Exotic Freshwater Fish Research Articles

Relative importance of exotic species traits in determining invasiveness across levels of establishment: Example of freshwater fish

Abstract Understanding the factors responsible for the success of exotic species is a prevalent issue in invasion biology. Although the ecological traits of exotic species are known to play a major role, it is still unknown which traits are responsible for the different dimensions of invasiveness among vertebrates. Here, we assessed the ecological, morphological and behavioural profile of 222 exotic freshwater fish along different levels of establishment, defined by the number of basins in which the exotic species are established and the location of establishment. Using a trait‐based multidimensional space complemented by a trait‐by‐trait analysis, we attempted to classified exotic vertebrates given their intrinsic traits across establishment levels ranging from species with low establishment to super‐established species. We found that fish with low establishment were clustered in the trait space, showing similar traits characterized by low‐temperature amplitude, no parental care and zoobenthic diet. By contrast, super‐established fish had a broader range of functional strategies, with a high proportion of species having multiple diets and a high level of parental care. Overall, fish with low establishment had low functional overlap with other fish at higher levels of establishment. Our findings highlight the importance of considering trait variability in the species' level of establishment to more accurately anticipate their ability to establish and spread. Read the free Plain Language Summary for this article on the Journal blog.

Variation over Time of Length–Weight Relationships and Condition Factors for Four Exotic Fish Species from a Restored Shallow Lake in NE Iberian Peninsula

Length–weight relationships (LWRs), condition factors, and their variation over time were analyzed for four exotic freshwater fish (bleak, common carp, pikeperch, and roach) in the Estany d’Ivars i Vila-sana shallow lake in Catalonia, Northern Spain. Fish samples were collected twice a year (early summer and autumn), between 2008 and 2016, by using between three and five multi-mesh nylon gillnets. This study provides novel information about four common exotic fishes outside of their natural range and within the context of a restored shallow lake, where the ichthyologic community is evolving in concordance with the ecosystem conditions and the fish community dynamics.

Partial decoupling between exotic fish and habitat constraints remains evident in late invasion stages

We investigated the relationships between exotic freshwater fish invasions, environmental factors and ecofunctional diversity (i.e. the combination of ecological traits in communities) in streams. We used data from 335 stream sites, belonging to 105 watersheds and 3 basins in Italy, to test whether the exotic species invasion was dominated by species with generalist traits and whether the environment-ecofunctional trait relationships of exotic and native species would differ from each other. We also tested the hypothesis that ecofunctional uniqueness patterns between exotic and native species would be substantially different. We found that generalist traits were widespread in nearly all areas where exotic species occurred, but not all generalist traits were equally abundant in exotic communities. Only temperature tolerant, low oxygen tolerant and eurytopic traits were typically more dominant in exotic communities than native ones, suggesting that not all generalist traits are equally important in the invasion process and that more complex mechanisms of trait selection could take place. Environment-ecofunctional trait relationships of exotic and native species partly differed both in direction and magnitude, suggesting that invasion dynamics could decouple the linkage between environment and biotic communities, but also that this decoupling might decrease at later invasion stages (i.e. > 30 years after major invasions). Finally, site and trait ecofunctional uniqueness differed between exotic and native species. Exotic species ecofunctional diversity hotspots were located in human-disturbed areas, suggesting that human disturbance might play a strong role in invasion patterns. We advocate for a wider use of ecofunctional approaches in conservation studies in the future, as they could be a key to understand complex ecological processes such as exotic invasions.

Effects of Nonnative Fishes on Commercial Seine Fisheries: Evidence from a Long-Term Data Set

Dozens of introduced exotic freshwater fish species inhabit the state of Florida. These nonnative fishes interact with freshwater commercial fisheries in a variety of ways, influencing catch abundance, composition, and revenue. Using a 22-year data set collected from a commercial haul seine fishery, we aimed to explore the dynamics of yield and revenue in relation to nonnative fishes, with emphasis on the suckermouth armored catfishes (Pterygoplichthys spp.). Using profit index metrics and the inverse Simpson’s diversity index, we found that non-native tilapia (Oreochromis spp.) and brown hoplo (Hoplosternum littorale) provided economic benefits while suckermouth armored catfishes seemed to disrupt catch consistency and lower profit index values. To reduce the negative impacts of the suckermouth armored catfishes and subsequently exert pressure on their population, we suggest marketing these edible fishes for human and/or animal consumption.

Distribution of fishes in the Río Guayalejo-Río Tamesí system and relationships with environmental factors in northeastern Mexico

A priority issue in ecology and biogeography is understanding the patterns in species diversity and the causal factors of their distribution, which allows the generation of information for conservation strategies. The longitudinal distribution of fishes and their relationships with environmental variables were studied in the Guayalejo-Rio Tamesi system (northeastern Mexico) from February 2000 to July 2001. A total of 5918 fish were caught in 27 collections along an altitudinal gradient in the main river course, from high mountain (1500 masl) to coastal plain near Tampico. Forty-three native and five exotic species, belonging to 35 genera in 23 families, were identified. Cluster analyses identified four major fish habitats in the river system. A distinctive euryhaline marine fish habitat (1) occurs near the mouth with native and two exotic species. Two other habitats consist essentially of freshwater fish species that are distributed along the longitudinal gradient. One of these habitats (habitat 4) shows greater diversity, as per the Shannon index value, and also includes amphidromous fish, in addition to two exotic freshwater fish; the other (habitat 2) includes freshwater, euryhaline and three exotic species. The changes in the frequency of occurrence and the abundance of Gambusia vittata, Astyanax mexicanus, and Xiphophorus variatus contribute to explaining differences between these habitats. Another habitat (3) is represented by two sampling sites located near the mouth and consist of freshwater and euryhaline fish and three exotic cyprinids with broad salinity tolerance. The low abundance and richness of exotic species suggest little impact on native fish fauna in this river. The fish assemblage of the Guayalejo-Tamesi river system species changes along a longitudinal gradient with the addition, replacement and presence of indicator species. Upstream fish fauna is mostly composed of freshwater species, some of them generalists that inhabit the entire longitudinal gradient, others that are restricted to certain sites, and the remainder of species is an assemblage composed of a mixture of euryhaline freshwater and marine species near the mouth.

Length-weight relationships of four freshwater fish species from the coastal drainage system in Peru

The morphometric relationships of three native and one exotic freshwater fish species from the Lower San Juan and Lower Pisco River basins, central Coast of Peru, are presented. Specimens were collected in May and November 2010 using seine nets and electrofishing. Length-Weight (LWR) relationships for Andinoacara stalsbergi, Trichomycterus punctulatus, Basilichthys archaeus and Poecilia reticulata are provided for the first time, contributing information towards the effort to conserve freshwater fishes.

Social organization and endocrine profiles of Australoheros facetus, an exotic freshwater fish in southern Portugal

Australoheros facetus is a neotropical cichlid and an exotic species in the Guadiana and Odelouca basins (Southern Portugal). In this research, we aimed to characterize the main behavioural patterns and circulating hormones, 17β-estradiol (E2) for females, and testosterone, 11-ketotestosterone (11KT) and cortisol for both sexes, during the formation of social groups, a crucial step in the life-history of A. facetus. A pair-breeding strategy with territorial behaviour and aggressive interactions was found, with a positive correlation between dominance and size for both sexes. There were no significant differences between non-territorial and territorial individuals in the baseline levels of hormones, but 11KT was higher in males when they became territorial, as E2 for territorial females, while there was no clear pattern for testosterone. In contrast, cortisol was higher in non-territorial males and correlated negatively with social dominance. These results suggest that size is the main driver for social dominance and that formation of stable hierarchies result in higher circulating 11KT and lowers stress in territorial males. Related to A. facetus’ behaviour, aggressiveness and biparental care may be an advantage during the invasion process of A. facetus, facilitating colonization of new habitats.

First report on the molecular characterization of Diaphorocleidus armillatus Jogunoori et al. 2004 (Monogenea: Dactylogyridae) infecting the gills of introduced fish, Gymnocorymbus ternetzi in India.

During an investigation of the diversity of monogenean parasites in Meerut, U.P., India, the exotic freshwater fish Gymnocorymbus ternetzi was found infected with the gill dactylogyrid species of Diaphorocleidus Jogunoori et al. 2004. Using morphological study, the present monogeneans were found similar in morphology of anchors, bars and male copulatory organ with D. armillatus Jogunoori et al. 2004. This is the first genetic characterization of D. armillatus based on the analysis of 18S ribosomal RNA sequence (1800 bp) and associated with morphological redescription. Our study suggests that more molecular investigation is required on Diaphorocleidus species for deducing correct phylogenetic position of D. armillatus.

An update on the status of native and exotic freshwater fishes of Italy

An updated, corrected checklist of both native and established alien freshwater fish species in Italy is given based on molecular, morphological and biogeographical data. Some 12 native species, reported as conspecific with transalpine species in official Italian ichthylogical literature, are in fact endemics. Previous taxonomic confusion has resulted in the introduction of several alien species, either with official stockings or mixed in as impurities. Rehabilitated species include the cyprinids Scardinius hesperidicus, Scardinius scardafa and Telestes savigny from northern Italy, as well as Squalius ruffoi and the Telestes comes from southern Italy. Squalius albus is a junior synonym of S. squalus. The endemic gudgeon, previously assigned to the genus Romanogobio, is returned to the genus Gobio (G. benacensis). Phoxinus lumaireul is a junior synonym of P. phoxinus. Among the Salmonidae, Salmo cenerinus is a junior synonym of S. marmoratus, while Salmo farioides represents the trout species of the Adriatic lineage for which a neotype is designated. Thymallus aeliani represents the endemic lineage of grayling of the Adriatic populations. The esocid Esox cisalpinus is an endemic pike species and Esox flaviae is a junior synonym; the extensive exportation as well as the presence of this species throughout Europe is possibly due to humans. Among sculpins, Cottus scaturigo and C. ferrugineus are junior synonyms of C. gobio. The International Union for Conservation of Nature (IUCN) categories for native species of Italy are updated. At present, 52 native freshwater fish species are listed: 2 are extinct (Acipenser sturio and Huso huso), 12 are critically endangered, 7 endangered, 10 vulnerable, 3 near-threatened, 15 low concern and 3 data-deficient; 35 species are the result of human transfers. Among the 51 introduced species, 6 are recently established (Leuciscus leuciscus, Oreochromis niloticus, Poecilia reticulata, Xiphophorus helleri, Amatitlania nigrofasciatus, Hemichromis sp.), 37 are already established, 5 are probably established and 3 are non-established Chinese carp, maintained in the wild by intensive stockings. The family most involved is the Cyprinidae, with 22 alien and 20 native species.

<b>Local ecological knowledge is not a useful source of information concerning impacts caused by non-native Nile tilapia on fishery stocks</b> - doi 10.4025/actascibiolsci.v35i3.18418

Exotic freshwater fish can have deleterious effects on local biodiversity, although these impacts often only become apparent many years after the introduction. Local Ecological Knowledge (LEK) may be a useful source of information in situations where formal technical studies are insufficient, but few works have examined the reliability of information generated through this approach. We examined the reliability of LEK by investigating the impacts of Nile tilapia on fishery stocks in an artificial reservoir in northeastern Brazil. We gathered LEK from 29 experienced fishermen and then confronted this information with official fishery statistics from the same site. Twenty-two fishermen stated that total catch in the Gargalheiras Reservoir had declined over the years, 68% (N=15) of them began fishing before 1976 (the year Nile tilapia was introduced into reservoir). Of those 15 fishermen, 87% (N=13) stated that tilapia has not negatively affected other species, which ran counter to analyses of fishery statistics. Our study suggests that the LEK of fishermen is not a useful source of information concerning the impacts caused by exotic tilapia. However, the LEK added an overfishing hypothesis of the decline in fishery stocks in the Gargalheiras reservoir.

Breeding programme priorities and management techniques for native and exotic freshwater fishes in Europe

The main goal of aquariums today is to raise public awareness and positively change visitor behaviour towards the environment. In addition, aquariums are becoming increasingly engaged in fish conservation programmes within their range country or overseas. The World Association of Zoo and Aquariums has developed a global aquarium strategy for conservation and sustainability. Within Europe, conservation‐breeding programmes are managed by the European Association of Zoos and Aquaria, and the European Union of Aquarium Curators Fish and Aquatic Invertebrate Taxon Advisory Group. The large and growing number of species of freshwater fish under threat can make deciding which species are priorities for aquarium collections very difficult. The Regional Collection Plan is a mechanism that defines the role a species plays within a zoological collection, helping collection managers make decisions about which species of freshwater fish are prioritized for ex situ conservation management with an associated action plan used to ensure that conservation goals are realized. We present clear and demonstrable roles that public aquariums can play in the conservation of freshwater fishes and discuss the challenges for such conservation initiatives in European aquariums with the increasing trend for marine exhibits and marine‐focused aquariums.

Dilution stress facilitates colonization of invasive mosquitofish in a saline Mediterranean stream: population biology response

Knowledge of the interplay of abiotic factors and the invasive success of exotic fish is fundamental both to proper management and the ability to predict consequences for native communities. The highly invasive eastern mosquitofish (Gambusia holbrooki) has been introduced worldwide; however, although salinity could limit its invasive success, the influence of variations in water salinity on its population biology has been scarcely studied. The present study aimed to analyse the effect of changes in water salinity on the life history and microhabitat use of a mosquitofish population inhabiting a hypersaline stream subjected to human-caused dilution stress. Dilution process and associated habitat changes, such as increased aquatic vegetation, available food and the spread of invasive riparian vegetation (the common reed Phragmites australis), seem to have favoured mosquitofish proliferation and colonization. Dilution caused an increased somatic condition for all individuals and a higher reproductive investment of males and larger females. This led to greater survival, recruitment rates, and abundance during the period of lower salinity. The species showed changes in microhabitat use which could be advantageous in less saline conditions; for instance, the species preferentially used areas with the presence of P. australis as a refuge, and this pattern increased during the dilution period. These results support the hypothesis that human activity is one of the main forces shaping the colonization and proliferation of exotic freshwater fishes. At least in a Mediterranean context, an increase in mosquitofish abundance and the improvement of its population status could be clear indicators of the degradation of natural saline systems. Copyright © 2012 John Wiley & Sons, Ltd.

The recent occurrence of exotic freshwater fishes in the tributaries of river Ganga basin: abundance, distribution, risk, and conservation issues

We record here the recent occurrence, abundance and distribution of six exotic fish species, viz. Oreochromis mossambicus, Cyprinus carpio, Hypopthalmicthys molitrix, Ctenopharyngodon idellus, Clarias gariepinus, and Pterygoplichthys disjunctivus (a new exotic in India) distributed through the four important tributaries of river Ganga basin in India. From the total catch, the abundance index of all exotic species in different rivers ranged from 1.1 to 14.5 % with highest value in River Gomti. The relative abundance of the exotic species in all the four tributaries demonstrated that a single species C. carpio contributed a considerable abundance (43.3–83 %) than that of the remaining exotic fishes. The Common Carp, C. carpio, was ubiquitous in all the four tributaries of Ganges basin studied and had the highest local distribution (52.63 %). Smaller size groups of endangered (Chagunius chagunio, Chitala chitala, and Tor tor) and migratory species (Bagarius bagarius, Ompok pabda, Wallago attu, and Sperata aor) in the four tributaries were recorded, and the increasing appearance of Common Carp and other exotic fishes is signaling biological invasion. Possible threats to the indigenous fish fauna, as a result of the invasion and proliferation of these exotics, are discussed.

Ecological determinants of parasite acquisition by exotic fish species

Disease‐mediated threats posed by exotic species to native counterparts are not limited to introduced parasites alone, since exotic hosts frequently acquire native parasites with possible consequences for infection patterns in native hosts. Several biological and geographical factors are thought to explain both the richness of parasites in native hosts, and the invasion success of free‐living exotic species. However, the determinants of native parasite acquisition by exotic hosts remain unknown. Here, we investigated native parasite communities of exotic freshwater fish to determine which traits influence acquisition of native parasites by exotic hosts. Model selection suggested that five factors (total body length, time since introduction, phylogenetic relatedness to the native fish fauna, trophic level and native fish species richness) may be linked to native parasite acquisition by exotic fish, but 95% confidence intervals of coefficient estimates indicated these explained little of the variance in parasite richness. Based on R2‐values, weak positive relationships may exist only between the number of parasites acquired and either host size or time since introduction. Whilst our results suggest that factors influencing parasite richness in native host communities may be less important for exotic species, it seems that analyses of general ecological factors currently fail to adequately incorporate the physiological and immunological complexity of whether a given animal species will become a host for a new parasite.

An annotated distributional checklist of exotic freshwater fishes from the Baja California Peninsula, Mexico

We documented the distributional status of 27 exotic fish species in the inland waters of the Baja California Peninsula, Mexico, based on voucher specimens collected from 122 sites between 1977 and 2010, and on published records. The species reported here are representatives of genera from the Atlantic drainages of North America (Ictalurus, Ameiurus, Pylodictis, Morone, Lepomis, Pomoxis, Dorosoma, Cyprinella, and Micropterus), Middle America (Poecilia, Gambusia, and Xiphophorus), Eurasia (Cyprinus and Carassius), and Africa (Tilapia and Oreochromis). The family containing the highest number of species is Centrarchidae (7 species) followed by Ictaluridae and Poeciliidae (6 species each). Four species were determined to be invasive due to their wide distribution and fast dispersal through the Peninsula (Gambusia affinis, Poecilia reticulata, Lepomis cyanellus, and Tilapia sp. cf. zillii). We analyze the impacts of exotic species on the native populations of 3 species with problems of conservation: Cyprinodon macularius (endangered), Fundulus lima (endangered), and Gasterosteus aculeatus (vulnerable). Alien fishes have been introduced for a variety of reasons in Mexico: ornament, sport, aquaculture, biological control, and by accident. In some cases fish introductions were carried out for more than one reason.

Parasites of native and exotic freshwater fishes in south‐western Australia

In this study, 1429 fishes of 18 different species (12 native and six exotic) were sampled from 29 localities to compare the levels of parasitism between native and exotic fish species and to examine the relationship between environmental degradation and parasite diversity. Forty-four putative species of parasites were found and most of these appear to be native parasites, which have not previously been described. Two parasite species, Lernaea cyprinacea and Ligula intestinalis, are probably introduced. Both were found on or in a range of native fish species, where they may cause severe disease. Levels of parasitism and parasite diversity were significantly greater in native fishes than in exotic species, and this may contribute to an enhanced demographic performance and competitive ability in invading exotics. Levels of parasitism and parasite diversity in native fishes were negatively related to habitat disturbance, in particular to a suite of factors that indicate increased human use of the river and surrounding environment. This was due principally to the absence in more disturbed habitats of a number of species of endoparasites with complex life cycles, involving transmission between different host species.

Contrasting patterns and mechanisms of spatial turnover for native and exotic freshwater fish in Europe

AbstractAim We compare the distribution patterns of native and exotic freshwater fish in Europe, and test whether the same mechanisms (environmental filtering and/or dispersal limitation) govern patterns of decrease in similarity of native and exotic species composition over geographical distance (spatial species turnover).Locations Major river basins of Europe.Methods Data related to geography, habitat diversity, regional climate and species composition of native and exotic freshwater fish were collated for 26 major European river basins. We explored the degree of nestedness in native and exotic species composition, and quantified compositional similarity between river basins according to the beta‐sim (independent of richness gradient) and Jaccard (dependent of richness gradient) indices of similarity. Multiple regression on distance matrices and variation‐partitioning approaches were used to quantify the relative roles of environmental filtering and dispersal limitation in shaping patterns of decreasing compositional similarity over geographical distance.Results Native and exotic species exhibited significant nested patterns of species composition, indicating that differences in fish species composition between river basins are primarily the result of species loss, rather than species replacement. Both native and exotic compositional similarity decreased significantly with increasing geographical distance between river basins. However, gradual changes in species composition with geographical distance were found only for exotic species. In addition, exotic species displayed a higher rate of similarity decay (higher species turnover rate) with geographical distance, compared with native species. Lastly, the majority of explained variation in exotic compositional similarity was uniquely related to geography, whereas native compositional similarity was either uniquely explained by geography or jointly explained by environment and geography.Main conclusions Our study suggests that large‐scale patterns of spatial turnover for exotic freshwater fish in Europe are generated by human‐mediated dispersal limitation, whereas patterns of spatial turnover for native fish result from both dispersal limitation relative to historical events (isolation by mountain ranges, glacial history) and environmental filtering.

First record of the common bream (Abramis brama) introduced to the Iberian Peninsula

This is the first record of the common bream, Abramis brama (Linnaeus, 1758), introduced into the Iberian Peninsula. Eight individuals of this cyprinid fish species were captured (of a total of 978 fish) in the Boadella Reservoir (Catalonia, Spain) on August 18, 2004. This reservoir is only 14 km away from France, where the bream is native, and contains several exotic freshwater fish that are still not widespread in Spain. The further introduction of species and the illegal translocation of the bream by anglers to other Iberian river basins should be controlled by the Spanish administration.

The western Pacific red lionfish, Pterois volitans (Scorpaenidae), in Florida: Evidence for reproduction and parasitism in the first exotic marine fish established in state waters

Many exotic fresh-water and brackish-water fish species have become established in Florida waters, but the red lionfish is the first entirely marine species that appears to have become established here. We give a detailed account of the initial collections of adult specimens from off St. Augustine and Jacksonville, including data on morphometrics, meristics, and gonad histology. Our review of historical sightings on Florida reefs and of the specimens reported herein suggests that the most plausible vector for the introduction of this fish was aquarium releases. We discuss our reasons for concluding that this species has probably become established in Florida, summarize the potential danger that these venomous fishes pose to the public, and examine the effect of a parasite hosted by the male lionfish. We also consider the potential effect of the red lionfish on marine communities in Florida, but limited information on its biology precludes a detailed assessment.

Evaluating Potential Effects of Exotic Freshwater Fish From Incomplete Species Presence–absence Data

Many freshwater ecosystems and biotas around the world are threatened with extinction. Freshwater fishes, for example, are the most endangered vertebrates after amphibians. Exotic fish are widely recognized as a major disturbance agent for native fish. Evaluating the ecological effects of invaders presents many challenges and the problem is greatly augmented in parts of the world where the native fauna is poorly known and where exotic species are commonplace. We use the fish community of Patagonia, a small and distinct native biota dominated by exotic salmonids, as a case study to ask: what can we learn about the effects of exotic fish species from fragmentary or partial data and how do such data point the way to what needs to be learned? We review the available data and literature on the distribution and status of native and introduced fish. We compile a novel regional presence/absence species database, build fish distribution maps, describe distribution patterns of native and exotic species, and identify critical information voids. A comparative review of literature from Patagonia and Australasia, where a similar native and exotic fish fauna is found, helps us to identify research priorities and promising management strategies for the conservation of native fish fauna. We conclude that the main challenge for fish conservation in Patagonia is to identify management strategies that could preserve native species while maintaining the quality of salmonid fisheries.