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This study shows how YouTube™, a popular video website, is a powerful tool to document and improve our ability to manage freshwater pet release in Brazil. Based on a series of 24 videos chosen randomly using 19 standardized keywords posted by pet-keeping YouTubers between January 1, 2020 and March 20, 2023 (650 h of searching time), we documented the intentional release of 12 translocated and five non-native species involving 11 fish species, two freshwater stingray species, two freshwater turtle species, one freshwater crab species, and one crayfish species in multiple watersheds/ecoregions of Brazil. This is the first record of intentional introduction for 17 species in Brazilian inland waters. The main drivers behind pet release were excessive growth, "agreeableness" (i.e., compassion, pet owner's reluctance to euthanize the animal), and aggressive behavior. The videos documented the release of multiple freshwater pets in numerous freshwater ecosystems. Pet releases were predominantly into rural freshwater ecosystems rather than urban, with an introduction hotspot identified in the Southeast region. This finding is important because pet release is more common in urban than rural areas. While colonization pressure (i.e., number of translocated/non-native species that each pet owner released) was high, overall propagule pressure (i.e., number of individuals of a translocated/non-native species released into a region) was low with a total of 49 individuals released over the monitored period. Proactive management is key in reducing the incidence of pet release in Brazil, attainable through transforming pet shop owners into disseminators of correct information about species traits. Environmental authorities should create "Non-native Pet Amnesty Day" to provide the opportunity for people to surrender their non-native aquatic pets; YouTubers can engage in awareness actions on YouTube™ such as show the negative effects that aquatic pets can cause if introduced into the wild; Brazilian scientists turn into "science YouTubers" and provide arguments that can be used to disseminate reliable scientific messages about freshwater pet release. [ABSTRACT FROM AUTHOR]

The pet trade is known to be one of the most important pathways of aquatic non-native species introduction and Indonesia is a significant trade partner. Popular ornamental South American river stingrays (Potamotrygon spp.) were introduced to Indonesia in the 1980s and the culture was established. Here we present a detailed Indonesian market and aquaculture survey, the volume of trade between January 2020 and June 2022, and the list of customer countries with the total amount of imported stingrays. Climate similarities between the native range of P. motoro and P. jabuti and Indonesia were analysed. A significant number of areas of Indonesian islands were identified as suitable for the establishment of this species. This was confirmed by the first record of probably established populations in the Brantas River (Java). In total 13 individuals including newborns were captured. The culture of potamotrygonid stingrays is unregulated in Indonesia, and the risk of the establishment of this predator and its potential spread is alarming for wildlife. Moreover, the first case of envenomation caused by Potamotrygon spp. in the wild outside of South America was recorded. The current condition is predicted as the 'tip of the iceberg' and continuous monitoring and mitigation of risks are strongly recommended. [ABSTRACT FROM AUTHOR]

Invasive species often co-occur in nature and positive or negative interactions among them can affect community structure and ecosystem functioning. Outcomes depend on the intrinsic traits of the species involved and on how species' performance is affected by the environmental conditions of the recipient ecosystem. Here, we investigated the impact of nitrate, a nutrient common in urban and agricultural sewage discharges, on two invasive crayfish species (Pacifastacus leniusculus and Faxonius virilis) co-occurring in a Nitrate Vulnerable Zone in the UK. Crayfish were exposed to two ecologically relevant nitrate concentrations (≤ 10 and 50 mg NO3−/l) and seven traits relating to foraging success and interspecific interactions were assessed. During monospecific experimental trials, elevated nitrate had a similar impact on the foraging efficacy of P. leniusculus and F. virilis, reducing their ability to sense and find food. However, during dyadic interspecific competition experiments, higher nitrate caused a greater reduction in the number of aggressive behaviours of F. virilis towards P. leniusculus. As such, changes in environmental nitrate regime may affect interactions between these invasive species in regions of sympatry with consequences for their respective invasion dynamics and the wider ecosystem. [ABSTRACT FROM AUTHOR]

Agricultural runoff and biological invasions alter native species interactions with implications for the management of pests. Here, we used live larvae of common house mosquito Culex pipiens to test the efficiencies of the invasive fish Gambusia holbrooki and the IUCN endangered fish Aphanius iberus to manage mosquitoes at three ecologically relevant concentrations of algae and clay. Both species reduced mosquito abundance in aquaria and outdoor mesocosms though A. iberus reduced it at a slower pace. However, G. holbrooki preferentially captured larger larvae at all fish sizes, whereas smaller individuals of A. iberus captured higher number of smaller larvae. Algal turbidity, but not clay, reduced the efficiency of both species, probably because of an adaptation to inorganic turbidity. Fish efficiency was not reduced in mesocosms where fish captured mosquito larvae interacting with natural invertebrate assemblages. Managers should maintain algal turbidity at < 10 FTU based on the visual detection threshold for both species. Our study shows that algal turbidity threatens the potential of waterbodies to naturally control mosquitoes and discusses why the faster foraging rates of alien species such as G. holbrooki should not be used to justify more introductions. [ABSTRACT FROM AUTHOR]

The relationship between fish and amphibians is thought to be antagonistic because of the frequent amphibian extirpations after fish introductions, although some field observations show that amphibians and fish often co-occur in rivers. Here, we used surveys in north-eastern Spain (99,700 km2, 15 river catchments, N = 535 sites) to identify the most frequent fish–amphibian associations and the riverine conditions that might concurrently promote the diversity of native fish and of five widely distributed amphibian species. Overall, there was little congruence between native fish and amphibian-diversity measures (species richness and the Shannon, Simpson and Pielou diversity indices). Different riverine conditions appeared to be important for the two vertebrate groups. Alien fish richness, which was highly correlated with alien fish abundance, was negatively associated with amphibian richness and Shannon diversity but was positively associated with native fish richness. River water depth was negatively associated with amphibian occurrence. While our snap-shot surveys may be a transitional stage in the fish–amphibian relationships, we found that some widely distributed amphibian species co-occur with fish in rivers in north-eastern Spain. Small rivers, such as tributaries often have the most intact fish assemblages, and probably are the best locations to explore fish–amphibian associations in greater depth. [ABSTRACT FROM AUTHOR]

Riparian areas have experienced long-term anthropogenic impacts including the effects of plant introductions. In this study, 27 plots were surveyed across three Mediterranean rivers in north-eastern Spain to explore the effects of the invader giant reed ( Arundo donax) on riparian habitat features and the diversity, trophic structure, body size, and abundances of epigeal and hypogeal arthropods in riparian areas. Using pitfall traps and Berlese funnels, this study detected a significant increase in collembola abundance and a decrease in the abundance, body size and diversity of macro-arthropods at order and family levels in invaded plots compared to native stands. Invaded and un-invaded areas also differed in the taxonomical structure of arthropod assemblies but not in trophic guild proportions. However, the fact that arthropods were smaller in A. donax soils, together with the absence of particular taxa within each trophic guild or even an entire trophic group (parasitoids), suggests that food-web alterations in invaded areas cannot be discarded. Habitat features also differed between invaded and un-invaded areas with the poorest herbaceous understory and the largest leaf litter deposition and soil carbon stock observed in A. donax plots. The type of vegetation in riparian areas followed by the total native plant species richness were identified as major causal factors to changes in the abundance, diversity and composition of macro-arthropods. However, our analyses also showed that some alterations related to A. donax invasion were inconsistent across rivers, suggesting that A. donax effects may be context dependent. In conclusion, this study highlights an impoverishment of native flora and arthropod fauna in A. donax soils, and suggests major changes in riparian food webs if A. donax displaces native riparian vegetation. [ABSTRACT FROM AUTHOR]

White muscle has been traditionally used in determining δC and δN signatures in fish but ethics and the current conservation status of many species mean the application of non-lethal sampling procedures is mandatory. In this study we test whether fins and scales can be used as non-lethal alternatives of muscle tissue for stable isotope analysis by comparing their δC and δN signatures, in two native ( Barbus haasi, Squalius laietanus) and three introduced fish species ( Rutilus rutilus, Lepomis gibbosus and Alburnus alburnus), collected in rivers from north-eastern Spain. Our results showed fins and scales were generally enriched in C and depleted in N compared to muscle, and that both tissues were generally a moderate predictor of the isotopic composition of muscle for most species with the exception of Ebro chub ( R = 0.59-0.97). This study highlights the importance of determining the isotopic relationship between lethal and non-lethally sampled tissues before making straightforward equivalences, and also pinpoints the need for a more comprehensive understanding of how isotopic discrimination occurs in fins, scales and muscle tissues. [ABSTRACT FROM AUTHOR]

The aquarium trade has been identified as an important vector of aquatic invasive species but this question has mostly been investigated in North America. We investigated the variation in diversity and species composition in different trade types in southwestern Europe (three major international wholesalers, different retail store types, and local internet forums), mostly in Spain and Portugal. As in previous studies, the diversity of fishes in the aquarium trade was vast, with a total of 20 orders, 79 families, and 1,133 fish species detected in the trade types analyzed. 248 species were observed in a single metropolitan area (Barcelona), with estimates of about 294 species being present. International wholesalers had higher species richness and evenness, with a single one having over 700 species. General pet stores had much lower evenness but due to high turnover had a total richness of over 200 species. Internet forums had the lowest evenness but similar richness. The different commerce types varied significantly in relative species abundance with about a dozen of popular fish species (e.g., goldfish, Siamese fighting fish, common carp, guppy, swordtails) dominating the retail stores, particularly the general pet stores. Our results imply that frequency in the trade varies strongly among species and commerce types and although general pet stores have usually low diversity, this is compensated with a higher species turnover. Many of the most popular species are well known invasive species and some of the species available are temperate species that might establish in Europe, reinforcing the need for more careful implementation of education programs, regulation and monitoring of trade, and internalization of environmental costs by the industry. [ABSTRACT FROM AUTHOR]

The current freshwater fish fauna crisis is such that natural resource managers urgently need to identify priorities and understand the management consequences of actions aimed at maximizing the preservation of biodiversity. Freshwater research is often poorly linked to conservation ecology; and interdisciplinary studies illustrating examples of freshwater ecosystem conservation are scarce. The Iberian Peninsula has a long history of anthropogenic disturbance that has led to the poor conservation status of its ichthyofauna, with 52 % of species now catalogued as critically endangered, endangered or vulnerable, according to UICN criteria. This paper gives an overview of the main threats (habitat degradation, hydrological alterations and exotic species) that have altered the function and connectivity of Iberian rivers. Case-study examples are provided to analyse the repercussions of these threats and the management actions planned or already performed in these systems. The interaction of many threats is responsible for native fish decline. However, freshwater managers and researchers should not let the trees prevent them from seeing the overall wood, when seeking to achieve practical solutions with the best balanced cost benefit and the collaboration of all ecosystem researchers and stakeholders. Conservation efforts should be focused on the preservation of ecological processes, in order to achieve the goals of the Water Framework Directive and guarantee the conservation of Iberian native fish species. [ABSTRACT FROM AUTHOR]

Sewage effluents are one of the main anthropogenic stressors in Mediterranean rivers. The establishment of a cause-effect relationship is hindered in natural systems by the existence of confounding factors (i.e. biotic interactions). Here we analysed the effects that anthropogenic stressors have on a mono-specific fish community (Iberian redfin barbel population, Barbus haasi) inhabiting the northern edge of its distribution range. In Spring 2004, a total of 40 consecutive sampling sites were surveyed in Vallvidrera creek, and 1,331 specimens were measured and weighed. A principal component analysis was performed to synthesize the information provided by 22 environmental variables. Analysis of variance, bivariate correlation analyses and multiple linear regressions were then used to determine the influence of the environmental gradients built (water quality, hydromorphology, woods and macrophytes, and degree of silting) on fish population features (fish size, body condition status, density and biomass). The findings revealed that water quality was the most significant environmental gradient for this fish population. In particular, fish density decreases and fish length increases in those sites exposed to sewage. Additionally, our results showed the best body condition of those specimens inhabiting fast flow reaches which confirms the rheophilous condition of B. haasi. However, these findings were unnoticed for the current version of the index of biotic integrity using fish as bioindicators in Catalonia. Resource managers need to refine diagnostic tools in order to detect subtle deleterious changes on fish communities before they become evident at population scale. Conservation measures should be focused in these small streams in where the best preserved native fish populations usually inhabit. This study suggests the need to change water management policies in Mediterranean rivers to improve the water quality of sewage effluents and increase the dilution power of these rivers. [ABSTRACT FROM AUTHOR]