalah, Javier; Bell, James J. (2013) Reproductive seasonality of the invasive ascidian Didemnum vexillum in New Zealand and implications for shellfish aquaculture, Aquaculture Environment Interactions 3: 197-211

Fletcher, Lauren M.; Forrest, Barrie M.; Bell, James J. (2012) Natural dispersal mechanisms and dispersal potential of the invasive ascidian Didemnum vexillum, Biological Invasions 15(3): 627-643

Forrest, Barrie M.; Gardner, Jonathan, P. A.; Taylor, Michael D. (2009) Internal borders for managing invasive marine species., Journal of Applied Ecology 46: 46-54

Forrest, Barrie M.; Hopkins, Grant A. (2013) Population control to mitigate the spread of marine pests: insights from management of the Asian kelp Undaria pinnatifida and colonial ascidian Didemnum vexillum, Management of Biological Invasions 4(4): 317-326

Freestone, Amy L.; Ruiz, Gregory M.; Torchin, Mark E. (2013) Stronger biotic resistance in tropics relative to temperate zone: Effects of predation on marine invasion dynamics, Ecology 94(6): 1370-1377

Gargan, Laura M.; Brooks , Paul R; ; Vye, Siobhan R.; . Joseph E. Ironside . Jenkins, Stuart R.; Crowe, Tasman P.;. Carlsson,Jens (2021) The use of environmental DNA metabarcoding and quantitative PCR for molecular detection of marine invasive non-native species associated with artificialstructures, Biological Invasions Published online: <missing location>

Giménez, Luis and 8 authors (2020) Exploring larval phenology as predictor for range expansion in an invasive species, Ecography 43: 1423-1434

Gittenberger, Adriaan (2007) Recent population expansions of non-native ascidians in the Netherlands., Journal of Experimental Marine Biology and Ecology 342: 122-126

Gittenberger, Adriaan (2009) Invasive tunicates on Zeeland and Prince Edward Island mussels, and management practices in The Netherlands., Aquatic Invasions 4(1): 279-281

Gittenberger, Adriaan; Rensing, Marjolein; Stegenga, Herre; Hoeksema, Bert (2010) Native and non-native species of hard substrata in the Dutch Wadden Sea, Nederlandse Faunistiche Mededelingen 33: 20-76

Graham, Jenifer; Collins, Catherine; Lacaze, Jean-Pierre; McCollin, Tracy (2015) Molecular identification of Didemnum vexillum Kott 1982 from sites along the UK coastline, BioInvasions Records 4: In press

Green, Stephanie J. and 7 authors (2021) Broad-scale acoustic telemetry reveals long-distance movements and large home ranges for invasive lionfish on Atlantic coral reefs, Marine Ecology Progress Series 673: 117-134

Griffith, Kate and 6 authors (2009) First records in Great Britain of the invasive colonial ascidian Didemnum vexillum Kott, 2002, Aquatic Invasions 4(4): <missing location>

Gröner, Frederike; Lenz, Mark; Wahl, Martin; Jenkins, Stuart R. (2011) Stress resistance in two colonial ascidians from the Irish Sea: The recent invader Didemnum vexillum is more tolerant to low salinity than the cosmopolitan Diplosoma listerianum, Journal of Experimental Marine Biology and Ecology 409: 48-52

Harris, Larry G.; Dijkstra, Jennifer A. (2007) <missing title>, New Hampshire Estuaries Project, <missing place>. Pp. <missing location>

Herborg, Leif-Matthias; O’Hara, Patrick; Therriault, Thomas W. (2009) Forecasting the potential distribution of the invasive tunicate Didemnum vexillum., Journal of Applied Ecology 46: 64-72

Hess, Jon E.; Swalla, Billie J.; Moran, Paul (2009) New molecular markers to genetically differentiate populations of Didemnum vexillum (Kott, 2002) - an invasive ascidian species., Aquatic Invasions 4(2): 299-310

Hewitt, Chad L. and 14 authors. (2004) Introduced and cryptogenic species in Port Phillip Bay, Victoria, Australia., Marine Biology 144: 183-202

Holt, Rohan (2011) Eradication of the non-native sea squirt Didemnum vexillum from Holyhead Harbour, Wales, UK, Aliens 31: 52-53

ICES Advisory Committee on the Marine Environment (2012) <missing title>, International Council for the Exploration of the Seas, Copenhagen. Pp. <missing location>

Janiak, Dean S.; Osman, Richard W.; Whitlatch, Robert B. (2013) The role of species richness and spatial resources in the invasion success of the colonial ascidian Didemnum vexillum Kott, 2002 in eastern Long Island Sound, Journal of Experimental Marine Biology and Ecology 443: 12-20

Kott, Patricia (2002) A complex didemnid ascidian from Whangamata, New Zealand., Journal of the Marine Biological Association of the United Kingdom 82(4): 625-628

Kott, Patricia (2004) A new species of Didemnum (Ascidiacea, Tunicata) from the Atlantic coast of North America., Zootaxa 732: 1-10

Lambert, Gretchen (2009) Adventures of a sea squirt sleuth: unraveling the identity of Didemnum vexillum, a global ascidian invader., Aquatic Invasions 4(1): 5-28

Lengyel, Nicole L.; Collie, Jeremy S.; Valentine, Page C. (2009) The invasive colonial ascidianDidemnum vexillum on Georges Bank ? Ecological effects and genetic identification., Aquatic Invasions 4(1): 143-152

Lenz, Mark and 11 authors (2011) Non-native marine invertebrates are more tolerant towards environmental stress than taxonomically related native species: Results from a globally replicated study, Environmental Research 111: 943-952

Liu, Wenliang; Liang, Xiaoli ; Zhu, Xiaojing (2015) A new record and mitochondrial identification of Synidotea laticauda Benedict, 1897 (Crustacea: Isopoda: Valvifera: Idoteidae) from the Yangtze Estuary, China, Zootaxa 4294: 371-380

Locke, Andrea (2009) A screening procedure for potential tunicate invaders of Atlantic Canada., Aquatic Invasions 4(1): 71-79

Locke, Andrea; Hanson, John Mark (2009) Rapid response to non-indigenous species. 1. Goals and history of rapid response in the marine environment., Aquatic Invasions 4(1): 237-247

Long, Holly A.; Grosholz, Edwin D. (2015) Overgrowth of eelgrass by the invasive colonial tunicate Didemnum vexillum: Consequences for tunicate and eelgrass growth and epifauna abundance, Journal of Experimental Marine Biology and Ecology 473: 188-194

Lord, Joshua P.; Calini, Jeremy M.; Whitlatch, Robert B. (2015) Influence of seawater temperature and shipping on the spread and establishment of marine fouling species, Marine Biology 162: 2481-2492

Martin, J. L. and 15 authors (2010) Rapid assessment for Didemnum vexillum in southwest New Brunswick, Canadian Technical Report of Fisheries and Aquatic Sciences 2882: 1-16

Martin, Jennifer L.; LeGresley, Murielle M.; Thorpe, Bruce; McCurdy, Paul (2011) Non-indigenous tunicates in the Bay of Fundy, eastern Canada (2006-2009), Aquatic Invasions 6(4): corrected proof

Massachusetts Office of Coastal Zone Management (2013) Rapid assessment survey of marine species at New England floating docks and rocky shores, Massachusetts Office of Coastal Zone Management, Boston MA. Pp. <missing location>

McCann, Linda D. and 5 authors (2013) Promoting invasive species control and eradication in the sea: Options for managing the tunicate invader Didemnum vexillum in Sitka, Alaska, Marine Pollution Bulletin published online: <missing location>

McCarthy, Anna; Osman, Richard W.; Whitlatch, Robert B. (2007) Effects of temperature on growth rates of colonial ascidians: A comparison of Didemnum sp. to Botryllus schlosseri and Botrylloides violaceus., Journal of Experimental Marine Biology and Ecology 342: 172-174

2004 Invasive sea squirt alive and well on Georges Bank.. Web page: http://woodshole.er.usgs.gov/project-pages/stell/wagen/didemnum/images/pdf/news/tunicata.pdf

Mercer, Jeffery M.; Whitlatch, Robert B.; Osman, Richard W. (2009) Potential effects of the invasive colonial ascidian (Didemnum vexillum Kott, 2002) on pebble-cobble bottom habitats in Long Island Sound, USA., Aquatic Invasions 4(1): 133-142

Millard, N. A. H.; Bouillon. J. (1975) Additional hydroids from the Seychelles, Annals of the South African Museum 69: 1-15

Miller, Katharine B. (2016) Forecasting at the edge of the niche: Didemnum vexillum in Southeast Alaska, Marine Biology 163: published online

Minchin, Dan; Cook, Elizabeth J.; Clark, Paul F. (2013) Alien species in British brackish and marine waters, Aquatic Invasions 8: in press

Minchin, Dan; Sides, Elizabeth (2006) Appearance of a cryptogenic tunicate, a Didemnum sp. fouling marina pontoons and leisure craft in Ireland., Aquatic Invasions 1(3): 143-147

2003-2008 Introduced and cryptogenic species of the North Atlantic. http://massbay.mit.edu/exoticspecies/exoticmaps/introduced.html

2006 Hitchhiker's Guide to Exotic Species. Web Page:http;//massbay.mit.edu/exoticspecies/hitchhikers/hitchhikers2.pdf

2009-2012 Marine Invader Tracking and Information System (MITIS). http://massbay.mit.edu/mitis/

Moore, Andrea M.; Vercaemer, Bénédikte; DiBacco, Claudio; Sephton, Dawn; Ma, Kevin C. K. (2014) Invading Nova Scotia: first records of Didemnum vexillum Kott, 2002 and four more non-indigenous invertebrates in 2012 and 2013, BioInvasions Records 3(4): 225-234

Morris, James A. Jr.; Carman, Mary R. (2012) Fragment reattachment, reproductive status, and health indicators of the invasive colonial tunicate Didemnum vexillum with implications for dispersal, Biological Invasions 14: published online

Morris, James A. Jr.; Carman, Mary R.; Hoagland, K. Elaine; Green-Beach, Emma R.M.; Carney, Richard C. K (2009) Impact of the invasive colonial tunicate Didemnum vexillum on the recruitment of the bay scallop (Argopecten irradians irradians) and implications for recruitment of the sea scallop (Placopecten magellanicuss) on Georges Bank., Aquatic Invasions 4(1): 207-211

Moura, Carlos J.; Collins, Allen G.; Santos, Ricardo S.; Lessios, Harilaos (2019) Predominant east to west colonizations across major oceanic barriers: Insights into the phylogeographic history of the hydroid superfamily Plumularioidea, suggested by a mitochondrial DNA barcoding marker, Ecology and Evolution 9: :13001–13016.

Murray, Cathryn Clarke; Therriault, Thomas W.; Martone, Patrick T. (2012) Adapted for invasion? Comparing attachment, drag and dislodgment of native and nonindigenous hull fouling species, Biological Invasions <missing volume>: published online

2003 Invasive marine species found on Georges Bank.. Web Page: http:///www.noaanews.noaa.gov/stories2003/s2125.htm

Needles, Lisa A. (2007) <missing title>, M.S. Thesis, California Polytechnic State University, San Luis Obispo. Pp. <missing location>

2013 Marine non-native invasive species in Northern Ireland. http://invasivespeciesireland.com/wp-content/uploads/2013/03/Julia-Nunn.pdf

Ordoñez, V.; Pascual, M.; Fernandez-Tejedor, M.; Pineda, M. C.; Tagliapietra, D.; Turon, X. (2015) Ongoing expansion of the worldwide invader Didemnum vexillum (Ascidiacea) in the Mediterranean Sea: High plasticity of its biological cycle promotes establishment in warm waters, Biological Invasions Published online: <missing location>

Osman, Richard W.; Whitlatch, Robert B. (2007) Variation in the ability of Didemnum sp to invade established communities, Journal of Experimental Marine Biology and Ecology 342: 40-53

Pannell, Aaron; Coutts, Ashley M. (2007) <missing title>, New Zealand Marine Farming Association; Biosecurity New Zealand, New Zealand. Pp. <missing location>

Parra-Rincón, Ernesto; Velandia-Huerto, Cristian A.; Gittenberger, Adriaan; Fallmann, Gatter, Brown, Thomas;; Federico D.; Stadler, Peter F.; Bermúd (2022) The Genome of the “Sea Vomit” Didemnum vexillum, Life 11(1377): https://www.mdpi.com

Pederson, Judith, and 13 authors (2021) 2019 Rapid Assessment Survey of marine bioinvasions of southern New England and New York, USA, with an overview of new records and range expansions, Bioinvasions Records 10(2): 22-–237

Prentice, M. B.; Vye, S. R.; Jenkins, S. R.;; Shaw, P. W.; . Ironside, J. E. (2021) Genetic diversity and relatedness in aquaculture and marina populations of the invasive tunicate Didemnum vexillum in the British Isles, Biological Invasions 23: 3613 - 3624

Rinkevich, Baruch; Fidler, Andrew E. (2014) Initiating laboratory culturing of the invasive ascidian Didemnum vexillum, Management of Biological Invasions 5: in press

Rodrigues, Antonio J. S.; Miyahira, Igor C. ; Rodrigues, Nathália; Ribeiro, Danielle; Santos, Luciano N.; ·Neves, Raquel A. F. (2022) Wide tolerance to environmental conditions and substrate colonization mediates the invasion of false mussels (Bivalvia: Dreissenidae) in brackish systems, Biological Invasions 24(Published onlin): 2245 - 2260

Rodriguez, Laura F.; Ibarra-Obando, Silvia E. (2008) Cover and colonization of commercial oyster (Crassostrea gigas) shells by fouling organisms in San Quintin Bay, Mexico, Journal of Shellfish Research 27(2): 337-343

Rogers, Tanya L.; Byrnes, Jarrett E.; Stachowicz, John J. (2016) Native predators limit invasion of benthic invertebrate communities in Bodega Harbor, California, USA, Marine Ecology Progress Series 545: 161-173

9/2/62012 Dive surveys help to track D. vex distribution. http://www.kcaw.org/2012/09/26/dive-surveys-help-to-track-d-vex-distribution/

Rosa, M. and 6 authors (2013) Biofouling ascidians on aquaculture gear as potential vectors of harmful algal introductions, Harmful Algae 23: 1-7

Ruiz, Gregory M.; Geller, Jonathan (2018) Spatial and temporal analysis of marine invasions in California, Part II: Humboldt Bay, Marina del Re, Port Hueneme, ,and San Francisco Bay, Smithsonian Environmental Research Center & Moss Landing Laboratories, Edgewater MD, Moss Landing CA. Pp. <missing location>

Sambrook, Katie; Holt, Rohan H.F.; Sharp, Rowland; Griffith, Kate; Roche, Ronan C. (2014) Capacity, capability and cross-border challenges associated with marine eradication programmes in Europe: The attempted eradication of an invasive non-native ascidian, Didemnum vexillum in Wales, United Kingdom, Marine Policy 48: 51-59

Santa Rosa Press-Democrat (10/15/2012) Invasive species known as 'marine vomit' found at Drakes Estero, Santa Rosa Press-Democrat posted online: <missing location>

Shatkin, Greg, Sumway, Sandra E., Hawes, Robert (1997) Considerations regarding the possible introduction of the Pacific Oyster (Crassostrea gigas) to the Gulf of Maine: A review of global experience, Journal of Shellfish Research 16(2): 463-477

Simkanin, Christina; Davidson, Ian C.; Dower, John F.; Jamieson, Glen; Therriault, Thomas W. (2012) Anthropogenic structures and the infiltration of natural benthos by invasive ascidians, Marine Ecology 33: 499-511

Simkanin, Christina; Fofonoff, Paul W.; Larson, Kriste; Lambert, Gretchen; Dijkstra, Jennifer A.; Ruiz, Gregory M. (2016) Spatial and temporal dynamics of ascidian invasions in the continental United States and Alaska, Marine Biology 163: Published online

Smith, Brian E.; Collie, Jeremy S.; Lengyel, Nicole L. (2014) Fish trophic engineering: Ecological effects of the invasive ascidian Didemnum vexillum (Georges Bank, northwestern Atlantic), Journal of Experimental Marine Biology and Ecology 461: 489-498

Smith, Ralph I. (1964) <missing title>, Systematics-Ecology Program, Marine Biological Laboratory, Woods Hole, Massachusetts. Pp. <missing location>

Sorte, Cascade J. B.; Stachowicz, John J. (2011) Patterns and processes of compositional change in a California epibenthic community, Marine Ecology Progress Series 435: 63-74

Sorte, Cascade, J. B.; Williams, Susan L.; Zerebecki, Robyn A. (2010) Ocean warming increases threat of invasive species in a marine fouling community, Ecology 91(8): 2198-2204

Stachowicz, John J.; Byrnes, Jarrett E. (2006) Species diversity, invasion success, and ecosystem functioning: disentangling the influence of resource competition, facilitation, and extrinsic factors., Marine Ecology Progress Series 311: 251-262

Stachowicz, John J.; Terwin, Jeffrey R.; Whitlatch, Robert B.; Osman, Richard W. (2002b) Linking climate change and biological invasions: ocean warming facilitates nonindigenous species invasions., Proceedings of the National Academy of Sciences of the U.S.A. 99(24): 15497-15500

Stefaniak, Lauren and 6 authors (2012) Determining the native region of the putatively invasive ascidian Didemnum vexillum Kott, 2002, Journal of Experimental Marine Biology and Ecology 422-423: 64-71

Stefaniak, Lauren; Lambert, Gretchen; Gittenberger, Adriaan; Zhang, Huan; Lin, Senjie; Whitlatch, Robert B. (2009) Genetic conspecificity of the worldwide populations of Didemnum vexillum Kott, 2002., Aquatic Invasions 4(1): 29-44

Switzer, S. E.; Therriault, T. W.; Dunham, A.; Pearce, C. M. (2012) Assessing potential control options for the invasive tunicate Didemnum vexillum in shellfish aquaculture, Aquaculture 318: 145-153

Tagliapietra, Davide; Keppel, Erica; Sigovini, Marco; Lambert, Gretchen (2012) First record of the colonial ascidian Didemnum vexillum Kott, 2002 in the Mediterranean: Lagoon of Venice (Italy), Bioinvasions Records 1: in press

Tracy, Brianna M.; Reyns, Nathalie B. (2014) Spatial and temporal patterns of native and invasive ascidian assemblages in a Southern California embayment, Aquatic Invasions 9: In press

2003-2015 Nonindigenous Aquatic Species Database. Gainesville, FL. http://nas.er.usgs.gov

2004-2011 Marine invasive species: <i>Didemnum vexillum</i>, a colonial tunicate; ascidian; sea squirt.. Web Page: http://woodshole1.er.usgs.gov/project-pages/stellwagen/didemnum/pdf_index.htm

Valentine, Page C.; Carman, Mary R.; Blackwood, Dann S.; Heffron, Erin J. (2009) Ecological observations on the colonial ascidianDidemnum sp. in a New England tide pool habitat., Journal of Experimental Marine Biology and Ecology 342: 109-121

Valentine, Page C.; Carman, Mary R.; Dijkstra, Jennifer; Blackwood, Dann S. (2009) Larval recruitment of the invasive colonial ascidian Didemnum vexillum, seasonal water temperatures in New England coastal and offshore waters, and implications for spread of the species., Aquatic Invasions 4(1): 153-168

Valentine, Page C.; Collie, Jeremy S.; Reid, Robert N.; Asch, Rebecca G.; Guida, Vince G.;Blackwood, Dann S. (2007) The occurrence of the colonial ascidian Didemnum sp. on Georges Bank gravel habitat — Ecological observations and potential effects on groundfish and scallop fisheries., Journal of Experimental Marine Biology and Ecology 342: 179-181

Valentine, Page; Carman, Mary R.; Blackwood, Dann (2016) Observations of recruitment and colonization by tunicates and associated invertebrates using giant one-meter 2 recruitment plates at Woods Hole, Massachusetts, Management of Biological Invasions 7(1): 115-130

Van den Brink, A. M.; Wijsman, J. W. M. (2010) <missing title>, ]IMARES - Institute for Marine Resources & Ecosystem Studies], Netherlands. Pp. 1-47

Van Name, Willard G. (1945) The North and South American ascidians, Bulletin of the American Museum of Natural History 84: 1-462

Vercaemer, Bénédikte; Sephton, Dawn; Clément, Pierre; Harman, Adam; Stewart-Clark, Sarah; DiBacco, Claudio (2015) Distribution of the non-indigenous colonial ascidian Didemnum vexillum (Kott, 2002) in the Bay of Fundy and on offshore banks, eastern Canada, Management of Biological Invasions 6: In press

Wells, Christopher D. and 23 authors (2014) Report on the 2013 rapid assessment survey of marine species at New England bays and harbors, Massachusetts Office of Coastal Zone Management, Boston MA. Pp. 32

Zerebecki, Robyn A.; Sorte, Cascade J. B. (2011) Temperature tolerance and stress proteins as mechanisms of invasive species success, PLOS ONE 6(4): e14806, online

Zhan, Aibin; Briski, Elizabeta; Bock, Dan G.; Ghabooli, Sara; MacIsaac, Hugh J. (2015) Ascidians as models for studying invasion success, Marine Biology 162: 2449-2470