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The 22nd International Conference on Aquatic Invasive Species (ICAIS) was held as a hybrid event in Oostende, Belgium from 18--22 April 2022. The conference addressed the theme of "Global Climate Change Amplifies Aquatic Invasive Species Impacts" and aimed to expand knowledge on the latest science and policy, inspire cooperation and collaboration on research and management projects at a global scale. Seven renowned international scientists provided keynote presentations on perspectives of climate change within their respective areas of expertise. This special issue of Aquatic Invasions presents nine academic papers addressing a range of aquatic invasive species issues including predation, life history dynamics, ecosystem impacts, and physiological tolerances. The papers highlight the need for regional, national, and international cooperation, collaboration on research and management projects, and targeted, specific, and actionable outreach to combat the growing threat posed by aquatic invasive species. [ABSTRACT FROM AUTHOR]

Silver carp, Hypophthalmichthys molitrix, escaped into the Lower Mississippi River (LMR) over 50 years ago, established reproductive populations, and spread across much of the Mississippi River Basin. Demographic rates of silver carp are needed to inform decisions on control and management of this invasive species, but have not been published for the LMR. The purpose of this paper is to report silver carp age and growth estimates from fish collected in riverine (mainstem) and backwater (lake) habitats in the LMR during the period 2011-2019, to compare our results with populations from other geographic areas in the Upper Mississippi River drainage, and to evaluate latitudinal and habitat differences in demographic parameters. Silver carp gained weight with increasing length similarly throughout the lower and upper basin. However, annual growth rates were higher in the LMR compared to northern rivers including the Illinois, Wabash, Missouri, and Middle Mississippi rivers. In the LMR, regression analyses demonstrated that females were heavier in lakes than males or females in the mainstem and that females in lakes had the lowest instantaneous mortality (-0.186). Maximum age was 8 and 10 years for females and males, respectively. The largest male weighed 13.8 kg with a total length of 1022 mm, and was 7 years old. The largest female weighed 16.0 kg with a total length of 1034 mm TL, and was 7 years old. Rapid growth rates, larger sizes, and lower mortality in the LMR, in combination with limited commercial fishing, extensive river-floodplain connectivity, and vast amounts of spawning areas, ensure that LMR silver carp will continue to act as a source of fast-growing invasive individuals for other reaches and other rivers throughout the Mississippi River Basin. [ABSTRACT FROM AUTHOR]

The article examines the papers presented in the past three International Invasive Sea Squirt conferences, held in 2005, 2007 and 2010, to determine whether research on invasive tunicate has changed over time. It is noted that all of the conferences have been held in eastern North America. Ecological interactions, which were the dominant topic of the first conference, have declined in 2010. In every conference, a few new records of species occurrences were presented.

As the impact of coastal development impinge on our natural ecosystem, we are increasingly compelled to study the effects of artificial habitats on the distribution and abundance of marine species. In particular, understanding how physical factors can influence distributional patterns of benthic communities along artificial structures built in ports that create possibilities for a variety of non-indigenous species (NIS) occur. This paper aims to compare the distribution of mollusc's assemblage along environmental factors known to influence the distribution of epibenthic species: depth, shading and locality features such as distance from shore and period of submersion of artificial structures. Molluscan assemblages were examined over a depth gradient extending from middle intertidal (0 m) to shallow subtidal (5 m). We also assessed and compared the distribution of Eualetes tulipa (established) and Isognomon bicolor (invasive) in two port locations at Northeast coast of Brazil. A total of 33 native species, 7 cryptogenic and two NIS were found. The most abundant was a native species, Crassostrea brasiliana, followed by the NIS I. bicolor and E. tulipa, respectively. Using PERMANOVA: depth gradient, locality and interaction between these fixed factors showed significant effects on the vertical distribution along the artificial structures sampled. Results suggest that recent substrata availability supports the colonization of NIS species and that these, in areas with more stable communities, cohabit with and are regulated by native species. Furthermore, this is the first study discussing the distribution of the established NIS vermetid E. tulipa in Northeast Brazilian coast. [ABSTRACT FROM AUTHOR]

Evidence is presented in this paper for the first time that reproduction without crossfertilisation can occur in the arhynchobdellid leech Barbronia weberi (Blanchard, 1897). The discovery of "virgin birth" in this invasive Asian species was serendipitous in that a single unmated hatchling reared in isolation to maturity unexpectedly laid viable cocoons. In order to confirm unequivocally that this reproduction was indeed non-sexual the experiment was repeated rigorously for five successive generations. The formal possibility that cross-fertilisation may have occurred in the cocoon prior to hatching was specifically investigated by isolating embryos at the earliest stages of viability, well before reproductive structures developed. The cocoons and eggs of each successive generation were carefully quantified. No evidence of diminution of fertility was found in spite of severe inbreeding by the fifth generation. In fact fecundity of the inbred laboratory leeches was comparable to that of the original wild population. A total of 1,147 cocoons containing 4,455 eggs were laid during this year-long study. This was undoubtedly an underestimate of reproductive potential in that a number of healthy individuals had to be culled for pragmatic reasons. That a single individual is capable of producing thousands of progeny in one year, without mating, is sufficient to explain the success of B. weberi as an invasive species. In recent years this alien leech has become established on every inhabited continent. The mechanism of reproduction without cross-fertilisation in B. weberi is unknown but is probably attributable to self-fertilisation linked to its hermaphroditism. Taxonomic and phylogenetic implications of self-fertilisation in B. weberi are discussed. [ABSTRACT FROM AUTHOR]

In this study, we performed a scientometric analysis of published scientific papers on the biological invasion of macrophytes in freshwater ecosystems to assess the main trends and gaps in research concerning this group of organisms. The analysis showed that publications on invasive macrophytes increased exponentially in the last decade. However, the activity index (a comparison of the quantitative trends of invasive macrophytes in relation to all of the papers on macrophytes) indicated that invasive macrophytes have not been consistently studied more than other topics in the field of limnology over the last decade. The most studied macrophyte species were Myriophyllum spicatum, Hydrilla verticillata, Phragmites australis and Eichhornia crassipes. Certain gaps were related to the limited number of studies on the important species threatening tropical ecosystems, under-representation of investigations on the impacts of invasive macrophytes on fish and lack of studies associating macrophytes with microorganisms (bacteria and fungi). Studies that encompassed several levels of biological complexity were also scarce, indicating that the studies were fragmented at specific levels. Finally, there was a clear geographical bias, with fewer studies occurring in Neotropical and Afrotropical regions. Identification of these gaps may be useful for addressing future studies that might help evaluate the causes of invasion by macrophytes and the impacts of such invasions on freshwater ecosystems. [ABSTRACT FROM AUTHOR]

The author discusses papers presented at the 18th International Conference on Aquatic Invasive Species (ICAIS) held in Niagara Falls, Ontario, Canada in April 2013. Topics covered include the resurgence of the focus of research outputs on Dreissena, presentations on freshwater molluscs like Corbicula fluminea and Limnoperna fortunei, a profile of the killer shrimp, Dikerogammarus villosus.

Fluridone-resistant hydrilla was first suspected in Florida in 1999 and was confirmed using molecular genetics techniques in 2003. Although the vast majority of species that evolve resistance to herbicides or other stressors do so through the genetic mutations that occur during sexual reproduction, all hydrilla in Florida is of the dioecious pistillate (“female”) biotype and all reproduction and spread is via vegetative means. The Hardy-Weinberg principle of constant allele frequencies (i.e., p + q = 1), used to predict allelic frequency shifts within populations due to selection, is based on a number of assumptions that are violated by species that reproduce asexually. In this paper, we address the assumptions of the model in the context of the clonally propagated species hydrilla and compare theoretical model predictions to the likely timeline of actual events that occurred in many bodies of water in Florida. The generational shifts in within-population allele frequencies from almost exclusively fluridone-susceptible to almost exclusively fluridone-resistant track well with the actual development of fluridone-resistant populations of hydrilla in Florida when considering fitness differences among fluridone resistance alleles after fluridone treatments. The present study illustrates how the Hardy-Weinberg principle of constant allele frequencies can be used as an exploratory tool to model resistance evolution in asexually reproducing species such as hydrilla. [ABSTRACT FROM AUTHOR]

Fluridone-resistant hydrilla was first suspected in Florida in 1999 and was confirmed using molecular genetics techniques in 2003. Although the vast majority of species that evolve resistance to herbicides or other stressors do so through the genetic mutations that occur during sexual reproduction, all hydrilla in Florida is of the dioecious pistillate ("female") biotype and all reproduction and spread is via vegetative means. The Hardy-Weinberg principle of constant allele frequencies (i.e., p + q = 1), used to predict allelic frequency shifts within populations due to selection, is based on a number of assumptions that are violated by species that reproduce asexually. In this paper, we address the assumptions of the model in the context of the clonally propagated species hydrilla and compare theoretical model predictions to the likely timeline of actual events that occurred in many bodies of water in Florida. The generational shifts in within-population allele frequencies from almost exclusively fluridone-susceptible to almost exclusively fluridoneresistant track well with the actual development of fluridone-resistant populations of hydrilla in Florida when considering fitness differences among fluridone resistance alleles after fluridone treatments. The present study illustrates how the Hardy-Weinberg principle of constant allele frequencies can be used as an exploratory tool to model resistance evolution in asexually reproducing species such as hydrilla. [ABSTRACT FROM AUTHOR]

The bait worm Marphysa victori Lavesque, Daffe, Bonifácio & Hutchings, 2017 was originally described from Arcachon Bay, France. In the original description, the authors suggested that it may have been introduced, although definitive evidence was lacking at the time. In this paper, we confirm that M. victori is an exotic species originating from East Asia, probably a native of China or Japan. This species was most likely introduced into Arcachon Bay in the 1970s with non-native oysters Crassostrea gigas Thunberg, 1793. The Asiatic origin of this species is confirmed based on both morphological and molecular evidence. Comparison of the type specimens of M. victori with those of Marphysa bulla Liu, Hutchings & Kupriyanova, 2018 described from the Yellow Sea, China, showed no morphological or molecular differences and therefore the more recently named M. bulla is relegated to a junior synonym. This is the first example of a large-sized errant invertebrate species being introduced with oysters into Arcachon Bay. [ABSTRACT FROM AUTHOR]

In order to assist the implementation of the European policies on Invasive Alien Species (IAS Regulation) and mitigate the impact of alien species that threaten the marine ecosystem services and biodiversity, accurate lists of alien species per European Member State are required. Although inventories of marine alien species and relevant information about them have been reported for the Black Sea marine region of Romania and Bulgaria, a validated list of alien species for the two countries is still lacking. In this paper we (i) propose a validated list of the marine alien species occurring in the Romanian and Bulgarian Black Sea regions, and (ii) address errors, gaps and uncertainties associated with listing alien species from the marine waters of the two countries. The list of alien species includes 37 species for Romania and 26 for Bulgaria, with the highest number of alien species belonging to the phylum Arthopoda for both countries. The majority of alien species have been classified as successfully established in the marine waters of both countries. Thirteen alien species were classified as invasive in Romania whilst eight alien species were classed as invasive in Bulgaria. The historical overview indicates that the number of alien species has steadily increased over the last 50 years both in Romania and Bulgaria. The results of our study provide the baseline list and information for addressing marine alien species at a national level and a starting point for selecting the invasive alien species for risk assessment towards an effective implementation of the IAS Regulation. In conclusion, this study provides supporting information for implementing measures to tackle the introduction of alien species in the western region of the Black Sea. These measures are needed to build an early warning, prevention, and control of invasive alien species in the Black Sea, a unique and fragile ecosystem. [ABSTRACT FROM AUTHOR]

The introduction and spread of non-native species is one of the least reversible human-induced global changes. In South Africa, non-native fish introductions have occurred over the last two and a half centuries. Resultant invasions have been cited as a primary threat to imperilled South African fishes and other aquatic fauna. Addressing a problem of this magnitude requires an organised approach. The aim of this paper is to summarise the current knowledge, risk and ecological impacts associated with non-native freshwater fish introductions in South Africa. A total of 55 fishes have been introduced into novel environments in South Africa. Of these, 27 were alien and 28 were extralimital introductions. Only 11 introduced species failed to establish and of the 44 species that have established, 37% are considered fully invasive. Introductions for angling were responsible for the highest proportion (55%) of fully invasive species with the remainder linked to inter-basin water transfers (15%), bio-control (15%), ornamental fish trade (10%) and aquaculture (5%). There was a general paucity of published literature on the introduction, establishment and spread of non-native fishes, and recent research has largely focused on impacts on native biota. While documented impacts spanned multiple levels of biological organisation, most papers focused on individual and population level impacts. Large taxonomic biases were also observed, and invasive impacts were estimated for less than 50% of fully invasive fishes. There is also an extensive knowledge gap on the impacts of associated parasites and diseases introduced with non-native fishes. These knowledge gaps constrain effective management of non-native fishes in South Africa and research at all invasion stages (introduction, establishment, spread and impact) is necessary to guide conservation practitioners and managers with information to manage current invasions and curb future introductions. [ABSTRACT FROM AUTHOR]

Forty-nine species of Western Pacific coastal bryozoans were found on 317 objects (originating from the Great East Japan Earthquake and Tsunami of 2011) that drifted across the North Pacific Ocean and landed in the Hawaiian Islands and North America. The most common species were Scruparia ambigua (d'Orbigny, 1841) and Callaetea sp. Of 36 bryozoans identified to species level, 15 are already known from North America, one of which (Schizoporella japonica Ortmann, 1890) is an earlier introduction from Japan; 18 species are known only from the Western Pacific, one of which (Bugula tsunamiensis McCuller, Carlton and Geller, 2018) is newly described in a companion paper. The 13 additional bryozoans, not taken to species level, are likely derived from the Western Pacific based upon evidence reviewed here; two of these species (Callaetea sp. and Arbocuspis sp.) are undescribed. Seven warm-water species, Metroperiella cf. biformis (Zhang and Liu, 1995), Celleporaria brunnea (Hincks, 1884), Drepanophora cf. gutta Tilbrook, Hayward and Gordon, 2001, Smittoidea spinigera (Liu, 1990), Biflustra grandicella (Canu and Bassler, 1929), Biflustra irregulata (Liu, 1991), and Celleporina cf. globosa Liu, 2001, not known from Japan, may have been acquired by Japanese Tsunami Marine Debris (JTMD) as these objects were carried by ocean currents into more southern waters. Three oceanic bryozoans (Jellyella tuberculata (Bosc, 1802), Jellyella eburnea (Hincks, 1891), and Arbopercula angulata (Levinsen, 1909)) provide insight into the routes that some JTMD items may have taken, and thus the conditions experienced, as they rafted from the Western Pacific to the Central and Eastern Pacific. The cooler-water species J. tuberculata and A. angulata were found primarily on JTMD objects arriving in the Pacific Northwest, whereas J. eburnea was most common on objects landing in the Hawaiian Islands. The most common bryozoan growth forms on these rafted objects were runners (creeping uniserial morphology) and arborescent forms capable of using available surface area provided by other organisms (such as hydroids) on space-limited objects. Species that form flat or mounded encrustations were less frequent, suggesting that they do not fare as well in a potentially space-limited environment. [ABSTRACT FROM AUTHOR]

Zebra mussels represent one of the most pervasive and expensive non-native species to be introduced into new aquatic ecosystems, negatively impacting human structures and infrastructure and acting as ecosystem engineers. Zebra mussels have demonstrated thermal plasticity, enabling expansion to semi-tropical aquatic systems including Texas ca. 2009. In this study we described spawning and population dynamics and water quality changes after colonization of two central Texas reservoirs, Lake Austin and Lady Bird Lake, ca. 2017. Veliger concentrations peaked in spring and early summer (Julian days 120-170) when water temperatures were between 20-25 °C. Adult population densities were initially highest nearest the busiest boat ramps and peaked in 2019-2020. Densities declined thereafter in the lower sections, but generally increased upriver in Lake Austin. However, the decline throughout Lady Bird Lake was three orders of magnitude from the peak. After colonization, chlorophyll a and suspended solid concentrations significantly declined, concomitant with significant changes in water total phosphorus concentrations; changes in different nitrogen-form concentrations were mixed. However, water quality changes were exacerbated by changing discharge volumes. Recent drought conditions and reduced discharges after 2021 have also resulted in elevated water temperatures, notably in Lady Bird Lake, that may have contributed to observed declines in adult zebra mussel densities nearshore. We hypothesize that other southern United States reservoirs should expect similar variations in population dynamics which will impact municipal, recreational, and water quality attributes. Preventing introductions remains essential as the species continues to rapidly spread to new regions. [ABSTRACT FROM AUTHOR]

The dependence of freshwater snails on the availability of ions through their ambient water varies widely across species and deficiencies may limit reproduction and other physiological functions. Nevertheless, in many studies on the New Zealand mud snail (NZMS) Potamopyrgus antipodarum, where reactions on components dissolved in the water are not the focus, the composition of the water the snails are kept in is not specified. We tested the sensitivity of reproduction to three types of artificial fresh water in three parthenogenetic lineages invasive to Europe. The three lineages descended each from a single mother collected in the same population in northern Germany. Reproduction was measured as the number of offspring sired within 12 weeks and varied across water types, however, lineages differed in their reaction norms. This indicates 1) that reproduction of the NZMS is indeed sensitive to the composition of the water and 2) that there is fitness relevant genetic variation which probably has arisen only within the 160-180 years the NZMS is present in Europe, i.e. we witness clonal evolution. For experiments, this means that the water composition should not be neglected and that potential genetic variation even among closely related clonal lineages has to be accounted for in order to ensure comparability and reproducibility. [ABSTRACT FROM AUTHOR]

Research on the ecology and impacts of the zebra mussel (Dreissena polymorpha) has developed in parallel with the long history of their spread across Europe and to North America. There is less scientific knowledge however about the quagga mussel (Dreissena rostriformis bugensis). The recent spread of both zebra and quagga mussels to the Western states of the USA, has spurred on dreissenid research. The 17th International Conference on Aquatic Invasive Species (ICAIS), was held in San Diego, California in September 2010. This special edition of Aquatic Invasions includes topical research presented at ICAIS and also extra subsequent papers on ecology, risk assessment and control of various aquatic invasive species in different parts of the globe. [ABSTRACT FROM AUTHOR]

Zebra mussel (Dreissena polymorpha) population dynamics were recorded between 2 September 2019 and 26 September 2020 at marina sites in each of two adjacent central Texas water bodies, Belton (BL) and Stillhouse Hollow (SHL) Lakes infested in 2013 and 2016, respectively. Lake water temperatures were insignificantly different while dissolved oxygen, pH and Secchi Disk depths were slightly higher in SHL. Veliger densities in both populations peaked in late Fall 2019 with veligers becoming absent by January 2020. Veliger densities again peaked in May-August 2020. These fall and spring spawning periods resulted in the presence of fall and spring mussel settlement cohorts. Mussel densities on settlement plates were greater at SHL than BL. At both sites, Fall 2019 cohorts had a lifespan of approximately one year or less, experiencing mass mortality during peak water temperatures in late summer/early fall the year after initial cohort settlement. Shell growth rates of the Spring 2020 BL and SHL cohorts were 91.4 and 67.3 µm/day, over a 126 day growing period, respectively, falling within the range reported for mussel populations in other southwestern US water bodies. Rapid shell growth and maturation allowed initiation of spawning earlier than zebra mussel populations in cooler, higher latitudes. Rapid growth and early maturity allows southwestern US zebra mussel populations to rapidly attain peak densities after infestation followed by population declines as recorded in BL. That southwestern mussel populations rapidly attain post invasion peak densities allows little time for water using facilities to develop effective, environmentally acceptable means of protecting infrastructure from mussel fouling. Thus, plans to prevent/minimize mussel fouling should be made in advance of invasion. Similarly, water body managers should develop and implement plans to minimize invasion likelihood and for rapid response before invasion occurs. [ABSTRACT FROM AUTHOR]

The cryptogenic nuisance alga Chondria tumulosa was first observed in 2016 at Manawai (Pearl and Hermes Atoll) in the Papahānaumokuākea Marine National Monument. It has since spread across the atoll, growing in thick mats and smothering benthic habitat. In September 2021 the species was observed at Kuaihelani (Midway Atoll), ~130 km to the northwest. Due to its growth habit and recent spread, considerable concern has been raised and management of the species may be warranted. We used publicly available oceanographic data and the Connectivity Modeling System software to assess how the potential for successful dispersal of C. tumulosa is affected by particle properties and oceanographic conditions. We found the likelihood of successful transit to be linked to particle density, oceanographic conditions at the time of release, and release location. Further modeling explicitly targeted the capacity of both reproductive tetraspores as well as drifting fragments to disperse. Model results indicated tetraspores of C. tumulosa are unlikely to survive the transit from Manawai to Kuaihelani, as none arrived at Kuaihelani above the depth limit of the species and those arriving below successfully settled at a rate of only 0.02%. In contrast, fragments modeled as rafting on marine flotsam such as macroalgae and marine debris settled at a rate of 3.85%. Rafting fragments also settled ~600 km further to the southeast (towards the Main Hawaiian Islands) than tetraspores. This study identified oceanographic conditions and particle properties likely to aid dispersal of C. tumulosa to Kuaihelani and suggests that fragments rafting on marine flotsam may accelerate its spread. [ABSTRACT FROM AUTHOR]

Aquatic ecosystems are particularly vulnerable to introductions of non-indigenous species, which potentially lead to major disruptions in the functioning of these invaluable habitats. Despite the significance of aquatic systems, there is no collated data available on the aquatic non-native plants in Serbia. Consequently, the aim of this paper is to provide a first overview of the aquatic alien plant species recorded in Serbia, their origins, current distribution, habitat preferences and invasiveness status. This study comprises the results of a comprehensive literature review and extensive field research on lake and river systems over a nine year period (2007–2015), with the addition of data from the IASV database and Joint Danube Surveys 2 & 3. The results of this study show the presence of seven non-indigenous aquatic plant species in Serbia which, despite being a relatively low number when compared to France and Germany, is in line with most of the countries of the region (e.g. Croatia, Bulgaria and FYR Macedonia). The majority of the species are native to the Americas, which concurs with the results of previous studies at the European level, with only one species of Asian origin. The most abundant of the registered non-natives is Vallisneria spiralis, followed by Azolla filiculoides and Elodea nuttallii, while Cabomba caroliniana, as the newest registered aquatic alien in Serbia, has the least number of records. All of the registered nonnatives predominantly occur in running waters, including as much as 91% of the records for Elodea canadensis and 85% for Elodea nuttalli. Vallisneria spiralis is present in five different EUNIS habitat types, while Paspalum distichum was recorded predominantly along the River Danube, thereby highlighting it as P. distichum's main corridor of spread in Serbia. The distribution of all the recorded non-indigenous species is primarily linked to the northern, low-lying part of Serbia—i.e. Vojvodina Province. Such a distribution pattern is concordant with the presence of adequate habitat types, the courses of potential international invasion corridors in the Sava and Danube rivers and the position of the elaborate irrigation canal network of the Danube-Tisa-Danube Hydrosystem; but also with the frequency of studies carried out in this region over the years. Of the seven aquatic aliens present in Serbian waterbodies, three are considered to be highly invasive and one potentially invasive, while two have also been included in the list of 150 most widespread alien species in Europe. [ABSTRACT FROM AUTHOR]

Taking into account the continuous increase in freshwater introductions, and to support the recent European legislation on invasive alien species, the identification of priority pathways and gateways of introductions is of utmost importance to develop adequate control strategies. The aim of this paper was to analyse the main pathways and gateways of introductions of freshwater alien species in Europe. Based on a thorough review of the scientific and grey literature, information on pathways, country and year of initial introduction of all freshwater alien species in Europe, was retrieved. The spatial and temporal patterns and trends of biological invasions in freshwater ecosystems in Europe, in relation to different pathways, were assessed. Our results pinpoint the major importance of aquaculture, pet/aquarium trade and stocking activities as pathways of introduction of freshwater alien species in Europe. For species native to some European countries, shipping and inland canals were the most important pathways, highly responsible for the entry of many harmful species. Germany, the United Kingdom and Italy were the main entry gateways of freshwater alien species in Europe. We found a geographical pattern related to some pathways of introduction in Europe: introductions through inland canals were concentrated in Central/North-eastern Europe, while introductions through pet/terrarium/aquarium trade were mainly observed in Central/Western Europe. While Chordata species entered Europe mainly through the three major above mentioned pathways, many harmful Arthropoda and Mollusca entered through shipping and inland canals. The information gathered in this study clearly indicates the entry routes that should be prioritised by Member States, for which stronger control and management actions should be implemented and prevention efforts concentrated under the scope of the related new EU Regulation. [ABSTRACT FROM AUTHOR]

The Australian native colonial ascidian Eudistoma elongatum has spread throughout harbours and oyster farms in Northland, New Zealand. This paper summarizes results of a study on the biology, ecology and potential methods of control of this recently introduced species. Colonies were reproductive for nine months of the year and embryos were present in zooids at water temperatures above 14oC. Low salinity was most likely the cause of variation in reproductive status observed. Larvae were able to swim for up to 6 hours, and remain viable at temperatures as low as 10°C at salinities above 20 psu. Only acetic acid was effective at killing colonies. Control using heat or other chemicals was not feasible for shallow subtidal populations identified in the study. E. elongatum has the potential to spread further within already occupied harbours, and to more southern harbours in New Zealand. [ABSTRACT FROM AUTHOR]

Asian swamp eels (Monopterus albus/javanensis) were first reported as introduced to Florida waterbodies in 1997 near Tampa and Miami; a third population was recorded by 1999 in Homestead. Initial assessments, published soon after swamp eels in southern Florida were first recorded in wetlands beyond canals and ponds (in 2007), concluded there was little threat to Florida’s aquatic ecosystems. Long-term data now suggest they precipitated population crashes of crayfishes and small fishes in the eastern Everglades. We used records from continuous long-term monitoring programs, sporadic monitoring studies, and online databases to reconstruct swamp eel presence across Florida. Monitoring studies provided wetland hydrologic variables to assess limits for swamp eels. From 1997–2007, populations in southern Florida remained restricted to canals; initial spread from 2007–2017 across southern Everglades National Park proceeded slowly and the two populations covered ~1500 km² of southern Florida. From 2017–2022, the rate of spread increased as they spread west and north (~5800 km² range). Through 2014, the Tampa population occurred only along southern/eastern Tampa Bay (~60 km²) but has since spread south along the Gulf Coast, east into central Florida, and south along the Lake Wales Ridge (~11,000 km²). We found evidence of two potentially new introductions, in Palm Beach County and Orlando. There was no clear evidence of limitation of wetland drying on swamp eel occurrence in the Everglades; they were captured in marshes that dried for 1–5 months during the previous dry season, but short-hydroperiod wetlands may have slowed spread. In the Everglades, evidence suggests swamp eels may have been inadvertently spread into marshes from canals used to deliver water for flood control and hydrologic restoration. Swamp eels are currently spreading unchecked across Florida, and there should be great concern about continued spread in this region and their establishment and spread elsewhere. [ABSTRACT FROM AUTHOR]

The invasive alien false mussels Mytilopsis leucophaeata cochleata and Dreissena polymorpha (Dreissenidae) have established populations in the North Sea canal in the Netherlands that connects the harbours of Amsterdam with the North Sea. The favourable and unfavourable salinity ranges of both species were earlier studied in long-term outdoor mesocosm experiments. Their occurrence in salinity gradients in estuaries or canals connecting seaways to freshwater harbours provides information on their salinity tolerance under field conditions. By the combination of laboratory experiments and field data using the same source population a high predictability can be expected for establishment of the gradients facilitated by constructions. The reliability of experimentally derived salinity-tolerance limits for both dreissenid species was tested using data on their distribution in a salinity gradient of the littoral zone along the North Sea canal. The mussels used for the survival experiments in mesocosms were also collected from this canal. Favourable salinity ranges for adult survival in the mesocosms were 0.2 – 17.5 for M. leucophaeata cochleata and 0.2 – 6.0 for D. polymorpha. Unfavourable salinities were outside these ranges and led to high and fast mortality of these species. Mytilopsis leucophaeata cochleata was present over nearly the whole length of the North Sea canal with the highest densities close to the sea sluices where also the highest salinities and water temperatures were measured. Their densities in the canal decreased gradually at larger distances from the sea. Dreissena polymorpha co-exists with M. leucophaeata cochleata at the east end of the canal with low salinity due to the influence of freshwater of the river Rhine. The occurrence of D. polymorpha was restricted to a salinity below 4 and M. leucophaeata cochleata only occurred at a salinity above 1.5 (maximum value measured in the canal 9.2). Shorter salinity gradients with lower salinity ranges provided additional information on the co-existence of both species. Co-existence was observed at a salinity range of 1.5–3.3 (own data), 1.0–3.5 (Van Couwelaar and Van Dijk 1989), both in the North Sea canal, and 0.2–2.8, in the Canal through Voorne (Janssen and Janssen-Kruit 1967). These data correspond with studies of both species by Walton (1996) in the Hudson River (salinity range 0–3). Found salinity ranges in the North Sea canal for both species match with the tolerance results obtained by mesocosm experiments. A new invading dreissenid mussel Dreissena rostriformis bugensis and a mytilid Ischadium recurvum occur in the North Sea canal since 2006 and 2012, respectively. Competition between recent and earlier invaders is likely when salinity tolerances are similar. It has already been observed that D. rostriformis bugensis outcompetes D. polymorpha under freshwater conditions (Bij de Vaate et al. 2014; Matthews et al. 2014). Ischadium recurvum has the potential to colonize large parts of the canal and to be a strong competitor of M. leucophaeata cochleata (Goud et al. 2019). Since January 2022, the new ‘Zeesluis IJmuiden’ with the biggest locks in the world is in use, affecting the probability of population establishment of new introduced and invasive alien mussel species. [ABSTRACT FROM AUTHOR]

This study sought to investigate the invasive mechanism of Myriophyllum aquaticum by subjecting it to simulation experiments in varying water temperatures ranging from 0 °C to 30 °C. The results showed that water temperature considerably affected both the growth and reproduction of M. aquaticum. The optimal temperature range for the growth of M. aquaticum was 25‒30 °C. Although the growth of M. aquaticum was inhibited at temperatures between 0‒5 °C, this did not result in mortality. The stem nodes, branches, and diameter reached maximum values over a temperature range of 20‒25 °C. High-temperature stress at 30 °C led to a gradual decrease or disappearance of branches. Compared to the 0 °C, 5 °C, and 30 °C treatment groups, a temperature of 20 °C led to biomass accumulation and significantly higher values. M. aquaticum’s physiological activities were affected by temperature. Except for 10 °C and 15 °C, the catalase activity varied among different water temperatures. M. aquaticum catalase activity was maximal at 5 °C and minimal at 25 °C. Conversely, the synthesis of photosynthetic pigments was highest at 10 °C and 15 °C. The plant’s optimal temperature for growth was between 20 °C and 25 °C. When the temperature was <10 °C, M. aquaticum adapted to the water temperature’s potential damage. This plant has a notable ability to tolerate various temperatures. [ABSTRACT FROM AUTHOR]

Invasive species are often in focus in the non-indigenous species (NIS) research while low-abundance species receive relatively little attention. However, tracking NIS dynamics since the early stages of an invasion provides valuable information on the ecology of invasions. In the current paper, we investigated the invasion history and population dynamics of the small-bodied cladoceran Evadne anonyx G. O. Sars, 1897 in the Gulf of Riga (Baltic Sea) almost since its first detection in 2000. The species already was widespread the Gulf of Riga in 2001 and has been found in nearly every subsequent sample collected during summer months. However, the abundance of the species remained low, seldom 100 individuals m-3. Both, salinity and water temperature affected the spatial distribution and population abundance of E. anonyx. The species was found to occur only sporadically at salinities below ca. 6. To obtain reliable presence/absence and density estimates on this small-bodied cladoceran, the entire zooplankton sample needed to be analysed. [ABSTRACT FROM AUTHOR]

An estimated 60- 75% of the world's infectious diseases of humans are zoonotic, infecting both humans and other animals. Many are vector- borne, relying on transmission by mosquitoes and biting flies that are aquatic for much of their lifespan. Others rely on aquatic molluscs, fishes, or other aquatic animals for completion of their transmission cycles, and others develop and thrive in diverse freshwater environments outside any host. While such diseases remain firmly endemic in many areas, new outbreaks of infectious diseases associated with freshwater have occurred throughout the world, and many others have spread to new locations. This may involve introduction of aquatic vectors into locations where the disease was previously unknown, as in the recent occurrences of mosquito-transmitted diseases such as West Nile Virus in North America, dengue fever in southern Europe, Chikungunya virus in the Caribbean and South America, and dirofilariasis in Central and Eastern Europe. Such a pattern is also possible with such major human pathogens as Schistosoma blood flukes and food-borne trematodes, through introduction of aquatic host snails from long-established foci in other areas. Alternatively, waterborne pathogens may be introduced directly, leading to disease outbreaks such as the cholera disaster still unfolding in Haiti. Accidental or intentional introduction of pathogens or their aquatic vectors and hosts are among the primary concerns that affect international trade, travel, and global health security. These concerns are compounded by the prospect of warming climate, potentially resulting in primarily tropical diseases encroaching into historically subtropical or temperate regions. Thus, we must be prepared for the possibility of geographic spread of diseases into areas where they have not occurred, or reintroduction into areas where they once occurred but have been eliminated through control measures. For example, North America and Europe are at risk for reintroduction of such major "tropical" diseases as malaria and yellow fever, and thus must come under increasing scrutiny, starting with surveillance of freshwater systems for both established and potentially invasive vector and host populations. This critical perspective paper briefly reviews selected previous cases in which aquatic invasive species have contributed to infectious disease emergence, re-emergence, or increase, and proposes One Health strategies for integrating human, animal, and environmental monitoring and surveillance to better prepare for or prevent geographic spread of major human health threats associated with aquatic systems. [ABSTRACT FROM AUTHOR]

This paper represents the first attempt to study the microfungal flora contained in the digestive system of the most widespread aquatic invasive invertebrate in the world: Procambarus clarkii (Cambaridae, Decapoda). Understanding its bioinvasion, in terms of ecological risk and environmental impact, requires a multidisciplinary approach that considers consequences on all levels, from macroscopic to microscopic. In this study, we investigated both the population dynamics and the dietary habits of the red swamp crayfish captured within a natural biotope in Northern Italy. The diet was mainly based on plant detritus. The analysis of microfungal flora in the crayfish stomach revealed a fairly constant composition, unrelated to season and diet. Since most of the fungi were associated with detritus and some species were particularly frequent, we formulate the hypothesis that the fungi may be selected to decompose plant material in the digestive tract, thus providing a source of energy to the crayfish. Procambarus clarkii is also shown to be a potential vector of plant diseases as some of the 45 isolated fungal taxa are potentially phytopathogenic. [ABSTRACT FROM AUTHOR]

After going unreported in the northwestern Atlantic Ocean for 18 years (1988 to 2006), the Asian tiger shrimp, Penaeus monodon, has recently reappeared in the South Atlantic Bight and, for the first time ever, in the Gulf of Mexico. Potential vectors and sources of this recent invader include: 1) discharged ballast water from its native range in Asia or other areas where it has become established; 2) transport of larvae from established non-native populations in the Caribbean or South America via ocean currents; or 3) escape and subsequent migration from active aquaculture facilities in the western Atlantic. This paper documents recent collections of P. monodon from the South Atlantic Bight and the Gulf of Mexico, reporting demographic and preliminary phylogenetic information for specimens collected between North Carolina and Texas from 2006 through 2012. The increased number of reports in 2011 and 2012, ranging from 102 mm to 298 mm total length, indicates that an adult population is present in densities sufficient for breeding, which is indicative of incipient establishment. Based on these reports of P. monodon, its successful invasion elsewhere, and its life history, we believe that this species will become common in the South Atlantic Bight and Gulf of Mexico in less than 10 years. Penaeus monodon is an aggressive predator in its native range and, if established, may prey on native shrimps, crabs, and bivalves. The impacts of an established P. monodon population are potentially widespread (e.g., alterations in local commercial fisheries, direct and indirect pressures on native shrimp, crab and bivalve populations, and subsequent impacts on the populations of other predators of those organisms) and should be considered by resource managers. The impacts of P. monodon on native fauna and the source(s) or vector(s) of the invasion, however, remain unknown at this time. [ABSTRACT FROM AUTHOR]

In 2010, the Asian clam, Corbicula fluminea, was found for the first time in Ireland. The species is considered to be one of the most aggressive freshwater invaders causing strong economic and ecological impacts. This paper provides predictions for the spread, population density, and impacts of Corbicula fluminea in Ireland. Water chemistry datasets from the Republic of Ireland and from Northern Ireland were analysed to determine suitable waters for colonisation. Only 3 rivers and 6 lakes have pH levels considered too low (<5.6) for invasion of this species. Corbicula fluminea densities within a waterbody will depend on suitable substrate and food availability, with greater populations in canals, rivers and lakes with a higher trophic level. Boating and angling are likely to be the highest vectors of spread. Redevelopment of any canal sections will require risk assessment, to minimise spread. Corbicula is likely to cause negative economic effects by creating blockages in drinking and industrial water abstraction systems. The ecological impacts of C. fluminea are associated with their role as biofilters, and are therefore determined by their filtration rate and the overall population density in a given waterbody. [ABSTRACT FROM AUTHOR]

Predicting and averting the spread of invasive species is a core focus of resource managers in all ecosystems. Patterns of invasion are difficult to forecast, compounded by a lack of user-friendly species distribution model (SDM) tools to help managers focus control efforts. This paper presents a web-based cellular automata hybrid modeling tool developed to study the invasion pattern of lionfish (Pterois volitans/miles) in the western Atlantic and is a natural extension our previous lionfish study. Our goal is to make publically available this hybrid SDM tool and demonstrate both a test case (P. volitans/miles) and a use case (Caulerpa taxifolia). The software derived from the model, titled Invasionsoft, is unique in its ability to examine multiple default or user-defined parameters, their relation to invasion patterns, and is presented in a rich web browser-based GUI with integrated results viewer. The beta version is not species-specific and includes a default parameter set that is tailored to the marine habitat. Invasionsoft is provided as copyright protected freeware at http://www.invasionsoft.com. [ABSTRACT FROM AUTHOR]

The occurrence of the non-indigenous species Limnoperna securis belonging to Mytilidae family is recorded for the first time in the Bay of Biscay. Numerous individuals were collected in intertidal and shallow waters in the inner part of Nervión estuary (Bizkaia, Basque Country, SE Bay of Biscay). In the present paper, notes about the history of this small brown mussel invasion, vectors of introduction and dispersal, as well as consequences of invasion are discussed. [ABSTRACT FROM AUTHOR]

Cyprinus carpio is known to be established in most of Mexico. Only the Mexican Gulf states were free of this species until recently. This paper reports the first record of the common carp in Tabasco, Mexico. Seven specimens of Cyprinus carpio var. communis and one specimen of Cyprinus carpio var. specularis were detected in a small scale fishing landing site near Frontera, Tabasco on January 24, 2011. Further sampling and monitoring is required to assess the ecological impacts of this exotic species on the native fauna. [ABSTRACT FROM AUTHOR]

The paper presents the first European records of the copepod (Crustacea, Calanoida, Diaptomidae) Skistodiaptomus pallidus in shallow eutrophic waters indirectly connected with the Weser River, Northern Germany. Its original distribution is in the Mississippi basin of the United States of America. It is probable that this species entered the Weser River via ship ballast. [ABSTRACT FROM AUTHOR]

Co-occurring and morphologically similar species have adapted to differential niches to minimize competition. An invasive alien species can occupy an 'empty niche' in introduced ranges. Alternatively, the invader may occupy an overlapping niche and compete with native species to a certain degree. In a Western European lowland brook with high nutrient loads, we studied a benthic community of five fish species, including two alien species: an Asian weatherfish (Misgurnus bipartitus) and the western tubenose goby (Proterorhinus semilunaris). The native species concerned stone loach (Barbatula barbatula), spined loach (Cobitis taenia), and gudgeon (Gobio gobio). Because of the unknown effects of the invaders on native benthic fish species, the trophic position, isotopic niche overlap, and potential food competition among these species were identified using nitrogen and carbon stable isotopes. The trophic levels of the five fish species indicated that they are secondary consumers. The body size of native fish species correlated significantly negatively with their d15N (?) signature, in contrast with the invaders indicating that the latter are generalists. Significant isotopic niche overlap was observed among all benthic species. The degree of niche overlap of M. bipartitus was the highest with G. gobio (91.8%). Proterorhinus semilunaris showed the highest degree of niche overlap with B. barbatula (91.2%). It was notable that the observed niche overlap between the native B. barbatula and C. taenia was high (99.2%). Overlap between M. bipartitus and P. semilunaris was low (8.9%), indicating little resource competition between these alien species. Native species showed wider isotopic niches than the invaders. Bayesian mixing models revealed that native and alien species slightly differ in their main diet. The results suggest that the invaders are plastic in their resource use, leading to niche differentiation and promoting the co-existence of benthic fish species. [ABSTRACT FROM AUTHOR]

The alien freshwater mussel Sinanodonta woodiana (Lea, 1834) has rapidly spread throughout Europe over the past decades. This species can cope with a broad range of environmental conditions and has a high reproductive capacity making S. woodiana a successful invader. Due to its negative effects on native freshwater mollusk communities and parasitized fish it is critical to identify suitable habitats where S. woodiana may persist and how these habitats may be altered under future climate projections. We applied multivariate ordination methods to analyze the space-time relationship and a maximum entropy approach (MaxEnt) to predict the recent (1970-2000) and future (2041-2060 and 2081-2100) distribution of S. woodiana using environmental and climate variables for the European continent. After first sightings in 1979 there were only a few new locations and findings which increased unevenly and exponentially to a maximum of about 100 new locations per year followed by decline during the last few years. Under recent climate condition, 2.3% of European watersheds are predicted as highly suitable habitat for S. woodiana and located in the temperate climate zone between 40°N and 60°N. Suitable habitat was associated with lowland watersheds characterized by fluviatile deposits and agriculture. Elevation, the distance between water bodies, land cover and mean temperature of the coldest quarter were the main factors influencing the modeling results. For future climate scenarios, highly suitable habitat increased to 2.4% by the middle of this century and decreased to 2.2% by the end of the century under the 'least radiative forcing' scenario. For the intermediate and high radiative forcing in 2050 and 2100, highly suitable habitat decreased to 2.2% and 1.7% and to 2.2% and 2.2%, respectively. Results from our study can be used as a baseline to better understand potential invasion pathways, identify high risk areas, and to initiate early detection and rapid response strategies. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are vulnerable to the invasion of exotic aquatic plant species because of the great likelihood of the introduction of exotic species, and the lack of barriers that block introduced species. Water hyacinth, Pontederia crassipes Mart., is one of the world's most invasive alien plant species damaging freshwater ecosystems worldwide. Here, we monitored the water hyacinth population on Jeju island, Korea, to assess current invasion risks. Furthermore, we investigated how water hyacinth affects water pH because pH is an important determinant of the distribution of other aquatic plants, and thus a good indicator of aquatic ecosystem health. Water containing water hyacinth had a pH of 5.3, while that with water hyacinth and soil had a pH of 4.8 72 hours after the start of the experiment. Water hyacinth extracts contained shikimic acid, stearic acid, and palmitic acid, which are possible compounds that caused a decline in water pH. Water hyacinth also inhibited the growth of the aquatic plant species, Spirodela polyrhiza and Lemna perpusilla. These results imply that invasion of water hyacinth adversely impacts the abiotic and biotic characteristics of aquatic ecosystems. Moreover, monitoring the water hyacinth population suggests that this invasive aquatic plant overwinters on Jeju island. Therefore, regular monitoring and subsequent control of water hyacinth population can prevent its expansion in the aquatic habitats of Jeju island and the southern region of the Korean peninsula. [ABSTRACT FROM AUTHOR]

A major challenge in invasion science is detecting overlooked introductions, their pathways of introduction and spread. One of the most successful introduced taxa in aquatic ecosystems are peracarid crustaceans. There are a growing number of reports of accidental introductions of peracarids worldwide, mostly related to human transport hubs (e.g., ports and marinas). Tanaidaceans are especially abundant in these communities. Most frequently given examples of natural and anthropogenic passive dispersers belong to the family Tanaididae. However, their wide distribution requires confirmation. Most records come from 70--80' of last century, when identification of the species relied only on morphological characters. The small size and large intraspecific variation of tanaidids generate a high taxonomic uncertainty, as in the case of Zeuxo turkensis. Population of this species was previously known from Turkish, Japanese, and Australian coasts. In the two last places this tanaidid was identified as Hexapleomera sasuke, despite there were some premises that it should be synonymized with Z. turkensis. Here we investigate specimens that resembled both Hexapleomera sasuke and Zeuxo turkensis collected in marinas around the Iberian and Moroccan coasts. Integrating morphological and molecular methods (barcoding) we confirmed: (1) the first record and presence of well-structured populations of Z. turkensis in Spain, Portugal and Morocco, representing the first record of the species for Atlantic waters; (2) the conspecificity between H. sasuke and Z. turkensis, which should be synonymized; and (3) the wide distribution of Z. turkensis associated with human transport hubs (i.e. marinas) in the study area, showing its potential for introduction and spread. Integrated approaches and greater taxonomic support are key to advancing knowledge on the origin and invasion patterns of this and other small and poorly known human-mediated widespread species. [ABSTRACT FROM AUTHOR]

As impacts on the Mediterranean Sea are expected to grow in the future, especially with climate change, habitat degradation, and displacement of native species by non-indigenous species (NIS), the investigation of significant alterations to trophic levels in this diverse marine habitat is important. Analysis of stable isotopes from targeted consumers has previously been shown to reliably reflect that of primary producers, thus enabling us to describe and highlight potential shifts in the food web of a particular ecosystem. In this study, we used δ13C values of essential amino acids (AA) in order to examine the dietary composition of established non-native, Lessepsian fish migrants in the Eastern Mediterranean Sea compared to that of the same fish species from their original population in the Gulf of Aqaba, Red Sea. Our data show that a clear variance in carbon isotopic signatures exists in food sources consumed by the same species between the different environments, with the exception of the classic herbivore, Siganus rivulatus (Forsskål & Niebuhr, 1775), whose very similar isotopic patterns reflect the algal source they predominantly consume in both locations. With the results of this research, we propose that Lessepsian fishes with the ability to maintain their nutritional patterns, though not necessarily that of their original food source, will acclimatize better in their new habitat. Consequences of flourishing Lessepsian fish populations include a further tropicalization of the Eastern Mediterranean Sea and the likely restructuring of local food webs. [ABSTRACT FROM AUTHOR]

Predator presence may result in non-lethal costs to prey; these costs may be even larger if both predators and prey do not naturally co-occur. We experimentally evaluated the survival of two aquatic invertebrates from the upper Paraná River basin (Chironomus sancticaroli - benthic and Daphnia magna - pelagic) exposed to a native mesopredator fish (Astyanax lacustris) in three non-lethal predation treatments: (i) the absence of piscivorous fish, (ii) the presence of a native piscivorous fish (Hoplias aff. malabaricus), or (iii) the presence of a non-native piscivorous fish (Astronotus crassipinnis). The treatments were crossed with the absence and presence of vegetated habitats. We predicted that the mesopredator might not have adapted foraging strategies to eat in the presence of an unfamiliar predator while invertebrate prey use vegetated habitats for protection. Therefore, we expected that the combination of piscivorous fish presence and vegetated habitat would lead to a classical additive response on invertebrate survival, which will be higher in the presence of non-native piscivorous fish than in the presence of native piscivorous fish. The presence of vegetated habitat and piscivorous fish increased invertebrate survival, but together they did not promote an additive response. Instead, the non-lethal cascade effects of the native piscivorous fish was similar between vegetation treatments, whereas the non-native piscivorous fish led to higher survival of the invertebrates in non-vegetated versus vegetated habitats. Although refuges are understood as elements that enhance predator-prey stability, the effectiveness of submerged macrophyte stands as safe habitats is dependent on some predator traits, such as origin and hunting mode. Our results also indicate that the invasion of A. crassipinnis has the potential to change mesopredator prey selectivity from a diet based on pelagic prey with the native H. aff. malabaricus to the random consumption of pelagic and benthic prey, which may have important consequences for the stability of natural aquatic food webs. [ABSTRACT FROM AUTHOR]

Non-native freshwater zooplankton species have been recorded from aquaculture ponds in New Zealand and Italy, while zooplankton invasions elsewhere have implicated the aquaculture industry as the vector for introduction. However, the prevalence of non-native species in international aquaculture facilities is unclear. We undertook a literature review of publications examining zooplankton assemblages in freshwater aquaculture ponds globally to determine; 1) the prevalence of non-native taxa, 2) the quality of the studies undertaken, 3) how well the major freshwater aquaculture nations are represented in studies, and 4) the representation of dominant aquaculture species. Thirty-two suitable publications were found that provided data on zooplankton assemblages from aquaculture facilities. We supplemented this by sampling Huka Prawn Park, Taupō, New Zealand, as knowledge of zooplankton in prawn facilities was scarce. Zooplankton data was obtained for 205 outdoor ponds and experimental tanks, from 39 different aquaculture facilities, across 13 countries. Non-indigenous taxa were recorded from 17.9% of facilities globally. Over half of these publications (53.1%) identified taxa to genus level only, with the remaining 46.9% attempting species level identifications. The high proportion of publications not identifying to species level indicates that non-native species will not be recognised in most studies; 31.8% of facilities were invaded when considering only studies with species level identifications. In total, 234 different taxa were identified (including 184 to species level), with only 4, located in Italy and New Zealand, recognised as non-native; only 3 of these 4 taxa were clearly identified as non-indigenous in their respective publications. Another species has been identified outside of its native range in North American aquaculture facilities, but no co-existing zooplankton species were reported. While aquaculture facilities were found to harbour only a small number of non-indigenous species, our findings indicate that there is a significant lack of taxonomic resolution used in most studies, and a lack of surveys in major aquaculture producing regions and from facilities holding many of the major aquaculture species. Importantly, few zooplankton invaders putatively originating from the aquaculture industry have been found within aquaculture facilities themselves. Overall, it is currently difficult to determine the prevalence of non-indigenous zooplankton species in aquaculture facilities globally, and our results suggest the risk may be far higher than is currently appreciated. As such, we recommend systematic surveys of ponds utilising species level identification from a variety of geographic regions, to better quantify invasion risks by non-native zooplankton taxa from the freshwater aquaculture industry. [ABSTRACT FROM AUTHOR]

In the last decade, invasive suckermouth armored catfish Pterygoplichthys spp. spread among many river systems of Vietnam. Extended distribution of armored catfish might be associated with using brackish water in estuaries for fish spread from one river system to another. The first goal of our study was to assess the occurrence of armored catfish in the estuary of the Da Rang River (Phu Yen Province, Vietnam) and their distribution depending on the horizontal salinity gradient (4--25 PSU). Fish were mainly caught by stationary bottom traps in water salinity from 4 PSU to 18 PSU. The second goal of our study was to experimentally evaluate the ability of armored catfish to move and breathe in seawater (33 PSU). Fish moved in horizontal and vertical planes after transfer into seawater during the first 15 minutes. Fish moved around less by the 13th--15th minutes in seawater. Armored catfish moved around more in seawater than in freshwater. The exposure to seawater for 6 minutes led to deterioration of fish breathing. The results of our field and experimental studies established that armored catfish are found and able to move in brackish waters but avoid high salinity water. These facts provide support for the hypothesis of armored catfish invasion through the estuaries and coastlines. [ABSTRACT FROM AUTHOR]

Introduced species constitute a critical bio-security issue worldwide and the precise monitoring of their spread is crucial for their management. For species forming cryptic complexes this may remain difficult. Using integrative taxonomy, we formally report for the first time, well-established populations of the cosmopolitan introduced bryozoan Watersipora subatra in the French Mediterranean Sea and compile worldwide existing genetic data for Watersipora species alongside newly acquired data to establish the most complete phylogeny of the genus to date. This revealed pervasive erroneous identifications in Genbank, which in turn perpetrate further errors in recent studies, primarily misidentifying W. subatra as W. subtorquata. High abundance and geographic spread of W. subatra in our Mediterranean sampling sites suggest that this species has been present for some time but has been misidentified until now. We provide an updated species identification for all current reference sequences in the Watersipora genus, which may help future monitoring of W. subatra and other Watersipora species. [ABSTRACT FROM AUTHOR]

To investigate the influence of non-native aquatic invertebrate species on food web structure, we selected two reservoirs located in the Grande River (upper Paraná River basin, Brazil) with similar fish communities, different age and different taxa introductions history. We quarterly collected fish and benthonic macroinvertebrates samples in the Volta Grande and Funil reservoirs between October 2015 and August 2016. We used conventional methods of diet evaluation to assess the sampled fish and measured the availability of invertebrates (i.e. composition and density) present in the sediment samples from each reservoir. In addition, we performed a structural analysis of trophic interaction networks. Based on the data obtained, it was possible to identify that in Volta Grande most of the energy flow, between benthonic invertebrates (prey) and the fish community (predators), occurred through non-native prey species, especially Limnoperna fortunei and Macrobrachium amazonicum, while in Funil it was shared between non-native and native prey. Species loss simulations indicated that the networks did not differ substantially between random losses and losses between groups. In general, there was a decrease in the probability of occurrence of highly connected species in both reservoirs and between non-native and native species. Results showed that the new interactions among species influenced the importance of the available energy sources for the fish in the Volta Grande reservoir. The presence of non-native prey, especially M. amazonicum, may influence the interaction network structure, promoting community dependence on non-native species to ensure robustness to environmental disturbances. In the absence of pre-invasion data, the comparative study between systems with similar fish communities may provide a better understanding of the impacts caused by the introduction of non-native invertebrate prey. [ABSTRACT FROM AUTHOR]

The freshwater Japanese mystery snail (Heterogen japonica) was introduced to the United States in the early 1900s and has since established populations throughout the continent. The species has ovoviviparous reproduction (i.e., eggs hatch within the mother and develop inside before being released as juveniles), which is one reason it has been successful. Despite its wide geographic range, little is known about its physiological tolerances. For example, high salinities and temperatures may limit its spread, and determining the species' tolerance to these environmental factors is crucial to predict its possible range expansion. To test this, 600 juvenile H. japonica (average shell length: 6.0mm, range: 4.5--8.3mm) were collected from 28 females from a lake in Virginia, USA and placed in a fully crossed design to test the interaction between salinity (0.2 and 2 PSU) and temperature (25 °C, 34 °C and 38 °C). Juveniles were monitored for mortality over two weeks. Kaplan--Meier survival analyses determined median survival probabilities, and generalized linear models compared differences in mean survival. All juveniles in 25 °C (except one in 0.2 PSU) survived (N=199/200), and all juveniles in 38 °C died by the end of 14 days (N=200), irrespective of salinity. However, juveniles kept at 38 °C showed higher early (≤4 days) mortality in 0.2 PSU, but lower early mortality in 2 PSU. Importantly, juveniles in 2 PSU survived for ≥2 days (N=294/300) across all temperatures, indicating that there may be scope for expansion through estuaries. Future work should examine temperatures between 34 and 38 °C and salinities above 2 PSU to understand the extent of covariance between salinity and temperature and create mathematical models to estimate survivability and spread. [ABSTRACT FROM AUTHOR]

Within the genus Carassius Jarocki, 1822, the crucian carp (C. carassius L., 1758) occurs naturally in the northern part of Middle Danube Basin (Austria, Morava, Slovakia). This species has the least concern status in this region, but observations in the last decades suggest that it is very close to extinction here. The distribution of crucian carp is limited to a small number of vanishing lentic habitats (oxbow lakes, marshlands). These biotopes are in the last stage of succession due to the drying up of the landscape and a reduction in the creation of new natural alluvial habitats. The non-native cyprinid, C. gibelio (Bloch, 1782), known as gibel carp and Prussian carp, has gradually become eudominant in a wide spectrum of habitats/biotopes since the 1960s Several biological adaptations of non-native species are generally considered the strong basis for the mass spreading in the invaded area. The other side of the expansion of non-native C. gibelio is affected by anthropic activities associated with fish farming, translocation and stocking the fish in open water ecosystems. In this study, we analysed historical scientific data on the distribution of Carassius spp. published from the 19th century to the present from the mentioned areas. The results suggest that the number of records of invasive C. gibelio has gradually increase in rivers, regulated channels and creeks, which could be considered as natural pathways of spreading. However, the presence of invasive C. gibelio in artificial biotopes (fishponds, reservoirs) is continuous from the 1960s. In the area mentioned, the artificial biotopes are managed by national fisheries associations and relate to the historical way of farming in Central and Eastern European countries. To show the current state of the fishing grounds of the Slovak Angling Association, we a created the distribution map based on the Carassius spp. catches recorded in last two decades. [ABSTRACT FROM AUTHOR]

Behavioural interactions between introduced predators and introduced prey are still largely underestimated. The present work takes advantage of the co-occurrence of two introduced species, the Asian shore crab Hemigrapsus sanguineus and the amphipod Ptilohyale littoralis, respectively first recorded on rocky shores along the French coast of the eastern English Channel in 2005 and 2016. In this context, the predation by male and female H. sanguineus on P. littoralis was examined under controlled laboratory conditions, by presenting either juveniles of the blue mussel Mytilus edulis or adult P. littoralis to H. sanguineus. We subsequently assessed the potential prey preference of the Asian shore crab for P. littoralis and M. edulis by presenting the two prey items simultaneously in the same proportion. In the absence of choice, male H. sanguineus preyed significantly more on M. edulis than P. littoralis. In contrast, females preyed significantly less on M. edulis than P. littoralis; however, male and female H. sanguineus consumed similar numbers of P. littoralis. When choice was possible between P. littoralis and M. edulis, the crab did not exhibit preference stricto sensu for any type of prey. These results suggest that the Asian shore crab cannot be considered as a naive predator when confronted to a newly introduced prey. Our results also suggest that the amphipod P. littoralis did not exhibit any effective antipredator response towards the crab. These observations nevertheless warrant further work on the effects of abiotic factors (e.g. temperature) as well as other biotic interactions (e.g. presence of other prey or predators for H. sanguineus) may have on the observed prey-predator interactions between H. sanguineus and M. edulis and P. littoralis. [ABSTRACT FROM AUTHOR]