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Non-indigenous invasive topmouth gudgeon (Pseudorasbora parva) was introduced to Europe in 1960s and it has passed an ongoing invasion into many European countries. It forms numerous populations particularly in pond aquaculture systems and small stagnant water bodies. The study was carried out on a 0.3 ha pond inhabited solely by the population of topmouth gudgeon. Monthly samplings of environmental variables, zooplankton, macrozoobenthos and fish were performed in 2016–2017. Topmouth gudgeon recruitment correlated with decrease of oxygen concentration and transparency in summer months, apparently due to topmouth gudgeon predation on the cladocerans. The macrozoobenthos community was dominated by large chironomid larvae (Chironomus plumosus), whose density and biomass were not affected by the topmouth gudgeon population. The habitat preferences varied within the population. The 0 + age cohort were abundant in rocky rip-rap, muddy and macrophyte habitats with low abundance in free water zone. In contrast, the 1 + and older fish significantly preferred the rocky rip-rap habitat and free water zone over muddy and macrophyte substrates. In spring, the rocky rip-rap was occupied mainly by males, while later in June and July, females predominated in this habitat. The study also documented disapperance of topmouth gudgeon population due to sudden spate flash-flood. [ABSTRACT FROM AUTHOR]

ABSTRACT Nest defence is one component of parental investment by which individuals can increase the survival of their offspring. Aggressive behaviours and the time spent protecting nests are determining factors in the reproductive success of cichlid species. The Mexican mojarra is the only cichlid native to the Balsas River Basin in Mexico. At least four invasive cichlids have been introduced, including the convict cichlid and the spotcheek cichlid. These three species establish their nests in the River and defend them aggressively. We quantified the number of nests, aggressive behaviours and time spent in the nest by parents of the native species and these two invasive species. We expected that the invasive parents would be more aggressive during defence, spent more time protecting the eggs, and would have a higher density of nests. We also explored differences in nest defence between the sexes within each species. We found that invasive cichlids had a greater number of nests than the Mexican mojarra. In the two invasive species, there was no difference between males and females in the time spent in the nest or the number of aggressive behaviours. In contrast, male Mexican mojarras spent less time in the nest and performed fewer aggressive behaviours than their mates. The smaller number of nests and nest defence behaviour of this native species could compromise its reproductive success and population size. This differential nest defence between the Mexican mojarra and the invasive cichlids could have negative implications for the physiology, reproduction, and health of this native cichlid. [ABSTRACT FROM AUTHOR]

Commercial farming of tilapia species has been spread to many countries worldwide to meet the need for animal protein at an affordable price, which has led tilapias to invade natural areas. Consequently, tilapias have established wild populations, causing a great negative impact on native biodiversity. The Sonora River, located in northwest Mexico, has an approximate length of 400 km, and at least four native fish species inhabit it. Nevertheless, the Sonora River has been severely reduced and contaminated by open-pit mining. According to existing knowledge, the presence of tilapias is not reported in the Sonora River; hence, the present study is the first report of the presence of the Nile tilapia Oreochromis niloticus in a site near the town of Baviácora, Sonora, Mexico. The presence of this invasive species may represent a severe threat to the biotic component of this ecosystem, which is already affected by mining pollution. [ABSTRACT FROM AUTHOR]

In the Mediterranean, the bluespotted cornetfish Fistularia commersonii Rüppell, 1838, presents a minor socioeconomic impact and the assessment of any environmental impact requires more relevant data. The congeneric red cornetfish Fistularia petimba Lacepède, 1803, has expanded its distribution range within the basin but only small numbers have been reported to date. A total of 207 individuals of F. commersonii were collected between April 2021 and March 2022 from the Levantine coast of Rhodes and 92 more from various locations. Additionally, 13 individuals of Fistularia petimba were caught in March 2024 from the Aegean coasts of the island. We aim to assess the current progression of the population of the two cornetfish, the possible further exploitation of F. commersonii to boost the local fishing economy, their possible dietary overlaps and to add valuable biological and ecological data. In F. commersonii, male to female ratio (1:1.33) significantly departed from 1:1, with length–weight relationships exhibiting positive allometric growth. Six age groups were identified. The highest reproductive intensity was observed during summer. The onset of sexual maturity was estimated at 65.52 cm in total length (1.8 years). Longevity was estimated at 11.1 years with females growing larger than males. The exploitation rate (E = 0.47) indicated that the population is underexploited. The optimum and target fishing mortality were higher in comparison with the present fishing mortality (F = 0.48), indicating a potential for commercial exploitation of the species. For F. petimba, the sex ratio was 1:2.25. The species preys on crustaceans, followed by fish and molluscs. The finding of Vanderhorstia mertensi (Klausewitz, 1974) in the stomach content of both cornetfishes constitutes the second published record for Hellenic waters and the first for the Dodecanese Islands. [ABSTRACT FROM AUTHOR]

In the Mediterranean, the bluespotted cornetfish Fistularia commersonii Rüppell, 1838, presents a minor socioeconomic impact and the assessment of any environmental impact requires more relevant data. The congeneric red cornetfish Fistularia petimba Lacepède, 1803, has expanded its distribution range within the basin but only small numbers have been reported to date. A total of 207 individuals of F. commersonii were collected between April 2021 and March 2022 from the Levantine coast of Rhodes and 92 more from various locations. Additionally, 13 individuals of Fistularia petimba were caught in March 2024 from the Aegean coasts of the island. We aim to assess the current progression of the population of the two cornetfish, the possible further exploitation of F. commersonii to boost the local fishing economy, their possible dietary overlaps and to add valuable biological and ecological data. In F. commersonii, male to female ratio (1:1.33) significantly departed from 1:1, with length–weight relationships exhibiting positive allometric growth. Six age groups were identified. The highest reproductive intensity was observed during summer. The onset of sexual maturity was estimated at 65.52 cm in total length (1.8 years). Longevity was estimated at 11.1 years with females growing larger than males. The exploitation rate (E = 0.47) indicated that the population is underexploited. The optimum and target fishing mortality were higher in comparison with the present fishing mortality (F = 0.48), indicating a potential for commercial exploitation of the species. For F. petimba, the sex ratio was 1:2.25. The species preys on crustaceans, followed by fish and molluscs. The finding of Vanderhorstia mertensi (Klausewitz, 1974) in the stomach content of both cornetfishes constitutes the second published record for Hellenic waters and the first for the Dodecanese Islands.

Pseudorasbora parva (Temminck and Schlegel, 1842) has a significant potential to spread outside of its current locations and regions, all-continents-spanning invasive range. The invasion of P. parva has threatened the existence of native species. Therefore, evaluation of the condition and fitness of the invasive P. parva population in different regions is necessary. However, no systematic reports of the P. parva length-weight relationships (LWRs) around the world has been documented, especially comparing indigenous and non-indigenous populations. Thus, the goal of the current study was to offer a systematic report of P. parva LWRs worldwide and a comparison of P. parva LWRs in native and non-native regions. In the present results, P. parva showed positive-allometric growth, it became more rounded as the length increases, and both native and invasive populations showed similar growth patterns and form factor. Considering its invasive potential, the harmful effects of this alien species cannot be ignored. The present research will also focus on eliminating or mitigating the adverse effects caused by the further expansion of the species through a series of prevention and management strategies proposed. [ABSTRACT FROM AUTHOR]

Allometric data of marine fish species from Rhodes, southeastern Aegean Sea are scarce. Their collection is crucial as they provide important information on the ongoing changes of small-scale fisheries in Rhodian coastal marine waters, a highly affected region of the Eastern Mediterranean by biological invasions. Monthly experimental trials and random samplings with static nets were conducted from April 2021 to March 2022 in the coastal marine waters of eastern Rhodes, Levantine Sea. Experimental boat seining was deployed in November 2022 in the coastal waters of northwest Rhodes, Aegean Sea. Total length and total weight of several individuals of 21 fish species were measured and the length-weight relationships of 12 indigenous and nine nonindigenous fish species were examined. The allometric coefficient (b) did not differ significantly from 3.00 for most of the species (70%), demonstrating isometric growth. Positive and negative allometry were found for three indigenous and three non-indigenous species. The largest and heaviest species were the bluespotted cornetfish (Fistularia commersonii), with a maximum TL of 117.60 cm and the silver-cheeked toadfish (Lagocephlaus sceleratus), with a maximum weight of 4640.90 g. Statistically significant positive allometric relationships were found for three non-indigenous fish, namely the bluespotted cornetfish, the devil firefish (Pterois miles) and the dusky spinefoot (Siganus luridus), suggesting that these species are thriving in the under-study area. [ABSTRACT FROM AUTHOR]

Nile tilapia [Oreochromis niloticus (Linnaeus, 1758)] is a widespread invasive fish, now present in lakes, rivers, and reservoirs around the world, and its dominance has led to serious ecological problems in many freshwater systems. However, little is known about its effect on macrophyte-dominated lake ecosystems. We conducted a 10-week mesocosm experiment to test the impact of tilapia on phytoplankton and water quality in model ecosystems with submerged macrophytes [Vallisneria natans (Lour.) Hara] and the presence and absence of tilapia. Tilapia led to an increase in concentrations of total phosphorus, total nitrogen, total dissolved nitrogen, ammonia nitrogen, and total suspended solids and had negative impact on submerged macrophyte and light intensity, thus causing an overall deterioration in water quality. Tilapia increased the abundance of rotifers and changed the zooplankton community structure. Tilapia increased the total biomass of phytoplankton but the effect depended on the phytoplankton size, i.e., the overall proportion of micro-phytoplankton increased, while that of pico-phytoplankton decreased. Thus, tilapia also caused changes in the phytoplankton community structure. Our research shows that tilapia deteriorates water quality and modifies phytoplankton and zooplankton Communities of shallow lakes. [ABSTRACT FROM AUTHOR]

Asian swamp eels (Monopterus albus/javanensis) were first reported as introduced to Florida waterbodies in 1997 near Tampa and Miami; a third population was recorded by 1999 in Homestead. Initial assessments, published soon after swamp eels in southern Florida were first recorded in wetlands beyond canals and ponds (in 2007), concluded there was little threat to Florida’s aquatic ecosystems. Long-term data now suggest they precipitated population crashes of crayfishes and small fishes in the eastern Everglades. We used records from continuous long-term monitoring programs, sporadic monitoring studies, and online databases to reconstruct swamp eel presence across Florida. Monitoring studies provided wetland hydrologic variables to assess limits for swamp eels. From 1997–2007, populations in southern Florida remained restricted to canals; initial spread from 2007–2017 across southern Everglades National Park proceeded slowly and the two populations covered ~1500 km² of southern Florida. From 2017–2022, the rate of spread increased as they spread west and north (~5800 km² range). Through 2014, the Tampa population occurred only along southern/eastern Tampa Bay (~60 km²) but has since spread south along the Gulf Coast, east into central Florida, and south along the Lake Wales Ridge (~11,000 km²). We found evidence of two potentially new introductions, in Palm Beach County and Orlando. There was no clear evidence of limitation of wetland drying on swamp eel occurrence in the Everglades; they were captured in marshes that dried for 1–5 months during the previous dry season, but short-hydroperiod wetlands may have slowed spread. In the Everglades, evidence suggests swamp eels may have been inadvertently spread into marshes from canals used to deliver water for flood control and hydrologic restoration. Swamp eels are currently spreading unchecked across Florida, and there should be great concern about continued spread in this region and their establishment and spread elsewhere. [ABSTRACT FROM AUTHOR]

The timing and causes of lake eutrophication are often obscured when multiple anthropogenic disturbances coincide in space and time. This issue is particularly problematic for shallow lakes in arid regions that experience strong climatic forcing which alters lake hydrology and water levels, and further conflates causal drivers.We used Utah Lake (Utah, U.S.A.) as a model system to examine how natural hydrological variability and anthropogenic forcing influence ecosystem structure of large shallow lakes in arid climates. Paleolimnological analyses of sedimentary biogeochemistry, pigments, DNA, and morphological fossils were used to identify shifts in primary production and evaluate the relative influence of regional climate‐driven hydrological variability and of humans on ecosystem structure.Sediment cores revealed that the phase prior to non‐indigenous settlement included numerous macrophyte and gastropod remains, sedimentary DNA from plants, low organic matter, and low algal production. An abrupt transition occurred in the late 19th century concomitant with agricultural and urban expansion and the introduction of common carp, which was characterised by a loss of macrophytes and an increase in phytoplankton abundance as indicated by sedimentary DNA and pigment concentrations. A further shift to increased cyanobacteria occurred c. 1950 when exponential population growth increased wastewater influx, as recorded by sedimentary δ15N values.Taken together, our data demonstrate that the current eutrophic state of Utah Lake is a function of anthropogenic forcing rather than natural climate‐driven hydrological fluctuations. Furthermore, large lakes in arid regions can exhibit similar patterns of abrupt ecosystem change between alternate states as those observed in northern temperate/boreal and subtropical ecosystems. [ABSTRACT FROM AUTHOR]

The high-elevation plateaus of the inter-Andean valleys are home to shallow lakes that have become eutrophic. These lakes share similarities with shallow lakes in temperate and subtropical areas. Because native species diversity is low, invasive species dominate the fish and macrophytes communities. The study aimed to investigate the behavioral response of the local Daphnia pulex from the Andean shallow Lake Yahuarcocha to the exotic submerged macrophyte Egeria densa and the exotic fish Poecilia reticulata. Laboratory habitat choice experiments revealed that D. pulex from Lake Yahuarcocha strongly avoid E. densa, irrespective of the presence of the fish P. reticulata or chemical cues indicating fish predation on D. pulex. This observation could be explained by the fact that P. reticulata displayed a strong attraction to E. densa during the daytime, probably to avoid bird predation. D. pulex from the nearby Lake San Pablo where P. reticulata is absent but where the fish community is dominated by Oncorhynchus mykiss displayed the same avoidance behavior to submerged macrophytes as D. pulex from Lake Yahuarcocha. These results indicate that macrophytes in these high-elevation shallow lakes may not facilitate top-down control of phytoplankton, since plants do not offer refuge to D. pulex from fish predation. [ABSTRACT FROM AUTHOR]

The African catfish Clarias gariepinus is a freshwater species native to nearly all of Africa and a small part of Asia. Due to being a generalist species, highly fertile and able to survive in a wide range of environmental conditions, the African catfish has become invasive in many non-native systems where it was introduced, bringing negative impacts to wild ecosystems. In Brazil, C. gariepinus was introduced from Africa for aquaculture in 1986 and established itself in the wild within a decade, after escaping from aquaculture ponds and being further translocated to be used in recreational fishing. As further evidence of the expansion of this invasive species in Brazil, we sequenced the mitochondrial control region and cytochrome b markers to confirm the occurrence of C. gariepinus in a major river in a protected area in the southeastern region, and to assess its genetic diversity. Morphometric data was also collected to aid species identification and to compare to other invasive populations in Brazil. The analysis of 24 specimens revealed a single haplotype for each marker. The single cytochrome b haplotype is identical to a haplotype from the Democratic Republic of the Congo, unveiling the possible genetic origin of the C. gariepinus lineage that invaded Brazil. Morphometric data suggests consistency in the morphometric traits of C. gariepinus invasive populations in Brazil. The assessment and monitoring of the distribution of C. gariepinus in non-native areas are crucial for the maintenance of native freshwater biodiversity and ecosystem functioning worldwide. [ABSTRACT FROM AUTHOR]

The introduction of non-native species causes a variety of negative ecological and economic-social impacts on aquatic ecosystems. One of the first studies conducted on these species was the study of their composition and abundance in recipient ecosystems. The present study aimed to investigate the distribution, composition, and abundance of non-native fishes in the lower Tigris basin in a fishing year from fall 2014 to summer 2015. To update and compare the information, the latest fishing situation in the fishing year 2022-2023 was also examined. In total, 31 species from 15 families, including eight non-native species were caught from the studied water bodies. According to the results, non-native species are widely spread to the most aquatic ecosystems of the studied area, among which tilapia, including the redbelly tilapia Coptodon zillii (Gervais, 1848) and the blue tilapia Oreochromis aureus (Steindachner, 1864) were the most abundant species. The redbelly tilapia showed the most distribution in the studied area. According to the local fishermen, the amount of catch in many areas of inland waters of Khuzestan province has decreased compared to 2014-2015, and their statements indicate that they are not satisfied with the state of fishing.

Round goby Neogobius melanostomus is one of the three invasive Ponto-Caspian gobies found in the Sava River basin in Croatia. It has a negative effect on the native ecosystems and is more abundant in highly polluted areas. The objective of this study was to determine the fluctuating asymmetry of four morphometric characters, as well as otolith width and length. Thirty individuals of N. melanostomus were collected and analysed at two sampling sites in the main course of the Sava (Babina Greda, Slavonski Brod) and in a modified habitat (Sava-Odra canal). The squared coefficient of asymmetry variation was used to analyse potential differences between populations. We identified variations in the asymmetry values of the analysed characters, as well as otolith width and length between sampling sites. The highest fluctuating asymmetry was observed in individuals at the Babina Greda sampling site, which could be due to high environmental stress. The results of the study show that the study of fluctuating asymmetry can be used on invasive fish species as a simple approach to identifying habitat quality.

Invasive species may differ from native species in terms of behavioural responses to the stress of encountering a novel environment. Learning about the nature of these differences can help us understand the mechanisms of dispersal and success of the alien species in colonized environments. Here, we investigated this topic using two Ponto-Caspian gobies as model species. They constitute a specific group of invasive fish spreading in North America and Europe. They are benthic, territorial fish of low mobility; they are poor swimmers and are strongly associated with shelters. We compared the behaviour of two invasive goby fishes (the racer goby, Babka gymnotrachelus, and the monkey goby, Neogobius fluviatilis) to that of their native counterparts (the European bullhead, Cottus gobio , and the gudgeon, Gobio gobio , respectively). We used three laboratory tests to measure boldness–shyness traits: shelter occupancy test, novel object test and open field test. The European bullhead left the shelter later and was less active, and avoided the open field to a greater extent than the racer goby. The gudgeon was more associated with the shelter and novel object than the monkey goby and, in contrast to the monkey goby, decreased its activity in the presence of the novel object and in the open field. All the species were attracted to the vicinity of the novel object. Our study suggests that the invasive Ponto-Caspian gobies are bolder when confronted with structural changes in their environment and have a greater potential to spread across the open bottom, devoid of hiding places, compared to their native analogue species. • We compared responses of native and invasive demersal fishes to novelty. • Invaders (Ponto-Caspian gobies) were less associated with the shelter than natives. • Invasive species were more exploratory in a novel area than natives. • Higher boldness may contribute to invasive potential of the Ponto-Caspian gobies. • Invasive gobies have a great potential to spread across the open bottom areas. [ABSTRACT FROM AUTHOR]

Caridean shrimps (Caridea) are the dominant macroinvertebrates in most anchialine ecosystems. Hawaiian anchialine ecosystems, primarily composed of shallow surface pools connected to the ocean via hypogeal networks of cracks, tubes, and other voids, support 10 caridean shrimp species, including two federally listed as endangered. Little is known about most of these species. The objective of this study was to identify factors that affect the abundance and distribution of Metabetaeus lohena (Alpheidae), an uncommon species found across the Hawaiian Archipelago, at Kaloko-Honokōhau National Historical Park, Island of Hawai'i. This park supports the highest concentration of anchialine pools in the State of Hawai'i and is critical to protecting this threatened ecosystem. During 2017, we measured the density of M. lohena during nighttime surveys, as well as a variety of other biological, physical, and chemical parameters, in 130 pools. Metabetaeus lohena occupied 71.5% of the pools surveyed, with a mean density of 7.32 individuals/m2 (95% CI = 5.14–9.49). Invasive fish and the endemic shrimp Halocaridina rubra (Atyidae) had the strongest effects on M. lohena density, with negative and positive relations, respectively. In the first estimate of M. lohena density at this scale, our data indicate that Kaloko-Honokōhau supports about 11,480 shrimp (95% CI = 8,054–14,906) in the pools surveyed. Furthermore, our models predict that this park could support an additional 1,695 individuals (95% CI = 955–3,008) for a population of about 13,175 shrimp if fish were removed from 19 pools in which M. lohena are absent. [ABSTRACT FROM AUTHOR]

The number of invasive species threatening freshwater habitats are increasing globally, and can be accelerated by climate change. Thus, risk assessments of potential invasive species are required for establishing prevention measures, in which quantitative risk assessments provide results objectively. In this study, the invasion risk of largemouth bass (Micropterus salmoides) in four major river basins (the Han, Nakdong, Geum, and Yeongsan) in South Korea was evaluated using an ensemble of species distribution models (SDMs). A weighted ensemble of the SDMs was developed to predict the probability of largemouth bass occurrence in the present (2011–2015) and two future periods: 2050 (2046–2055) and 2080 (2076–2085). The invasion risk of largemouth bass was evaluated using two approaches: relative and absolute risk assessments. Both approaches predicted an increase in Tier 1 (the highest risk) areas under representative concentration pathway (RCP) 4.5; however, a decrease in the areas of concern under RCP 8.5. In particular, the upper streams of the Nakdong and Han river basins are expected to be at risk in the future. In addition, Tier 1 risk areas are predicted to shift northward under both RCP 4.5 and 8.5 scenarios, especially in the Nakdong River Basin. This study provides a quantitative risk assessment tool based on the SDMs for the management of largemouth bass invasion under climate change. [ABSTRACT FROM AUTHOR]

The introduction of non-native species causes a variety of negative ecological and economic-social impacts on aquatic ecosystems. One of the first studies conducted on these species was the study of their composition and abundance in recipient ecosystems. The present study aimed to investigate the distribution, composition, and abundance of non-native fishes in the lower Tigris basin in a fishing year from fall 2014 to summer 2015. To update and compare the information, the latest fishing situation in the fishing year 2022-2023 was also examined. In total, 31 species from 15 families, including eight non-native species were caught from the studied water bodies. According to the results, non-native species are widely spread to the most aquatic ecosystems of the studied area, among which tilapia, including the redbelly tilapia Coptodon zillii (Gervais, 1848) and the blue tilapia Oreochromis aureus (Steindachner, 1864) were the most abundant species. The redbelly tilapia showed the most distribution in the studied area. According to the local fishermen, the amount of catch in many areas of inland waters of Khuzestan province has decreased compared to 2014-2015, and their statements indicate that they are not satisfied with the state of fishing. [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]

Experimental fishing was conducted in three different locations along the coastal marine waters of eastern Rhodes Island, Levantine Sea, Hellas, from April 2021 to March 2022 on a monthly basis. Twelve samplings with gill nets and 12 with trammel nets at each of three selected locations resulted in a total of 72 samplings. The numbers of indigenous and non-indigenous species, as well as their abundances, biomasses and frequencies of occurrence, were recorded. Overall, the samplings yielded 71 species, of which 14 were non-indigenous. The total abundance was 1879 individuals, corresponding to a fish biomass of 433.57 kg. Fistularia commersonii, Sparisoma cretense and Pterois miles exhibited the highest numbers of individuals, whereas three of the invasive alien species in the Hellenic seas, namely, F. commersonii, Lagocephalus sceleratus and P. miles had the highest biomasses. The results exhibited a strong presence of P. miles in the Rhodian fisheries as the dominant invasive species based on the examined indicators (i.e., abundance, catches and frequency of occurrence). Comparisons in regard to the collected biomass between the locations, seasons, species origins and types of fishing gear were performed. All three locations were characterized by a good ecological status based on the relationship between abundance and biomass. The results of this study contribute valuable information on the ongoing changes in small-scale fisheries in the marine waters of Rhodes Island, which is one of the Eastern Mediterranean regions most affected by biological invasions. [ABSTRACT FROM AUTHOR]

The presence of fish within navigation locks can introduce an environmental challenge for construction crews when maintenance is required. This study examined the effectiveness of a dual-deterrent fish herding technique using electricity and acoustic stimuli to reduce the abundance of fish within a navigation lock before a scheduled dewatering for maintenance. Fixed-location multi-beam imaging sonar was used to evaluate fish per minute (FPM) detections near the lock entrance before, during, and after the herding effort. Standardized mobile side-scan sonar surveys were also conducted before and after the herding to examine fish presence throughout the entire lock. Collectively, a 73% reduction in fish targets detected by side-scan sonar and a 43% reduction in FPM detected by imaging sonar were observed following the herding technique. Post-fish herding, an 88% reduction in FPM > 400 mm and a 35% reduction in FPM < 400 mm were observed. Fish abundance within the lock chamber was reduced and did not result in construction delays, which was problematic and costly during previous dewatering events. Because data from this study are limited to a single lock dewatering and fish clearing event, caution is warranted with the extrapolation of these results. However, the applied methods show promise and may inform future fish clearing efforts to aid lock maintenance. [ABSTRACT FROM AUTHOR]

In the last decade, invasive suckermouth armored catfish Pterygoplichthys spp. spread among many river systems of Vietnam. Extended distribution of armored catfish might be associated with using brackish water in estuaries for fish spread from one river system to another. The first goal of our study was to assess the occurrence of armored catfish in the estuary of the Da Rang River (Phu Yen Province, Vietnam) and their distribution depending on the horizontal salinity gradient (4--25 PSU). Fish were mainly caught by stationary bottom traps in water salinity from 4 PSU to 18 PSU. The second goal of our study was to experimentally evaluate the ability of armored catfish to move and breathe in seawater (33 PSU). Fish moved in horizontal and vertical planes after transfer into seawater during the first 15 minutes. Fish moved around less by the 13th--15th minutes in seawater. Armored catfish moved around more in seawater than in freshwater. The exposure to seawater for 6 minutes led to deterioration of fish breathing. The results of our field and experimental studies established that armored catfish are found and able to move in brackish waters but avoid high salinity water. These facts provide support for the hypothesis of armored catfish invasion through the estuaries and coastlines. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine changes in the abundance of Ameiurus nebulosus and native fish in four lakes after 4–7 years. It was hypothesised that A. nebulosus would be the dominant species of fish in various types of lakes. The study was conducted in the summer of 2014 and 2018–2021, using Nordic multi-mesh gillnets. We indicated that relative numbers and biomass of A. nebulosus decreased in the oligo-mesotrophic lake, while increased in lakes of higher trophic conditions. Body weight and total length of A. nebulosus fluctuated from 3.2 to 283.3 g and 64 to 267 mm, respectively. The coefficient of condition of this species varied widely from 0.2 to 1.8 with the highest and lowest values in the meso-eutrophic lake. Ameiurus nebulosus accounted for 0.2–34.1% of the total numbers and 2.4–36.5% of the total biomass of the fish community. In the mesotrophic and meso-eutrophic lakes, A. nebulosus was a dominant component of the fish community after 7 years. The percentage contribution of A. nebulosus to the total numbers of fish decreased with the increasing trophic status of the studied lakes. Our study showed that A. nebulosus could be one of the factors responsible for a decrease in the number of native fish species and a change in the taxonomic structure of native fish in lakes of different trophic status (from oligo-mesotrophy to eutrophy). [ABSTRACT FROM AUTHOR]

Pseudorasbora parva is a non-native species that has long been established in Croatia and Europe and has been on the European list of Invasive Alien Species of Union concern since 2016. The species is known for its high invasiveness, negative impact on native species and rapid rate of spread, which is facilitated by its specific life history characteristics. Therefore, increased monitoring and control measures are needed to limit the spread of P. parva in Croatia and other European countries. This study aimed to investigate the current distribution of P. parva in lowland streams and canals of the River Sava basin and to determine environmental factors associated with its occurrence using Bernoulli Generalized Linear Model with an information theoretic approach. The species was found at 33 of 111 sampled sites where its occurrence was previously unknown. The model identified the absence of gravel in the substrate and a rich fish community as the best predictors of P. parva occurrence. Streams with natural water regimes and low numbers of specialised fish species are least likely to support the occurrence of this species, so such habitats should be protected from further alteration to be preserved as refugia for native ichthyofauna. [ABSTRACT FROM AUTHOR]

Amphibians are more threatened than any other vertebrate class, yet evidence for many threats is missing. The Cape lowland fynbos (endemic scrub biome) is threatened by habitat loss, and natural temporary freshwater habitats are removed in favour of permanent impoundments. In this study, we determine amphibian assemblages across different freshwater habitat types with special attention to the presence of invasive fish. We find that anuran communities differ primarily by habitat type, with permanent water habitats having more widespread taxa, while temporary water bodies have more range restricted taxa. Invasive fish are found to have a significant impact on frogs with toads most tolerant of their presence. Temporary freshwater habitats are a conservation priority in the area, and their amphibian assemblages represent endemic taxa that are intolerant of invasive fish. Conservation of a biodiverse amphibian assemblage in lowland fynbos areas will rely on the creation of temporary freshwater habitats, rather than a northern hemisphere pond based solution. [ABSTRACT FROM AUTHOR]

Boldness is closely related to fish species' adaptative strategies and invasiveness and has become the focus of fish personality research. However, due to the lack of studies on behavioral stages, the ecological functions of certain behaviors remain unclear. To better understand the link between boldness and invasiveness in stone moroko (Pseudorasbora parva), an invasive Asian fish species, we exposed the fish to an open-field environment for 60 min and assessed their behavioral patterns, profiles, and stages. The results show that the boldness behavior of stone moroko was characterized by high activity, low average velocity, and diverse swimming postures. Five behavioral stages with significant differences were revealed: outbreak, inhibition, slow swimming, exploration, and adaptation. These observations suggest that stone moroko can quickly habituate to new environments. In addition, stone moroko spent more energy on exploring the living area and less on environmental risk assessment, as revealed by an analysis of their energy trade-off strategy. The behavioral strategies of stone moroko may explain their extremely high environmental adaptability and ability to invade multiple environments. [ABSTRACT FROM AUTHOR]

The increasing success of invasive warm water species is often explained as a direct consequence of a warming climate, but other environmental variables are seldomly taken into account. Here, running RandomForest models with many combinations of relatively uncorrelated environmental predictors, we investigate the factors influencing the distribution of Red Sea fishes in the Mediterranean Sea, which was invaded through the Suez Canal. Our results highlighted the fundamental role of salinity, not only temperature, in determining the distribution of these tropical species, with average values (primarily salinity and surface sea temperatures) performing the best of the respective groups. Noteworthy, models based on surface variables only resulted in higher evaluation scores than those including also bottom variables. These findings contribute to identifying the most relevant factors that explain tropical fish distribution in the Mediterranean Sea and provide advice to the selection of environmental variables in species distribution modeling. [ABSTRACT FROM AUTHOR]

In the last 30 years, the natural life in the inland waters of the Turkish Thrace has been threatened by water pollution, deterioration of river continuity, the presence of non-native or invasive fish, and drought. The aim of the present study is to determine the recent status of fish fauna in the river systems lying at the Turkish Thrace, under these threats. The field surveys were conducted in a total of 164 sampling sites in both Marmara and Meriç-Ergene water basins between July and August 2017. A total of 36 freshwater fish species representing 12 families (Acheilognathidae, Atherinidae, Centrarchidae, Cobitidae, Cyprinidae, Esocidae, Gobiidae, Gobionidae, Leuciscidae, Percidae, Poeciliidae, and Salmonidae) were determined. The most widespread species of the region was Cobitis strumicae and it was followed by Rhodeus amarus and Squalius orpheus. This study provides first detailed information on the distribution of the species of Barbus tauricus, Chondrostoma vardarense, Cobitis strumicae, Squalius orpheus, and Vimba melanops. [ABSTRACT FROM AUTHOR]

Simple Summary: In Italy, there is a growing concern over the survival of an endemic subspecies of newt, Ichthyosaura alpestris inexpectata, commonly known as the Calabrian Alpine newt, due to the recent fish introduction and acclimatisation into three of the few localised lentic habitats where this glacial relict occurs. Results of a recent survey focused on this rare endemic taxon are presented. We provide updated information on the Calabrian Alpine newt distribution, adding two new localities, documenting local extinction at a few historical sites, providing a rough estimation of population size, and giving a description of breeding habitat features. The results of our pilot study will facilitate future research activities, conservation measures for the amphibian assemblage, and habitat management after fish introduction in the Natura 2000 site. We also pinpoint some actions useful to avoid the extinction of this remarkable taxon. The Calabrian Alpine newt (Ichthyosaura alpestris inexpectata) is a glacial relict with small and extremely localised populations in the Catena Costiera (Calabria, Southern Italy) and is considered to be "Endangered" by the Italian IUCN assessment. Climate-induced habitat loss and recent fish introductions in three lakes of the Special Area of Conservation (SAC) Laghi di Fagnano threaten the subspecies' survival in the core of its restricted range. Considering these challenges, understanding the distribution and abundance of this newt is crucial. We surveyed the spatially clustered wetlands in the SAC and neighbouring areas. First, we provide the updated distribution of this subspecies, highlighting fish-invaded and fishless sites historically known to host Calabrian Alpine newt populations and two new breeding sites that have been recently colonised. Then, we provide a rough estimate of the abundance, body size and body condition of breeding adults and habitat characteristics in fish-invaded and fishless ponds. We did not detect Calabrian Alpine newts at two historically known sites now invaded by fish. Our results indicate a reduction in occupied sites and small-size populations. These observations highlight the need for future strategies, such as fish removal, the creation of alternative breeding habitats and captive breeding, to preserve this endemic taxon. [ABSTRACT FROM AUTHOR]

Amphibians are more threatened than any other vertebrate class, yet evidence for many threats is missing. The Cape lowland fynbos (endemic scrub biome) is threatened by habitat loss, and natural temporary freshwater habitats are removed in favour of permanent impoundments. In this study, we determine amphibian assemblages across different freshwater habitat types with special attention to the presence of invasive fish. We find that anuran communities differ primarily by habitat type, with permanent water habitats having more widespread taxa, while temporary water bodies have more range restricted taxa. Invasive fish are found to have a significant impact on frogs with toads most tolerant of their presence. Temporary freshwater habitats are a conservation priority in the area, and their amphibian assemblages represent endemic taxa that are intolerant of invasive fish. Conservation of a biodiverse amphibian assemblage in lowland fynbos areas will rely on the creation of temporary freshwater habitats, rather than a northern hemisphere pond based solution.

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 (

Intraspecific variation in stoichiometric traits was thought to be an adaptive response to reduce the elemental imbalance between organism and diet in the habitat. Studying the spatial variation of stoichiometric traits of non‐native species and the factors contributing to the variation could help to better understand the invasion mechanism of non‐native fish. In this study, stoichiometric traits (i.e. carbon [C], phosphorus [P], calcium [Ca] and their ratios) variation in the body and organs of non‐native sailfin catfishes Pterygoplichthys spp. were investigated across 13 river sections in the main river basins of Guangdong province. The relationships between environmental factors and stoichiometric traits were analyzed using a general linear model and an information‐theoretic approach. A manipulated feeding experiment was conducted to investigate the impact of food quality on the stoichiometry of sailfin catfishes in a greenhouse. Sailfin catfishes exhibited considerable variability in body and organ elemental composition. Site identity was the main factor contributing to the variation, which could be explained by a combination of environmental factors including climate, diet quality, fish species richness and trophic status in the invaded rivers. Water chemistry (i.e. total nitrogen and phosphorus, ammonia nitrogen and soluble reactive phosphorus) contributed to the most variation of stoichiometric traits. Imbalances of P and Ca between sailfin catfishes and food resources varied among sampling sites, reflecting the spatial heterogeneity of nutrients limitation. Juvenile sailfin catfishes exhibited stoichiometric homeostasis (0 < 1/H < 0.25) for all elemental contents and ratios in the feeding experiment. These findings suggested variation in stoichiometric traits of sailfin catfishes might be attributed to the changes in elemental metabolism to cope with context‐specific environments. This study provided heuristic knowledge about environmental‐related variation in stoichiometric traits, which could enhance the understanding of the non‐native species' adaptation to resource fluctuation in the invaded ecosystems. [ABSTRACT FROM AUTHOR]

We report on the discovery of a wild, reproducing population of Channa aurolineata (Pisces: Channidae) in west-central Florida (USA), and first documented occurrence of snakeheads in the Gulf Coast region. Channa aurolineata is a large, predatory fish of the bullseye snakehead "Marulius group" species complex from Asia. Adult and juvenile specimens were captured in June 2020 in a 1.8-hectare pond that connects during high water to a small stream within the Manatee River-Tampa Bay Basin. The pond site is 250-km from the only other wild C. aurolineata population in the USA (present in southeast Florida since ca. 2000) and is considered a separate introduction and not the result of natural dispersal. Morphological and molecular comparisons revealed high overlap between the two Florida populations, evidence humans may have transported fish between sites. To verify identification, we compared Florida samples to C. aurolineata from Thailand and found mtDNA-COI barcode sequences to be identical or to differ by only a single base pair. Life body coloration of Florida samples matched their Asian counterparts, but Florida specimens averaged fewer dorsal fin rays (53.6 vs. 56.0), anal fin rays (34.2 vs 36.1), lateral line scales (65.3 vs. 67.4), and vertebrae (62.1 vs. 64.3), differences implying possible founder effect or sampling bias. Existence of this invasive predator is a concern because of the risk of spread and negative ecological effects, including an observation of terrestrial hunting behavior. In 2020-2021, several hundred C. aurolineata were removed from the pond by nets and electrofishing, and surveys suggested the population had not spread to nearby waters. In May 2021 the pond was treated with rotenone and 48 more specimens were recovered. No additional snakeheads have been sighted since the piscicide operation, although verification of eradication will require monitoring of the watershed. [ABSTRACT FROM AUTHOR]

Abstract Intraspecific variation in stoichiometric traits was thought to be an adaptive response to reduce the elemental imbalance between organism and diet in the habitat. Studying the spatial variation of stoichiometric traits of non‐native species and the factors contributing to the variation could help to better understand the invasion mechanism of non‐native fish. In this study, stoichiometric traits (i.e. carbon [C], phosphorus [P], calcium [Ca] and their ratios) variation in the body and organs of non‐native sailfin catfishes Pterygoplichthys spp. were investigated across 13 river sections in the main river basins of Guangdong province. The relationships between environmental factors and stoichiometric traits were analyzed using a general linear model and an information‐theoretic approach. A manipulated feeding experiment was conducted to investigate the impact of food quality on the stoichiometry of sailfin catfishes in a greenhouse. Sailfin catfishes exhibited considerable variability in body and organ elemental composition. Site identity was the main factor contributing to the variation, which could be explained by a combination of environmental factors including climate, diet quality, fish species richness and trophic status in the invaded rivers. Water chemistry (i.e. total nitrogen and phosphorus, ammonia nitrogen and soluble reactive phosphorus) contributed to the most variation of stoichiometric traits. Imbalances of P and Ca between sailfin catfishes and food resources varied among sampling sites, reflecting the spatial heterogeneity of nutrients limitation. Juvenile sailfin catfishes exhibited stoichiometric homeostasis (0

Alien species are menacing global biological diversity by causing significant disruption of native species. The invasive fish species Pterygoplichthys sp. and Oreochromis sp. were eaten by smooth-coated otter at Vaduvoor Bird Sanctuary, Tamil Nadu. In total, six encounters were detected by both direct and indirect (corpses) observation. The invasive species play a major and important role in the smooth-coated otter's diet. Hence, the observations showed that otter predation on invasive fish species could be as a promising potential bio-controller in inland waters and wetlands. [ABSTRACT FROM AUTHOR]

In this study, the new occurrence of Carassius gibelio belonging to the genus Carassius in Ulugöl Plateau Pond (Mesudiye-Ordu, Turkey) and Perşembe Plateau Pond (Aybastı-Ordu, Turkey) in the Middle Black Sea Region (Turkey) is reported. The distribution data of Prussian carp was updated in the Middle Black Sea Region of Turkey in comparison to the previously known data. Presenting morphological data of samples collected from two different areas in the Middle Black Sea Region may contribute to revealing the current distribution status of this invasive species and determining the potential distribution areas.

Smallmouth bass (Micropterus dolomieu) are a globally introduced fish species that have experienced widespread range expansions in recent decades and which can have deleterious effects on native fish communities. Rapidly assessing their expansions will aid conservation and management actions geared towards controlling their spread and mitigating their impacts. Smallmouth bass have recently experienced a rapid upstream expansion in a Great Plains river (Laramie River, Wyoming, USA), which provided an opportunity to evaluate the drivers and impacts of this expansion by using a modified before-after, control-impact (BACI) design. Our objectives were to test whether climatic drivers (temperature, precipitation, flow) were related to this range expansion and subsequent effects of the expansion on native fish communities. Smallmouth bass population size in Grayrocks Reservoir increased following a climatically extreme wet year, with statistically extreme amounts of spring-time and June precipitation creating high discharge events that coincided with the upstream expansion. Unlike previous studies highlighting the invasive nature of smallmouth bass, the modified BACI analysis revealed no declines in species richness induced by the expansion. However, there was evidence that native small-bodied minnow species (family Leuciscidae) declined in relative abundance and that community-level and species-level trophic niches were compressed for invaded sites. Our findings provide important insight into how climatic extremes can prompt biological invasions that can alter community composition and food web structure even if local extirpations do not occur. [ABSTRACT FROM AUTHOR]

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Oxidative stress in fish is the result of the water quality in the ecosystem and the degree of water pollution. The aim of the study was to determine the oxidative potential in the muscles of selected fish species found in lakes with different trophy status. Values of redox indexes (MDA, Vit. C, SOD and CAT) in the muscle tissue of two native (roach (Rutilus rutilus) and perch (Perca fluviatilis)) and one invasive fish species - brown bullhead (Ameiurus nebulosus) were determined. The differences in redox indexes in muscle tissue of fish from lakes with different trophy status were noted. This indicates differentiated sensitivity of individual fish species to oxidative stress resulting from changes in water quality parameters. The changes in the redox parameters in the tissues of selected fish species were more influenced by the lake trophy than the effect resulting from interspecies differences. Fish from a hypertrophic lake had poorer meat quality due to the greater intensity of oxidation processes in relation to fish from the eutrophic lake. The present study gives the need for further studies that will take into account more fish species and a longer period of time, including changes resulting from the functioning of these reservoirs in different seasons. [ABSTRACT FROM AUTHOR]

Aquatic invasive species (AIS) are a major threat to aquatic ecosystems worldwide. Despite management efforts, human assisted dispersal continues to distribute AIS within and across waterbodies. An understudied translocation vector for AIS, especially for invasive fish, are the cooling systems of small watercraft motors. Here, we investigate the contents of boat motor cooling systems for the presence of invasive goby larvae in a collaboration with local boat owners. Because of the exclusively nocturnal drift activity of goby larvae, to collect samples we drove boats in the first hours after sunset. For an estimate of the translocation potential, we quantified drift density of goby larvae as well as boat traffic after sunset. We found a goby larva in a boat motor once in 30 boat drives of 1-2 hours duration each. Peak drift densities of goby larvae were 2.5 per 100 m3, which is comparable to previously reported data. Recreational boats were active after sunset throughout the reproductive season of invasive gobies and are therefore a realistic translocation vector for goby larvae. Additionally, evidence of fish and other animals inside boat motor cooling systems, gathered from online boating forums, demonstrates the potential of AIS transport in small watercraft. Translocation inside motors is especially likely for in-water transport of boats, which should be a management focus in interconnected aquatic systems. [ABSTRACT FROM AUTHOR]

In recent decades, the Amur sleeper (Perccottus glenii) is one of the most impressive east-to-west invaders of European inland waters, but there are insufficient data on its biology in the countries it has entered. Specimens of two sets of samples from November 2015 (n=25) and October 2016 (n=39) were caught in the Danube River channel near Veliko Gradište (Serbia) by electrofishing. Thirty morphometric and eight meristic characteristics of the collected fish were measured with the aim of describing the general body shape in more detail using the “point-to-point” method. This is the first attempt to obtain morphometric and meristic characteristics of Amur sleeper caught in Serbia. The results revealed a relatively low variability in the morphometric and meristic characters of the studied population. When compared to other studies, there was a great variability of the studied characteristics between geographically distant European populations that inhabit different water body types. Female fish had more robust bodies compared to males of the same length, while males had longer pectoral, anal and dorsal fins. Additionally, 2+ individuals had more robust heads and jaws, as well as longer anterior parts of the body compared to 1+ individuals of the same size

Predicting the shift of invasive species distribution in response to climate change is essential for ecological risk assessment. In this study, the distribution of invasive largemouth bass (Micropterus salmoides) was predicted from 2016 to 2085 in the Han River basin of South Korea using HadGEM3-RA based climate change scenarios (representative concentration pathway [RCP] 4.5 and 8.5 scenarios). A random forest model was developed using largemouth bass occurrence data and environmental variables (temperature, precipitation, flow rate, water quality, elevation, and slope) for five years (2011–2015). The annual mean temperature was the second most contributing variable after elevation. The occurrence of largemouth bass in the Han River basin was expected to increase in the future with increasing annual mean temperature, especially after the 2060 s (2056–2065) in the RCP 8.5 scenario. The latitudinal, longitudinal, and altitudinal shifts of largemouth bass distribution were expected to be −1.76 km, 4.19 km, and 9.07 m per 10 years under the RCP 8.5 scenario, respectively, indicating a gradual southeastward shift to higher locations. Given that invasive fish can disturb the habitat of endemic species, three-dimensional distribution shift under climate change should be considered for the ecological risk assessment of invasive species.

Background: Divergent morphology and placentation of Poeciliids make them suitable model for investigating how evolutionary selection has altered and conserved the developmental mechanisms. However, there is limited description of their embryonic staging, despite representing a key evolutionary node that shares developmental strategy with placental vertebrates. Here, we describe the embryonic developmental stages of Gambusia holbrooki from zygote to parturition using freshly harvested embryos. Results: We defined 40 embryonic stages using a numbered (stages 0‐39; zygote to parturition, respectively) and named (grouped into seven periods, ie, zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and parturition) staging system. Two sets of quantitative (ie, egg diameter, embryonic total length, otic vesicle closure index, heart rates, the number of caudal fin rays and elements) and qualitative (ie, three‐dimensional analysis of images and key morphological criteria) data were acquired and used in combination to describe each stage. All 40 stages are separated by well‐defined morphological traits, revealing developmental novelties that are influenced by narrow perivitelline space, placentation, internal gestation, and sex differentiation. Conclusions: The principal diagnostic features described are quick, reliable, and easy to apply. This system will benefit researchers investigating molecular ontogeny, particularly sexual differentiation mechanisms in G. holbrooki. Key Findings: Comprehensive developmental staging system.Well‐defined morphological traits.Introduced novel indices in stage identification.Chronological description of different systems.Presented staging system is quick, reliable, and easy to apply. [ABSTRACT FROM AUTHOR]

China's mangroves provide important habitat for many endangered fish species, but, there has been little research upon the diversity and the distribution of fish species within mangroves habitats. To compile an inventory of fish fauna in this field, a total of 14 ichthyological surveys were conducted in Zhanjiang Mangrove during different seasons between August 2016 and December 2019. A total of 208 fish species have identified belonging to 18 orders, 69 families and 142 genera from Zhanjiang Mangroves National Nature Reserve, the largest mangrove habitat in China. Of these 17 species are listed as threatened species in the IUCN Red List. Our research indicates that nonnative species, overfishing, and pollution from aquaculture have severely threatened the fish biodiversity of the mangrove habitat in Zhanjiang. To better protect native biodiversity and fisheries, specific measures and management strategies should be adopted and enforced. This study recommends management approaches to better protect, sustain and manage fisheries and fish biodiversity in Zhanjiang mangrove habitat. [ABSTRACT FROM AUTHOR]

Ponds are increasingly being constructed to enhance amenity values in human-dominated lowland landscapes, but little is known of design features that influence macroinvertebrates which can provide important food resources for fish and waterbirds. We quantified pond characteristics, sampled benthic and water-column macroinvertebrates in winter, and related abundance, biomass and community composition to characteristics of 34 ponds on the lower Waikato River floodplain, northern New Zealand. Compositionally different macroinvertebrate communities occupied water-column and benthic habitats. Landscape setting had a significant effect on benthic composition in terms of biomass, while the independent effects of frequency of pond drying or flooding, respectively, influenced benthic (abundance, biomass) or water-column (abundance) communities. Distance-based linear models highlighted physicochemical conditions, water depth regimes and riparian vegetation composition as key variables accounting for dissimilarity in total macroinvertebrate biomass between ponds. Our results indicate that managing hydrological stability of ponds in terms of permanence and flooding influences the composition and biomass of invertebrate communities. Within this hydrological template, design of appropriate depth regimes and riparian conditions can enhance accrual of macroinvertebrate biomass, thereby increasing food resources for fish and waterbirds. [ABSTRACT FROM AUTHOR]

As a first step towards developing genetic option to control pest populations of Gambusia holbrooki , this study investigated the efficacy of oestradiol (E2) to feminise the species. The oestrogen was administered orally via food to neonates (Experiment 1) or embryos through gravid females (Experiment 2) at dosage between 50 and 400 mg kg–1 of feed. Two control groups consisted of (C1) normal feed and (C2) feed mixed with 70% ethanol. In Experiment 1, 100% feminisation was observed at all E2 concentrations except at 400 mg kg–1 where no treated individuals survived. There was a significantly (P < 0.05) lower mean survival rate (MSR) of all E2-treated juveniles than of controls (C1: 71.73 ± 22.86%; C2: 70.02 ± 18.26%), with 50 mg kg–1 showing the best MSR (66.38 ± 12.34%). In Experiment 2, 100% feminisation was achieved at E2 concentrations of 200–400 mg kg–1 food, with the best MSR (59.33 ± 12.54%) at 200 mg kg–1 concentration, which was, however, significantly lower than in control groups (C1: 79.96 ± 20.33%; C2: 77.09 ± 10.32%). The reproductive output and gestation period of gravid females were not affected by E2 exposure. The outcomes provide a framework for reliable sex reversal (feminisation) in this fish, paving way for developing genetic strategies to manage and eradicate this pest fish. Sex reversal (feminisation) using oestradiol was performed in pest fish, Gambusia holbrooki. Oestradiol was administered orally via food to two groups of G. holbrooki at different life stages, namely, neonates and embryos through gravid females. A complete feminisation was achieved at both life stages. Feminised fish showed comparable survival rate and the reproductive fitness of treated female broodstock was not jeopardised. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems have a greater value for biodiversity per surface area than terrestrial and marine ecosystems. Streams and lakes are notably prone to biodiversity loss, being the greatest threats habitat destructions and nonnative species. The aim of the present study is to assess the fish composition of lotic and lentic water systems of an island ecosystem (Gökçeada Island, Turkey), which is poorly studied, and to highlight the entry routes and possible impacts of translocated fish species in an island ecosystem. The field surveys were conducted in a total of 14 sampling sites (five reservoirs and nine streams) in the inland waters of Gökçeada Island between September 2019 and January 2021. Fish samples were collected by electrofishing (SAMUS 1000; a backpack electro-shocker). A total of eight fish species belonging to six families (Anguillidae, Atherinidae, Cyprinidae, Leuciscidae, Mugilidae, and Poeciliidae) were determined. As a result fish community of the island was mostly composed by the introduced species Carassius gibelio, Gambusia holbrooki and Pseudorasbora parva. This study provides the first detailed information on the distribution of the fish species encountered in the inland waters of Gökçeada Island. Results showed that the fish fauna of the island was predominantly shaped by fish stocking activities. [ABSTRACT FROM AUTHOR]

The brown bullhead (Ameiurus nebulosus) is a non-native, invasive fish species in Europe, and since it is sometimes present in high numbers in aquatic ecosystems, it may affect their functioning. The aim of the study was to determine the composition of the diet of A. nebulosus depending on its body size; the body size at which the brown bullhead becomes a predator and what share of its diet consists of fish. We determined the diet composition, frequency, and biomass of individual food types for 260 A. nebulosus individuals belonging to three classes in two shallow lakes. Analysis of the diet of A. nebulosus showed that it was highly varied, which manifested as a wide range of food types (15 types) as well as changes in its composition depending on the size of the fish. The nature of the habitat may influence the composition of the diet of A. nebulosus, which was most evident in the smallest individuals (total length