DOI: 10.3391/ai.2026.21.1.181482

Authors: Mingkai Leng, Xiaodong Wu, Zhenzhen Feng, Xuguang Ge, Haoran Liu, Xing Wang, Haoyue Li, Wenhui Li

Abstract: The aquatic plant Myriophyllum aquaticum, native to South America, has been introduced to China as an aquarium ornamental plant species over the past 20 years and has now established itself as an invasive species in multiple regions of southern China. In the present study, we conducted a controlled pot experiment with Myriophyllum aquaticum planted at seven different water depths (0, 25, 50, 75, 100, 125, and 150 cm) to investigate its growth patterns and adaptive mechanisms in various aquatic environments. As expected, underwater light decreased exponentially with increasing water depth. Spectral analysis indicated significant attenuation across all wavelength bands, with the blue light band being reduced to a greater extent than the red light band, consequently leading to a gradual elevation in the red-to-blue ratio (Red/Blue) with depth, which has a significant effect on the survival rate of M. aquaticum. With an increase in water depth, the survival rate of M. aquaticum showed a decreasing trend; the plants did not survive at a depth of 150 cm. The effect of water depth on the growth and reproduction of M. aquaticum is evident. The growth indices, namely plant height, the number of stem nodes, internodes, the number of branches, the number of tillers, root length, wet weight, and the RGR were all shown to decrease with increasing water depth. Growth conditions gradually diminished with the increase in depth: the Chl-a content of the M. aquaticum leaves gradually decreased, and when the water depth was ≥ 50 cm, the chlorophyll synthesizing ability of the leaves gradually decreased. Increased water depth – and the corresponding stress of low light – resulted in an increase in the malondialdehyde content of the leaves. The results of this experiment demonstrate that M. aquaticum is more likely to become established in shallow-water areas (depth up to 25 cm).

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DOI: 10.3391/ai.2025.20.4.175069

Authors: Yang Zhao, Qichen Zhang, Andy J. Green, Sixian Tang, Xiaodong Jiang

Abstract: The potential role of waterbirds in the dispersal of invasive apple snail Pomacea canaliculata was evaluated by feeding their eggs to mallards Anas platyrhynchos and quantifying the recovery of intact and viable eggs in their faeces and regurgitations. A total of 30,400 eggs were ingested by eight male mallards in 19 feeding trials. Endozoochory potential was detected in 14 trials, in which a total of 46 intact eggs were recovered from mallard faeces, and 684 intact eggs were regurgitated. Most intact snail eggs in faeces were egested 2–6 hours after feeding (72%), whereas 81% of those regurgitated were egested less than 1 hour after feeding. Two snail eggs from faeces and 74 eggs from regurgitations were successfully hatched (jointly representing 0.25% of ingested eggs). These data suggest that apple snail eggs can survive gut passage by waterbirds, and long-distance endozoochory events may contribute to the spread of the snail in the introduced range. In addition, short-distance dispersal is crucial and should not be overlooked as a means to sustain population, increase the extent of invaded range, and maintain gene flow.

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DOI: 10.3391/ai.2025.20.3.161320

Authors: Shoujie Tang, Ying Xing, Temesgen Tola Geletu, Jinliang Zhao

Abstract: In recent decades, the redbelly tilapia (Coptodon zillii) has become one of the most serious invasive alien fish species worldwide. The successful invasion of this fish may largely depend on the plasticity of its life-history traits. In order to explore the life-history traits of the invasive population of C. zillii, we chose Shuikou Reservoir of Minjiang River, China, as a typical invasive habitat, and 1,041 specimens were collected monthly from March 2023 to February 2024. Life-history traits were systematically investigated. The results showed that the entire population consists of individuals from age 1 to age 6, with the highest percentage (95.10%) of younger individuals at 1–2 years old. The sex ratio of males to females was 1.05:1. The equation of the length-weight relationship was W = 0.048*L2.938, and the parameters of von Bertalanffy growth equation were L∞= 32.937 cm, W∞= 1381.010 g, k = 0.131, and t0 = -2.056. The breeding season ranged from March to November, and the minimum sexually mature standard lengths of females and males were 8.7 and 9.0 cm, respectively. Mean absolute fecundity was 3854.38±254.43 eggs, while mean relative fecundity to standard length and body weight were 301.95±16.94 eggs/cm and 60.44±3.56 eggs/g, respectively. These results indicated that the population of C. zillii in Shuikou Reservoir presented characteristics such as a high proportion of young individuals, low growth rate, long spawning season, high fecundity, and smaller size at first maturity compared with the native and other invasive populations. Both opportunistic and equilibrium life-history strategies might have contributed to their successful invasion, and there is a potential risk of further population expansion.

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DOI: 10.3391/ai.2025.20.3.160924

Authors: Xiaolong Huang, Heyun Wang, Songyang Li, Leyang Xu, Zhaoshi Wu, Hu He, Kuanyi Li

Abstract: As global warming continues, increasing minimum winter temperatures may no longer limit the northward expansion of invasive species, particularly those from tropical zones. A mesocosm experiment with a chronosequence approach (space-for-time trade-off) was used to examine the effects of water level variation on the traits of the invasive aquatic plant water hyacinth [Pontederia crassipes (formerly Eichhornia crassipes)] collected from freezing, chilling and warm overwintering locations in China. We hypothesized that the phenotypic plasticity of the plant, particularly its ability to adjust its root morphology and topology in response to vernal water level rise, enhances its capacity to invade freshwater ecosystems. The results revealed significant plasticity in the response of the plants to water level, with plant traits such as total biomass, diaspore number, leaf area, specific leaf area, root length, and photosynthetic efficiency significantly increasing under a 10-cm water level, which can be regarded as a moderate overwintering water level. However, the plants from the warm location did not perform better than did those from the freezing or chilling locations, possibly because the harsh winter conditions reduced plant biomass but did not negatively affect the plants at the gene level. These findings highlight phenotypic plasticity in rooting behavior, which enables plant survival and growth during overwintering in the littoral zone, allowing P. crassipes to withstand low temperatures and to rapidly proliferate during the vernal water rise period. This study highlights the importance of early detection and management strategies to control the spread of P. crassipes, particularly given the trends in global climate change, which may facilitate its northward expansion. The use of P. crassipes as a model plant is recommended for studying the responses of invasive aquatic plants to global change in freshwater ecosystems.

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DOI: 10.3391/ai.2025.20.3.162564

Authors: Efim D. Pavlov, Tran Duc Dien, Ekaterina V. Ganzha

Abstract: Non-native suckermouth armoured catfish Pterygoplichthys spp. have spread extensively across many river systems in Vietnam. It is possible that their expanded distribution occurred through the brackish waters of estuaries and coastal zones, facilitating movement from one river system to another. It has been previously hypothesized that, for successful dispersal through brackish water, armoured catfish can tolerate changes in water salinity and are capable of avoiding high salinity levels that threaten their survival. In this study, we experimentally estimated the movements and the directions of juvenile and adult wild loricariids in fresh and brackish water. Our results showed that juveniles exhibit a circadian rhythm of locomotor activity similar to that of adults. However, juveniles display a more pronounced reaction to increasing water salinity ‒ at 5 PSU ‒ while adults respond at 15 PSU. This likely explains the absence of juveniles in natural brackish water environments and their reduced potential to spread through brackish waters compared to adults. Adult loricariids are likely capable of recognizing and avoiding high-salinity zones (>10 PSU) by increasing locomotor activity, predominantly directed toward the surface. Their ability to grasp air helps maintain positive buoyancy, allowing them to remain in the surface layer of freshwater over extended periods of time. Variability in salinity tolerance among adults (ranging from 2 to 16 hours in 15 PSU) may enable some individuals to be more successful in dispersing through estuaries and along coastlines.

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DOI: 10.3391/ai.2025.20.2.153557

Authors: Wen Xiong, Wei Zhang, Zhen Deng, Peter A. Bowler, Kang Chen, Baoqiang Wang

Abstract: The Yellow River is the second largest river in China and it supports a rich biodiversity and numerous endemic fish species (Atrilinea macrolepis, Brachymystax lenok tsinlingensis, and Hucho taimen). It is one of China’s most important freshwater aquaculture and mariculture regions, and many non-native species have been introduced into the region. This study provided the Yellow River Basin’s first and current list of non-native aquatic species including a total of 112 species comprised of 59 fishes, 27 aquatic plants, 21 Mollusca, three reptiles, one crustacean and one amphibian. The primary introduction pathway is aquaculture (69 species), followed by the aquarium and ornamental trade (30 species), forage (four species), unintentional introductions (four species), ecological restoration (two species), religious releases (two species), and one species for biocontrol. Asia is the primary geographic origin of non-native species (39 species), followed by North America (33 species), South America (16 species), Europe (10 species), Africa (nine species) and Oceania (five species). Many non-native species have become important species in local aquaculture, the aquarium and ornamental trade or for other human uses. Many non-native species have caused significant negative economic, ecological and societal impacts. More research, field investigations and new guiding policies should be applied for the effective control and management of non-native species in the Yellow River Basin.

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DOI: 10.3391/ai.2025.20.1.136400

Authors: Elena K. Kupriyanova, Guillemine Daffe, Samaneh Pazoki, Manal Al-Kandari

Abstract: Spirobranchus tetraceros (Schmarda, 1861), originally described from New South Wales, Australia, was later reported as a widely distributed succesful species of Indo-Pacific origin, including as Lessepsian migrant to the Mediterranean, until evidence has accumulated that the nominal taxon is a large complex of morphologically similar species. Specimens of Spirobranchus cf. tetraceros recently discovered in the Western Mediterranean (Valencia, Spain) morphologically resembled those of S. multicornis from the Red Sea rather than S. tetraceros sensu stricto from Australia. However, genetic studies proved that sequences of the introduced specimens match neither those of the S. tetraceros morphotype from warm temperate Australia (NSW) nor those of S. multicornis from the Red Sea. Subsequently, Kupriyanova et al. (2022) designated a neotype of S. tetraceros from New South Wales supported by DNA sequence data and demonstrated that several species of the S. tetraceros complex exist in Australia alone. This study examined several populations of the S. tetraceros complex world-wide in search of the source population for the Western Mediterranean invader and demonstrated its identity with S. arabicus widely distributed in the Persian (Arabian) Gulf.

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DOI: 10.3391/ai.2025.20.1.131343

Authors: Dan B. Golanski, Alona Nachmias, Gal Kahn, Amir Fireman, Ori Hepner Ucko, Noa Shenkar, Gitai Yahel

Abstract: The rapid increase in the arrival of tropical-origin species into the Levant region has dramatically changed local ecosystems. Non-indigenous species are known for their ability to utilize available ecological niches and in some events expand their non-native niche over time. Here, as an example of such expansion, we report on a massive colonization by the non-indigenous solitary ascidian, Microcosmus exasperatus (Heller, 1878), on soft bottoms along the Mediterranean coast of Israel. While this tropical-origin species is well-known for its ability to form dense aggregations on rocky substrates and artificial structures, only limited reports exist from soft-bottom habitats. In September 2022, a massive settlement of M. exasperatus was sighted on the sandy bottom (15–22 m depth) in front of Mikhmoret, Israel. M. exasperatus had settled on miniature “islets” of hard substrates, such as polychaete tubes, shells, or pebbles. By October, the population had reached a peak density, with a mean of 1.8±1.3 individuals m-2 (±95% confidence interval for the mean). Longshore visual surveys by towed divers revealed similar populations scattered along the central Israeli coast. Monthly compass surveys monitoring the population density, revealed a gradual population decline during late fall and winter, leading to a complete eradication in February 2023, probably due to a severe winter storm. No population was detectable throughout the spring but in August 2023 a few specimens were again detected on the sandy bottom, albeit at densities several orders of magnitude lower than the previous year. It is postulated that the ephemeral colonization of soft-bottom areas serves as “stepping stones” for the species’ dispersal into new habitats, potentially amplifying its invasive potential. Long-term monitoring across a more comprehensive depth range will reveal whether the observed massive colonization was a singular event or a recurring phenomenon that had previously remained unnoticed.

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DOI: 10.3391/ai.2025.20.1.154604

Authors: Amy E. Fowler, Alejandro Bortolus, João Canning-Clode, Tamara B. Robinson, Thomas W. Therriault

Abstract: The Eleventh International Conference on Marine Bioinvasions (ICMB-XI), held May 15–19, 2023, in Baltimore, Maryland, USA, convened 213 attendees from 24 countries to discuss the challenges and advancements in managing marine non-indigenous species (NIS). The conference emphasized the urgent need for international collaboration to address the increasing threats posed by marine bioinvasions, which transcend geopolitical boundaries. Participants explored six key themes through 119 oral presentations, 37 posters, and six keynote speakers, providing a platform for researchers, policymakers, and industry professionals to exchange knowledge and strategies. Notably, ICMB-XI implemented the first Code of Conduct for the Society for the Study of Marine Bioinvasions, promoting inclusivity and ethical scientific discourse. Here, we review articles published in Aquatic Invasions and Management of Biological Invasions based on research presented at ICMB-XI. Studies highlighted novel findings on species settlement dynamics, NIS ecological impacts, and advancements in detection methods such as environmental DNA monitoring. Research also examined the role of climate change in facilitating NIS, the influence of biofouling on NIS establishment, and the expansion of NIS into new ecological niches. Beyond scientific discussions, ICMB-XI celebrated the intersection of art and science through a collaboration with artist April Flanders, whose work communicated the impacts of marine invasions to broader audiences. The conference also provided travel awards and student achievement prizes to support early-career scientists. As ICMB-XI concluded, participants reinforced the need for sustained, large-scale efforts to mitigate marine bioinvasions through enhanced research, policy integration, and cross-sector collaboration. The next ICMB, scheduled for 2025 in Madeira, Portugal, aims to continue advancing the field and fostering international partnerships in marine bioinvasion management.

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DOI: 10.3391/ai.2024.19.4.136332

Authors: Natalia Z. Szydłowska, Marek Let, Pavel Franta, Miloš Buřič, Susanne Worischka, Luise Richter, Bořek Drozd

Abstract: The round goby (Neogobius melanostomus) is a well-known invasive fish. Knowledge of its feeding habits and means of food processing is key in understanding its impact on aquatic food webs. The present study assessed the gut evacuation rate of round gobies feeding on three different types of prey occurring naturally in the diet of this species (small native freshwater clams, an invasive amphipod and chironomid larvae), at two different temperatures (14 and 20 °C) and under different food availability scenarios (continuous and non-continuous feeding). Gut evacuation rates varied significantly between the prey availability scenarios and, specifically, round gobies processed prey significantly faster in the continuous feeding mode when food was regularly available than when fed only once. The highest evacuation rates were detected for individuals fed with clams, in which complete gut clearance was observed within 16 h, compared to within 24 h and 36 h for chironomid larvae and amphipods, respectively. Our study shows that round gobies evacuate chironomid and mollusc prey most rapidly, which suggests that potentially the highest predatory pressure will be exerted on these prey types, assuming that all three prey species are locally present. The slower processing and digestion of amphipods may be due to their bulkier shape, which makes them more difficult to swallow. The relatively high evacuation efficiency of the round goby observed in the continuous feeding mode suggests overall increased pressure on food resources, thereby potentially reducing availability for other consumers and accelerating resource depletion, mainly driven by the high local densities of the round goby populations.

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DOI: 10.3391/ai.2024.19.2.124920

Authors: Nuoxi Wang, Chuyu Luo, Xiaodong Wu, Liang Chen, Xuguang Ge, Cheng Huang, Xiaowen Lin, Shunmei Zhu

Abstract: This study sought to investigate the invasive mechanism of Myriophyllum aquaticum by subjecting it to simulation experiments in varying water temperatures ranging from 0 °C to 30 °C. The results showed that water temperature considerably affected both the growth and reproduction of M. aquaticum. The optimal temperature range for the growth of M. aquaticum was 25‒30 °C. Although the growth of M. aquaticum was inhibited at temperatures between 0‒5 °C, this did not result in mortality. The stem nodes, branches, and diameter reached maximum values over a temperature range of 20‒25 °C. High-temperature stress at 30 °C led to a gradual decrease or disappearance of branches. Compared to the 0 °C, 5 °C, and 30 °C treatment groups, a temperature of 20 °C led to biomass accumulation and significantly higher values. M. aquaticum’s physiological activities were affected by temperature. Except for 10 °C and 15 °C, the catalase activity varied among different water temperatures. M. aquaticum catalase activity was maximal at 5 °C and minimal at 25 °C. Conversely, the synthesis of photosynthetic pigments was highest at 10 °C and 15 °C. The plant’s optimal temperature for growth was between 20 °C and 25 °C. When the temperature was <10 °C, M. aquaticum adapted to the water temperature’s potential damage. This plant has a notable ability to tolerate various temperatures.

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DOI: 10.3391/ai.2024.19.1.117161

Authors: Md Shakhawate Hossain, Surya Gentha Akmal, Miloš Buřič, Jiří Patoka

Abstract: Amazon sailfin catfish are native to Latin Arica (Siluriformes: Loricariidae: Pterygoplichthys) and are popular around the world as ornamental fish. It is well-documented that these species are highly successful invaders and very prone to forming new geographical ranges. However, once established, eradicating a new population is a very challenging task. In Bangladesh, species of the genus Pterygoplichthys are expected to spread widely and have a severe detrimental impact on ecosystem health, biodiversity and economics. Here we provide new information on the future probable establishment of non-native populations of these species in the wild using a climate-matching analysis and highlight their potential area of occurrence. The potential socio-economic consequences are also discussed, as are the public perception of these species and probable economic damages caused. Control of the import of similar species, their culture and intentional or unintentional release into open water is urgently required.

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DOI: 10.3391/ai.2024.19.1.117155

Authors: Uhram Song, Seok Hyeon Oh, Byoung Woo Kim, Seonah Jeong, Hojun Rim

Abstract: Freshwater ecosystems are vulnerable to the invasion of exotic aquatic plant species because of the great likelihood of the introduction of exotic species, and the lack of barriers that block introduced species. Water hyacinth, Pontederia crassipes Mart., is one of the world’s most invasive alien plant species damaging freshwater ecosystems worldwide. Here, we monitored the water hyacinth population on Jeju island, Korea, to assess current invasion risks. Furthermore, we investigated how water hyacinth affects water pH because pH is an important determinant of the distribution of other aquatic plants, and thus a good indicator of aquatic ecosystem health. Water containing water hyacinth had a pH of 5.3, while that with water hyacinth and soil had a pH of 4.8 72 hours after the start of the experiment. Water hyacinth extracts contained shikimic acid, stearic acid, and palmitic acid, which are possible compounds that caused a decline in water pH. Water hyacinth also inhibited the growth of the aquatic plant species, Spirodela polyrhiza and Lemna perpusilla. These results imply that invasion of water hyacinth adversely impacts the abiotic and biotic characteristics of aquatic ecosystems. Moreover, monitoring the water hyacinth population suggests that this invasive aquatic plant overwinters on Jeju island. Therefore, regular monitoring and subsequent control of water hyacinth population can prevent its expansion in the aquatic habitats of Jeju island and the southern region of the Korean peninsula.

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DOI: 10.3391/ai.2024.19.1.113978

Authors: Yaron Tikochinski, Talya Ohana, Uzi Motro, Daniel Golani

Abstract: The Yellowspotted Puffer Torquigener flavimaculosus (Hardy & Randall, 1983) invaded the Mediterranean from the Red Sea via the Suez Canal. In the present study, we analyzed two mitochondrial loci, the cytochrome c oxidase 1 (COI) and the control region (D-loop), from the Mediterranean and the Red Sea populations. Both the COI and the D-loop showed no decrease of genetic variability in the Mediterranean population compared to the source population from the Red Sea. When comparing the genetic variability to two other species of the Tetraodontidae family (Takifugu rubripes and Takifugu obscurus), the mean divergence within the T. flavimaculosus is almost twice as large. T. flavimaculosus has two distinct genetic groups, similarly represented both in the Red Sea and in the Mediterranean, with similar coefficients of differentiation in COI, in D-loop, and, not surprisingly, in the two genes combined. This suggests that T. flavimaculosus has most likely established a sustainable population in the Suez Canal, that has gradually dispersed northward and eventually entered the Mediterranean with a large number of individuals, carrying a great deal of its genetic variability.

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DOI: 10.3391/ai.2024.19.1.115111

Authors: Ningning Chen, Yan Liu, Lin Yuan, Huixian Wu, Junzeng Xue

Abstract: Chthamalus challengeri Hoek, 1883 (Crustacea, Cirripedia) is typically found in the Bohai Sea and Yellow Sea along the coast of China. However, until 2009, it was never seen in the East China Sea. In 2010, C. challengeri was discovered at Yangshan Port in Zhoushan, East China Sea, and it has since been found to invade several islands in the Zhoushan Islands area successfully. Although the population that invaded Yangshan Port has disappeared in recent years, the population that successfully invaded the other islands in Zhoushan has been increasing in density. To study the ecological adaptability of C. challengeri larvae from the Zhoushan Sea Area, we conducted an experiment observing the larvae’s response to different temperatures and salinity gradients. The results indicate that the C. challengeri larvae are highly adaptable to different temperatures and salinities, and under temperatures ranging from 10–25 °C and salinities of 25–35, nauplius can complete all six stages of development and reach a settlement. We found that the survival and settlement rates during larval development were highest at 20 °C and salinity 30, which could be considered the optimum conditions for C. challengeri larvae. At these conditions, it took approximately 11.5 days for the larvae to undergo development from nauplius I to complete settlement. However, lower temperatures slowed down the development rate and settlement of C. challengeri larvae to some extent, while high temperatures can directly lead to the death of C. challengeri. According to the results of this study, the settlement period of C. challengeri in a new habitat can last as long as 7 months (April to November) compared to its original environment. This extended settlement period could provide favorable conditions for the long-distance dispersal of C. challengeri and enhance its invasive ability in new habitats.

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DOI: 10.3391/ai.2023.18.4.113532

Authors: Rami Tsadok, Ziv Zemah-Shamir, Eli Shemesh, Stephane Martinez, Debra Ramon, Itai Kolski, Anat Tsemel, Dan Tchernov

Abstract: As impacts on the Mediterranean Sea are expected to grow in the future, especially with climate change, habitat degradation, and displacement of native species by non-indigenous species (NIS), the investigation of significant alterations to trophic levels in this diverse marine habitat is important. Analysis of stable isotopes from targeted consumers has previously been shown to reliably reflect that of primary producers, thus enabling us to describe and highlight potential shifts in the food web of a particular ecosystem. In this study, we used δ13C values of essential amino acids (AA) in order to examine the dietary composition of established non-native, Lessepsian fish migrants in the Eastern Mediterranean Sea compared to that of the same fish species from their original population in the Gulf of Aqaba, Red Sea. Our data show that a clear variance in carbon isotopic signatures exists in food sources consumed by the same species between the different environments, with the exception of the classic herbivore, Siganus rivulatus (Forsskål & Niebuhr, 1775), whose very similar isotopic patterns reflect the algal source they predominantly consume in both locations. With the results of this research, we propose that Lessepsian fishes with the ability to maintain their nutritional patterns, though not necessarily that of their original food source, will acclimatize better in their new habitat. Consequences of flourishing Lessepsian fish populations include a further tropicalization of the Eastern Mediterranean Sea and the likely restructuring of local food webs.

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DOI: 10.3391/ai.2023.18.4.113911

Authors: Pavel Franta, Radek Gebauer, Lukáš Veselý, Natalia Z. Szydłowska, Bořek Drozd

Abstract: Abundance and per-capita foraging efficiency are essential factors for predicting and quantifying an invasive predator impact on prey, i.e., the impact potential (IP). However, population structure is not included in the calculation, and IP accuracy might be improved by incorporating predator body size. The population structure of the round goby Neogobius melanostomus, a highly invasive predator, was surveyed in the Elbe River. We determined the functional response (FR, per capita foraging) of the three most abundant size classes of N. melanostomus on the water louse Asellus aquaticus. We then calculated the IP for each size class and for the entire population with (the actual impact potential – IPA) and without (the impact potential for limit size rage – IPLSR) population body size structure (based on FR of the medium size class). All three size classes of the predator showed type II FR with respect to A. aquaticus. The estimated FR parameters, attack rate and handling time, as well as the maximum feeding rate, were size dependent. Despite the lowest per capita foraging efficiency, small individuals displayed the highest IP among the tested size classes because of their high abundance. Conversely, medium and large individuals, although showing highest per capita foraging efficiency, displayed lower IP. Hence, IPA showed more precise IP calculations compared to IPLSR. Overestimation of the potential impact as a consequence of omitting predator population size structure was negligible at the investigated locality. The IP of the N. melanostomus population five years post-invasion can be accurately calculated based on the FR of medium-sized fish.

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DOI: 10.3391/ai.2023.18.3.104066

Authors: Efim D. Pavlov, Tran Duc Dien, Ekaterina V. Ganzha

Abstract: 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.

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DOI: 10.3391/ai.2023.18.3.104556

Authors: Sungtae Kim, Cheol Yu, Jennifer Ruesink, Jae-Sang Hong

Abstract: Smooth cordgrass (Spartina alterniflora Loisel.), an aggressive non-native species worldwide, colonized tidal flats on the west coast of Korea in two regions differing in tidal amplitude between 1990–2004. By the time of our study in 2015, expansion had occurred both clonally and through formation of new patches, providing an opportunity to determine intertidal range, which is a key component of understanding the threat posed by S. alterniflora through competition with native halophytes or transformation of unstructured mudflat. At Ganghwa (5.69 m tidal range), S. alterniflora ranged from 3.52 to 1.34 m above Mean Sea Level (MSL). At Jindo (2.02 m tidal range), S. alterniflora ranged from 1.57 to -0.18 m relative to MSL. Thus, a wider absolute intertidal range was occupied by S. alterniflora at the megatidal vs mesotidal region, but the lower limit of S. alterniflora did not extend below MSL under megatidal conditions, a pattern that now appears to emerge consistently in both the native and introduced range. In both study regions, S. alterniflora occurred at the same elevations as other salt marsh plants, occupying an upper zone with Phragmites australis (non-native) and middle zone with several native species including Suaeda japonica. S. alterniflora occurred below native marsh vegetation at all sites, which would result in transformation of the extensive mudflats along the Korean coast.

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DOI: 10.3391/ai.2023.18.2.105548

Authors: Christine Ewers, Monika Normant-Saremba, Heleen Keirsebelik, Jonas Schoelynck

Abstract: The geographic expansion and abundance fluctuations of invasive species offer unprecedented insights to investigate potential mechanisms underlying the distribution-abundance relationship, one of the most universal patterns in community ecology. However, the abundance of invasive species is rarely documented in the needed detail. Data from historical records, scientific and popular literature, citizen science and expert interviews were synthesized to obtain insights into the long-term expansion and abundance cycles of the Chinese mitten crab, one of the world’s 100 worst invasive species. Thus for the first time, global long-term data on population size fluctuations have been correlated with the global spatiotemporal invasion history of a non-native species. Geographic expansions and increases in abundance co-occurred in the 1930s and again since the 1990s in agreement with the distribution-abundance relationship. Furthermore, a regional case study for the German river Elbe indicates that increases in abundance may be driven by improved riverine water quality and rising sea surface temperatures. Environmental restoration and climate change therefore benefit this invasive species, and could lead to further geographic expansion and increases in abundance.

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DOI: 10.3391/ai.2023.18.1.103610

Authors: Wen Xiong, Dong Xie, Qiang Wang, Hui Wang, Zhigang Wu, Heying Sun, Tao Li, Peter A. Bowler

Abstract: Poyang Lake is the largest freshwater lake in China and sustains a high level of biodiversity in the mid-reach area of the Yangtze River watershed. Poyang Lake is also one of the most important aquaculture regions in China, and a great number of non-native species have been introduced into it. We present a current and well-documented list of the non-native species of plants, molluscs, crustaceans, fishes, reptiles, and amphibians currently found in Lake. We found that there are 103 non-native species (83 vascular plants, 12 fishes, three crustacea, two molluscs, two reptiles and one amphibian) that have invaded Poyang Lake Basin, of which 96 non-native species were introduced after 2000. The invasion rate of non-native species reached 4.36 species year-1, which is the highest invasion rate recorded in freshwater ecosystems. The primary pathways of introduction are through the ornamental trade and unintentional escapes (30 species each, respectively), followed by food (19), aquaculture (15), forage grass (four), medicinal and oil (two, respectively), and biocontrol (one). The origins of non-native species are North America (29.12%), Asia (25.24%), South America (20.38%), Africa (18.44%), Europe (5.82%) and Oceania (0.97%). Many non-native species provide significant support for the rapid development of the local economy (such as aquaculture). However, many non-native species pose a great threat to local biodiversity and societal development. More studies that include monitoring and the development of strategies for managing and eliminating non-native species in Poyang Lake are needed.

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DOI: 10.3391/ai.2023.18.1.103301

Authors: Tuantong Jutagate, Wachira Kwangkhwang, Samnao Saowakoon

Abstract: The Australian red-claw crayfish (RCC) Cherax quadricarinatus (von Martens 1868) (Crustacea: Decapoda: Parastacidae) has been introduced and promoted for freshwater aquaculture in many countries including Thailand. This study i) evaluates the growth performance of RCC in near-natural conditions relative to captive conditions and ii) investigates how successfully RCC can compete with a trophically and functionally analogous native species. Growth of RCC was compared among two aquaculture systems (concrete tank and earthen pond) and a treatment with simulated natural conditions. After 12 months of rearing, total length and weight were greatest in the earthen pond and poorest in the near-natural treatment, with significant differences in total length between the near-natural treatment and the two culture systems. Length-weight relationships showed that the RCC had positive allometry in the culture systems but negative allometry in the near-natural treatment. Competition was evaluated by means of a biotic resistance test and an additive–substitutive experiment between RCC and the native freshwater crab Esanthelphusa dugasti (Rathbun, 1902) (Crustacea: Decapoda: Gecarcinucidae). Specific growth rates after 90 days of the experiments suggest that the crab inhibited growth of RCC. This implies that the invasion of RCC in Thai waters could be limited by competition from resident freshwater crabs.

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