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In connection with the expansion of alien gobies in European waters, a question arises whether this process can be enhanced or inhibited by global warming. The gobies are of Ponto‐Caspian origin, where the climate is warmer than in invaded European areas. Therefore, they are likely to cope physiologically with climate warming better than native species. Our aim was to identify differences in metabolic traits under elevated summer temperature between the invasive gobies and their native counterparts.Using a laboratory respirometer, we compared the effect of elevated summer temperature (25 vs. 17°C) on the metabolic responses of fish in two species pairs consisting of an invasive goby versus its native counterpart from the same ecological guild: the invasive racer goby Babka gymnotrachelus versus native European bullhead Cottus gobio, and the invasive monkey goby Neogobius fluviatilis versus native gudgeon Gobio gobio. The paired species share functional traits, including morphological characteristics, despite belonging to different fish families. After 4 weeks of acclimation, standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope (AS = MMR–SMR) of the fish were determined.We found that SMR increased under elevated temperature irrespective of species, yet it was always lower in the gobies than in natives. The MMR of the racer goby was lower than that of the bullhead across all temperatures, whereas no differences in MMR were found between the gudgeon and monkey goby. On the one hand, the elevated temperature did not affect the AS of the racer goby and bullhead. However, the AS of the racer goby was consistently lower than that of the bullhead across all temperatures. On the other, elevated temperature caused a decrease in AS in both the monkey goby and gudgeon. However, this temperature‐induced change in AS was higher in the gudgeon than in the monkey goby.In terms of AS, the invaders did not always outperform the natives at higher temperatures. However, the invaders had lower living costs by maintaining a lower SMR. These results suggest that invasion by gobies may be facilitated by global warming, which is likely to increase their occurrence and effect on local fish communities in freshwater temperate systems. [ABSTRACT FROM AUTHOR]

Clams from the Corbicula species complex of Asian origin are invasive all over the world, currently extending their distribution to waters of the natural thermal regime in Central European areas. Features linking the clams to their habitats in newly invaded areas have not been fully examined. These include substratum preferences and mobility, which may be key to determining potential niche overlap with native bivalves and gaining a better knowledge of their potential active dispersal and impact. Therefore, our aim was to determine the substratum preferences, horizontal locomotion and burrowing behaviour of three Corbicula morphospecies from Poland, Central Europe: two populations of undetermined Corbicula sp. from an artificially heated habitat and water of the natural thermal regime (cold water), as well as Corbicula leana, and Corbicula fluminea (from artificially heated and cold water, respectively).To determine the preferred substratum range, we used pairwise choice tests with a range of muddy, sandy, and gravelly substrata, as well as zebra mussel shells. Then, we conducted behavioural observations (locomotion and burrowing) by CCTV cameras on substrata found as preferred and non‐preferred by clams.All morphospecies preferred fine‐grained over coarser substrata. C. fluminea from cold water had the widest range of substratum preferences. By contrast, C. leana from artificially heated water and Corbicula sp. from cold water showed the narrowest substratum preferences and spent the longest time deeply burrowed. The longest duration of burrowing activity was noted on non‐preferred coarser substrata, which may indicate difficulties in burrowing. On non‐preferred coarse substrata, C. fluminea (cold water) crawled more than the other morphospecies.Our results show that sediment preferences and behaviour (burrowing and locomotion) differ among various Corbicula morphospecies in Europe, probably also varying their invasive potential.This knowledge is important for determining the overlap of habitat preferences of non‐native Corbicula clams with native bivalves, which is critical for determining potential competition strength, impact, and/or displacement. Our results also indicate that habitats with fine sediments could be more threatened by Corbicula invasions. [ABSTRACT FROM AUTHOR]

Ponto–Caspian goby fish belong to the most successful invaders in freshwater ecosystems of Europe and North America. So far, three alien goby species have been present in the Polish section of the Dnieper–Rhine River corridor: the monkey goby Neogobius fluviatilis, the racer goby Babka gymnotrachelus, and the western tubenose goby Proterorhinus semilunaris. Their assemblages in this region are unique because, in contrast to their native region or the Danube–Rhine corridor, they are unaffected by other gobiid species. We conducted electrofishing and habitat quality surveys to gather information on key environmental factors associated with the distribution of these fish in the lower river Vistula, which constitutes a vast middle part of the corridor used by the Ponto–Caspian species to migrate westward in Europe. We showed that the sandy bottom was beneficial for the monkey goby allowing the species to attain the highest abundance among the gobies in the river. Habitat complexity generated by artificial bank structures, as well as dense macrophyte coverage in the main channel, favoured mostly the expansion of the racer goby. Off‐channel areas with vegetation and a muddy bottom (old river beds and pools) were the most suitable habitats for the western tubenose goby. We did not find any negative spatial relationships among gobies of various species and sizes except the avoidance of the monkey goby by small western tubenose goby. Thus, our study demonstrates substantial habitat partitioning, suggesting a low level of interspecific competition among the three species in a lowland river. [ABSTRACT FROM AUTHOR]

The European mudminnow (Umbra krameri) is a strictly protected, threatened fish species, endemic to the River Danube and Dniester basins. Population decreases have been observed for several decades, primarily due to habitat loss, but, recently, the adverse impact of invasive species, including the Amur sleeper (Perccottus glenii), has also been implicated in its decline.The correspondence in the disappearance of the European mudminnow and the appearance of the Amur sleeper has been observed in some waters, but the mechanism by which the invader has an impact has remained speculative until now.As both species have similar dietary preferences and habitat requirements, competitive interactions between them for the same limited food resource (gammarids) in the same space (aquarium with artificial plants) were investigated experimentally. The foraging of two‐species and single‐species pairs and single individuals was tested.Feeding rates and prey capture efficiency were similar in both species, but the Amur sleeper was a superior competitor compared with the European mudminnow; it negatively influenced the foraging efficiency of the latter, preventing its access to prey through aggressive interactions. In the presence of the alien competitor, the feeding rate of European mudminnow decreased to one third of that observed in single‐species or single‐individual treatments.These results demonstrate that interference competition for food may be the mechanism explaining the rapid decline of this threatened species. We conclude that the invasion of the Amur sleeper will accelerate the extinction of the European mudminnow, especially in isolated, small, shallow water bodies.The study illustrates that monitoring the Amur sleeper invasion is essential for the active conservation of the European mudminnow. For reintroduction attempts, special care must be taken to avoid invaded water bodies. Moreover, prevention of the introduction of the Amur sleeper, especially in waters occupied by the European mudminnow, must be pursued. [ABSTRACT FROM AUTHOR]

We conducted underwater surveys using SCUBA gear to examine habitat and microhabitat competition between the Ponto-Caspian racer goby Babka gymnotrachelus and native European bullhead Cottus gobio to assess the potential for competitive displacement of the native species by the invading species. In summer, 88 surveys were made in a tributary of the River Vistula within defined benthic areas across the entire width of the river bed. The occurrence of fish by total length class (small: <6 cm; large: >6 cm) and environmental conditions (depth, water velocity, substratum type, plant cover, shelter type) was recorded. We found a substantial separation between the species and size classes in relation to substratum, shelter type and water velocity. European bullheads were limited to lotic areas with stony bottoms, whereas racer gobies also occupied lentic areas over sand or mud. European bullheads usually took refuge under stones in contrast to a wider range of shelters used by racer goby, including tree roots and rubbish. In general, the breadth of habitat used by the racer goby was wider than that of the European bullhead, although habitat overlap between the species was not statistically significant except for the type of shelter occupied by small fish, selecting smaller stones. An inverse relationship was observed between small European bullheads and all racer gobies in areas where they co-occurred, suggesting that invader may be having an adverse effect on the distribution and habitat use of small native bullheads, particularly in areas of moderate water velocities over small stones and gravel. [ABSTRACT FROM AUTHOR]

Reductions in water level and temporary exposure of substratum to air are two of the most important factors structuring communities in temperate near-shore zones. Snails are suitable model organisms to study responses of aquatic communities to water-level fluctuations, as they often inhabit near-shore zones and are relatively mobile., In a laboratory study, we investigated survival and behavioural responses (horizontal migration and burrowing) of three freshwater gill-breathing snails: Viviparus viviparus (L.) (large and small individuals), Bithynia tentaculata (L.) and Potamopyrgus antipodarum (Gray) to substratum drying. We studied the effect of distance to a suitable habitat (24 and 48 cm) and rate of dewatering (gradual: eight days or sudden) on horizontal migrations of snails as well as their burrowing depth., Large V. viviparus individuals were best adapted to dewatering: they were resistant to drying (surviving more than 3 weeks of air exposure) and migrated in response to decreasing water level and/or burrowed into the substratum. Their horizontal movement was negatively related to the rate of dewatering and distance needed to get to a submerged area. However, they were able to migrate to some extent even after a sudden dewatering and to reach a distant submerged refuge. Small V. viviparus exhibited similar behavioural responses as large individuals, but were less resistant to drying, surviving approximately one week of air exposure. Neither B. tentaculata nor P. antipodarum exhibited behavioural adaptations to desiccation, although resistance to drying differed markedly from approximately 3 weeks for B. tentaculata to 3-4 days for P. antipodarum., Resistance to drying and behavioural adaptations are two factors enabling benthic organisms to survive in harsh near-shore environments. Our study revealed marked intra- and interspecific differences in response to dewatering, depending on body size, distance to a refuge and rate of dewatering. Appropriate physiological and behavioural responses may increase fitness of organisms under changing environmental conditions and contribute to their survival. [ABSTRACT FROM AUTHOR]

The racer goby is an invasive Ponto-Caspian fish spreading throughout Europe. They threaten a native species of similar biology, the European bullhead, by displacing them from shelters. These shelters are necessary for reproduction as well as for protection against predators and hydrodynamic forces. However, abiotic conditions may strongly modify the outcome of an interspecific competition in the wild. Nevertheless, little is known of the effect of flow velocity on the competition between these rheophilic species, although this factor is crucial for their distribution in the field. We video-recorded fish behaviour for 2 h in single-species and mixed-species pairs in the presence of single shelters at three flow velocities: 0, 10 (a velocity preferred by the racer goby) and 30 cm·s−1 (a velocity greater than preferred by the racer goby) to determine whether the invader can deprive the native species of its shelter. At the flow of 0 and 10 cm·s−1, the racer goby exhibited aggressive behaviour towards bullhead, and this restricted the time spent by the bullhead in the shelter. Moreover, although the flow of 30 cm·s−1 inhibited racer goby aggression, the time spent by the bullhead in the shelter in interspecific competition was still reduced when compared to intraspecific controls. Our results suggest that under natural conditions, the racer goby displace bullheads from their shelters even at flow velocities greater than optimal for the racer goby. [ABSTRACT FROM AUTHOR]