The Ponto-Caspian amphipod Dikerogammarus haemobaphes, known as the demon shrimp, arrived in the UK in 2012 and has since spread rapidly, invading waterways particularly in central England. In this paper we use data from routine Environment Agency surveys to explore how D. haemobaphes has spread and assess whether it fits the 2013 predictions of Gallardo and Aldridge, which identified southern, eastern and central England as most vulnerable to Ponto-Caspian invaders. We then focus on two rivers, the Thames and the Trent, utilising a mixture of recent and long term datasets to track the presence of D. haemobaphes along the course of each river and compare it to that of the native amphipod Gammarus pulex. We observed that D. haemobaphes is now the dominant amphipod in the navigable stretches of both rivers and that the spread of the species nationally appears closely linked to the canal network. We suggest that focussing biosecurity controls on the movement of boats and equipment between affected and unaffected catchments will be key to limiting the further spread of this and similar invasive species.

Since 1996, the invasive Conrad's false mussel Mytilopsis leucophaeata (Conrad) has been recorded in brackish water bodies in the Ponto-Caspian region, which includes the basins of the Black Sea, Azov Sea, and Caspian Sea. In the Azov-Black Sea basin, where the number of records is increasing, its range currently includes the Dniester, Dnieper-Southern Bug, and Don River estuarine systems, and the mouth of the Tuapse River near the town of Tuapse. In the Caspian Sea basin, M. leucophaeata is present in areas near the mouths of the Volga and Ural rivers, and in the south Caspian Sea, near Bandar Anzali town. The present study analyses new records from this region as well as previously published records. All sites in the Azov-Black Sea basin with records of living specimens of M. leucophaeata were characterized by changes in the hydrological regime due to the effect of hydraulic engineering (mostly along deep-water shipping canals or for fish ladders). The most probable vector for long-distance dispersal of M. leucophaeata is transatlantic shipping to the Black Sea basin; while for secondary spread, coastal and inland shipping across adjacent ports is likely. Introduction of this species to the Caspian Sea could have resulted from specimens first present in the Black Sea or from independent long-distance transfer.

The diet of an invasive crayfish, Cherax quadricarinatus (Von Martens 1868), in Lake Kariba, was investigated using stomach content analysis (SCA) and stable isotope analysis (SIA). The frequency of occurrence of macrophytes and detritus ranged between 63.6–97.1% and 20–45.5%, respectively, and the index of relative importance ranked these as the two most important food items across all size classes. Significant differences in the ranking of fish, macroinvertebrates and crayfish were found between size classes 29–37.9, 38–46.9 and 47–55.9 mm. Stomach content analysis showed 16% of crayfish stomachs were empty. Feeding intensity differed significantly between size classes and ranged from 3.46 to 5.21. Stable isotope analysis was done by comparing δ¹³C, δ¹⁵N and C/N ratios in crayfish muscle and potential dietary items in the lake. Macrophytes were the most dominant food item (57%), followed by macroinvertebrates (20%), then detritus, and finally fish and crayfish. Stable isotope analysis revealed that all crayfish size classes analysed were in the same trophic level. Nevertheless, while SCA showed high dietary overlap among all crayfish size classes (>65%), SIA showed that small crayfish (< 28.9 mm) had limited overlap with large crayfish (> 56 mm), with the former showing a higher proportion of macroinvertebrates in their diet. In Lake Kariba, C. quadricarinatus predominantly feeds on macrophytes, macro¬invertebrates and detritus, which may bring about nutrient cycle alterations in the lake. Littoral habitat changes caused by the feeding characteristics of C. quadricarinatus might also lead to competition with, and eventual displacement of, some native littoral fishes in this lake.

The porcelain crab Porcellana africana Chace, 1956, a species native to NW Africa, between Western Sahara and Senegal, is reported from Saldanha Bay, South Africa, and both morphological evidence and DNA analysis are used to confirm its identity. The taxonomic history of P. africana is summarized, and the taxonomic implications of the DNA analysis are discussed. The observations that the South African population appeared suddenly and that it is located in and around a major international harbour, strongly suggest that it represents a recent shipping introduction. Porcellana africana was first detected at a single site within Saldanha Bay in 2012, but by 2016 was abundant under intertidal boulders and within beds of the invasive mussel Mytilus galloprovincialis across most of the Bay. It remains absent along the adjacent oceanic coastline and in other regional harbours, but these should be monitored to detect any subsequent range expansion.

During the past few decades, rapid expansion of Ponto-Caspian gobies has been observed in the rivers connected to the central European invasion corridor. The Nemunas River catchment has been connected to this corridor for more than two hundred years, yet there is no evidence of Ponto-Caspian gobies in the Nemunas River. This study aimed to assess the presence of Ponto-Caspian gobies within the Nemunas River and its main tributaries, specifically in the Lithuanian part of the Nemunas and Neris Rivers, which may serve as possible routes for these fishes’ expansion. Of all the presumptive Ponto-Caspian goby species only Neogobius fluviatilis (Pallas, 1814) and Neogobius melanostomus (Pallas, 1814) were caught. The relative abundance and biomass of both species was very low. The pilot analysis of piscivorous fish diet revealed that N. fluviatilis is already selectively consumed by Esox lucius. Although both species can reproduce and sustain viable populations in the Nemunas River, different scenarios for their future establishment within the Nemunas River drainage basin are predicted. The hypothesized distribution of N. melanostomus will remain restricted only to the outlets of the Nemunas River; while the distribution of N. fluviatilis in the future will be wider. We presume that the area colonised by N. fluviatilis will expand until the species establishes in the entire Nemunas River drainage system.

The Three Gorges Dam Reservoir (TGDR) in China is the world’s largest hydropower project, which has significantly impacted ecosystems and environments within the reservoir region. However, the extent and identity of non-native species in the TGDR area is unknown. In this study, we investigated and summarized the literature on non-native species in the TGDR. We found that there are at least 42 non-native aquatic species that have invaded the TGDR. From 2003 to 2015, non-native aquatic species were discovered at a rate of 3.5 species year^-1. To our knowledge, this is one of the highest rates of invasion recorded for freshwater ecosystems. Non-native species have mainly been introduced via aquaculture, biocontrol, and the aquarium trade. Some species, such as mosquitofish and water hyacinth, have caused great ecological and economic problems. In the future, additional non-native species are likely to invade the TGDR as a result of human activity. This research can help improve biodiversity conservation and environmental management in the TGDR.

Five samples of Diplosoma listerianum, a non-indigenous colonial ascidian species complex, were collected via SCUBA between August 27 and September 28, 2017, from four sites in the coastal waters (depth ranging between 3.1 and 18.0 metres) around Brier Island, Nova Scotia, Canada. These samples constitute the second record of D. listerianum in Nova Scotia—five years after the first discovery and 280 kilometres (by sea) from the site of the first record. Semi-quantitative abundance of D. listerianum from Brier Island was determined and was found to be frequent or common in three of these four sites that were surveyed via SCUBA. The occurrence at several sites, coupled by the presence of eggs, ovaries, and larvae in some tissue samples suggest that there is presently an established population of D. listerianum off of Brier Island.

Platorchestia platensis (Krøyer, 1845) is a cosmopolitan and cryptogenic semiterrestrial amphipod species inhabiting marine coasts all over the temperate and tropical regions of the world. Very little is known about its dispersal mechanisms, and there is little data on the genetic relatedness among local populations in various regions of the world. In this study, we provide first and preliminary molecular evidence that suggests conspecificity of P. platensis populations inhabiting European and North American marine coasts and potentially some genetic isolation of Mediterranean populations.

The invasive isopod Ianiropsis serricaudis Gurjanova, 1936, originally described from the North-West Pacific Ocean, is herein reported for the first time on the French Atlantic coast. Its presence is probably due to oyster import activity, and the sampling of many brooding females in Arcachon Bay since 2013 suggests a well-established species. Its current European distribution is summarised and some morphological characters are discussed.

The virile crayfish Faxonius virilis (Hagen, 1870) is a widespread non-native species across North America, and may be an emerging invasive species globally. We report new records for F. virilis from the upper Snake River drainage and northern Bonneville Basin of the western United States. We sampled 162 sites for crayfish during the summers of 2016 and 2017, detecting F. virilis at 22 of these sites, which ranged from small streams to wadeable rivers, as well as artificial reservoirs and a large natural lake (Bear Lake, Idaho and Utah). We also report the first records for F. virilis from the large, mainstem Snake River. However, we did not find F. virilis in the Snake River headwaters of western Wyoming, and detections of this species were few in the Snake River drainage below Shoshone Falls in south central Idaho. We also found no F. virilis in eastern Oregon. The widespread distribution of F. virilis in the upper Snake River drainage and northern Bonneville Basin may be a conservation concern for native crayfishes in this region, specifically the pilose crayfish Pacifastacus gambelii (Girard, 1852) and the Snake River pilose crayfish Pacifastacus connectens (Faxon, 1914). We recommend that research is undertaken to address ecological interactions of non-native F. virilis with native species, communities, and ecosystems in the western United States, and that education, outreach, and regulatory options be pursued to further limit the introduction and spread of this species.

The redclaw crayfish, Cherax quadricarinatus, is a freshwater crayfish native to north-eastern Australia and southern New Guinea. In 2016, the species was found for the first time west of the Wallace Line in Java, Indonesia and, based on climate matching, its further spread within Indonesian territory was predicted. In this study, surveys of selected localities within Indonesia were performed to examine the species occurrence. Redclaw crayfish were found throughout Indonesia, in numerous rivers, lakes, ponds and reservoirs in Batam and Bintan Islands (Riau Archipelago), Java, Kalimantan (Borneo), Sulawesi and Sumatra. Some stocks were apparently well established, providing a food source for local people and sustaining capture for pet trade purposes. Because there are no effective regulations of introductions and exploitation of this crayfish in Indonesia, its further spread to new localities is expected. Increased attention to this issue, especially regarding crayfish management and policy implementation, is urgently needed.

The introduction of species is a major threat to biodiversity conservation. Island biodiversity is especially sensitive to the arrival of new species, and species introductions are one of the major concerns of conservation management policies. Here, we report for the first time the arrival of Callinectes sapidus, a new potentially invasive crab species from the East coast of America to the Balearic Islands (Spain). It appeared simultaneously in both Mallorca and Menorca islands. Nine different records of 20 individuals were documented in six different localities, suggesting an initial colonization process of the territory.

The half-smooth golden puffer fish (Lagocephalus spadiceus) is a member of the Tetraodontidae family and one of the earliest lessepsian fishes, originally reported in the Mediterranean during the early 1920s. Since then, the species has extended its distribution from the Egyptian coasts to the Sea of Marmara yet remaining confined near the shore or to regions adjacent to the coastline. In May 2016, a single specimen of L. spadiceus was fished in South Crete. This is the first time the species has been recorded in the island and the first verified indication that the species is expanding its range westwards over open-sea areas since its entrance in the basin. Thorough morphological and biological description as well as DNA verification of the captured specimen is provided. This record, coupled with the recent first record in the Sea of Marmara, may be an indication of a change in the expansion pattern of the species or of its population status.

To date, the Mediterranean Sea has been subjected to numerous non-indigenous species’ introductions raising the attention of scientists, managers, and media. Several introduction pathways contribute to these introduction, including Lessepsian migration via the Suez Canal, accounting for approximately 100 fish species, and intentional or non-intentional aquarium releases, accounting for at least 18 species introductions. In the context of the citizen science project of iSea “Is it alien to you?… Share it”, several citizens are engaged and regularly report observations of alien, rare or unknown marine species. The project aims to monitor the establishment and expansion of alien species in Greece. In this study, we present the first records of two popular high-valued aquarium species, the scissortail sergeant, Abudefduf sexfasciatus and the sohal surgeonfish, Acanthurus sohal, in along the Mediterranean coastline of Greece. The aggressive behaviour of the two species when in captivity, and the absence of records from areas close to the Suez Canal suggest that both observations are the result of aquarium intentional releases, rather than a Lessepsian migration.

The impact of biological invasions is unpredictable, and hence it is important to provide information at the earliest stage of invasion. This is the first report of the web spinner Haploembia solieri (Rambur, 1842) (Insecta: Embioptera) in Japan. We found this species in the Port of Kobe, on an artificial island in Hyogo Prefecture. The locality is clearly distant from its known distribution; H. solieri is native in the Mediterranean region and introduced into the United States. In our surveys, 90 individuals were collected, but no males. This is also the first report of H. solieri in East Asia. Because we observed the H. solieri population in the fall of 2016 and early summer of 2017, this species may have been able to overwinter in Japan.