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During the past decade, a lot of study has been conducted in the favor of biomimicry and its applications in our daily lives. Fish scales, specifically, are being investigated with quite a lot of detail, and there are several species which possess an impressive mechanical property when under impact loadings and these impact loadings are naturally observed on the fish scale of the prey by the sharp teeth of predator fish when under attack. Considering such a reputation of fish scales, this article provides a concise look into the structural dependability of a fish scale from a species called Arapaima Gigas, which is a freshwater fish species found in the Amazon River. [ABSTRACT FROM AUTHOR]

The study of fish movement patterns in freshwater ecosystems remains a major focus of contemporary research. Small freshwater fish are known to migrate between tributaries and mainstems at different stages of their life history, helping to avoid local extinctions and maintain genetic diversity. However, fitting small fish species with telemetry equipment is difficult, making it challenging to track their detailed migration history via conventional methods. We evaluated the suitability of otolith isotope analysis for verifying the migration histories of small fish species inhabiting small tributaries. In this study, we compared the 87Sr/86Sr values in stream water and the otoliths of two fish species (Nipponocypris temminckii and Rhinogobius flumineus) inhabiting small streams. The 87Sr/86Sr ratios in the stream waters within the study area displayed considerable variation among tributaries. Our findings indicate that only N. temminckii has high dispersal ability, showing movement between tributaries or between tributaries and the mainstem in some locations. In contrast, such movement was not generally observed for R. flumineus. These results show the potential of 87Sr/86Sr as a tool for estimating the migration patterns of small fishes that inhabit small tributaries. [ABSTRACT FROM AUTHOR]

This study aimed to conduct a multidisciplinary investigation integrating detailed morphology, molecular characterization, water parameters, histopathology alteration, and the trials of treatment of Clinostomum spp. In this study, 300 Nile tilapia (Oreochromis niloticus) were collected from the farmed and wild Nile River at Al Bahr Al Aazam, Giza Governorate to assess Clinostomid infection prevalence. Fish and water samples were collected from private fish farms, and water drains at Dakahlia, and Giza, Egypt. Analysis of the water revealed inadequate water quality, particularly in the fish farms. Snails and piscivorous birds were abundant at fish collection sites. The recovered Clinostomid MCs morphological characteristics and COI gene sequence analysis identified them as Clinostomum complanatum, C. phalacrocoracis, and Euclinostomum heterostomum. Clinostomid MCs disturbed the fish's hematological and biochemical blood parameters. Bath treatment of parasitized fish with praziquantel (2 mg/L for 24 h) revealed a significant reduction in the number of vital MCs vs. infected fish (non-treated). Praziquantel (PZQ) is an effective and safe therapy for controlling Clinostomid infections affecting farmed Nile tilapia. The current findings indicate a link between poor environmental conditions and Clinostomum infections in tilapia. The study highlights the impacts of Clinostomid MCs on fish health and recommends bath treatment with PZQ as an efficient control method for these dangerous parasites to protect human and fish health. [ABSTRACT FROM AUTHOR]

The Myxosporea subclass harbours cnidarians myxozoans adapted for parasitism that infect mainly fishes worldwide. A total of 159 myxosporean species were described in South American waters until December 2016. These species were distributed by 24 genera, infecting 114 different host species in seven countries. Here, we present an update of the species described in South American countries from January 2017 to the present date, or those for which molecular data were made available in GenBank during this period. A total of 105 species distributed by 13 genera, parasitizing 59 host species are depicted in tabulated format including the species characteristics. Reports of infection with these parasites were found only in Argentina, Brazil, Colombia, and Peru. The most common parasites were Myxobolus spp. and Henneguya spp., and freshwater fish were about four times more parasitized than saltwater ones. Thus, the knowledge of myxosporean diversity in South America seems to be shaped more by the presence of research groups in each country than by the continent's biogeographical conditions. In recent years, freshwater ecosystems in South America have become the site of discovery for a significant diversity of myxosporean genera previously associated with marine environments. [ABSTRACT FROM AUTHOR]

Elucidating the habitat-related processes driving variation in juvenile recruitment and population fluctuation is crucial for the conservation of freshwater fishes, particularly for species at risk, where recruitment variation increases at small population size. We used a combination of instream enclosure experiments and habitat use observations to investigate between-stream variation in recruitment of juvenile Nooksack Dace (Rhinichthys cataractae sp. cataractae), a federally endangered stream-dwelling minnow endemic to the lower Fraser Valley of British Columbia, Canada. There was no evidence for a recruitment bottleneck associated with high water temperature or low dissolved oxygen in spawning riffles at the egg incubation stage, or during a two week juvenile growth experiment in enclosures, although larval dace growth was positively related to temperature. However, immediately post-hatch dace showed a very strong preference for shallow (<5 cm deep), fine substrate marginal shoal habitat with no overhanging or instream vegetation cover, which was associated with well-developed pool-riffle channel structure. Shallow marginal rearing habitat was absent in the stream experiencing recruitment failure, where encroachment by invasive reed canarygrass (Phalaris arundinacea) created homogenous steep-bank habitat with heavy instream vegetation cover, implicating loss of critical marginal rearing habitat as the recruitment bottleneck. [ABSTRACT FROM AUTHOR]

Taylor's power law (TPL) describes the expected range of parameters of the mean–variance scaling relationship and has been extensively used in studies examining temporal variations in abundance. Few studies though have focused on biological and ecological covariates of TPL, while its statistical inherences have been extensively debated. In the present study, we focused on species‐specific features (i.e. functional traits) that could be influential to temporal TPL.We combined field surveys of 180 fish species from 972 sites varying from small streams to large rivers with data on 31 ecological traits describing species‐specific characteristics related to three main niche dimensions (trophic ecology, life history, and habitat use). For each species, the parameters of temporal TPL (intercept and slope) were estimated from the log–log mean–variance relationships while controlling for spatial dependencies and biological covariates (species richness and evenness). Then, we investigated whether functional traits explained variations in TPL parameters.Differences in TPL parameters among species were explained mostly by life history and environmental determinants, especially TPL slope. Life history was the main determinant of differences in TPL parameters and thereby aggregation patterns, with traits related to body size being the most influential, thus showing a high contrast between small‐sized species with short lifespans and large‐bodied migratory fishes, even after controlling for phylogenetic resemblances.We found that life history traits, especially those related to body size, mostly affect TPL and, as such, can be determinants of temporal variability of fish populations. We also found that statistical effects and phylogenetic resemblances are embedded in mean–variance relationships for fish, and that environmental drivers can interact with ecological characteristics of species in determining temporal fluctuations in abundance. [ABSTRACT FROM AUTHOR]

Invasions of freshwater habitats by marine fishes provide exceptional cases of habitat-driven biological diversification. Freshwater habitats make up less than 1% of aquatic habitats but contain ∼50% of fish species. However, while the dominant group of freshwater fishes (Otophysi) is older than that of most marine fishes (Percomorphaceae), it is less morphologically diverse. Classically, scientists have invoked differences in the tempo and/or mode of evolution to explain such cases of unequal morphological diversification. We tested for evidence of these phenomena in the superfamily Cottoidea (sculpins), which contains substantial radiations of marine and freshwater fishes. We find that the morphology of freshwater sculpins evolves faster but under higher constraint than that of marine sculpins, causing widespread convergence in freshwater sculpins and more morphological disparity in marine sculpins. The endemic freshwater sculpins of Lake Baikal, Siberia, are exceptions that demonstrate elevated novelty akin to that of marine sculpins. Several tantalizing factors may explain these findings, such as differences in habitat stability and/or habitat connectivity between marine and freshwater systems. [ABSTRACT FROM AUTHOR]

In a baseline study, we investigated microplastic contamination in fish from the Pinang and Kerian Rivers in Northwest Peninsular Malaysia. In recognition of the growing concern over microplastic pollution in aquatic environments, we aimed to assess the abundance and characteristics of microplastics ingested by various fish species. Fish samples were collected from local fishermen, followed by a digestion process using 10% potassium hydroxide (KOH). Microplastics were isolated and analyzed through visual examination and attenuated total reflectance Fourier transform infrared spectroscopy. The results revealed a high prevalence of microplastics, with Johnius borneensis and Oreochromis sp. exhibiting the highest abundance, averaging 48.6 and 42.8 microplastics/g, respectively. The predominant shapes were fibers (55.6%) and fragments (25.9%), with colors primarily transparent (48.19%) and black (30.12%). Our results indicate significant contamination levels in freshwater fish, emphasizing the need for further research and effective mitigation strategies. These findings provide crucial baseline data on microplastics in Malaysian freshwater ecosystems. Environ Toxicol Chem 2024;43:2189–2198. © 2024 SETAC [ABSTRACT FROM AUTHOR]

The aim of this survey was to investigate the latest insights on different aqua inputs available in freshwater fish farming in Andhra Pradesh, India. The present survey on the use of aqua inputs was conducted in 520 freshwater fish farms, 50 aquaculture dealer shops, and 10 manufacturing units between September 2020 and December 2022 using a prescribed questionnaire. The present study documented a total of 336 different aquaculture inputs represented by more than 50 different manufacturing and packaging units. The aquaculture inputs was dominated by disinfectants and toxin binders (29.8%), followed by feed additives and growth promoters (21.5%), probiotics (20%), unlabeled group (10.4%), pesticides (8.9%), antibiotics (5.2%), and fertilizers (4.2%). Furthermore, the present survey revealed that infectious diseases, inadequate knowledge on aquaculture practices, lack of professionals, over-the-counter sales of antimicrobials, reliance of farmers largely on peers and company representatives, inconsistency in recommending dosage, and a lack of stringent regulations are major risk factors in aquaculture. Educated and experienced farmers were aware of the risks associated with antimicrobial use. This may help to implement successful interventions towards reduced antibiotic use in freshwater fish farming in Andhra Pradesh. In addition, the present survey identified a large number of aqua inputs that are currently in use, but that require further regulations and evaluation. Hence, there is an urgent need for awareness, effective surveillance, proper diagnosis, and disease advisory services. Stringent regulation and evaluation regarding the imprudent use of antimicrobials and their environmental and human health impacts can make a significant difference in promoting sustainable aquaculture for many years to come. [ABSTRACT FROM AUTHOR]

The introduction of non-native fish species poses a significant threat to biodiversity. In Spain, the common carp Cyprinus carpio (Linnaeus, 1758) and the bleak Alburnus alburnus (Linnaeus, 1758) are both established and sometimes co-occurring non-native species. Here, we investigated the trophic ecology of these species using an integrative approach, combining dietary and stable isotope analyses, to understand seasonal variations in their feeding ecology and potential niche overlap. We found a variable pattern for the gonadosomatic index of the two species in spring and autumn, suggesting the occurrence of extended reproductive periods for both A. alburnus and C. carpio. The gut content and isotopic niche analyses showed seasonal niche shifts, as well as interspecific niche partitioning and potential feeding competition. Notably, we found remains of small fish in the gut of both species and one entire individual of Gambusia holbrooki (Girard, 1859) in the carp gut, highlighting the potential of both species to prey also upon native fish fry or juveniles. Moreover, A. alburnus showed an ontogenetic shift toward prey from higher trophic levels and from the littoral/benthic environment, while C. carpio showed an increase in the proportion of prey from the pelagic environment with size. [ABSTRACT FROM AUTHOR]

Spawning Pacific salmon (Oncorhynchus spp.) provide marine‐derived resources (MDR) to freshwater food webs in the form of eggs, flesh and maggots that consume salmon carcasses, all of which positively impact stream‐dwelling fish growth. Pink salmon (O. gorbuscha) are widely distributed throughout coastal catchments along the North Pacific Ocean and display increased spawning abundances in odd years, owing to a fixed 2‐year life history. While many studies have found that foraging and growth of stream‐dwelling salmonids are improved by increased adult salmon spawning abundance, few studies have investigated the importance of alternating pink salmon spawning abundance between years. Here, we examined how patterns of pink salmon spawning abundance impact the foraging and growth of juvenile coho salmon (O. kisutch). First, we used bioenergetic simulations to generate a hypothesis that coho salmon growth would increase during odd relative to even years. We then collected empirical juvenile coho salmon diet and growth data from a Southeast Alaska catchment in 2021 (pink salmon spawning) and 2022 (no pink salmon spawning). Field data were compared against simulation predictions to understand impacts of biennial pink salmon spawning patterns on juvenile coho salmon growth. Empirical growth data revealed similar patterns to bioenergetic simulations. Age‐1 coho salmon grew 16.6 mm longer and 5.5 g heavier on average in 2021 compared to 2022. Age‐0 coho salmon displayed minor growth differences between years. These results support bioenergetic model predictions and suggest that patterns of pink salmon spawning abundance can impart interannual growth disparities to juvenile coho salmon. Moreover, we show that distinct spawning characteristics of Pacific salmon species are important when understanding patterns of MDR transfer and growth responses in stream fishes. [ABSTRACT FROM AUTHOR]

Background: This research investigated the impact of selenium-nanoparticles (Se-NPs) supplemented in sunflower meal (SM)-based diets on digestibility, mineral absorption, and growth performance of Catla catla. Se-NPs were added to seven test meals in varying amounts (0, 0.5, 1, 1.5, 2, 2.5 and 3 mgkg− 1). A total of 315 fish were evenly allocated three replicate tanks, with 15 fish per tank, and given diets equivalent to (5%) of their wet biomass daily for a period of 90 days. Results: The test diet (T-D) supplemented with 1.5 mgkg− 1 Se-NPs yielded remarkable results, including a significant increase in mean weight gain (14 g), an impressive average weight gain percentage (208%), a 100% survival rate, with no mortality observed and the highest specific growth rate (1.25). Moreover, 1.5 mgkg− 1 Se-NPs (T-D-IV) demonstrated superior nutritional digestibility (CP, 76%; CF, 79% and GE, 74%). Additionally, the diet 1.5 mgkg− 1 Se-NPs showed enhanced mineral absorption (K, P, Ca, Na, Zn, Cu and Fe) than other diets. Conclusion: It was practically proven that the growth indices, nutrient absorption, and mineral status of C. catla were significantly improved by Se-NPs supplemented SM-based diets, with the optimum level of supplementation being 1.5 mgkg− 1. [ABSTRACT FROM AUTHOR]

Seeking out appropriate habitat or food resources is one of the key reasons why animals move. Despite the benefits of movement, some individuals in a population remain resident or express alternative movement phenotypes. Movement, however, is energetically costly and can result in resources being diverted away from growth and reproduction. The presence of multiple movement phenotypes within populations suggests that each can have commensurate levels of performance depending on the underlying environmental conditions. Here we explore the context‐dependent costs and benefits of upstream and downstream juvenile dispersal in a large river system. We expect that if the energetic costs of moving (upstream against a current or downstream with a current) exceed any benefits to growth, then residents (who do not move) will have faster growth. Alternatively, movement costs may be offset if individuals move to more favourable environments, resulting in dispersers benefiting with faster growth. We used biological information naturally archived in the otoliths of a potamodromous fish, golden perch Macquaria ambigua, to quantify how movement phenotypes affect growth across individuals exposed to spatiotemporally varying environmental conditions. We found that juvenile growth differed considerably among dispersal phenotypes (resident, upstream, downstream, stocked): in general, surviving wild‐spawned downstream and upstream dispersers and hatchery‐stocked fish all grew faster than individuals that remained resident within their natal reach. Further, juvenile growth was sensitive to local environmental conditions and had carryover effects from an individual's natal‐year. Juvenile growth of all dispersal phenotypes was higher in years with below average natal‐year summer discharge (when fish are ~2–3 months old), likely because of increased concentrations of food resources. In contrast, the effects of natal‐year spring discharge (around the time individuals were spawned) were dependent on dispersal direction, with positive effects for downstream dispersers and upstream dispersers, and negative effects for resident individuals. Our results suggest that an individual's growth can benefit from early‐life movement, although the magnitude of this effect depends on local environmental conditions and the direction travelled. Our study reinforces the importance of heterogeneous and connected riverscapes that foster a diversity of individual growth responses. [ABSTRACT FROM AUTHOR]

A new species of Characidium shared by adjacent tributaries of the upper portions of the Tapajós and Xingu river basins is described. Characidium varii, new species, can be distinguished from the congeners by having distinctly speckled pattern of colouration, including dark blotches on cheek and ventral surface of head, by having conspicuous dark marks on fins, along with a single row of dentary teeth, isthmus completely covered by scales, 14 circumpeduncular scales, and swimbladder reduced. Molecular data reinforce the validation of the new species. The distribution of C. varii supports the hypothesis of the existence of a faunistic mixing between Tapajós and Xingu river basins, corresponding to the region of the Serra do Cachimbo and surrounding areas, previously proposed in the literature. [ABSTRACT FROM AUTHOR]

The southern catfish (Silurus meridionalis) is an economically important carnivorous freshwater fish in China. In this study, we compared the properties of skin collagen from southern catfish fed with raw food (RF) and cooked food (CF). The skin collagen yield in the RF group (8.66 ± 0.11%) was significantly higher than that of the CF group (8.00 ± 0.27%). SDS-PAGE, circular dichroism spectroscopy, and FTIR analyses revealed that the collagen extracted from southern catfish skin in both groups was type I collagen, with a unique triple helix structure and high purity. The thermal denaturation temperature of collagen in the RF group (35.20 ± 0.11 °C) was significantly higher than that of the CF group (34.51 ± 0.25 °C). The DPPH free radical scavenging rates were 68.30 ± 2.41% in the RF collagen and 61.78 ± 3.91% in the CF collagen, which was higher than that found in most fish collagen. Both the RF and CF groups had high ability to form fibrils in vitro. Under the same conditions, the CF group exhibited faster fibril formation and a thicker fibril diameter (p < 0.05). In addition, the RF group exhibited significantly higher expression of col1a1 compared to the CF group. These results indicated that feeding southern catfish raw food contributed to collagen production, and the collagen from these fish may have potential in biomaterial applications. [ABSTRACT FROM AUTHOR]

Riverine fishes face many challenges including habitat degradation and climate change, which alter the productivity of the riverscapes in which fish live, reproduce, and feed. Understanding the watershed portfolio of foraging and growth opportunities that sustain productive and resilient fish populations is important for prioritizing conservation and restoration. However, the spatiotemporal distribution and availability of fish food are poorly understood relative to other factors such as abiotic habitat quantity and quality (e.g., water temperature). In this paper, we build on the concept of “foodscapes,” and describe three components of food for fish, including abundance, accessibility, and quality. We then discuss methodological advances to help address three key questions: (1) Why is food availability hard to estimate? (2) What are the consequences of uncertainty in food availability estimates? and (3) What approaches are available or emerging for quantifying food available to fish? To address the first question, we characterize data acquisition and analytical challenges; for the second, we demonstrate the importance of evaluating and communicating potential consequences of uncertainty; and for the third, we posit opportunities for future work. Collectively, we highlight the need for greater appreciation of the role food plays in stream fish conservation, especially given its critical influence on responses to warming temperatures.This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Conservation, Management, and Awareness Water and Life > Methods [ABSTRACT FROM AUTHOR]

Summary This study explores the potential of hydrothermal extraction as an innovative valorisation method for the simultaneous production of gelatin and fish oil from fish byproducts. It offers an environmentally friendly alternative to conventional solvent‐based techniques by minimising the use of chemical solvents and water. We researched various major commercial freshwater fish species: striped catfish, catfish, and tilapia, and achieved a gelatin product that reflects commercial standards in chemical structure, gel strength, and pH level. The striped catfish gelatin showed the highest gel strength and viscosity (66.01 ± 0.83 g bloom and 15.3 ± 0.1 cP), but was produced at a lower yield than the catfish gelatin. On the other hand, striped catfish produced the highest yield of fish oil (13.56 ± 0.21%) and has the highest omega 3 content (3.72 ± 0.02%) than other fish oil. This innovative study demonstrates the potential of hydrothermal extraction as a sustainable method for producing gelatin and fish oil, offering eco‐friendly and nutritional benefits across a range of applications. [ABSTRACT FROM AUTHOR]

Variations in the size and shape of the eye have been observed in many species of fish. As eye size is positively related to visual acuity, larger eyes should favour foraging and detection of predators. However, few studies have examined the variation in eye morphology in relation to the complexity of lake conditions, including environmental perturbation and spatial variation in predation and competition. Such tests are especially important as the degrading of the visual climate is expected due to climate change, where browning, turbidity and variations in structural complexity should set different demands for visual acuity of foraging fish under predation risk. In this study, we tested the variation of the eye size among 667 individuals of an aquatic predator perch, Perca fluviatilis, from littoral and pelagic habitats of 14 lakes. We used Secchi depth to assess the effects of the visual climate of our lake systems, as fish foraging is highly related to visual conditions, and studied eye size variation in relation to the contribution of the pelagic resources to an individual's diet and the risk of predation. Secchi depth, the pelagic contribution to the diet and the percentage of piscivores had significant effects on eye size. These variable outcomes suggest that the lake environment in terms of visual climate, predation landscape and diet are major factors of eye size variation in this generalist predator. As many fish species trade off foraging against predation risk, future studies will show whether the complexity of intra‐ and interspecific interactions contribute to the variation in eye size in freshwater fish. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The common carp is one of the most economically valuable freshwater fish worldwide and its aquaculture can be severely affected by the koi sleepy disease (KSD)/carp edema virus disease (CEVD). This study explores a natural outbreak of CEVD in a pond containing both clinically healthy and diseased fish of various origins exposed to the virus. We investigated mRNA expression of genes associated with known antiviral immune mechanisms, such as type I interferon signalling and cell‐mediated cytotoxicity, and performed a comprehensive protein expression analysis to highlight differences between the two groups in various organs. Significant differences in expression profiles of common carp with and without clinical signs were found to be strongly dependent on the organ from which the sample originated. Components of the complement cascade, including various C3 proteins, exhibited upregulation only in less affected organs, specifically the head kidney and spleen. Other complement proteins such as B/C2 and C9 showed upregulation in the kidney, spleen, and gills but not in the skin. Conversely, lysozymes C and G, were observed to be upregulated in the most affected organs of the skin and gills. This study submits the first description of the immune system related proteome using a mass spectrometry on the samples isolated from fish infected with CEV. It also offers a unique comparison of immune reaction of CEV infected and healthy fish under an infectious pressure. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are crucial for global biodiversity through supporting plant and animal species and providing essential resources. These ecosystems are under significant threat, particularly in island environments such as Madagascar. Our study focuses on the Amboaboa River basin, home to the rare and endemic fish species Rheocles derhami, last recorded in 2013. To assess the status of this and other threatened fish species including Ptychochromis insolitus and Paretroplus gymnopreopercularis, and to understand freshwater fish population dynamics in this biodiversity hotspot, we conducted a comprehensive survey using both environmental DNA (eDNA) and traditional fishing methods. While traditional methods effectively captured a diverse range of species, including several invasive aliens and the critically endangered endemic species that were the focus of this study, the eDNA approach detected only a fraction of these introduced species and struggled to identify some critically endangered endemics at the species level. This highlights the value of combining methods to enhance species detection. We also investigated the trade-offs associated with multi-primer assessments in eDNA analysis, focusing on three different primer combinations targeting the 12S mitochondrial gene: MiFish, Tele02, and Riaz. Additionally, we provided 12S reference barcodes for 10 species across 9 genera of fishes from the region to increase the coverage of the public reference databases. Overall, our study elucidates the current state of freshwater biodiversity in the Amboaboa River basin and underscores the value of employing multiple methods for effective conservation strategies. [ABSTRACT FROM AUTHOR]

The bigmouth buffalo Ictiobus cyprinellus (Catostomidae) is a freshwater fish native to North America that is known for its longevity. During the 1970s, the bigmouth buffalo was recorded as declining in Canada, Minnesota, and North Dakota and became a protected species in Canada. In the USA, population declines are exacerbated by wasteful recreational bowfishing, lack of fisheries management, and overall lack of knowledge. However, recent studies have revealed the exceptional lifespan of bigmouth buffalo, their negligible senescence, slow growth, delayed maturity, and episodic recruitment. Yet little is known about the spawning phenology of bigmouth buffalo, nor their age demographics in east central Minnesota. In this 2021–2023 study of bigmouth buffalo from Rice Lake National Wildlife Refuge we found that 99.7% (389 of 390) of the extant population hatched prior to 1972 despite annual spawning in Rice Lake. Moreover, recruitment success declined significantly since water control measures were established (1953). We found males arrive to spawning grounds with females but depart later, that both the midpoint and duration of spawn significantly vary across years, and that more massive females of the same age range invest disproportionately more in ovaries. Extensive post-spawn seining revealed bigmouth buffalo young-of-the-year in low numbers, but by mid-to-late summer they were no longer evident having likely succumbed to predation. Overall, these findings thoroughly reveal one of the oldest populations of vertebrate currently known (median age of 79 years as of 2024) and expose the stark vulnerability of a bigmouth buffalo population for which substantial recruitment has not occurred for more than six decades. Multiple lines of evidence indicate that the long-lived bigmouth buffalo is vulnerable, that a precautionary approach is immediately needed, and that the unlimited and unregulated kill-fishery be closed. [ABSTRACT FROM AUTHOR]

In this work, we describe a new species of the genus Oreonectes, Oreonectes yuedongensis sp. nov., collected from the Lianhua Mountains in eastern Guangdong, China. Phylogenetic trees constructed based on the mitochondrial cytochrome b (Cyt b) gene showed that this new species represents an independent evolutionary lineage, with uncorrected genetic distances (Kimura 2‐parameter model) from congeners ranging from 5.1% to 8.3%. In addition, nuclear DNA analysis indicated O. yuedongensis as an independent lineage separate from its closely related species. Morphologically, the new species can be distinguished from other six species in the genus Oreonectes by a combination of serial characters. The description of this new species suggests that it is necessary to reassess the biodiversity of Oreonectes platycephalus as a complex, especially in the middle reaches of the Pearl River near the border between Guangdong and Guangxi. Morphological and genetic evidence supports O. yenlingi as a synonym of O. platycephalus. [ABSTRACT FROM AUTHOR]

Based on the habitat types, thirty species of cyprinids in nine streams located in the Western Ghat mountain ranges, hotspot of biodiversity have been classified into six guilds. Shallow pools (<60cm deep and velocities <30 cm/s) were preferred by juveniles and adults of big sized barbs such as Hypselobarbus micropogon, Tor khudree and Neolissochilus wynaadensis. Slow riffles (< 60 cm deep and velocities 30-59 cm/s) were preferredby juveniles of surface dwellers such as Barilius canarensis, B. gatensis, Devario aequipinnatus, Salmophasia boopis, Salmophasia acinaces and Chela labuca; bottom and substrate dwellers such as Garramullya and Garra stenorhynchus. Fast riffles (< 60 cm deep and velocities ≥ 60 cm/s) were preferred by the surface dwelling species and species of Garra. Almost all the cyprinid species preferred the medium pool (60-149 cmdeep and velocities <30 cm/s). Big sized barbs and torines (game fish) were confined to deep pools (≥150 cm deep). Among the nine streams raceway is identified in one stream (60-149cm deep and velocities ≥30 cm/s) which was preferred by juveniles and adults of Garra stenorhynchus and Barilius gatensis. Guild structures ofcyprinid species are consistent in almost all the streams. [ABSTRACT FROM AUTHOR]

This work provides new molecular data on seven species representing three genera (Protoancylodiscoides, Schilbetrema and Synodontella) in the order Dactylogyridea. The results help to explain the origin of Synodontella spp. and to elucidate the phylogenetic position of Synodontella in relation to the other genera. The findings also highlight the importance of the haptoral elements in determing phylogenetic relationships between and within Dactylogyridea taxa, which are monogenean parasites of mostly cyprinid fishes in fresh water. A total of 36 catfish specimens representing five species in three genera (Synodontis, Schilbe and Chrysichthys) were collected from two rivers in Cameroon: the Sanaga River (at Edéa and Nachtigal, in the Littoral and Cental regions, respectively) and Boumba River (at Mang-kaka, East Region), and examined for gill parasites. The novel 28S rDNA sequences of seven species belonging to Dactylogyridea were obtained and their phylogenetic relationships inferred. Synodontella resulted as a monophyletic lineage; the samples obtained from the catfish in Cameroon were well-differentiated into two groups. Synodontella appears to be more closely related to Schilbetrema than to the other Dactylogyridea species investigated here. The shape of the ventral bar should be considered an important feature for distinguishing among Dactylogyridea genera. The existence of two or more lineages within the genus Synodontella, as suggested by previous morphological studies, is here molecularly confirmed, indicating speciation as likely an outcome of ecological influences or the phylogenetic relationships among parasites and/or hosts. [ABSTRACT FROM AUTHOR]

Imaging sonars (ISs) are high-frequency acoustic devices that are increasingly being used to study fish in marine and freshwater habitats. Acoustic devices are limited in quantifying species richness, and previous attempts to identify fish species using IS have mostly focused on assemblages of low species richness or high morphological diversity. This study aimed to determine the ability of IS for identifying fish species at a subtropical artificial reef off Perth, Western Australia. Several fish traits that could be defined using IS were identified and described for all fish species observed with simultaneous optical footage. These traits were used to create a clustering algorithm to infer the species identity of IS detections of the five most abundant species at the reef. The identities of all fish from two species (Chromis westaustralis and Neatypus obliquus) were inferred with 100% success, though no individuals from the remaining three species (Seriola dumerili, Coris auricularis , and Pempheris klunzingeri) were correctly identified. An alternative clustering-based approach to categorising fish detected by IS independent of taxonomic inference was also implemented. Overall, this study demonstrates that IS can identify reef fish with variable success, and proposes an alternative method for describing fish assemblages irrespective of species identity. [ABSTRACT FROM AUTHOR]

Neotropical tetras of the family Characidae form the largest and most taxonomically complex clade within the order Characiformes. Previous phylogenetic relationships concur on the recognition of four major subclades, whereas knowledge on intergeneric and interspecific relationships remains largely incomplete or nonexistent. We sampled 575 specimens of 494 species and 123 genera classified in Characidae, generated new molecular data of ultraconserved elements (UCEs), and used likelihood and Bayesian analyses. The phylogeny (1348 UCE loci: 538 472 bp) yielded clades with unprecedented resolution at species- and genus-levels, allowing us to propose a new classification of former Characidae into four families: Spintherobolidae, Stevardiidae, Characidae, and Acestrorhamphidae. The family Stevardiidae includes nine subfamilies: Landoninae, Xenurobryconinae, Glandulocaudinae, Argopleurinae, Hemibryconinae, Stevardiinae, Planaltininae, Creagrutinae, and Diapominae. The family Characidae includes five subfamilies: Aphyocharacinae, Cheirodontinae, Exodontinae, Tetragonopterinae, and Characinae. The family Acestrorhamphidae congregates 15 subfamilies: Oxybryconinae, Trochilocharacinae, Stygichthyinae, Megalamphodinae, Stichonodontinae, unnamed subfamily, Stethaprioninae, Pristellinae, Jupiabinae, Tyttobryconinae, Hyphessobryconinae, Thayeriinae, Rhoadsiinae, Grundulinae, and Acestrorhamphinae. The phylogeny resolves intergeneric relationships and supports revalidation of Myxiops , Megalamphodus , Ramirezella , Holopristis , and Astyanacinus , synonymy of Aphyodite , Genycharax , and Psellogrammus , and expansion of Cyanogaster , Makunaima , Deuterodon , Hasemania , Hemigrammus , Bario , Ctenobrycon , and Psalidodon. The phylogeny opens avenues for new systematic reviews and redefinitions of included genera. [ABSTRACT FROM AUTHOR]

In a warming world, the input of glacier meltwater to inland water ecosystems is predicted to change, potentially affecting their productivity. Meta-ecosystem theory, which posits that the nutrient availability in the recipient ecosystem can determine the extent of cross-ecosystem boundary utilization, can be useful for studying landscape-scale influences of glacier meltwater on inland waters. Here, we investigate how the input of glacier meltwater in a river system in Southern Greenland influences the utilization of marine subsidies in freshwater fish. Our study system comprised four sites, with controls for glacial meltwater and marine subsidies, harboring a partially migrating population of arctic char, meaning that some individuals migrate to the ocean and others remain in freshwaters, and two fully resident populations as a freshwater reference. We assessed the incorporation of marine carbon in freshwater resident char using both bulk and amino acid stable isotope analysis of muscle tissue. In the population with partial migration, marine subsidies were a significant resource for resident char individuals, and estimates of trophic position suggest that egg cannibalism is an important mechanism underlying the assimilation of these marine subsidies. In proglacial streams, namely those with high glacial meltwater, the total dependence on marine subsidies increased and reached 83% because char become cannibals at smaller sizes. In the configuration of our focal meta-ecosystem, our results suggest that the importance of marine subsidies to freshwater fish strengthens within increasing meltwater flux from upstream glaciers. [ABSTRACT FROM AUTHOR]

Background: For the past 25 years, the ITS rDNA (ITS1-5.8S-ITS2) of Gyrodactylidae has been crucial for species identification, description, and phylogeny. This family includes 25 genera parasitizing marine and freshwater fish, initially distinguished by morphological differences in attachment and/or male copulatory organs. Gyrodactylus Nordmann, 1832, the most species-rich genus, has approximately 500 described species and an additional 25,000 species suspected. The genus is not monophyletic, and the functionally adaptive nature of morphological diagnostic characters complicates the delimitation of new genera. Methods: A phylogeny based on ITS rDNA was proposed to address these challenges, using only complete sequences of primitive taxa. Fifty-four sequences were aligned with the MUSCLE v5.1 algorithm, creating a 1590 ps long matrix. Maximum Likelihood (ML) and Bayesian Inference (BI) methods with the models TVM+F+G4 and SYM+G4 for ITS1–ITS2 and 5.8S, respectively, were inferred using IQ-TREE v2.3.5 and BEAST v2.7.6.0. Results: The findings revealed eleven main lineages. Four of them are proposed for classification into new genera: Cichlidarus gen. nov., Iraqemembranatus gen. nov., Macracanthus gen. nov., and Rysavyius gen. nov. Elevating the subgenus G. (Gyrodactylus) to genus rank was supported. Conclusions: The presented phylogeny provides a foundation for developing a classification system within Gyrodactylidae that is both reasonable and comprehensive. [ABSTRACT FROM AUTHOR]

Some East Asian rivers experienced repeated rearrangements due to Indian–Asian Plates' collisions and an uplift of the Tibetan Plateau. For the upper Changjiang (Yangtze/Jinsha River), its ancient south-flowing course and subsequent capture by the middle Changjiang at the First Bend (FB) remained controversial. The DNA of freshwater fishes possess novel evolutionary signals of these tectonic events. In this study, mtDNA Cyt b sequences of endemic Schizopygopsis fish belonging to a highly specialized grade of the Schizothoracinae from the eastern Tibetan Plateau were used to infer the palaeo-drainages connectivity history of the upper Changjiang system. Through phylogenetic reconstruction, a new clade D of Schizopygopsis with three genetic clusters and subclusters (DI, DII, DIIIa, and DIIIb) were identified from the upper Yalong, Changjiang, and Yellow Rivers; the Shuiluo River; the FB-upper Changjiang; and the Litang River; respectively. Ancient drainage connections and capture signals were indicated based on these cladogenesis events and ancestral origin inference: (1) the upper Yalong River likely acted as a dispersal origin of Schizopygopsis fish to the adjacent upper Yellow and Changjiang Rivers at ca. 0.34 Ma; (2) the Litang River seemed to have directly drained into the upper Changjiang/Yangtze/Jinsha River before its capture by the Yalong River at ca. 0.90 Ma; (3) the Shuiluo River likely flowed south along a course parallel to the upper Changjiang before their connection through Hutiao Gorge; (4) a palaeo-lake across the contemporary Shuiluo, Litang, and Yalong Rivers was inferred to have served as an ancestral origin of clade D of Schizopygopsis at 1.56 Ma. Therefore, this study sheds light on disentangling ambiguous palaeo-drainage history through integrating biological and geological evidence. [ABSTRACT FROM AUTHOR]

The Shennongjia Forestry District (Shennongjia) located in the northwestern region of Hubei Province, serves as the watershed between the upper and middle Chang-Jiang basin. Due to the unique natural environment and well-developed river networks, Shennongjia harbors a relatively high species diversity of freshwater fish, thus making it one of the hotspots areas of biodiversity research in China. However, there is still a lack of essential understanding of the fish diversity in this region. An updated checklist of fishes in the Shennongjia is provided, based on the results of the field survey conducted from 2021 to 2022 and combined with historical records of fish diversity in this district and the latest taxonomic progress of relevant taxa in the known literature. This updated checklist includes a total of 52 species, 44 of which are native and eight alien. The Cypriniformes dominates the fish fauna of Shennongjia. Two families of Cyprinidae and Xenocyprididae have the highest number of species. There are six newly recorded species, three previously undescribed species, and 12 species undergoing nomenclatural changes. Eight historically recorded species are excluded from this list, but 27 historically recorded species uncollected during this field survey are remained. The updated checklist presented here can serve as a fundamental reference for future biodiversity analyses and the biodiversity conservation of Shennongjia. [ABSTRACT FROM AUTHOR]

One of the top ten foodborne parasitic infections of global concern is human infection of liver fluke through the consumption of raw or undercooked freshwater fish. This article examines the influences of human–environmental interactions of raw fish sharing and procurement connections on the geographic variation in liver fluke infection. We first discuss the networks embedded in the parasite life cycle that propagates disease transmission. Then, we collect 820 questionnaires from three provinces in northeast Thailand to visualize their fish-sharing and sharing-procurement networks, analyze how the connectivity differences in these networks might be linked to participants' consumption behaviors and environmental settings, and determine how all these together affect liver fluke infection risks. The results show that infection was positively associated with procuring fish from ponds, but negatively associated with procuring fish from rivers. Incorporating fish procurement sites substantially increases network connectivity, reinforcing the human connection to key fish sources as a potential risk factor for infection. The consideration of the connections between human, disease hosts, and the environment, compared to the previously human-centric approach of deworming, offers new insights for public health intervention. [ABSTRACT FROM AUTHOR]

Simple Summary: Detour behavior refers to the ability to reach a goal object that is not directly accessible due to an obstacle (opaque or transparent) by circumventing it. It varies among species, suggesting that environmental adaptation may drive insight behavior. Some species of marine and freshwater fish were placed in a corridor with social stimuli at the end, not directly accessible due to an opaque barrier. Two symmetrical apertures positioned midline in the corridor allowed the fish to temporarily abandon the view of the goal and attempt to circumvent the barrier. All fish showed the ability to move around an interposed obstacle. This is the first evidence of detour behavior in marine fishes within the "four-compartment box task", while results in freshwater fishes confirmed previous evidence. The comparable performance of marine and freshwater fishes suggests similar selective ecological pressure even in different aquatic habitats (e.g., sea and freshwater basins). Moreover, different exploratory behaviors emerged between correct and incorrect compartments (particularly in Danio rerio), providing evidence for a possible mental representation or "permanence in existence" of the goal while performing the obstacle circumvention, as opposed to a more parsimonious idea suggesting that the detour ability emerges only from primitive forms of exploratory behavior such as taxis. Evidence of detour ability to reach a salient goal in marine fishes (Chromis viridis, Chrysiptera parasema, Dascyllus aruanus) and freshwater fishes (Xenotoca eiseni, Danio rerio) has been observed using a "four-compartment box task" with an opaque barrier. The first experiment investigated this ability in marine fishes (Chromis viridis, Chrysiptera parasema, Dascyllus aruanus). Fish were placed in a four-compartment box, with social stimuli not accessible due to an opaque barrier. Two symmetrical apertures midline in the corridor allowed the fish to temporarily abandon the goal's view and attempt to circumvent the barrier. Marine fish showed searching behavior in the two compartments near the social stimuli. In the second experiment, the detour abilities of a marine fish (Dascyllus aruanus) and two freshwater fishes (Xenotoca eiseni, Danio rerio) were compared using a modified version of the apparatus, with elongated compartments continuing further from the obstacle barrier and social stimuli. This enabled the evaluation of the dependence on effective distance to achieve the social goal. Both marine and freshwater fish exhibited detour skills. Additionally, Danio rerio's differential spatial explorations inside compartments supported an active interest in searching for conspecifics, suggesting possible social object permanence retention. Overall, these results highlight the ecological salience of detour skills in fishes, irrespective of species-specific adaptations. [ABSTRACT FROM AUTHOR]

Freshwater streams are frequently fragmented by infrastructure that has the potential to alter stream fish assemblage structure. However, separating natural vs anthropogenically derived assemblage structuring mechanisms within fragmented riverscapes can be challenging. Riverscape concepts such as the river continuum concept (RCC), serial discontinuity concept (SDC), and network dynamics hypothesis (NDH) conceptualize the roles of natural and anthropogenic regulators of assemblage structure along longitudinal gradients in streams. Each of these theories approaches the influence of stream continuity and discontinuity differently, and their application to metacommunity ecology might identify natural vs anthropogenic drivers of assemblage structure. Over 3 y, we surveyed fish assemblages and habitat variables from 40 sites along the longitudinal dimension of White Creek, a headwater stream in College Station, Texas, USA, to test theory-based hypotheses regarding the structuring of fish metacommunities. To achieve this goal, we constructed asymmetric eigenvector maps (AEMs) that integrated aspects of the RCC, NDH, and SDC theories and used these AEMs to test 3 hypotheses: (H1) fish species richness increases longitudinally downstream, but fragmentation by road–stream crossings causes repeated disruptions to this increase, as predicted by the SDC; (H2) spatial contexts based on the SDC explain more variation in metacommunity structure compared with RCC, NDH, or a neutral model; and (H3) distinct fish assemblages exist within fragments of stream created by impassable road–stream crossings. Competing generalized additive models based on stream theories indicated the SDC was the top-ranked model for predicting longitudinal increase in species richness, supporting H1. Spatial variables from the theory-integrated AEMs explained more variation in assemblage structure relative to the neutral model (particularly for the SDC model), supporting H2. Assemblage clustering and ordination showed unique assemblage structure in 3 of the 4 fragments, providing partial support for H3. Our results advance the goal of bridging the gap between theory and conservation of stream fishes by indicating that integration of stream ecosystem theories provides insight to the origins of spatial processes that regulate assemblage structure. Moreover, our results highlight that management of fragmented stream ecosystems might benefit from perspectives that frame anthropogenic alterations within the context of the natural architecture of riverscapes. [ABSTRACT FROM AUTHOR]

Flatfish are ecologically diverse species that commonly occur in marine environments, but also in estuarine and riverine habitats. This complicates the examination of the potential role of flatfish in the 'marine fish event horizon', an economic shift in human exploitation from freshwater to marine fish species during the 10–11th centuries CE around the southern North Sea. This study represents the first multi‐disciplinary investigation of flatfish remains to make species‐specific interpretations of flatfish exploitation. Peptide mass fingerprinting and multi‐isotope analysis of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S) was performed on collagen from 356 archaeological flatfish and 120 comparative archaeological marine or freshwater species to explore the catch habitat of individual flatfish species between 600 and 1600 CE from the North Sea area. European flounder show signals reflecting both freshwater and marine environments, while other flatfish show only those of marine habitats. A subtle shift towards more marine exploitation towards the end of the period is identified, corresponding to the observed transition in targeted species from flounder to plaice throughout the medieval period. Sites show slight differences in δ13C and δ34S within the same species, related to the local environments. Remarkable is the high abundance of marine plaice and flounder during the early medieval period, which shows clear marine or coastal exploitation of flatfish early on, well before the previously accepted onset of the marine fish event horizon. This indicates a gradual shift from coastal to open marine fish exploitation over the medieval period. [ABSTRACT FROM AUTHOR]

Aim Location Methods Results Main Conclusions The assembly of real‐world ecological communities in human‐modified landscapes is influenced by a complex interplay of spatial, temporal, environmental and invasion gradients. However, understanding the relative importance of these drivers and their interactions in shaping functional assembly remains elusive. Our study aimed to investigate the relative influence of these drivers on the functional assembly of a stream fish metacommunity.Streams of the Lake Balaton catchment, Hungary.We analysed a long‐term (18‐year) dataset of the stream fish metacommunity, focusing on changes in functional diversity (Q), redundancy (R) and species dominance (D). Ternary diagrams were utilized to decompose functional diversity into Q, R and D components and to visualize diversity patterns. Linear mixed‐effect regression and separate structural equation models were employed to identify significant drivers of Q, R and D.Native fish communities exhibited low functional diversity (Q) but high redundancy (R) and dominance (D), indicating functional convergence and dominance. Stream habitat size, network position and associated spatial, physical and chemical gradients emerged as consistently significant drivers of D and R. Changes in Q were additionally linked to non‐native community properties and subtle shifts in land use and within‐stream habitat characteristics.Our findings suggest that both environmental filtering and interspecies interactions, particularly trait similarity between invaders and natives shape functional assembly of stream fish metacommunities. Despite minimal temporal directional changes, environmental drivers predominantly influence long‐term diversity patterns of native fish communities, overshadowing invasion effects. Our findings underscore the importance of considering both environmental filtering mechanisms and interspecies interactions in understanding functional assembly. Additionally, the joint application of diversity decomposition frameworks with predictive modelling provides comprehensive insight into patterns of functional diversity and assembly across ecological communities. [ABSTRACT FROM AUTHOR]

Fish biologists have long assumed a link between intestinal length and diet, and relative gut length or Zihler's index are often used to classify species into trophic groups. This has been done for specific fish taxa or specific ecosystems, but not for a global fish dataset. Here, we assess these relationships across a dataset of 468 fish species (254 marine, 191 freshwater, and 23 that occupy both habitats) in relation to body mass and fish length. Herbivores had significantly relatively stouter bodies and longer intestines than omni- and faunivores. Among faunivores, corallivores had longer intestines than invertivores, with piscivores having the shortest. There were no detectable differences between herbivore groups, possibly due to insufficient understanding of herbivorous fish diets. We propose that reasons for long intestines in fish include (i) difficult-to-digest items that require a symbiotic microbiome, and (ii) the dilution of easily digestible compounds with indigestible material (e.g., sand, wood, exoskeleton). Intestinal indices differed significantly between dietary groups, but there was substantial group overlap. Counter-intuitively, in the largest dataset, marine species had significantly shorter intestines than freshwater fish. These results put fish together with mammals as vertebrate taxa with clear convergence in intestine length in association with trophic level, in contrast to reptiles and birds, even if the peculiar feeding ecology of herbivorous fish is probably more varied than that of mammalian herbivores. [ABSTRACT FROM AUTHOR]

The taxonomy of the freshwater featherback fish genus Chitala (Osteoglossomorpha: Notopteridae) remains unsettled because delimiting and naming Chitala species based solely on morphology led to different hypotheses. In this study, we aim to determine the number and identity of Chitala species present in Peninsular Malaysia by employing an integrative taxonomic approach that combines morphology and two mitochondrial markers: the cytochrome c oxidase subunit I (COI) and cytochrome b genes. A total of 60 specimens of Chitala were collected throughout Peninsular Malaysia. Initially, all specimens were sorted into three distinct categories based on their body marking patterns. A molecular phylogenetic analysis revealed that each of these groups was monophyletic, and an automated species partition method further recognized them as distinct species. These results support the presence of three Chitala species in Peninsular Malaysia, even though a multivariate morphometric analysis failed to fully differentiate each of these three species. Comparison with original species descriptions and genetic data from an additional 70 Chitala specimens from neighbouring regions allowed us to name these species as Chitala lopis, Chitala borneensis, and Chitala ornata. We also showed the presence of two undescribed species in Indonesia. [ABSTRACT FROM AUTHOR]

The bridle shiner (Notropis bifrenatus) is a small cyprinid native to the eastern United States and Canada. Bridle shiner populations have declined across their range, and the species now receives concern status or legal protection in 13 states and two provinces. Bridle shiners were historically found in southern and western Maine in densely vegetated, shallow habitats along the shorelines of streams and ponds. We surveyed areas of Maine that supported historical bridle shiner populations using environmental DNA (eDNA) and traditional seine netting methods, and then used eDNA sampling to survey areas with unknown bridle shiner presence. We rediscovered bridle shiner populations at 11 of 32 historically occupied waterbodies and documented bridle shiners in four additional waterbodies. We determined that both eDNA and seine net surveys are viable options for monitoring bridle shiners in Maine and identified ways to streamline the eDNA methods used in this study to reduce the time and cost of future surveys. [ABSTRACT FROM AUTHOR]

Grass carp was an important economic fish for freshwater aquaculture. The exploring and utilization of high-quality grass carp germplasm resources were important for ensuring a domestic supply of high-quality aquatic protein. However, natural grass carp populations in China were facing severe threats because of the effects of frequent human activities, water environment damage, overfishing, etc. Against this background, high-quality grass carp germplasm resources were the foundation for the healthy and sustainable development of the grass carp aquaculture industry, so systematic collection, preservation, identification, evaluation, protection, and utilization of them carry great strategic importance. This paper summarizes major research results of grass carp in morphology, cytogenetics, molecular population genetics, etc. It not only introduced genetic improvement techniques such as gynogenesis, hybrid breeding, and polyploid breeding, but also discussed the existing research on the protection measures of grass carp germplasm resources. On this basis, the paper proposed new methods to improve the protection of grass carp germplasm and create improved varieties, which could provide high-quality resources for the sustainable development of the grass carp industry. [ABSTRACT FROM AUTHOR]

Aim: Temperature is regarded as an important driver of broad‐scale biodiversity patterns. However, less is known of the role of dispersal in shaping broad‐scale species and trait distributions, particularly given that species had to disperse out of glacial refugia after the Last Glacial Maximum (LGM). Here, we used a unique dataset describing the distributions of freshwater fauna combined with trait information to evaluate biodiversity relationships to distance to glacial refugia and temperature. Location: Twenty‐five biogeographical regions across Europe. Time Period: Data from species occurrence were gathered in 1978. Major Taxa Studied: A total of 2816 freshwater invertebrate species and 230 freshwater fish species. Methods: Using the occurrence of invertebrate and fish species in the biogeographical regions, and publicly available trait information, we analysed patterns in diversity indices (i.e. species richness, trait richness and trait redundancy), trait distribution and species and trait β‐diversity, and their relationship to distance to known glacial refugia and regional temperature. Results: We show that distributions of European invertebrate and fish species and traits are primarily explained by distance to refugia and its covarying effect with temperature (i.e. refugia tend to be warmer). Specifically, species and trait richness were higher in regions proximate to refugia and lower in distant regions. Additionally, communities in colder and distant regions exhibited reduced niche dimensions and slower life histories, suggesting increased vulnerability to environmental change. Main Conclusions: Species more distant from their refugia were characterized by higher dispersal capacities. Accordingly, since the LGM, only a subset of species was able to colonize distant regions, while many species have spatial ranges constrained by their dispersal capacity, increasing their potential for extinction under ongoing climate change. Therefore, additional conservation measures considering species' dispersal capacities are required. [ABSTRACT FROM AUTHOR]

The effects of different dietary lipid levels on lipid accumulation, inflammatory response, serum bio-chemical index and histological features of intestine and hepatopancreas of O. macrolepis was experimentally evaluated in an eight-weeks study. Fish (initial weight 50.11 ± 2.86 g) were fed with five iso-nitrogenous diets (around 390 g/kg protein) varying with lipid level (5%, 7%, 9%, 11%, 13%, being LL5, LL7, LL9, LL11, and LL13 respectively) in triplicates. Results showed that the content of crude lipid in carcass and hepatopancreas were not affected by dietary lipid levels (P > 0.05). Serum ALT, TP, HDL-c and MDA, etc., were not significantly affected by diets (P > 0.05), while serum total antioxidant capacity in LL9 and LL11 groups were significantly higher than the other groups (P < 0.05). Histological features of hepatopancreas and intestine showed no significant difference among the five diets (P > 0.05), while the height of intestine villus showed the higher trend in LL9 compared with other groups. The relative expression of lipid metabolism related genes (ppar α, cpt-1α, fas, and hsl) and immune response related genes (tlr 22, nrf 2, tnfα, and il-γ) in the hepatopancreas of fish fed diets differing in their crude lipid levels were not significantly different (P > 0.05). The results suggested that a proper dietary lipid level of 9%--11% could maintain higher antioxidant and health status of adult O.macrolepis. [ABSTRACT FROM AUTHOR]

The topmouth culter (Culter alburnus) is at the top of the food chain and plays an important role in the maintenance of freshwater ecosystem stability. It is also a commercially important aquaculture fish species in China. To establish conservation strategies and breeding programs, a total of 16 polymorphic microsatellite loci were isolated from transcriptome-derived sequences of C. alburnus. Characterization of these loci was assessed against 1 wild and 3 cultured populations in Huzhou, China. The number of alleles per locus ranged from 3 to 10 with an average of 5.25. A bottleneck effect was observed in all 4 populations; The ChangXing population showed moderate genetic differentiation when compared with other populations (FST values, 0.0695--0.0788). The microsatellite loci would be useful for further studies on population genetic diversity, genetic structure, and assessments of the artificial propagation release effect of C. alburnus. [ABSTRACT FROM AUTHOR]

Prostaglandin E2 (PGE2) has been reported to be involved in reproduction as one of the most abundant and widely distributed prostaglandins in invertebrates. Regulating gonad development and gamete production in mollusks can greatly assist artificial breeding, which is believed to promote the commercial benefits of various mollusk species. In the present study, the contents of PGE2 in the gonads of abalone at different developmental stages (maturing stage, ripe stage, and spawning stage) and reproduction states (before and after spawning) were measured. A higher PGE2 level was found in the gonads of abalones at the ripe stage than other stages, and the highest PGE2 level was detected in the ovaries of female H. diversicolor in the UV-stimulated group. Then the effects of PGE2 injection on the spawning efficiency were explored, and the gamete emission rates of female and male abalone were significantly increased after PGE2 injection. Through qRT-PCR and in situ hybridization assay, higher expression levels and wide distribution of phospholipase A2 (PLA2), cyclooxygenase 2 (COX2), prostaglandin E synthases (PGES2), and prostaglandin E2 receptor 4 (EP4) in the gonads of H. diversicolor were observed after spawning. It is speculated that PGE2 may promote the reproductive cycle in both male and female H. diversicolor, although the regulation mechanism of PGE2 in female and male abalone might be different. The results will be useful for the application of PGE2 in the abalone aquaculture practices to increase the reproduction efficiency in future. [ABSTRACT FROM AUTHOR]

Olfaction, the sense of smell, is crucial for animal survival, especially in localizing prey or food. However, little is known about the fish behavioral responses to specific food odors and which olfactory receptor might be activated by the food odors. Here, we examined the evolutionary relationships and classified the subfamilies of olfactory receptors (ORs), and conducted behavioral and gene expression analysis in grass carp (Ctenopharyngodon idellus). We identified 196 intact ORs in the grass carp genome and classified them into 8 subfamilies: β, δ, ε, η, γ, κ, θ, and ζ. 12 representative ORs (4 β, 4 δ, and 4 ε) were highly expressed in the olfactory epithelium (OE) of 24-monthold grass carp. Behavioral exploration found that grass carp showed different behaviors to different food odors at a series of concentrations. Specifically, 0.01 μmol/L amino acid mixtures and 0.005 x Hydrilla verticillata extracts strongly changed the preference index and swimming trajectories in 6-month-old grass carp. In addition, the two food odors stimulation differentially induced ORs expression in three tissues, especially strong in the olfactory bulb and brain. Altogether, our results suggest that olfaction plays an important role in the regulation of fish feeding behavior and provide a basis for further studies on the function and specific recognition of olfactory receptors in fish. [ABSTRACT FROM AUTHOR]

During the survey of potential pathogens in the Tian-e-zhou National Reserve for Lipotes vexillifer in Shishou, China, isolate SS20210504 was isolated from the diseased prey fish-Pelteobagrus fulvidraco and was identified as Aerococcus viridans through 16S rRNA gene, morphological observation, and physiological and biochemical analysis. Artificial infection trials with fish through different methods were conducted. Results indicated that the isolate of SS2021504 caused mortality in fish with the LD50 of 1.0 x 106.2 CFU/mL, 1.0 x 107.9 CFU/mL and 1.0 x 106.8 CFU/mL with the infection method of intraperitoneal injection, co-immersion, and scratch immersion, respectively. Challenged fish exhibited hemorrhages signs similar to naturally diseased fish. Histology analysis showed that the liver and kidney were the principal target organs of isolate SS2021504 in fish, and obvious vacuolation and karyopyknosis occurred in the above organs. To evaluate the pathogenicity of isolate SS20210504 in mice, healthy mice and immunosuppressed mice were further experimentally infected with bacteria, respectively. No death was observed either in healthy mice or in immunocompromised mice. However, the immunocompromised mice inoculated with bacteria showed obvious clinical symptoms and severe damage to multiple organs. The inflammatory signaling pathways were significantly activated with upregulated levels of Myd88, TNFα, AP-1, IL-1β, IL-6, and IFN-γ gene in the spleen from the immunocompromised mice after infected with isolate SS20210504. These findings imply that isolate SS20210504 has the potential risk to YFPs and residents. Continued surveillance of A. viridans and other pathogens in the TZO reserve is suggested to prevent outbreaks in prey fish, YFPs, and residents as well. [ABSTRACT FROM AUTHOR]

There are major gaps in illustrating the risk to freshwater fish that are exposed to environmental microplastics (MPs), even though MPs in freshwater environments has drawn much concern. To explore the potentially negative effects of microplastics on freshwater fish, grass carp (averaging 9.215 ± 0.035g) were exposed to microplastics (32-40 μm in diameter) at two environmental concentrations (100 and 1000 μg/L) for 21 days, and evaluated for physio-biochemical performance, gut microbiome, and metabolome responses. After exposure, microplastics were detected in the intestine and within basal nuclei and goblet cells hyperplasia. Antioxidant enzyme activities (superoxide dismutase and catalase) also significantly decreased within the intestines (P < 0.05). Through 16S rRNA gene sequencing analysis, a decrease in diversity and richness was observed in the MPs-H and MPs-L groups. The abundance of opportunistic pathogens increased and beneficial bacteria decreased in both MP treatments. For example, Acinetobacter and Bosea proportions were higher in the MPs-L group, while Bacteroides and Shewanella increased in the MPs-H group. Furthermore, abundance of Lactobacillus decreased both in the MPs-H and MPs-L groups. Metabolomics analysis revealed primary bile acid biosynthesis metabolism upregulated in the MPs-L and purine metabolism downregulated in the MPs-H group. Additionally, an integration analysis of the gut microbiome and metabolomics identified significant associations between several bacteria taxa and metabolites related to intestinal repair. Taken together, these results highlighted the negative effects on intestinal morphology, oxidative stress, and microbiome and emphasized the relationship between microbiota and metabolites in response to microplastics, which could provide comprehensive insights into the potential risks of MPs on freshwater fish intestines. [ABSTRACT FROM AUTHOR]

The aquaculture industry in China is not complete without the freshwater industry. The scientific assessment of the regional competitiveness of the freshwater aquaculture industry has significant theoretical and practical implications for fostering the industry's sustainable development. Based on the diamond model, this study developed a competitiveness evaluation index system for Chinese freshwater aquaculture industry which included six primary indicators and sixteen secondary indicators. The primary indicators included resource endowment, production capacity, science and technology promotion capacity, related and supporting industries, market demand and guiding development policy. The study analyzed freshwater aquaculture industrial competitiveness during 2012-2020 and classified the Chinese 18 major freshwater aquaculture provinces into five competitive levels. The results showed that the development of related and supporting industries has the greatest contribution to the competitiveness, followed by resource endowment and market demand capacity. The analysis and tier classification showed that the competitiveness of Jiangsu Province and Hubei Province has always been at the forefront, and the province of Guangdong, Fujian, Hunan, Jiangxi, Zhejiang, Anhui, Liaoning, and Guangxi were above the middle level. Moreover, the results indicated that the competitiveness of most provinces showed an upward trend. [ABSTRACT FROM AUTHOR]

The increasing significance of the aquaculture sector and commercially valuable species underscores the need to develop alternatives for controlling diseases such as Ichthyophthirius multifiliis‐induced ichthyophthiriasis. This ciliated protozoan parasite threatens nearly all freshwater fish species, causing substantial losses in the fishery industry. Despite this, effective large‐scale treatments are lacking, emphasizing the necessity of adopting preventive strategies. While the pathogenesis of ichthyophthiriasis and its immune stimulation allows for vaccination strategies, precise adjustments are crucial to ensure the production of an effective vaccine compound. Therefore, this study aimed to evaluate the impact of immunizing Astyanax lacustris with a genetic vaccine containing IAG52A from I. multifiliis and the molecular adjuvant IL‐8 from A. lacustris. Transcript analysis in immunized A. lacustris indicated mRNA production in fish muscles, demonstrating an expression of this mRNA. Fish were divided into five groups, receiving different vaccine formulations, and all groups received a booster dose 14 days after the initial immunization. Samples from vaccinated fish showed increased IL‐1β mRNA expression in the spleen within 6 h post the second dose and after 14 days. In the head kidney, IL‐1β mRNA expression showed no significant difference at 6 and 24 h but an increase was noted in fish injected with IAG and IAG + IL‐8 after 14 days. IL‐8 mRNA expression in the spleen and kidney did not significantly differ from the control group. Histological analysis revealed no variation in leukocyte concentration at 6 and 24 h post‐vaccination; however, after 14 days, the groups injected with IAG and IAG + IL‐8 exhibited a higher leukocyte density at the application sites than the control. The obtained data suggest that the used vaccine is transcribed, indicating its potential to stimulate innate immune response parameters through mRNA cytokine expression and leukocyte migration. [ABSTRACT FROM AUTHOR]

Parasitism is increasingly seen as an ecological factor contributing to behavioural variation among individuals. Yet, the causal direction of the relationship between animal personality and parasites remains unclear. We measured behavioural traits (i.e. exploration, activity, boldness) in pumpkinseed sunfish, Lepomis gibbosus , before and after an experimental infection using cages in a lake where sunfish were naturally exposed to trematode and cestode infection for 1 month. Despite our initial assumptions (i.e. that all individuals would have the same risk of infection within a cage), we found that initial behavioural traits strongly influenced infection susceptibility: initially bolder and less active fish acquired a higher density of trematode and cestode parasites during the infection period. Following infection, fish body condition decreased with increasing cestode density, suggesting that infection is costly to hosts. Body condition was positively correlated with distance moved, a measure of activity, regardless of individual infection status. The repeatability of exploration and activity behaviour and the strength of the activity–exploration correlation (i.e. behavioural syndrome) were reduced following parasite exposure. Distance moved and trematode density were negatively correlated, suggesting that this infection decreases host activity levels. Since trematodes have a complex life cycle with piscivorous birds as a final host, a decrease in activity following infection may make infected fish more susceptible to bird predation, benefiting the parasite. Our results highlight the close links between behaviour and parasitism. We propose that two mechanisms may simultaneously operate: initial host behaviour influences their risk of infection, and infection introduces variation in the behavioural traits of infected hosts. • We infected pumpkinseed sunfish using cages in a lake with high parasite prevalence. • We measured exploration, activity and boldness before and after parasite exposure. • Less active and bolder fish were more susceptible to infection within cages. • Fish body condition decreased with high density of a parasite causing liver damage. • Fish activity was reduced with trematode infection causing black spot disease. [ABSTRACT FROM AUTHOR]