The Australian invasive weed Atriplex semilunaris Aellen – in the Canary Islands known so far from the islands of Fuerteventura and Lanzarote, where it is listed among the most invasive species – was recently recorded for the first time in the islands of Gran Canaria and Tenerife, a significant expansion of its distribution in the archipelago. Details about these first records, including a distribution map and new illustrations, are presented. Its recent appearance in Gran Canaria and Tenerife is very important, as it may be the gateway for its introduction to the rest of the islands of the archipelago. The ecological threats associated with the expansion of the species are discussed and the measures that seem appropriate are indicated. Finally, it cannot be ruled out that the species will spread further to the nearby North African coastal areas (or is already occurring there unnoticed), where the chance of establishment and expansion is optimal.

I report on the distribution of White snakeroot (Ageratina altissima) (Asteraceae, Magnoliopsida) in Austria. The first established occurrence of this species in Austria was recorded in Lower Austria in 2006. Here, I summarize the current distribution of the study species at this locality. In 2006, the species had invaded several 100 m². In 2024, it has spread over c. 2.7 ha forming open to dense stands. The composition of the invaded vegetation was documented by four plots. Ageratina altissima invades mesic to temporarily wet tall herb vegetation in forest clearcuts, forest fringes, open conifer plantations, and broadleaved forests. Thus, given the substantial expansion in the last two decades, I suggest that the future spread of Ageratina altissima should be monitored, and if necessary, management actions should be taken.

Amelanchier ×lamarckii F. G. Schroed., a shrub or small tree native to North America, has escaped from cultivation in Lithuania and is recorded as a new casual alien plant in Lithuanian flora. Most of the recorded young individuals have grown from seeds and spread locally through saplings. The population consists of about 50 individuals, of which approximately 10 have grown to a height of 0.5–2.5 m and are fruiting. Amelanchier ×lamarckii is recorded from the Kelmė district, between Panūdžiai and Palendriai villages, in a dry grassland habitat along the roadside. Amelanchier ×lamarckii has already been reported to have escaped to several European countries. This hybrid shares similar growth traits as its invasive congener Amelanchier spicata (Lam.) Koch. The naturalization and spread to natural habitats in Lithuania are highly probable. Amelanchier ×lamarckii has been reported from northern latitudes; therefore, the spread of this plant in Lithuania should be monitored. Planting of A. ×lamarckii close to dry grassland habitats as well as forest edges should be avoided, considering the possible spread by birds into these habitats.

The expansion of myriapod species outside their native range is a well-known phenomenon, although well-studied only in the western part of Europe. Our study reports a recent rapid eastward range extension of Polydesmus angustus Latzel, 1884, from Germany to Poland, where its new eastern limit of distribution is probably the Vistula River. We confirm that the species occupies disturbed, anthropogenic habitats, supporting its human-mediated dispersal scenario. We also consider the possibility of competition between this species and its closest relative, Polydesmus complanatus (Linnaeus, 1761). We also point out that in the case of taxonomic groups containing externally similar species, the verification of citizen science-based records by specialists examining morphological details of specimens and, if possible, by DNA barcodes, is necessary for reliable insight into the range extension of alien species.

Two species of the genus Greenidea Shouteden, 1905, associated with Psidium guajava L. and Ficus benjamina (L.), are described morphologically and molecularly, expanding their distribution. The latest reports of the plague are in South America and probably follow trade routes from the east. This is the first record in Atacama Desert, northerm Chile.

Kellicottia bostoniensis (Rousselet, 1908), originally native to North America, has recently expanded its distribution worldwide. Meanwhile, Notholca bipalium (Müller, 1786), typically associated with marine environments, has been identified in scattered locations across different regions. This study reports new records of K. bostoniensis and N. bipalium, found in a large river in Central Europe. A total of 361 zooplankton samples were collected from 20 sampling stations throughout the Oder (Odra) River system. Temperature values, electrolytic conductivity and chlorophyll a concentration were measured to characterize the investigated environment. Kellicottia bostoniensis was recorded at four of the 20 sampling sites, representing 1.39% of all analyzed samples (5 out of 361). The highest recorded density did not exceed 1 individual per liter. The species was found in water temperatures ranging from 2.4 °C to 13.1 °C, with low chlorophyll a concentrations (up to 3.69 µg/L) and conductivity between 1.05 mS/cm and 2.12 mS/cm. Notholca bipalium was recorded at seven out of the 20 sampling sites, constituting 3.60% of all analyzed samples (13 out of 361). The highest recorded density reached 8 individuals per liter. This species was present in water temperatures ranging from 2.5 °C to 12.1 °C, with conductivity between 0.63 and 2.71 mS/cm, and a wide range of chlorophyll a concentrations (1.82–59 µg/L). Our research on zooplankton in the Oder River has revealed two species that were previously unrecorded in this river system, both characterized by low frequency and abundance. The identification of K. bostoniensis in this region indicates the spread of the species in Central European waters. In contrast, the presence of N. bipalium in the Oder River suggests significant salinity levels in the river system. We associate the spread of these species with anthropogenically altered habitats within the Oder River system.

Assessments of the current status of non-native species and verification of its identity are essential for establishing their impacts on native ecosystems and determining their origins. True taxonomic accounts and recent conditions of non-native Semisulcospira snails introduced into the Tone River system in Japan, which were morphologically identified as “S. cf. forticosta” (Martens, 1886), have not been investigated. We rediscovered living snails of the introduced Semisulcospira snails in Lake Sotonasakaura in the lower reaches of the Tone River system. Although the identities of the most introduced snails could not be determined due to their mitochondrial DNA polymorphisms, molecular phylogenetic analysis confirmed that the population in Lake Sotonasakaura includes true S. forticosta indigenous to South Korea. The centre of its current distribution seemed to be in the lake and the snails may have been brought into the lake along with other non-native freshwater molluscs. The large morphological variation observed in the snails suggests a previously overlooked morphological variation of S. forticosta or the inhabitation of other Korean species in the Tone River system. Thus, further attempts to verify the identity of non-native snails are required, along with assessments of their dispersal and competition with other congeners.

Lakes and their catchment area, which are of great interest for tourism, are now heavily modified and subject to urbanisation and other forms of shoreline development. All these processes can contribute to the appearance and spread of non-native species. Although Theodoxus fluviatilis (L., 1758) appeared in Lake Balaton (Hungary) in 2013, we have limited information on the spread of the species as well as on the ecological preference of the species in the lake. To address these shortcomings, we surveyed the spatial distribution of the species, examined how land-use pressures along with the geographical location of sampling sites influence the abundance of T. fluviatilis, and investigated the depth preference of the species along the shoreline of the lake. We found that the species has successfully conquered the artificial rocky shoreline of Lake Balaton eight years after its first appearance. Our results indicate that the geographic location of the sampling sites had a significant role since the abundance of T. fluviatilis decreased from southwest to northeast, corresponds to the nutrient gradient in Lake Balaton. This result suggests that, beyond local factors like artificial rip-rap habitats, lake-level factors also significantly influence the distribution of the species. We observed that T. fluviatilis favours 70–80 cm water depth, which might be due to the decreasing rate of wave-induced disturbances along the depth gradient and the available food for the species. We argue that the occurrence and the spread of the species in the lake can be explained by the existence of shoreline modification and by the water management practice that maintains high water levels. These assumptions are consistent with literature evidence stating that the high water level can influence key environmental variables such as wind-induced turbidity, sediment resuspension, and underwater light conditions, which may affect the distribution of aquatic organisms in the littoral zone.

The Oriental river prawn (Macrobrachium nipponense) is an East Asian decapod, recently recorded as invasive in Europe. Here, we describe key morphological and morphometric features (sex, total length and weight, lengths of both 2nd pereiopods and number of dorsal and ventral rostrum spines) for distinguishing populations in different waterbody types in Ukraine (one brackish and two freshwater). Over the year, males tended to slightly dominate e with a mean catch of 54.79%. Females became more prevalent in catches during the June–October spawning period when ovigerous individuals were recorded, a pattern that differed from both tropical and temperate parts of its native range. We recorded no significant difference in linear growth characteristics between the invasive prawns and native populations, and both sexes displayed a stable mass-length correlation with isometric growth characteristics typical of the species. Our results indicated that dentition number (dorsal and ventral) was the most stable morphological feature, while the other parameters examined could be used for both population tagging and observation of seasonal changes. In Ukraine, female prawn size was greater in freshwaters than brackish waters, opposite to the trends observed in its native range. The larger size and growth rate of prawns in the Danube delta suggests that brackish water bodies in Ukraine have a relatively low potential for fisheries and prawn farming.

There is a steadily growing database of host-parasite interactions between the Asian fish tapeworm and Mexican freshwater fishes, but to date, no research in Mexico has addressed the biological aspects of the invasion. There is a need for analysis to differentiate populations of the cestode found in introduced Asian carp and native freshwater fish in Mexico. In this study, we therefore analyzed the genetic diversity of the Asian fish tapeworm in populations from introduced and native freshwater fish. We explored 12 variable microsatellite loci from 65 adult Schyzocotyle acheilognathi recovered from freshwater fish including the introduced Asian carp Cyprinus carpio and native Notropis boucardi (Cyprinidae), Profundulus hildebrandi (Profundulidae), Cichlasoma istlanum (Cichlidae) and Poecilia maylandi (Poeciliidae) from four locations in two neotropical basins (Chiapas and Morelos). For the first time, we present data using a cluster analysis approach to define genetic groups. Overall, geographical isolation of the populations contributed to genetic differentiation (overall F_ST = 0.184), and cestode populations from cyprinids (LN and PLC) presented the highest polymorphism: 61.25% and 72.5% of total number of alleles amplified in all loci. Our results show that S. acheilognathi populations have invaded and established in Mexican native fish species, becoming self-sustaining populations in the invaded ecosystems. Our study offers valuable insights for developing strategies to manage cestode invasions in Mexican freshwater fish. We recommend that authorities consider including epidemiological data based on this type of evaluation as part of sanitary protocols for restocking programs of certain fish species in different localities.

Several non-native fish successfully occupy many water systems in Vietnam, including reservoirs. The aim of our study was to identify non-native and native fish species in the Suoi Trau reservoir and to estimate their distribution during the dry season. Gill nets and sectional net traps were used at multiple locations of the reservoir to capture and identify fish during the year 2019–2020. To assess the distribution and abundance of fish in the Suoi Trau we maintained numerous gill nets near bottom and near surface across the reservoir from April to May 2024. Thirty-four native species and three non-native species were identified: the African catfish Clarias gariepinus (first recorded in the reservoir), Nile tilapia Oreochromis niloticus, and loricariids Pterygoplichthys spp. In 2024, were captured only eleven native fish species, as well as non-native Nile tilapia and armoured catfish. We observed that loricariids frequently occupied areas in the reservoir along with native fish, and their numbers positively correlated with the numbers of native fish. However, the high occurrence of Nile tilapia did not correspond with a high occurrence of native fish in the reservoir. The total biomass of the two non-native species constituted 19% of the total biomass of all captured native fish in Suoi Trau reservoir, and the biomass of armoured catfish highly dominated in four of the nine sampled locations. The loricariids are gradually could replace the native ichthyofauna in the reservoir.

Pseudorasbora parva was first documented in Europe in 1961 and spread across Eurasia in less than 40 years. Its rapid expansion can be attributed to its opportunistic life history traits. Current data on P. parva life history in Ukrainian populations are incomplete. However, some information is available from Slovak populations. Samples of P. parva for the current study were collected from canals, rivers, and fish farms in Ukraine and Slovakia to analyze population age structure and growth. A total of 1244 specimens (563 from Slovakia, 681 from Ukraine) were analyzed. Standard lengths ranged from 13 to 71 mm, while weights varied between 0.01 and 7.4 g. The populations comprised age groups from 0+ to 6+. P. parva reached reproductive maturity at age 1+ and lengths of 35–40 mm in Slovakia, and at age 1+ with lengths 30–40 mm in Ukraine. In both Ukrainian and Slovak fish farms, older age groups were more common. In habitats with natural food supply (rivers, irrigation canals) younger age groups (0+ and 1+) predominated.

Inland fisheries play a critical role in sustaining livelihoods and ensuring food security worldwide. Accurate fish species identification is vital for effective fish stock management and offers insights into ecosystem functioning. A study was conducted in January 2022 to validate the species of fish previously identified in the literature as Carassius carassius, purportedly present in Lake Ziway, Ethiopia. Ten individuals of the genus Carassius were collected from local fishermen, and morphological and genetic analyses, including CT scanning and mitochondrial gene sequencing, were performed to identify the established Carassius species in the lake. Our findings confirm the presence of Carassius cuvieri, a species endemic to Lake Biwa, Japan, within Lake Ziway, Ethiopia. Further investigations are needed to confirm the possible presence of other Carassius species previously reported in the region, enhancing fisheries management strategies. These fish species significantly contribute to inland fisheries in Ethiopia, emphasising the importance of their accurate identification and management.

Ictalurid bullheads are freshwater fish species native to North America that were introduced to Europe in the late 19th century, where they negatively impact native aquatic species. In Belgium, brown bullhead (Ameiurus nebulosus) was introduced decades ago, and is already established and widespread. Here, we report the first occurrence of a congeneric non-native invasive bullhead species in Belgium, the black bullhead (Ameiurus melas). In early May 2023, electric fishing in the Zonderikbeek, a stream situated in the northeast of Flanders (Northern region of Belgium), led to the capture of a suspicious bullhead specimen. Diagnostic PCR analysis identified this specimen as a hybrid between black and brown bullheads. The following spring, in 2024, 21 Ameiurus specimens were additionally captured in a nearby lake that is connected to the Zonderikbeek. Diagnostic PCR revealed that 17 of the captured individuals were pure black bullheads, three were pure brown bullheads, and one specimen appeared to be a hybrid. Morphological examination of the main distinguishing key features of these bullhead species, such as the pigmentation of the anal and caudal fin membrane, gill-raker count, and the serration of the pectoral spine, were in line with these molecular analyses. Notably, hybrid individuals were morphologically characterized with features of both A. melas and A. nebulosus. The discovery of multiple individuals of A. melas, along with hybrids with the already established A. nebulosus is concerning especially given the extensive network of lakes, creeks, and small rivers in vicinity of these observations. This interconnected system of water bodies could facilitate the further dispersal of both species and their hybrids. Given the significant potential ecological and socio-economic impacts of both species, urgent management efforts are needed to remove or contain not only the brown bullhead, but also the black bullhead as emerging non-native invasive species in Belgium.

This study reports on the first discovery of the marine bryozoan Amathia verticillata (delle Chiaje, 1822) from South Africa. In November 2023, an unusual soft-bodied bryozoan was observed within the Langebaan Lagoon Marine Protected Area on the west coast of South Africa. Taxonomic investigations confirmed it to be A. verticillata. In response, surveys were conducted to assess its abundance and distribution within the MPA. The tidal estuarine lagoon was divided into 15 sampling areas, with each searched for A. verticillata colonies. Additionally, colonies were collected to identify associated epifaunal assemblages. Amathia verticillata was detected in 60% of areas, with a total of 2333 colonies recorded. Colonies varied greatly in size, with some more than two meters long. Most concerning was the presence of A. verticillata within meadows of the regionally endangered seagrass Zostera capensis. A total of 33 epifaunal species were recorded within the stolonal matrices, of which three were alien and one was cryptogenic. This highlights the role that A. verticillata may play in habitat provisioning. Amathia verticillata was most likely introduced to the system via biofouling, with spread facilitated by local tidal flow regimes. It is recommended that a seasonal monitoring plan be implemented to track the spread and density of the species within the lagoon. Given the potential impacts that A. verticillata may have on vulnerable native species, it is recommended that best practice to prevent spread be established, and that areas susceptible to secondary spread be monitored, to support rapid response to additional incursions by this invader.

The Lebanese coastal area (Eastern Mediterranean Sea), despite being only 220 km long, is a sentinel zone for detecting and monitoring thermophilic newcomers entering the Mediterranean Sea from the Red Sea and the Indo-Pacific province. This is due to its strategic geographical position near the Suez Canal and the high sea surface temperature. In the framework of the Blue Tyre Project – Local Partnership for Sustainable Marine and Coastal Development (AID 012314/01/6), the coastal area of the Tyre Municipality was investigated to update the existing list of the sea slug species (Mollusca, Heterobranchia) known from this area. A total of 24 species were observed and studied through snorkelling, scuba diving and fishing by-catch census during three scientific expeditions in June and November 2022, and June 2023, at depths ranging from 0.5 to 65 meters. Results allowed to increase from 35 to 55 the number of known Lebanese species of the orders Nudibranchia, Cephalaspidea, Pleurobranchida, Sacoglossa and Umbraculida. The Nudibranchia order had the highest increase, rising from 19 previously documented species to a total of 35 species now reported for Lebanon. Among the newly reported sea slugs, five were not identifiable as already known species and will require additional analysis, being potentially new species to science. Four species were new records for the entire Mediterranean fauna, and 42% of the total recorded taxa were non-indigenous species (NIS). These results highlight the area great potential as a hot spot for heterobranch diversity, particularly regarding cryptic and/or unknown diversity. They also confirm the paramount role of Lebanese waters in providing early warning of NIS reaching the Mediterranean basin.

Invasion of new environments by fouling organisms is facilitated via artificial substrates. In this communication, we report the occurrence of the Asian green mussel Perna viridis on nautical mooring ropes discarded at a voluntary drop off point for end-of-life fishing and nautical gear (EOLFG) in a port area in Ubatuba, northern São Paulo, Southeast Brazil. Individuals were classified as P. viridis based on morphological characteristics and were estimated to be less than six months old. We have been performing the characterization of EOLFG (i.e. size, composition, presence of associated fouling organisms) in this location for over 13 months, with this record representing the first documented instance of the green mussel in the state of São Paulo. Given the possibility of competition with the brown mussel Perna perna, the only farmed mussel in São Paulo, and the proximity to marine protected areas, urgent monitoring efforts are needed to determine the extent of P. viridis settlement in the region, and whether this species is capable of colonizing natural substrates along the Brazilian coastline.

Over the last few decades, the introduction of non-indigenous species (NIS) has become a growing concern for the scientific community and international agencies. Maritime transport, in particular ballast waters and hull fouling, as well as floating marine debris, are the main vectors of these introductions. A striking example of NIS introduction occurred after the Ciaran and Domingos storms in November 2023, when a piece of wood, covered in living Lepas anatifera barnacles, washed up on the beach at Boulogne-sur-Mer along the French shores of the eastern English Channel. Ten crabs of the genus Planes were found, including three belonging to the species Planes marinus, which to the best of our knowledge was never reported in the north-east Atlantic and on the French coast in particular. Planes marinus is a species known mainly from the Pacific, but its growing presence in other oceans highlights the importance of marine debris as a dispersal vector. In this context, the present work highlights the potential impact of extreme weather events, amplified by climate change, on the distribution of NIS, as well as the need to monitor stranded debris to better understand and manage these introductions, which is crucial to the preservation of European marine ecosystems.

In the study, the registration of the Korean rockfish, Sebastes schlegelii Hilgendorf, 1880 (Actinopterygii: Scorpaeniformes: Sebastidae) is described for a blackish estuary of the North-Western Black Sea, Ukraine. Two individuals are found in the Sukhyi Lyman, which is already known as a hot spot for biological invasions. The further spread of the Korean rockfish in the Black Sea is discussed.

Raillietiella orientalis is an invasive pulmonary parasite that is native to Southeast Asia and Africa and is rapidly spreading throughout Florida since its initial identification in South Florida in 2012. This obligate parasite utilizes invertebrates, anurans, and lizards as intermediate hosts and most often infects snakes as definitive hosts. While parasitism causes minimal fitness consequences to snakes in the native range of R. orientalis, in the introduced range it can cause severe infections in native snake species, sometimes leading to mortality. Through collaborative and opportunistic sampling, we examined snakes in the southeastern United States for R. orientalis infection. We documented 14 new Florida county records of R. orientalis infection in snakes sampled from August 2022 through October 2024. These new localities fill gaps in the known geographic range of R. orientalis in Florida and extend the parasite’s range 435 km northwest into the Florida panhandle. We also document R. orientalis infections in four wild-caught snakes from South Florida that entered the pet trade. Human-aided dispersal of intermediate hosts and snakes, including those in the pet trade, is likely to rapidly increase the geographic range and conservation threat of this invasive parasite. Our results highlight the importance of monitoring biological invasions of parasites to clarify impacts on novel host species.