Gracilaria vermiculophylla (Ohmi) Papenfuss, 1967 is a red alga native to the northwest Pacific, but over the last 100 years, this ecosystem engineer has invaded estuaries throughout the Northern Hemisphere. Despite previous studies documenting populations in estuarine habitats in British Columbia, California, and Baja California, our knowledge of its distribution along the North American Pacific is incomplete. In 2017, we surveyed 61 sites from Chusini Cove (Prince of Wales Island, Alaska) to Bayside Park (San Diego Bay, California), spanning more than 23º of latitude. We documented 33 new sites where G. vermiculophylla is currently found, but may have been previously overlooked, or not recognized. Many of these locations were areas of intensive shellfish aquaculture, particularly oysters, and are also important flyover stops for migrating birds, possibly contributing to the spread of this seaweed. Our study fills in the significant gaps in the distribution of G. vermiculophylla in North America, and, as such, will be an important contribution to future studies on the ecological and evolutionary consequences of this widespread marine invasion along this coastline.

We report a first record of the widely invasive bryozoan Bugula neritina in Ketchikan, Alaska (USA), on Revillagigedo Island (southeast Alaska). This represents the northernmost record of this fouling organism in the northeast Pacific Ocean. We also report a new occurrence of the solitary ascidian Ciona savignyi not found in Alaska since 1903, along with recent occurrences of the invasive colonial ascidians Botryllus schlosseri and Botrylloides violaceus in new localities. The high level of vessel traffic in this region and the precedent for historical ship-borne invasions worldwide suggest that future population growth and establishment of these taxa in the Ketchikan area could set the stage for further poleward range expansion, highlighting the need for continued monitoring.

A second record of the non-indigenous species Botryocladia madagascariensis G. Feldmann (Rhodophyta) along the coasts of the “Ustica Island” Marine Protected Area (Tyrrhenian Sea, Italy) is reported. With this additional record for the Sicilian coasts, we provide a description of collected specimens of B. madagascariensis and habitat details. Numerous fertile female gametophytes with cystocarps immersed in vesicles were also observed, for the second time in the Mediterranean Sea, and described.

The presence of Hygrophila corymbosa (Blume) Lindau within the Mexican aquatic flora is recorded for the first time. This species is native to Asia and is commonly used as an ornamental plant in aquariums, so it is possible that its introduction was accidental. Due to its high potential for reproduction and dispersion, H. corymbosa represents a great threat to the native aquatic flora of the wetlands of Mexico. More studies are recommended to explore ecological aspects of the plant to facilitate its control and/or eradication.

Egeria densa is a South American aquatic plant species considered highly invasive outside of its original range, especially in temperate and warm climates and artificially heated waters in colder regions. We report the first occurrence and the spread of E. densa in Southeast Europe, along with physicochemical and phytosociological characteristics of its habitats. Flowering male populations were observed and monitored in limnocrene springs and rivers in the Mediterranean part of Croatia from 2013 to 2017. The populations inhabited clear, slow flowing, oligohaline water with high alkalinity and conductivity. Over the course of our research, the species displayed its invasive potential forming monospecific stands and surpassing the native flora in particular localities, while being obviously codominant with indigenous species in others. Although we cannot specify the exact path of introduction, we presume two possible scenarios: release from aquaria or epizoochory through water birds. The current situation in SE Europe, including Croatia, seems satisfactory regarding the number of aquatic alien species; nevertheless a careful and systematic approach to research into the management of invasive alien species is needed.

The benthic foraminiferal genus Amphistegina is currently expanding its range in the Mediterranean Sea after being introduced through the Suez Canal from the Red Sea. Over the previous decade, Amphistegina spp. has colonized the eastern part of the Mediterranean Sea including the Egyptian and Libyan coasts, but the present southern limit in the Mediterranean Sea is along the southern Tunisian coast. However, this limit has never clearly been defined, and existing models predict an expansion along the entire Tunisian coastline. The Gulf of Gabes, in the southern part of Tunisia, is heavily polluted by local phosphate industries that discharge untreated waste directly into the sea. Amphistegina spp. is sensitive to water quality and marine pollution. Based on our surveys and recent investigations, the present distribution area of Amphistegina spp. along the south Tunisian coast includes the coastline east of Djerba Island, located in the Gulf of Gabes. Possible limiting factors for Amphistegina spp. expansion in the Gulf of Gabes may be the unfavourable environmental conditions generated by the phosphate industry.

The upside-down jellyfish—Cassiopea andromeda (Forsskål, 1775)—is considered an established alien within the eastern Mediterranean Sea, but the species exhibits a highly sporadic occurrence further west within the basin. This study reports the second documented bloom of the species within coastal waters in the Maltese Islands and the third bloom of the species in the westernmost part of the eastern Mediterranean, a full nine years after its first appearance in this part of the Mediterranean.

Melanoides tuberculata (Müller, 1774), a mollusc native to the Afrotropical and Palearctic regions, has established populations in a number of localities in the Neotropical region. This non-native species was introduced to Brazil prior to 1970, but this record was only reported in the literature in 1986, and its invaded range has continued to expand. In this work, based on scientific literature and specimens deposited in biological collections, we provide an update on the distribution of M. tuberculata in Brazilian waters. Our results show that M. tuberculata currently occurs in 351 municipalities, 20 Brazilian States and the Federal District. We also provide a brief discussion about its potential as a vector for zoonotic diseases, and possible pathways for its introduction in Brazilian waters.

The present paper documents the further spread of the invasive, non-indigenous sea snail Haminoea cyanomarginata Heller & Thompson, 1983 in the Mediterranean Sea. Since its original description in the Red Sea, this sea slug has been subsequently reported since 2001 from various locations throughout the Central, Eastern, and Western Mediterranean Sea. This is the first record of H. cyanomarginata in Libyan waters and the whole Southern Mediterranean Sea.

A live specimen of Gari pallida was collected in June 2017 off Palmahim, on the Mediterranean coast of Israel. This is the first record of the species, previously known from the tropical western Pacific to the Indian Ocean and the Red Sea, in the Mediterranean Sea, and the second Erythraean alien psammobiid bivalve. It is differentiated from congeners recorded from the eastern Mediterranean.

The South American multiradiate sunstar Heliaster helianthus (Lamarck, 1816) and the Chilean stone crab Homalaspis plana (H. Milne Edwards, 1834) are marine predators that, previous to this report, have no invasion history. However, during subtidal maintenance of a pier within Saldanha Bay along the South African west coast during 2015–2017, a single individual of each species was detected on the seafloor. Following this, intertidal and subtidal surveys were undertaken in surrounding natural habitats, but no further individuals were recorded. Both species are native to Chile, a region with very similar environmental conditions to the west coast of South Africa and from which other South African marine alien species originate, highlighting the connectedness between these regions and the risk for future transfers and establishment. The presence of two pathways from Chile to South Africa (shipping and aquaculture imports) and closely matching environmental conditions are likely to play a role in future successful introductions of Chilean species to the South African west coast. It is, therefore, recommended that particular attention be paid to monitoring aquaculture imports from the west coast of South America and that incoming vessels from that region be inspected upon arrival. Additionally, both H. heliaster and H. plana should be added to alien species watchlists in South Africa and other regions connected to Chile via marine vectors and which experience similar environmental conditions.

This study presents findings on metacercariae of Posthodiplostomum centrarchi (Digenea: Diplostomidae) in largemouth black bass, Micropterus salmoides (Actinopterygii: Centrarchidae), transported from France to Ukraine for aquacultural purposes. The parasite was co-introduced with the fish host with a prevalence of 100% and an infection intensity range of 14–90 (mean 52.1 ± 28.5). The metacercariae were morphologically and genetically identical to those recently described from largemouth black bass in Portugal. Fish translocation for aquacultural purposes is discussed as a source of disease transmission.

The tropical aquarium business is thriving worldwide and typical aquarium fishes are being recorded in several parts of the Mediterranean Sea. In this study, we report the occurrence of an individual Arothron hispidus in the Mediterranean, off the coast of Cyprus (Protaras, 34.969733ºN; 33.963550ºE). The puffer record was based on high resolution photos and a movie taken on 2 February 2018 and uploaded on social media. Among the possible introduction modes, an aquarium release event seems to be the most likely reason for the presence of the species in the Mediterranean Sea.

On July 2017 during a scientific survey, a single individual of Ophioblennius atlanticus (Valenciennes, 1836) was caught at the entrance of Lampedusa harbour, in proximity to the Marine Protected Area of the Pelagie Islands. This record confirms the introduction of this fish into Mediterranean waters, adding a new species to the list of Italian NIS. Possible pathways of introduction and the relevance of this finding for Mediterranean MPAs are briefly discussed.

The variable-lined fusilier Caesio varilineata Carpenter, 1987 is firstly reported from the northwestern coast of Egypt in February 2018, constituting the first record in the Mediterranean Sea. Several dozen of individuals were encountered at two fish landing sites in Alexandria suggesting that this species may have an established population in the southeastern Mediterranean Sea. Considering the nearness of the Suez Canal, it is likely that this new alien fish migrated through the canal.

The croaking gourami Trichopsis vittata (Cuvier, 1831), a small Southeast Asian freshwater fish, has long been a non-native enigma to the ichthyologists and hobbyists of Bangladesh. The species has been seen regularly in the Ganges Delta and exotic fish keepers are well aware of its presence there, although nothing is known about the source of introduction. Its first scientific documentation in Bangladesh only occurred in 2012 and in India in 2015. In this paper, we report observation records of T. vittata in Bangladesh through field work, and photographic and literary evidence. From March 2014 to August 2017, 33 confirmed observations were made pinpointing 25 different distribution localities. Plotting observations and localities against time indicated that T. vittata, already a proven sturdy invader in Florida, USA, is steadily spreading its range across the deltaic floodplains of Bangladesh.

An established population of bullseye snakehead (Channa marulius), a large predatory fish from southeastern Asia, was identified for the first time in North America from waters in southeastern Florida, USA, in the year 2000. Since then, it has dispersed throughout the extensive canal system in the area from West Palm Beach south to Miramar. Collection data were compiled to determine the extent of the distribution. The range encompasses three separate areas totaling approximately 830 km². Over an 18-year period, the range increased an average of approximately 46 km² per year. There is concern that this non-native species may threaten the fauna in unique protected natural areas of southern Florida, such as Everglades National Park.

The first records of the maritime earwig Anisolabis maritima from South Africa are reported. The species was first discovered in 2015 in the upper intertidal zone of an artificial rubble causeway at Port Shepstone, on the east coast of South Africa, where it appears to feed on driftline isopods and amphipods. The study site operated briefly as a harbour from 1880–1902, suggesting that this introduction took place via shipping at that time and has remained undetected for more than a century.

Tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious pest of tomato Solanum lycopersicum L. (Solanaceae) originating from South America. Due to previous outbreaks in neighbouring West African countries, surveillance was ongoing since 2014 in Benin. Tomato plants were regularly inspected and pheromone traps placed in tomato-producing localities in northern and central Benin, including fields close to the border with Niger and Nigeria. In late 2017 and beginning of 2018 Gelechiidae moths were obtained from both the traps and the reared plant material. Morphological examination and molecular analysis of the gained specimens allowed to confirm the presence of the pest in the northern and central regions of Benin. We hence confirm the presence of T. absoluta in yet another West African country.

Sparrows (Passer spp.) have long been presumed to rely on railway traffic during their long-distance terrestrial dispersion. The currently ongoing range expansions of the Spanish Sparrow (Passer hispaniolensis) and the Red-rumped Swallow (Hirundo daurica) in Central Europe provide an opportunity to develop this idea into a testable hypothesis. Both species are small, synanthropic passerines but the latter one is highly aerial and mobile. Therefore, Red-rumped Swallows are not supposed to rely on railways for spatial dispersion so that their distance from railway lines is supposed to reflect observers’ distribution, but not otherwise influenced by railway proximity. I have analyzed published data from Hungary and North Serbia (Vojvodina, except for its South Banat District) from 2000 onward. During this period, both species exhibited a slow northward range expansion on the Southern edge of the study area but have not yet established self-sustaining populations. Vagrant individuals of the Spanish Sparrow and its hybrid Italian Sparrow (Passer italiae) occurred significantly closer (N = 8, range = 0.01–3.36 km) to railway lines than vagrant Red-rumped Swallows (N = 23, range = 0.45–13.76 km). This constitutes an empirical evidence supporting the idea that sparrows tend to rely on railway traffic for long-distance dispersion.