Distribution Of Freshwater Fishes Research Articles

Vertical oscillations of the thermocline caused by internal waves modify coldwater pelagic fish distribution: Results from a large stratified lake

Fishes typically occupy a species-specific temperature range, with their occupied depth being related to the lake’s temperature profile. When a fish’s preferred temperature range coincides with the thermocline, the location of their preferred thermal habitat is influenced by the rise and fall of internal waves, leading to possible changes in fish depth. These internal waves are common in large, stratified lakes, yet we do not know how they affect the spatial distribution and behavior of freshwater fishes. We conducted nighttime hydroacoustic surveys in a large, deep embayment of a large thermally stratified lake to observe whether pelagic fish respond to vertical oscillations of the thermocline caused by internal waves. The coldwater pelagic fish in our study (primarily cisco, Coregonus artedi) typically occupied a narrow vertical band approximately 5–8 m thick and temperatures between 10.8 ± 0.8–13.6 ± 1.6 °C (fishes sized 106–500 mm), just below the thermocline (centered around 15–17 °C). Importantly, the upper bound of fish depth varied in response to vertical thermocline movements associated with internal waves, suggesting fish respond to changes in their physical environment on timescales commensurate with basin-scale internal wave periods (hours to days), to remain within their preferred thermal habitat. Dissolved-oxygen levels were typically above avoidance thresholds of these fish, thus not likely exerting a strong influence on fish location. Our findings emphasize the need to account for internal waves when designing hydroacoustic and netting surveys, as thermocline movements can influence where fish are located.

Keeping up with the status of freshwater fishes: A California (USA) perspective

AbstractFreshwater biodiversity loss exceeds that in terrestrial systems; fishes are a predominant indicator of this catastrophe. Current worldwide estimates of freshwater fish species threatened with extinction are about 30%. We discuss why standard monitoring of the status of most fishes is inadequate to keep up with declines. Rapid population declines and shrinking freshwater fish distributions result in shifting baselines that make it challenging to evaluate conservation status reliably and promptly and effectively address further decreases. We present the California Method for Status Evaluation of Fishes as an alternative to existing methods for assessing the regional status of freshwater fishes. This method uses local expertise to score metrics and generates a fish status rating to inform short‐term management decisions. This approach applies to Distinct Population Segments, subspecies, species, and entire regional fish faunas and is adaptable to local, changing environmental conditions. Using this method, we update the freshwater status scores for 131 native California fish species, a fauna in rapid decline.

Allopatric differentiation in the Enteromius anoplus complex in South Africa, with the revalidation of Enteromius cernuus and Enteromius oraniensis, and description of a new species, Enteromius mandelai (Teleostei: Cyprinidae).

The chubbyhead barb, Enteromius anoplus, as currently described, is the most widely distributed freshwater fish in South Africa. The species occurs in almost all the major river systems across the country, with the exception of the small coastal drainages on the south coast. The use of a comprehensive data set of mitochondrial (mtDNA) cytochrome b (cyt b) sequences uncovered the presence of four distinct lineages or operational taxonomic units (OTUs) within E. anoplus: (a) the Gouritz lineage endemic to the Gouritz River system, (b) the Olifants lineage endemic to the Olifants-Doring River system, (c) the Orange lineage endemic to the Orange River system and (d) the Eastern Cape lineage which is distributed across six river systems from the Great Fish to the Buffalo rivers in the Eastern Cape Province of South Africa. The present study provides a new diagnosis for E. anoplus s.s. (the Gouritz lineage), revalidates Enteromius cernuus (the Olifants lineage) and Enteromius oraniensis (the Orange lineage) as distinct species. The study also provides a description for a new species, Enteromius mandelai sp. nov (the Eastern Cape lineage). E. cernuus and E. mandelai differ from both E. anoplus and E. oraniensis by having a complete lateral line (vs. an incomplete lateral line in the latter species). E. cernuus further differs from the other three species by having long maxillary barbels which reach or exceed the vertical through the middle of the eye and the lowest number of circumpendicular scales (10-12 vs. 12-16 for the other three species). E. oraniensis is distinctive from the other three species by having inconspicuous barbels. These findings add to the growing body of literature that shows that the freshwater fishes of the Cape Fold and adjacent freshwater ecoregions have narrow geographic ranges. This has ramifications for conservation planning and management, as well as the understanding of the evolutionary history of the stream fishes in these global endemic hotspots.

Skin bacteria of rainbow trout antagonistic to the fish pathogen Flavobacterium psychrophilum

Rainbow trout fry syndrome (RTFS) and bacterial coldwater disease (BCWD) is a globally distributed freshwater fish disease caused by Flavobacterium psychrophilum. In spite of its importance, an effective vaccine is not still available. Manipulation of the microbiome of skin, which is a primary infection gate for pathogens, could be a novel countermeasure. For example, increasing the abundance of specific antagonistic bacteria against pathogens in fish skin might be effective to prevent fish disease. Here, we combined cultivation with 16S rRNA gene amplicon sequencing to obtain insight into the skin microbiome of the rainbow trout (Oncorhynchus mykiss) and searched for skin bacteria antagonistic to F. psychrophilum. By using multiple culture media, we obtained 174 isolates spanning 18 genera. Among them, Bosea sp. OX14 and Flavobacterium sp. GL7 respectively inhibited the growth of F. psychrophilum KU190628-78 and NCIMB 1947T, and produced antagonistic compounds of < 3 kDa in size. Sequences related to our isolates comprised 4.95% of skin microbial communities, and those related to strains OX14 and GL7 respectively comprised 1.60% and 0.17% of the skin microbiome. Comparisons with previously published microbiome data detected sequences related to strains OX14 and GL7 in skin of other rainbow trout and Atlantic salmon.

Ichthyofaunal diversity in the upper-catchment of Kabini River in Wayanad part of Western Ghats, India

We present here a detailed account of the diversity, distribution, threats, and conservation of freshwater fishes in the upper-catchment of the Kabini River in the Wayanad part of the Western Ghats Biodiversity Hotspot. A total of 136 fish species belonging to 13 orders, 29 families, and 69 genera were recorded. Order Cypriniformes dominated with five families, 36 genera, and 84 species, and Cyprinidae was the dominant family represented by 51 species within 21 genera. The true diversity of ichthyofauna in this catchment, is still unclear and requires further exploration and taxonomic studies. At least 44 species recorded during the study are endemic to the Western Ghats, of which 16 are endemic to the Cauvery River System and two species endemic to the Kabini Catchment. A total of 20 non-native fish species were recorded from the study area, of which six species were inter-basin (within India) transplants and 14 species were exotic. Among the native species with confirmed identity, four are Critically Endangered (CR) and nine Endangered (EN) as per the IUCN Red List of Threatened Species. As a part of the study, we also extend the distribution ranges of Opsarius malabaricus, Laubuka trevori, Opsarius bendelisis, Puntius cauveriensis, Oreichthys coorgensis, Mesonoemacheilus pambarensis, Hypselobarbus curmuca, and Pseudosphromenus cupanus to the Kabini Catchment. The presence of four species, which were earlier considered to be endemic to the west flowing rivers of the Western Ghats, viz, Laubuka fasciata, Hypselobarbus kurali, Sahyadria denisonii, and Puntius mahecola, in an east flowing stream is reported and discussed. Deforestation and removal of riparian vegetation, pollution, stream channel modification, sand mining, destructive fishing practices, dams and other impoundments, monsoon fishing, and non-native species are the major threats to freshwater fishes in the region. Strategies for the conservation of aquatic ecosystems in the Kabini Catchment are discussed.

Island colonization by a ‘rheophilic’ fish: the phylogeography ofGarra ceylonensis(Teleostei: Cyprinidae) in Sri Lanka

AbstractDespite exhibiting multiple morphological adaptations to living in swiftly flowing water (rheophily), Garra ceylonensis is one of the most widely distributed freshwater fish in Sri Lanka. It is thus an ideal organism to reconstruct the evolutionary history of a widespread, yet morphologically specialized, freshwater fish in a tropical-island setting. We analysed the phylogenetic and phylogeographic relationships of G. ceylonensis based on two mitochondrial and one nuclear genes. G. ceylonensis is shown to be monophyletic, with a sister-group relationship to the Indian species Garra mullya. Our results suggest a single colonization of Sri Lanka by ancestral Garra, in the late Pliocene. This suggests that the Palk Isthmus, which was exposed for most of the Pleistocene, had a hydroclimate unsuited to the dispersal of fishes such as Garra. G. ceylonensis exhibits strong phylogeographic structure: six subclades are distributed as genetically distinct populations in clusters of contiguous river basins, albeit with two exceptions. Our data reveal one or more Pleistocene extirpation events, evidently driven by aridification, with relict populations subsequently re-colonizing the island. The phylogeographic structure of G. ceylonensis suggests inter-basin dispersal largely through headwater capture, likely facilitated by free-swimming post-larvae. The Peninsular-Indian species G. mullya comprises two genetically distinct parapatric clades, which may represent distinct species.

Historical distribution of freshwater fishes and the reference conditions concept in a large Mediterranean basin

Abstract The European Water Framework Directive 2000/60/EC (WFD) defines the ecological status of aquatic systems as the deviation between their present biological state and that which would be expected in the absence of any major human disturbance, referred to by the WFD as the ‘reference condition’ (RC). It assumes that their biotic composition should remain balanced and constant over time. This study tested both assumptions against an analysis of the historical distribution of the fish fauna in a large and highly disturbed Mediterranean basin. If fish communities change substantially over time, it will mean that the validity of the RC concept comes into question. Using presence/absence data for historical native fish fauna from the Guadalquivir Basin, distribution changes among sub‐basins were quantified by mapping between the nineteenth century and today. The range of two native species (Anguilla anguilla and Salmo trutta) has changed significantly. In addition, the diadromous species assemblage has almost become locally extinct, with the exception of the eel. Finally, most Guadalquivir sub‐basins (94.7%) have suffered major changes in the composition of their fish communities, either by losing native species or by adding new non‐native species. These results render the definition of any RC unlikely. In Mediterranean areas, the WFD objective of ‘good ecological status’ recovery based on the integrity of aquatic communities is a theoretical rather than a real goal. Nonetheless, the WFD provides an ecological guiding principle that can also be transferred to the conservation of freshwater ecosystems. As an alternative to the RC concept in Mediterranean lotic ecosystems, specific multimetric indices can be used, based on expert criteria, the metrics of which can also relate to the conservation value of water bodies, and not only to their ecological status.

Distribution of freshwater fish from the Southern Neotropics reveals three new areas of endemism and show diffuse limits among freshwater ecoregions

Abstract Ecoregions and areas of endemism are central concepts in biogeography. Based on collection records and the Endemic Analyses implemented with NDM/VNDM method we analyzed fish areas of endemism in the junction of three freshwater ecoregions related to the Rio de la Plata estuary (Lower Parana, Lower Uruguay, Laguna dos Patos) in Southern Neotropical region. Using two grid cell sizes, results obtained showed the same general patterns. Areas of endemism recovered were mainly associated either to Lower Uruguay or to Laguna dos Patos. In both ecoregions nested areas of endemism were identified within larger patterns of endemism. Noteworthy, one area recovered occurred across Lower Uruguay and Laguna dos Patos limits. Our results also suggest a revision of the Lower Uruguay and Lower Parana ecoregion limits, and highlight the relevance of the Rio de la Plata estuary as a barrier and corridor for freshwater fishes in the area.

Corrigendum to: Carbon sources supporting Australia's most widely distributed freshwater fish, Nematalosa erebi (Günther) (Clupeidae: Dorosomatinae)

Both brown (detrital-based) and green (algal-based) food pathways support freshwater food webs, although the importance of either source may vary within species, regions and different phases of the flow regime. The bony bream (Nematalosa erebi Clupeidae: Dorosomatinae) is one of Australia's most widely distributed freshwater fish species and is a key component of freshwater food webs, especially in northern Australia. We sought to better define the feeding habits of this species, previously classified as a detritivore, algivore or zooplanktivore (or combinations thereof), by undertaking meta-analyses of published accounts based on stomach content analysis and 13C and 15N stable isotope analysis. Stomach content analysis clearly indicated that detritus was the dominant food item, although benthic algae could be an important dietary component in some habitats (inland river flood plains) and during the wet season. Zooplankton were important for small fish (i.e. juveniles 13C enriched, indicating the latter source was not the dominant contributor to the biomass of this species. However, using site-specific data and a regression approach, a significant relationship was revealed between algal carbon and that of large fish, suggesting that carbon derived from benthic algae contributed ~20% of the carbon of adult bony bream. Zooplankton contributed a similar amount. Zooplankton provided the majority of carbon for small fish. We contend that detritus derived from terrestrial vegetation is the likely remaining carbon source for large bony bream, and this interpretation was supported by the outcomes of multiple regression analyses. Although previous studies of aquatic food webs in northern Australia have emphasised the importance of high-quality algal basal resources, this study indicates that terrestrial sources may be important for some species and demonstrates the need to better consider the circumstances that cause biota to switch between different food sources.

Predicting the Impact of Climate Change on Freshwater Fish Distribution by Incorporating Water Flow Rate and Quality Variables

In this study, water flow rate and quality variables that restrict freshwater fish distribution were incorporated in species distribution modeling to evaluate the impacts of climate change. A maximum entropy model (MaxEnt) was used to predict the distribution of 76 fish species in the present (2012–2014) and in the future (2025–2035 and 2045–2055) based on representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios for five major river basins (Han, Nakdong, Geum, Seomjin, and Yeongsan) in South Korea. The accuracy of MaxEnt performance was improved from 0.905 to 0.933, and from 0.843 to 0.864 in the model training and test, respectively, by introducing flow rate, total nitrogen, total phosphorus (TP), and total suspended solids (TSS). TSS and TP were ranked as the second and fourth contributing parameters, respectively, among the 17 variables considered in this study. There was a greater decline in species richness index under scenario RCP 8.5 than under scenario RCP 4.5, and in 2050 compared with 2030. However, the tolerance guild index (TGI) was predicted to improve in the future. The increase in TGI coupled with the decrease in species richness index (SRI), indicated that climate change is likely to have adverse effects on freshwater fish. Notably, the habitat of Korean spotted barbel (Hemibarbus mylodon), an endemic species of South Korea, is expected to contract largely in 2050 based on the RCP 8.5 scenario. These findings demonstrate that the incorporation of flow rate and water quality parameters into climatic variables can improve the prediction of freshwater fish distribution under climate change.

DISTRIBUSI SPASIAL DAN TEMPORAL JENIS IKAN AIR TAWAR YANG TERTANGKAP DI DANAU IE SAYANG, WOYLA BARAT, ACEH BARAT.

Research on the distribution of freshwater fish in Lake Ie Sayang, West Woyla is still limited. whereas these fish species are generally of economic value and are ecologically also very important in the balance of freshwater habitats. The purpose of this study was to determine the catch of freshwater fish caught using fishing nets and spatial and temporal distribution patterns of freshwater fish communities in Ie Sayang lake. The study was conducted from June to August 2019 with the direct survey method of spaciousness by catching fish at each fish sampling station in the lake ie Sayang. Determination of the station based on the area of the flow of water in and out of the lake. The number of fish obtained is counted and identified to species level. There were 30 fish found during the study. The highest fish catch in August was 11 fish, and the lowest fish catch in June was 9 fish. Based on the spatial distribution of freshwater fish found in station I and station II, while station III is less than station I and II. The highest temporal distribution of fish was found in August. This is allegedly due to the influence of water temperature. In August it has entered the rainy season in the Ie Sayang lake area. Based on the measurement of water quality, this study shows that the capture of fish is in line with the suitability of water temperature and complexity of the habitats available in Ie Sayang lake.

Multiscale effects on freshwater fish distribution in a highly disturbed Mediterranean-type basin: community-level and species-level responses

Fish–habitat relationships are a key element for conservation and management strategies, especially in highly disturbed areas where fish communities are subjected to many human pressures. In this regard, multiscale studies help to improve the knowledge of the spatial components and identify local (e.g. water width) and regional (e.g. elevation) key variables in species distribution. We examined local and regional requirements to study freshwater fish assemblage and occurrence at 216 locations in a highly disturbed basin, the Guadalquivir River Basin (S Spain). Fifteen environmental variables were considered at local scale and twenty at regional level. A total of eighteen species were captured during field sampling. The global prevalence for introduced species was 25%, which can be considered a high value. The most extended introduced species were eastern mosquitofish (Gambusia holbrooki) and pumpkinseed (Lepomis gibbosus), with around 10% prevalence. Regional and local scales showed different relevance according to the level-study approach (community or species). At the community level, the local, regional and shared components revealed similar influence on the fish assemblage, while at individual species level the local component was the main factor to explain most of fish occurrences. Moreover, variables’ interaction was scarcely selected and almost no introduced species distribution was affected by the interaction of any variable. Our results highlight the poor conservation status of the native fish fauna of the Guadalquivir River Basin as well as the importance of analyzing fish–habitat relationships at different scales and approach. These results provide useful information to assess and design conservation strategies in Mediterranean-type basin.

Carbon sources supporting Australia's most widely distributed freshwater fish, Nematalosa erebi (Günther) (Clupeidae: Dorosomatinae)

Both brown (detrital-based) and green (algal-based) food pathways support freshwater food webs, although the importance of either source may vary within species, regions and different phases of the flow regime. The bony bream (Nematalosa erebi Clupeidae: Dorosomatinae) is one of Australia’s most widely distributed freshwater fish species and is a key component of freshwater food webs, especially in northern Australia. We sought to better define the feeding habits of this species, previously classified as a detritivore, algivore or zooplanktivore (or combinations thereof), by undertaking meta-analyses of published accounts based on stomach content analysis and 13C and 15N stable isotope analysis. Stomach content analysis clearly indicated that detritus was the dominant food item, although benthic algae could be an important dietary component in some habitats (inland river flood plains) and during the wet season. Zooplankton were important for small fish (i.e. juveniles &amp;lt;100mm in length). When data were pooled across a large number of locations, stable isotope analysis indicated that detritus derived from terrestrial vegetation was better aligned isotopically with values for both adult and juvenile bony bream, whereas algae were comparatively 13C enriched, indicating the latter source was not the dominant contributor to the biomass of this species. However, using site-specific data and a regression approach, a significant relationship was revealed between algal carbon and that of large fish, suggesting that carbon derived from benthic algae contributed ~20% of the carbon of adult bony bream. Zooplankton contributed a similar amount. Zooplankton provided the majority of carbon for small fish. We contend that detritus derived from terrestrial vegetation is the likely remaining carbon source for large bony bream, and this interpretation was supported by the outcomes of multiple regression analyses. Although previous studies of aquatic food webs in northern Australia have emphasised the importance of high-quality algal basal resources, this study indicates that terrestrial sources may be important for some species and demonstrates the need to better consider the circumstances that cause biota to switch between different food sources.

Artificial flow regime promotes abiotic and biotic gradients: Testing the concept of longitudinal zonation in an off-river reservoir

Fragmentation and interconnection of water bodies cause severe changes in the natural flow regime of continental water systems. However, assessments of these impacts on the freshwater fish distribution are still scarce. We investigated whether an artificial flow regime generated by discharges from an aqueduct would promote a longitudinal environmental gradient in an off-river reservoir. We tested the hypothesis that the incoming water from aqueduct discharges promotes environmental gradient between lotic and lentic conditions. We expect that environmental changes and the artificial flow regime promote the structuring of fish assemblage and that the lotic-lentic transition areas present the highest fish species richness. A longitudinal gradient in environmental characteristics with differing fish assemblage structure was found. Temporal changes in the fish assemblages occurred only in areas near the discharge of the aqueduct. The highest fish richness and diversity were recorded in the transition zone during the wet season, associated with the greater environmental heterogeneity of this ecotone, whereas the lowest was found in the lotic zone, probably associated with the altered flow regime. The greatest abundance was recorded in the upper lentic zone in the wet season, whereas the lowest was found in the lower lentic zone in both seasons. Our results corroborate the hypothesis that the artificial flow regime, modulated by the seasonality of discharges and the influence of environmental variables, promotes longitudinal gradients in reservoirs when rivers are not present. The findings are relevant in a scenario where ever more interconnections of aquatic bodies have been diffused around the world.

Evidence of an ancient connectivity and biogeodispersal of a bitterling species, Rhodeus notatus, across the Korean Peninsula

The modern-day distribution of freshwater fishes throughout multiple rivers is likely the result of past migration during times when currently separate drainages were once connected. Here, we used mitochondrial and microsatellite analyses for 248 individuals of Rhodeus notatus collected from seven different rivers to obtain better understand historical gene flow of freshwater fish on the Korean Peninsula. Based on our phylogenetic analyses, this Korean species originated through the paleo-Yellow River from China and first colonized near the west coast. These genetic data also provided evidence of estuary coalescences among the rivers flowing to the west and southwest coast on well-developed continental shelf. In addition, the pattern of population structure revealed the biogeodispersal route from the west coast to the south coast. It could be inferred that massive migration was not involved in the formation of southern populations, since the signature of historical genetic drift was clearly observed. Our study is the first genetic attempt to confirm hypotheses describing the migration of freshwater species towards the end of East Asia, which have previously been developed using only geological reasoning.

The role of spatial units in modelling freshwater fish distributions: Comparing a subcatchment and river network approach using MaxEnt

Species Distribution Models (SDM) are frequently used in ecological research, but the effects of model extent and granularity on model outcomes are rarely addressed. In freshwater SDMs, two different approaches are commonly used to define the granularity of the models, i.e. to subdivide entire river systems into appropriate spatial modelling units: river reaches on the actual river network or subcatchments. We built maximum entropy (MaxEnt) SDMs for barbel (Barbus barbus) and grayling (Thymallus thymallus) in the River Ruhr catchment in Germany with identical environmental predictor data and analysed the difference between these two approaches. All models performed well (AUC > 0.9) and geographic predictors (e.g. distance to the river source) dominated over hydromorphological predictors in explaining species distributions. There was high agreement between the two model setups in river parts of low and high habitat suitability but considerably lower agreement in river parts of medium habitat suitability. In these medium suitable river parts, model results were spatially very heterogeneous and alternated at fine spatial scales especially in models based on river reaches. Increasing model regularization, a setting to control overfitting, had a smoothing effect on the environmental variables in the river reach models similar to the coarser subcatchment granularity. A restriction of the spatial extent led to a shift in predictor contributions to the model and an increase of the importance of hydromorphologic predictors by ca. 45 %. Restricting the model extend to the natural core distributional area of a given fish species might therefore be considered beneficial for the application of SDMs in a management context. By decreasing the weight of fixed geographic predictors in the model, predictors relating to hydromorphological river structures (i.e. which are accessible for restoration projects) gain importance. We conclude that SDM setups based on river reaches and subcatchments can both give valuable complementary information about the distribution of species. The high-resolution model based on river reaches might better discover individual local habitat features, whereas the subcatchment model might better account for the minimum spatial requirements of a fish population.

Scale effects on the performance of niche-based models of freshwater fish distributions: Local vs. upstream area influences

Niche-based species distribution models (SDMs) play a central role in studying species response to environmental change. Effective management and conservation plans for freshwater ecosystems require SDMs that accommodate hierarchical catchment ordering and provide clarity on the performance of such models across multiple scales. The scale-dependence components considered here are: (a) environment spatial structure, represented by hierarchical catchment ordering following the Strahler system; (b) analysis grain, that included 1st to 5th order catchments; and (c) response grain, the grain at which species respond most, represented by local and upstream catchment area effects. We used fish occurrence data from the Danube River Basin and various factors representing climate, land cover and anthropogenic pressures. Our results indicate that the choice of response grain – local vs. upstream area effects – and the choice of analysis grain, only marginally influence the performance of SDMs. Upstream effects tend to better predict fish distributions than corresponding local effects for anthropogenic and land cover factors, in particular for species sensitive to pollution. Key predictors and their relative importance are scale and species dependent. Consequently, choosing proper species dependent spatial scales and factors is imperative for effective river rehabilitation measures.

Phylogenetic relationships and historical biogeography of Oligosarcus (Teleostei: Characidae): Examining riverine landscape evolution in southeastern South America

The pike-characin Oligosarcus is a group of Characidae composed of 22 species, which have mostly allopatric distributed species in southeastern South America and sympatric occurrence of few species. Oligosarcus shares a similar distribution pattern with other fish genera and therefore, can help us to understand biogeographic events that influenced freshwater fish distribution in the southeastern South America. Our paper presents the most extensive taxonomic coverage for molecular analysis of Oligosarcus and uses various methods to examine the evolutionary history of the genus. Phylogenetic relationships among species of Oligosarcus were examined using a multilocus dataset by Maximum Likelihood and Bayesian methods. A relaxed molecular clock was used to estimate lineage divergence times, which provide a framework to examine the biogeographic history of this clade across the drainage basins of southeastern South America. Oligosarcus was resolved as monophyletic with strong support, and related to lineages currently assigned to the genus Astyanax. Within Oligosarcus, two groups of approximately equal species richness were resolved as monophyletic, mainly restricted to continental and coastal drainages of southeastern South America. Oligosarcus radiation is estimated to the late Neogene, with its origin in the Pliocene and most speciation events occurring in the Pleistocene. Some apomorphic characteristics associated with piscivory (e.g. large caniniform teeth) in Oligosarcus likely have evolved once, and are convergent to similar phenotypes observed in a distantly related clade of Astyanax (formerly Bramocharax). In addition, the presence of morphological convergence within the genus Oligosarcus (e.g. trophic morphology) seems to explain the difference between the present molecular hypothesis and some previous morphological studies. Ancestral geographical range estimation using analytical methods (e.g. DIVALIKE and DEC) demonstrated the effects of different Landscape Evolution Models (LEMs) on diversification of Oligosarcus. The results suggest that the two main Oligosarcus clades evolved in allopatry in continental and coastal drainages, with subsequent range extension and vicariance events that established the modern distributions. LEM analyses indicate the importance of formation of riverine barriers across the watershed of the La Plata basin and the effects of sea-level changes during the Pleistocene for delineating lineage distributions of Oligosarcus.

Drivers of diet patterns in a globally distributed freshwater fish species

We analysed data of a globally distributed model organism (brown trout, Salmo trutta) in an attempt to understand relationships among biogeography, prey communities, and climate on diet composition at regional spatial scales (Scandinavia) and thereafter explored whether diet patterns remained the same at global scales. At regional scales, we uncovered comprehensive patterns in diet composition among neighbouring freshwater ecoregions, with site-specific prey communities as the best predictor of the observed prey utilization patterns. Thus, we posit that environmental gradients altering site-specific prey communities and consequently the trophic niche of the predator through bottom-up mechanisms are key in understanding spatial dietary patterns. Proximity was also important for the revealed biogeographic patterns at global scales. We suggest that geographic location (latitude and elevation) as a proxy of environmental heterogeneity is key at small spatial scales, and climate at global extents, to understand spatial dietary patterns. Our findings support the hypothesis that future shifts in prey communities due to climate change will strengthen biographical patterns in feeding of freshwater fishes, with consequences for invasiveness assessment and nature management and conservation.

Between disgust and indifference: Affective and emotional relations with carp (Cyprinus carpio) in Australia

As the product of not always rational human thought, emotions are either excluded from or considered to be barriers to effective invasive species management. In a context where fish are still disregarded, in this paper I consider the affective and emotional geographies of the world's most broadly distributed freshwater fish, carp (Cyprinus carpio) in Australia, in emerging sites of management that involve killing. Invasive species management is yet to reconcile emotion and the affective politics of killing invasive animals as a normative and ongoing practice of care for the environment. This paper advances animal geographies by developing a conceptual understanding of the biopolitics of invasive life and invasive species management by thinking through carp as affective and emotional subjects. To do this I look to feminist approaches that conceptualise emotion as relational, including Ahmed's analysis of emotion as movement, and visceral geographies’ extension of embodied meaning‐making beyond the human. Drawing on original empirical analysis of managing carp, I identify how carp are performed as collectively disgusting or monstrous objects and how emotions are submerged and people can become indifferent to, or “pull away” from, ethical deliberation. However, attending to affect and emotion beyond the human subject also allows carp to emerge as different kinds of “spooky” subjects who, through conflicting, constantly changing, and more‐than‐invasive relationships, resist singular and hegemonic understandings. Taking a feminist approach allows me to consider how carp have affective biopolitical agency, in life and death, across these multiple subjectivities with power to transform human relationships with nature by situating and re‐engaging people in the problems of the world. Indeed, I argue that it is through the affective and emotional practices of managing carp that people might also begin to apprehend their responsibilities and limitations in the Anthropocene.