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Simple Summary: The round goby is considered one of the most widespread Ponto-Caspian invasive species, which poses a threat to ecosystems and food web alterations. While it is known for direct predation, its interactions with native higher predators and its feeding behaviour upon their presence remain unclear. Therefore, we investigated how the exposure to chemical alarm cues emitted by conspecifics and the odour of a native predator, the European eel, affects the round goby's feeding activity. Surprisingly, the gobies did not exhibit any pronounced threat sensitivity to both types of chemical stimuli, which was observed in unchanged food consumption probability and gut evacuation rates. The obtained outcomes suggest boldness, great efficiency in food processing, and a potential competitive advantage over native counterparts when colonising new ecosystems, irrespective of local higher predator presence. 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. [ABSTRACT FROM AUTHOR]

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 L t = 483 1 − e − 0.71 (t − 0.40) in Dinh River and L t = 346 1 − 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 (<10%), indicating that these fish breed nearly all year round. The main reproductive season is April–October, with a peak in July–August, as indicated by the gonado-somatic index and monthly changes in the percentage of matured fish. The lengths at 50% maturity were 234.3 and 179.7 mm for females from lotic and lentic habitats, respectively. Lotic fish had a fecundity (4812 ± 383 oocytes/ind.) which was five times greater than that of lentic fish (841 ± 91 oocytes/ind.); however, the relative fecundity of the fish was not statistically different between the two habitats (≈13 oocytes/g). This result was consistent with the larger oocytes: 2.95 ± 0.04 and 2.58 ± 0.01 mm for fish from Dinh River and Suoi Trau Reservoir, respectively. The faster growth and bigger fish with higher fecundity in the lotic habitats suggest that their population growth can accelerate more quickly, potentially affecting local communities more than those in lentic habitats. Our study sheds light on substantial phenotypic divergences in the reproduction and growth of the suckermouth armored catfish between lotic and limnetic habitats in Vietnam. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]