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Broadleaf water milfoil (Myriophyllum heterophyllum) is an emerging invasive alien plant in Europe, and thus a priority for European Union (EU)-level surveillance, monitoring, and eradication. This species is native to North America and threatens aquatic ecosystems by creating dense stands that can fill an entire water body, leading to high economic costs and the loss of native biodiversity. Although its presence in Portugal is not reported, the species has already been established in several European countries, including neighboring Spain. In this study, we assessed the risk of invasion by this species in mainland Portugal by jointly considering environmentally suitable areas and the risk of human-mediated introduction. Environmental suitability was estimated using MaxEnt, which relates the known species distribution to climate, topography, and soil variables. The model achieved a mean area under the curve value of 0.96 ± 0.008 and identified the mean temperature of the warmest quarter as the most relevant variable for explaining the species distribution (67.2 %). Predictions from the model indicated that the peaks of suitability values were distributed mainly in temperate climate regions along central and northern coastal areas in Portugal. The risk of introduction was estimated by mapping and calculating the spatial density of the aquarium stores. Jointly considering environmental suitability and risk of introduction, we observed that hotspots at risk of invasion are concentrated on the Portuguese central and northern coasts and in the two main metropolitan areas, Lisbon and Porto. Several risk hotspots fall within protected areas and sites designated under the EU Habitats Directive, comprising water bodies of high significance for maintaining local vegetation and fauna. Therefore, it is necessary to take measures to reduce the risk of invasion by this species, namely, surveillance and monitoring efforts confirming its absence in the national territory and preventing its future arrival.

In recent years, cyanobacterial invasions have increased in European temperate lakes. Climate warming is highlighted as a key driver of the distribution and establishment of alien cyanobacteria, and water bodies in poor ecological status, characterized by meso-eutrophic conditions, are underlined as a suitable habitat for invasion. The establishment of newly arrived species is directly related to fluctuating physicochemical factors such as temperature, and nutrient concentrations, especially phosphorus and nitrogen, or biotic factors such as competition. Cyanobacterial invasions can have profound ecological impacts, such as displacing native species, causing the biodiversity loss of local communities, and modifying the ecosystem’s cyanotoxins profile. This study presents the occurrence of four alien bloom-forming potentially toxic cyanobacteria - Chrysosporum bergii, Cuspidothrix isstaschenkoi, Raphidiopsis raciborskii and Sphaerospermopsis aphanizomenoides - in the northern parts of their current range in temperate Europe and provides insights into their ecology. Special attention was paid to the lakes of Lithuania (Simnas, Jieznas and Gineitiškės), which is the northernmost location of distribution zone for some alien cyanobacteria and provides as a dispersion route to Norther Europe via the continental area. We i) described dynamics of indigenous cyanobacteria community invaded by alien cyanobacteria; ii) assessed concentrations of cyanotoxins in field and culture samples, and suggested toxin producers; and iii) detailed the correlation between the biomass of alien cyanobacteria and environmental conditions. These species were found in three human-affected shallow hyper-eutrophic lakes during warm period of the year; however, their biomass was low. We assume that present temperatures do not limit the occurrence of these alien species but are insufficient for their successful proliferation. In addition, we provided the first evidence of anatoxin-a production by isolated strains of C. issatschenkoi in Lithuania. Alien cyanobacteria were detected at an early stage of their development, however, a rise in global temperatures and the spread of strains with toxigenic potential could lead to increased proliferation and further northward expansion of these alien species.

Ships’ ballast water and sediments are vectors that contribute to the unintentional spread of aquatic non-native species globally. Ballast water management, as well as commissioning testing of ballast water management systems and compliance monitoring under the regulations of the International Maritime Organization (IMO) aim at minimizing the unwanted spread of organisms. This study compiles data for treated ballast water samples collected and analyzed from 228 ships during 2017–2023. The samples were collected from the ballast discharge line or directly from the ballast tank for enumeration of living organism concentrations in the categories of ≥50µm and

The round goby Neogobius melanostomus is a notoriously invasive fish originating from the Ponto-Caspian region that in recent decades has successfully spread across the globe. One of its primary impacts is direct predation; in addition, when entering new ecosystems, the round goby is likely to become a food resource for many higher native predators. However, little is known either about the indirect effects of predators on the round goby as prey or its feeding behaviour and activity. The non-consumptive effect of the presence of higher native predators presumably plays an important role in mitigating the impact of non-native round gobies as mesopredators on benthic invertebrate communities, especially when both higher- and mesopredators occupy the same habitat. We tested the food consumption probability and gut evacuation rates in round gobies in response to chemical signals from a higher predator, the European eel Anguilla anguilla. Gobies were placed individually in experimental arenas equipped with shelters and exposed to water from a tank in which (a) the higher predator had actively preyed on a heterospecific prey, earthworms Lumbricus sp. (the heterospecific treatment; HS); (b) the higher predator had fed on round gobies (the conspecific treatment; CS); or (c) the water was provided as a control treatment (C). To ensure exposure to the chemical stimuli, this study incorporated the application of skin extracts containing damaged-released alarm cues from the CS treatment; distilled water was used for the remaining treatments. No significant differences were observed in either the food consumption probability or gut evacuation rate in the tested treatments. Despite the lack of reaction to the chemical stimuli, round gobies did exhibit high evacuation rates (R = 0.2323 ± 0.011 h−1; mean ± SE) in which complete gut clearance occurred within 16 h regardless of the applied treatment. This rapid food processing suggests high efficiency and great pressure on resources regardless of the presence or not of a higher predator. These findings hint at the boldness of round gobies, which did not exhibit any pronounced threat sensitivity. This would seem to suggest great efficiency in food processing and a potential competitive advantage over local native species when colonising new ecosystems, irrespective of the presence of native predators. Our study did not detect any non-consumptive effect attributable to the higher predator, given that the feeding activity of the invasive round goby was not altered.

Suckermouth armored catfish (Pterygoplichthys disjunctivus) is one of the most widespread invasive species in Vietnam. However, it is relatively unknown how the species underwent its divergent adaptations to varying local conditions and habitat types, an understanding of which is essential for managing its invasion in Vietnam. We addressed this by analyzing a large number of fish (662 samples) collected in lotic (Dinh River) and lentic (Suoi Trau Reservoir) habitats in southern Vietnam during one year. The allometric growth patterns estimated by von Bertalanffy growth functions were Lt=4831−e−0.71(t−0.40) in Dinh River and Lt=3461−e−1.01(t−0.62) in Suoi Trau Reservoir. The estimated fish ages were 2.9 to 4.2 years old with an average total length from 206.10 ± 2.09 mm in Suoi Trau Reservoir to 319.22 ± 3.29 mm in Dinh River. The percentage of fish with matured ovaries peaked in August (100%) and was lowest in February (

Citizen science is emerging as a powerful tool for the early detection of biological invasions. The exotic pet trade has been deemed as the most significant cause of establishment for reptiles, and among them, turtles have the highest number of introduction events. In Europe, at least 13 species of alien freshwater turtles have been recorded in the wild. In Greece, only two species of alien turtles have been reported, namely the American pond slider Trachemys scripta and the Florida cooter Pseudemys floridana. In this study, we provide an updated checklist of the alien freshwater turtles recorded in Greece, using citizen science, personal observations, and literature. Our results provide the first records for the country of five species, namely the Florida red-bellied cooter Pseudemys nelsoni, the Eastern river cooter Pseudemys concinna, the Chinese stripe-necked turtle Mauremys sinensis, the Chinese soft-shelled turtle Pelodiscus sinensis, and the Common snapping turtle Chelydra serpentina and new localities for T. scripta. Similar to the myth of the Lernaean Hydra (i.e., for every head chopped off, more would regrow), the pet turtle trade has been proven to have multiple heads.

This Special Issue intended to collect articles focusing on the assessment of the possible effects of climate changes on aquatic species inhabiting inland waters all over the world, including the possible synergistic effects in combination with other anthropogenic stressors. A total of six original articles were published that report on investigations of different freshwater ecosystems across the world, including the mountain streams of the Western United States and Northwest Italy, river basins of Northwest China and Central Italy, a larger lowland river in north Italy, and a high-elevation temporary pond in Central Italy. In most of these papers, special attention was devoted to the repercussions of the climate change and its effects on three important components of the biotic community: the fish, benthic macroinvertebrates, and zooplankton. According to the aims of this Special Issue, three of the articles offer new insight into the synergistic effects of global warming together with other anthropogenic stressors, including water exploitation and alien species invasions. In light of the studies’ aim to highlight the effects of climate change, three papers provided analyses of environmental data collected through long-term monitoring. The scientific findings provided by these studies could help to create sound management strategies for freshwater biodiversity conservation.

Italian freshwater ecosystems were strongly affected by biological invasions during the last few decades. Recreational angling contributed to this, through the widespread use of invasive alien species for fish restocking. To date, no research is available about the psychological and structural determinants of deliberate fish restocking in Italy. This work aims to fill this research gap, through structured questionnaires administered to a sample of recreational anglers (n = 276) in the Arno river basin (Central Italy). A predictive model for fish restocking, based on a quasi-binomial logistic regression, was fit and multi-model inference was drawn, to highlight the most significant predictors. Respondents, who expected that most anglers practiced restocking and who believed restocking could create closer fishing spots, were more prone to illegally restock fish. Our findings indicate that expectations about illegal fish restocking might exist among specialized segments of anglers. Targeted communication campaigns must be enforced as soon as possible to change them. Furthermore, fish restocking is supposed to reduce the travel costs for angling: future research about this is needed to model invasion hotspots.

Crangonyx pseudogracilis, a North American crangonyctid amphipod, was found in a stream of Santarém District (Portugal) in September 2011. It is the first record of this species from the Iberian Peninsula. Exact time, mode of introduction and distribution of C. pseudogracilis in the area remain unknown. So far its occurrence was reported only from several countries in north-western Europe. A short overview upon the species general distribution, ecology and invasive potential is provided.