Non-native Fish Research Articles

Can the introduction of non-native fish induce variation in life-history traits of a native species in a neotropical lake?

Top predator fish, such as peacock bass (Cichla kelberi) and red-bellied piranha (Pygocentrus nattereri), were introduced in the lacustrine system of the Rio Doce basin and these introductions are associated with loss of aquatic biodiversity. The present work aims to investigate the life-history traits of a native species, thraira (Hoplias malabaricus), in the context of the pressures caused by the introduction of top predator fishes. Two lakes were selected in a conservation unit Doce River State Park (PERD), namely, Lake Carioca, where P. nattereri and C. kelberi were introduced, and Lake Gambazinho, where H. malabaricus occurs in the absence of introduced fish. In total, 146 specimens of H. malabaricus were caught, including 95 in Lake Gambazinho and 51 in Lake Carioca. Significant differences were found in the length–weight relationship (LWR) in the diet, the reproductive period, the vitellogenic follicle size, and the gonadosomatic index (GSI). In the lake with introduced species, thrairas showed allometric growth, a less diversified diet, longer duration of the reproductive period, and high GSI values compared with the control lake. The results indicated that the life-history traits of thrairas can be influenced by the environmental modification caused by the introduction of non-native peacock bass and red-bellied piranha.

More non-native fish species than natives, and an invasion of Malawi cichlids, in ancient Lake Poso, Sulawesi, Indonesia

More non-native fish species than natives, and an invasion of Malawi cichlids, in ancient Lake Poso, Sulawesi, Indonesia

城镇化背景下深圳典型流域鱼类群落特征及驱动因子研究

PDF HTML阅读 XML下载 导出引用 引用提醒 城镇化背景下深圳典型流域鱼类群落特征及驱动因子 DOI: 10.5846/stxb202106071510 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 深圳市主要河流水生态监测与评价项目（2019-07-233） Characteristics of fish communities and driving factors under urbanization in typical river basins in Shenzhen City, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:理解城镇的快速发展对河流鱼类群落结构的影响，是城镇河流科学管理和生物多样性保护的关键基础。研究于2019年丰水期（8月）和枯水期（11月），选取我国城镇化典型城市-深圳域内两个处于不同城镇化程度的代表性流域，应用多重统计方法比较分析了流域间鱼类群落结构的差异，并探讨了驱动鱼类群落变异的关键环境要素。结果发现，城镇化程度高的观澜河流域其鱼类种类组成、优势类群、生物多样性指数与城镇化程度低的坪山河流域有明显差别。具体表现为：城镇化程度高的流域土著敏感种类如异鱲、吸鳅等几近消失，优势类群为外来入侵耐受种类，其物种多样性显著低于城镇化程度低的流域（P<0.05）。同时，外来鱼类在城镇河段其数量占比平均达92.5%，广泛分布于深圳城镇河流中。在环境因素方面，城镇化程度高的观澜河流域水体理化指标总氮、总磷、氨氮、化学需氧量、生化需氧量、高锰酸盐指数均显著性高于城镇化程度低的坪山河流域（P<0.05）。基于Bray-Curtis距离的冗余分析显示：城镇用地占比和总氮是影响观澜河和坪山河流域鱼类群落差异的主要因素。城镇化进程中河流生境的改变已影响到土著鱼类的生物多样性。因此，推动以恢复土著鱼类生物多样性的河流生态治理与保护是今后水生态目标管理的重要方向。 Abstract:Understanding impacts of rapid urbanization on structure of river fish communities is the key basis for scientific management and biodiversity conservation for urban rivers. We selected two representative basins with different degrees of urbanization in the typical urbanized city, Shenzhen City, China. Field sampling was conducted in both wet (August) and dry (November) seasons in 2019. We compared and analyzed the differences of fish communities between the two basins using the multiple statistical methods, and explored the key environmental factors driving the variations of fish communities. Results showed that species composition, dominant species, and biodiversity of fish in the highly urbanized Guanlan River Basin were significantly different from those in the less urbanized Pingshan River Basin. In particular, the sensitively indigenous fish species such as Schistura fasciolatus and Parazacco spilurus disappeared while the invasive tolerant species were the dominant species in the highly urbanized basin. Fish biodiversity was significantly lower in the highly urbanized basin than the less urbanized basin (P<0.05). Meanwhile, non-native fish species had spread rapidly in urbanized rivers of Shenzhen City, which accounted for more than an average of 92.5% in the urbanized river sites. For environmental factors, total nitrogen, total phosphorus, ammonia, chemical oxygen demand, biochemical oxygen demand, and permanganate index in the highly urbanized Guanlan River Basin were significantly higher than those of the less urbanized Pingshan River Basin (P<0.05). Redundancy analysis based on the Bray-Curtis distance showed that the proportion of urban land and total nitrogen were the main factors affected the difference of fish communities in the Guanlan and Pingshan River Basins. Changes of river habitat from urbanization reduced biodiversity of the native fishes. Thus, restoring native fish biodiversity in river ecological management and protection is the important direction of aquatic objective-based management. 参考文献 相似文献 引证文献

Aqui vem o grande “jaú” Zungaro jahu (Ihering 1898) (Teleostei, Pimelodidae): um novo caso alarmante de introdução de peixes em uma ecorregião neotropical com alto endemismo

Abstract: Aim Non-native fish species have been closely related to serious damage to aquatic biodiversity due to their negative effects on native fauna. We aim to report the first and alarming occurrence of the non-native catfish “jaú” Zungaro jahu in the Iguaçu River basin above the Iguaçu Falls, a high-endemism Neotropical ecoregion for fish. Methods Fish samplings were taken with a bottom gill net in the Segredo Reservoir, where they were anesthetized in benzocaine hydrochloride and fixed in formaldehyde in the field, later identified in the laboratory and housed at the Museu de História Natural do Capão da Imbuia (MHNCI). Results Our recent samplings in the Iguaçu River basin recorded one non-native individual of the catfish “jaú” Zungaro jahu in the Segredo Reservoir. Conclusions We mainly intend to alarm about the risk of expansion of the occurrence of this non-native species throughout the cascading reservoirs in the Iguaçu River where it could potentially develop serious damage to the trophic chain, predation of small-sized endemic species, and competition, especially in the sites where the endemic and endangered pimelodid “surubim-do-iguaçu” (Steindachneridion melanodermatum) maintains viable populations, currently restricted to the Lower Iguaçu River basin exhibiting recent signs of a population bottleneck.

Diversity of Freshwater Fish in Fragmented Forest of Wilmar Oil Palm Plantation, Miri, Sarawak

The study was conducted in the river system located at Wilmar oil palm plantation in Miri, Sarawak. The objective of the study is to determine the fish species diversity and composition in the streams and rivers in the oil palm plantations. Fish were sampled using a variety of fishing methods, including, scoop nets, cast net, and gill nets of different mesh sizes (1.0, 1.5, 2.0, 2.5, 3.75 and 4.0 cm) from 2 to 7 of February 2014. A total of 326 individual fish including 32 species of native fishes and one species of non-native fish from 19 genera, seven families and five orders were collected from seven locations. The cyprinid fish represented 62.20% of the total fish caught and was found in all the rivers surveyed. About six endemic species in Borneo such as Barbonymus collingwoodii, Barbodes banksi, Barbodes sealei, Hampala bimaculata Nematabramis borneensis and Nematabramis everetti were identified. However, only one species from families Bagridae, Balitoridae, Clariidae, and Hemiramphidae was sampled from the study sites. The higher fish species composition found in streams and rivers of the oil palm plantation landscapes could be attributed to the conservation of some areas of the plantation as high conservation value forest (HCVF) status, which have provided suitable habitat for fish species within the plantation aquatic environments.

Seasonal movement patterns and habitat use of sub-adult Striped Bass Morone saxatilis in a highly managed and tidally influenced Pacific Coast Watershed

Purposely introduced in 1879, Pacific coast Striped Bass Morone saxatilis once supported a commercial fishery and currently supports a recreational fishery in the San Francisco Estuary Watershed, CA, USA; however, the population has been in decline for decades. Since little is known about sub-adult behavior on the Pacific coast, we used acoustic telemetry to investigate seasonal movement patterns and habitat use across three regions (bay, delta, and river) and the effects of temperature and salinity on habitat use over a 2-year period. Sub-adult movement and habitat use differed by year and age. In spring, age-I and age-II sub-adults moved within the delta (60%), river (20%), and bay (20%) regions, and by summer, some individuals moved to the bay (36%), while others remained in the delta (42%) and river (22%). Fall and winter showed equal movement between the bay and delta regions. During year 2, age-II and age-III fish inhabited the bay region across all seasons with the exception of spring when a few individuals migrated up river. Generally, sub-adults did not inhabit the river region in fall or winter. Sub-adults were not detected in water temperatures < 10 °C and occurred most often in 20–25 °C. Younger sub-adults inhabited limnetic habitat where older fish inhabited mesohaline and polyhaline habitats. Our findings suggest that sub-adult seasonal movement patterns and habitat use hotspots have important fishery management implications and can be useful to address concerns over how this non-native fish’s predation impacts native and endangered fishes.

Decline in Thermal Habitat Conditions for the Endangered Delta Smelt as Seen from Landsat Satellites (1985-2019).

This study uses Landsat 5, 7, and 8 level 2 collection 2 surface temperature to examine habitat suitability conditions spanning 1985-2019, relative to the thermal tolerance of the endemic and endangered delta smelt (Hypomesus transpacificus) and two non-native fish, the largemouth bass (Micropterus salmoides) and Mississippi silverside (Menidia beryllina) in the upper San Francisco Estuary. This product was validated using thermal radiometer data collected from 2008 to 2019 from a validation site on a platform in the Salton Sea (RMSE = 0.78 °C, r = 0.99, R2 = 0.99, p < 0.01, and n = 237). Thermally unsuitable habitat, indicated by annual maximum water surface temperatures exceeding critical thermal maximum temperatures for each species, increased by 1.5 km2 yr-1 for the delta smelt with an inverse relationship to the delta smelt abundance index from the California Department of Fish and Wildlife (r = -0.44, R2 = 0.2, p < 0.01). Quantile and Theil-Sen regression showed that the delta smelt are unable to thrive when the thermally unsuitable habitat exceeds 107 km2. A habitat unsuitable for the delta smelt but survivable for the non-natives is expanding by 0.82 km2 yr-1. Warming waters in the San Francisco Estuary are reducing the available habitat for the delta smelt.

Evaluating establishment success of non-native fishes introduced to inland aquatic habitats of tropical Pacific islands

An information-theoretic approach was used to evaluate non-native freshwater fish species introduced to insular habitats of Hawaii and Guam comparing successful establishments vs. failures. Since the late 1800s, as many as 81 non-native freshwater fish species have been recorded as introduced to Hawaii and Guam (combined) and 50 (62%) of these are documented as having one or more established populations. We examined eleven independent variables to investigate establishment success by creating 21 a priori logistic regression models ranked using Akaike's Information Criterion adjusted for small sample size. An additional eight post-hoc models were included that comprised the best a priori model and various combinations of individual variables. The best overall model of establishment probability included effects of taxonomic affinity (family membership), prior establishment success on other tropical islands, and hypoxia tolerance. Establishment success in Hawaii and Guam was highest for those species established on many other islands, and according to our best model air-breathing fishes were more likely to become established. Six fish families, each with from three to 18 species introduced to Pacific islands, were highly successful at establishment: Cichlidae (16 established of 18 species introduced), Poeciliidae (seven of eight), Cyprinidae (four of seven), Centrarchidae (four of four), Clariidae (three of three), and Loricariidae (three of four). Those that successfully established include both small and moderately large-bodied taxa, while representing a diverse array of other morphological and life-history traits. Pathways and motives associated with fish introductions in the Pacific have been linked to desires to develop aquaculture, enhance wild stocks of food, sport, and bait fishes, for use as biological control agents, or are linked to the ornamental fish trade. We found that many established species were introduced via multiple pathways (up to eight) and our analyses suggest that the combination of prior establishment success on other tropical islands and presence of non-native fishes in multiple pathways was indicative of high propagule pressure. Our study results and conclusions on Pacific tropical island introductions are in general agreement with previous studies on non-native freshwater fishes in other regions of the world and similar to observations in continental ecosystems and temperate zones.

Behavioral Interactions between a Native and an Invasive Fish Species in a Thermally Heterogeneous Experimental Chamber

Mechanisms of the displacement of native fish by nonnative fish can include agonistic behaviors that push native fish species out of their preferred habitat, including their thermal optima. To examine these interactions, we built an experimental thermal preference chamber to evaluate: (1) the thermal preference of native, glacial relict northern redbelly dace Chrosomus eos; (2) if the thermal preference and movement changed in the presence of the invasive western mosquitofish Gambusia affinis; and (3) the direction of agonistic interactions. We hypothesized that G. affinis would express agonistic behavior toward C. eos, because G. affinis is widely recognized as an aggressive invader. Given the temperature range of the experimental chamber, i.e., 20–30 °C, C. eos selected an average of 24.3 °C as its thermal preference. After G. affinis’ introduction, the thermal preference of C. eos increased by 1.7 °C and the movement, given by distance (cm) travelled, increased by 21%. Contrary to our prediction, more agonistic interactions were observed in C. eos toward G. affinis. These results indicate that agonistic behavior of G. affinis toward native fish species may be species- and condition-specific, and may not always be the primary mechanism of native species’ displacement. Biological invasions are a global issue and altered thermal regimes are expected to continue. This study provided the novel approach using of a thermally heterogeneous thermal chamber to examine thermal preferences and aggressive interactions between a native and an invasive species. Future research should examine other life history traits that may be conveying the competitive advantage to G. affinis.

Non-Indigenous Parasites of Fish in Inland Waters of Croatia

AbstractNon-indigenous parasite fauna of freshwater fish has not been studied extensively in Croatia, despite the long history of introductions and translocations of alien fish species into inland waters. Negative implications for aquaculture production and wild native fish species have been frequently associated with the introduction of non-native parasite species. Hence, the present paper attempts to lay out a historical overview of the suspected localities, time frames and pathways of introduction for non-indigenous fish parasites into inland waters of Croatia, therefore producing a list of species. In total, 16 non-native fish parasites have been recorded in inland waters of Croatia, aquaculture establishments being identified as initial points of introduction. However, a paucity of information exists on the overall prevalence of infection as well as the economic impact on aquaculture production. In addition, limited information is available about the presence and potential ecological impact of non-indigenous parasites on endemic fish fauna in areas of high biodiversity, such as the water bodies of the Adriatic Sea Basin. Therefore, there is an urgent need and opportunity for multidisciplinary cooperation between different stakeholders, including government, scientists, in both biological and veterinary disciplines, and the industry, with the aim of extensive surveys to determine the potential impact on aquaculture production and wild fish population of high conservation value.

Non-native gobies share predominantly immature parasites with local fish hosts

Non-native species are known to escape their parasites following introduction into a new range, but they also often acquire local parasites as a function of time since establishment. We compared the parasite faunas of five non-native Ponto-Caspian gobies (Gobiidae) and local fish species (Perca fluviatilis, Gymnocephalus cernua, Gobio gobio) in three European river systems; the Rivers Rhine, Vistula and Morava, where Ponto-Caspian gobies were introduced 4-13 years prior to the study. Overall parasite species richness was considerably lower in non-native gobies compared to local fish species, and the same result was found at the component and infra-community levels. Both parasite abundance and diversity greatly varied among the regions, with the highest values found in the River Vistula (Wloclawski Reservoir), compared to a relatively impoverished parasite fauna in the River Morava (Danube basin). While only half of parasite species found in local hosts were acquired by non-native gobies, most of the parasites found in gobies were shared with local fish species related either phylogenetically (percids) or ecologically (benthic gudgeon), including the co-introduced monogenean Gyrodactylus proterorhini. As a result, similarity in parasite communities strongly reflected regional affiliation, while phylogenetic distances between fish host species did not play a significant role in parasite community composition. In accordance with other studies, all parasites acquired by gobies in their new range were generalists, all of them infecting fish at the larval/subadult stage, indicating the possible importance of gobies in the life cycle of euryxenous parasites. The absence of adult generalists, particularly ectoparasites with low host specificity, in non-native fish may reflect their generally low abundance in the environment, while an absence of adult endoparasitic generalists was probably related to other factors.

Dietary flexibility of Wood Storks in response to human-induced rapid environmental change

Human-induced rapid environmental change (HIREC) has altered landscape processes and negatively impacted many species globally. Some of the most dramatic changes have been in wetlands where flows have been disrupted, and new wetlands have been created to retain runoff. In response to disrupted natural wetland conditions, Wood Stork (Mycteria americana) populations in South Florida have significantly declined over the past several decades. Despite the well-documented sensitivity of Wood Storks to natural wetland conditions, Wood Storks are often observed foraging in roadside created wetlands; however, the availability of prey in created wetlands is currently unknown. We sampled natural and created wetlands to determine aquatic fauna available for foraging Wood Storks. To determine prey use, we collected food boluses from Wood Storks in both natural wetland and urban landscapes. Historical studies found nonnative fish were absent in Wood Stork diet prior to the dominance of created wetlands in the landscape; however, we found nonnative fish frequently in both created wetlands and boluses. Furthermore, urban nesting Wood Storks consumed large-bodied prey species that were more characteristic of created wetlands whereas Wood Storks nesting in natural wetlands consumed large-bodied prey more characteristic of natural wetlands. Overall, Wood Storks consumed prey that were more similar to the fish community in created wetlands than those in natural wetlands. These dietary patterns suggest that Wood Storks have behavioral plasticity in both foraging habitat and prey use to cope with HIREC. Conservation efforts for species existing in both natural and urban habitats should consider the importance of novel prey and foraging habitats, as they may assist in sustaining populations in a rapidly changing world.

A 40-year perspective of an alpine lake: Is everything the same?

Mountain lakes are the most affected by climate change; however, few of these lakes are regularly sampled because of their remoteness. We discussed limnological data (e.g. water temperature, light transparency, and plankton diversity) of Lake Campo (1944 m above sea level, Adamello Mountains, Italy) scattered over almost forty years in the light of climate change. Specifically, occasional samplings in 1980, 1988, 2016, 2017, and 2018 and more extensive surveys in 1997 and 2015 were carried out. Among the investigated years, 2015 was the warmest. Inter-year variability in water temperature was quite marked in Lake Campo. Water temperature profiles of July (1980, 1997, 2015) showed increased surface warming, while the deeper layers (> 15 m) were always isothermal at around 5 °C. Hypolimnetic dissolved oxygen never decreased below 50 % saturation. Secchi disk depth was not substantially different among years. Summer profiles of light transparency showed discontinuous light attenuation, which was tentatively attributed to algae located in deeper layers. In cluster analysis of phytoplankton and zooplankton data, differences between seasons but not years were found. The autumn decline of Bacillariophyta and the increase of mixotrophic Cryptophyta was linked to decreasing silica concentrations towards autumn. Apart from this general pattern, several observations (e.g. high abundance of Tovellia sanguinea, requiring warmer temperatures and thermal stratification to compete with Bacillariophyta; a spatially extended metalimnetic oxygen maximum in July 2015) showed the effects of particularly warm conditions of 2015 compared to 1997. The continuous presence of crustacean males and first generation of rotifers (Polyarthra f. aptera) hatching from sexual eggs indicated the importance of sexual reproduction in the lake. Length measurements of Daphnia gr. longispina before (1997) and after (2015) non-native fish removal and Arctic char introduction were similar and indicated no apparent change in predation pressure. Studies like this, despite scattered data, can provide valuable insights into the changes mountain lakes undergo through time.

Can Plants Be Engineers?

When we think of engineers, we think of making a machine, like a car. Are there engineers for ecosystems? When an organism can make big changes to its environment, we call it an ecosystem engineer. In aquatic ecosystems like the San Francisco Estuary, underwater plants can be important ecosystem engineers because they can change water flow and water clarity. In the Estuary, a plant called Brazilian waterweed, which was introduced by humans, is one of the most important ecosystem engineers. With its leaves and stems, this plant traps tiny particles floating in the water, making the water clearer. Clearer water has made it easier for more plants to grow and these changes helped some non-native fish species to increase in number, while some native species declined. Introduction of Brazilian waterweed has led to an entirely different ecosystem, which has also affected how people use and take care of the Estuary.

Patterns and drivers of native, non-native, and at-risk freshwater fish richness in Canada

Understanding the relative roles of the historical, environmental, and anthropogenic processes underlying spatial biodiversity patterns is crucial to predict the impacts of global environmental changes. We quantified the relative roles of these factors in influencing species richness of total, native, non-native, and at-risk freshwater fishes in 985 tertiary watersheds across Canada while accounting for correlations among descriptors and spatial autocorrelation. Our findings indicate differences in factors influencing richness patterns among species categories. Environmental factors related to energy availability and historical factors related to post-glacial recolonization both played roles in shaping spatial variation in native species richness. In contrast, variation in non-native species richness was largely related to human activities increasing propagule pressure and habitat disturbance, which were greater for foreign species (i.e., not native to Canada) than for translocated native species. Anthropogenic processes and environmental conditions were both important determinants of at-risk species richness. Our study emphasizes the importance of an integrated approach that simultaneously considers natural and anthropogenic processes to better predict the fish biodiversity change at the landscape scale.

Predicting successful reproduction and establishment of non-native freshwater fish in peninsular Florida using life history traits

Identification of factors that facilitate successful completion of invasion process stages by nonnative species is a major priority among invasion biologists. Stage-based analyses of non-native fish species traits have been conducted for several regions, but not for a subtropical non-native species hotspot like peninsular Florida. Typically, establishment is the first stage of analysis but Florida is home to many nonnative fish species that have successfully reproduced, yet failed to establish. Therefore, we used life history traits and three model types (categorical and regression trees, logistic regression, and discriminant analysis) to predict successful reproduction and establishment by non-native fishes in peninsular Florida. Statistical models for predicting both successful reproduction and establishment suggested parental care was the most important variable, but other traits included in the best models differ between the two stages. The high level of parental care in successful non-native fishes of Florida is unique among non-native freshwater fish faunas across the United States. Other studies also found that suites of traits used to predict various stages of the invasion process differ, suggesting that stage-based analyses provide a good foundation for better understanding invasion processes. Our results may be applied to stage-based risk screening tools for nonnative fishes in Florida.

Aggressive interactions and consistency of dominance hierarchies of the native and nonnative cichlid fishes of the Balsas basin.

Dominance hierarchies are generally established based on the levels of aggressiveness that animals present. Frequently, animals fight to establish a dominance hierarchy and obtain a disputed resource. The Mexican mojarra Cichlasoma istlanum is a native species of the Balsas river basin and coexists there with four nonnative cichlids: tilapia Oreochromis sp., convict cichlid Amatitlania nigrofasciata, spotcheek cichlid Thorichthys maculipinnis, and green terror Andinoacara rivulatus. These five cichlid species compete for spaces for reproduction, feeding, and shelter and frequently engage in aggressive interactions to obtain these resources. We quantified dominance indices to evaluate the hierarchical structure of dominance among these five cichlids and the duration of aggressive behaviors of the Mexican mojarra during experimental contests between the native species and each of the four nonnative species. The Mexican mojarra was consistently dominant over the other four cichlid species, performing a larger number of aggressive behaviors and investing more time in attacking than the nonnative cichlids, which resulted in a higher hierarchical position. Our results show that the native fish, Mexican mojarra, established dominance over all four nonnative cichlid fish of the Balsas basin. Thus, the establishment of nonnative cichlid species in the Balsas basin is likely associated with factors other than behavioral dominance.

Ecological and biological traits of non-native freshwater fish species differentiate them from native species in China

China’s freshwater ecosystems are gradually invaded by an increasing number of non-native fish species. However, to date, some controversy about the number of native and non-native freshwater fish species in wild habitats and very limited information on ecological or biological traits mediating fish introduction success at a national scale have prevented the proposal and implementation of targeted conservation and management strategies. To address these urgent issues, first we compiled an up-to-date inventory of 1,797 fish species (1,597, 84, and 116 native, exotic (originating from outside China), and translocated (originating from within China) species, respectively) along with 13 traits encompassing various ecological and life-history strategies for each species, which is the most comprehensive freshwater fish database in China as we know. Here, we found that non-native species mainly belonged to three orders (Perciformes, Siluriformes, and Cypriniformes) and three families (Cichlidae, Cyprinidae, and Salmonidae). Native species were significantly (P < 0.001) different from both exotic and translocated species according to their quantitative traits, while no remarkable differences between exotic and translocated species were detected (P = 0.93). Specifically, G-tests of independence, Similarity Percentage Analysis (SIMPER), and Mann-Whitney-Wilcoxon rank sum tests showed that compared to native species, species with relatively higher vulnerability (intrinsic vulnerability of fishes to fishing), trophic level, and pectoral fin vertical position, but less resilience and lateral body shape were deemed as potential candidates for introduction and dispersal in China.

Does aquaculture aggravate exotic fish invasions in the rivers of southern China?

Human-induced fish introduction in aquaculture always be considered the most important driver of biological invasions in freshwater ecosystems, yet most introduced species fail to establish though having great economic benefits. Explaining the varying success of introduced fish species is a central question both in invasion biology and aquaculture management. Southern China is a good region to test the invasion hypotheses where lots of non-native fish species were cultured and invaded. In this study, we used four human activities related to aquaculture to test their effects on the establishment of non-native fish species in the rivers of southern China. Our results showed that: open-water aquaculture significantly increased the establishment probabilities of non-native species relative to standardised aquaculture in ponds; the establishment and spread of non-native fish species in rivers had no significant correlation to their production and distribution in standardised aquaculture; non-native fish species with low economic value were more prone to escape and establishment in natural rivers, and had higher establishment probabilities in rivers due to the lower fishing pressure. These results indicate that standardised aquaculture and cultivated species with high economic value do not always result in biological invasions. To mitigate the invasion of exotic species caused by aquaculture, stricter management practices and more optimized economic assessments should be implemented for the introduction and cultivation of non-native fish species.

TROPHIC INTERACTIONS OF THE FISH COMMUNITIES IN CIRATA RESERVOIR, WEST JAVA

The utilization of food resources by the fish communities in the Cirata Reservoir depends on the environmental conditions of the reservoir. Eutrophication and the presence of potentially invasive alien fishes could affect the trophic interactions of food utilization by the fish communities in the Cirata reservoir. This study aimed to analyze the trophic interactions of the fish communities in the Cirata Reservoir, West Java. The samplings were conducted in October, December 2018, and April 2019. The fish samples were collected using experimental gill nets with different mesh sizes. The stomach contents were dissected to study their food habits under a stereoscopic microscope. Data analysis was performed using the index of preponderance, niche breadth, trophic level, and index Schoener. A total of 21 species of fishes in the Cirata Reservoir utilized food resources, including phytoplankton, zooplankton, aquatic plants/macrophytes, molluscs, insects (adult and larvae), worms, a body part of fishes and crustaceans, pellets and detritus. The fish communities had a wide range of niche between 0.00-0.32 and trophic levels between 2.00-3.63. The non-native fishes in the Cirata Reservoir had the food overlapping potential with native fishes, from low to high categories, especially from the Cichlidae. Trophic interaction of fish communities in the Cirata reservoir was still relatively stable, characterized by overlapping food niche in the low to medium categories. The fish stock enhancement effort such as fish introduction or restocking in the Cirata Reservoir could still be carried out with a precautionary approach to filling empty niches and avoiding the potential for invasive alien fish species.