Black Carp Research Articles

PKACα negatively regulates TAK1/IRF7 signaling in black carp Mylopharyngodon piceus

Protein Kinase A catalytic subunit α (PKACα), plays an important role in the PKA and NF-κB signaling pathway in mammals. However, the function of PKACα in teleost fish remains largely unknown. In this study, PKACα from black carp (bcPKACα) has been cloned and its role in the innate immune antiviral signaling pathway was investigated. The open reading frame of bcPKACα gene contains 1056 nucleotides and the immunofluorescence assay verified that PKACα was mainly distributed in the cytoplasm. The reporter assay showed that bcPKACα expression and co-expression of bcPKACα and black carp TAK1 (bcTAK1) could activate the transcription of NF-κB. However, bcTAK1/bcIRF7-mediated IFN transcription was inhibited by bcPKACα. Knockdown of bcPKACα showed slightly enhanced antiviral activity against spring viremia of carp virus (SVCV) compared with control group. Accordingly, the antiviral activity against SVCV and grass carp reovirus (GCRV) of EPC cells co-expressing bcPKACα, bcTAK1 and bcIRF7 was obviously lower than that of EPC cells co-expressing bcTAK1 and bcIRF7. The similar subcellular distribution and interaction between bcPKACα and bcTAK1 were detected by immunofluorescent staining and co-immunoprecipitation assay separately. The data generated in this study demonstrates that bcPKACα associates with bcTAK1 and positively regulates NF-κB signaling, however, negatively regulates TAK1/IRF7 signaling pathway.

Invasive Black Carp as a Reservoir Host for the Freshwater Mollusk Parasite Aspidogaster conchicola: Further Evidence of Mollusk Consumption and Implications for Parasite Dispersal

Black Carp (Mylopharyngodon piceus) has invaded the Mississippi River and is a potential threat to native mollusks. During prior diet research, we discovered that the fluke Aspidogaster conchicola, a mollusk parasite, occurs regularly in the gastrointestinal tract of Black Carp. The fluke remains in fish intestines for extended periods after the fish has consumed its host. Flukes were found in 33% of the wild Black Carp examined, and numbers ranged from 1 to 802, with no pattern evident across seasons of fish capture. Treating the flukes as indicators of prior mollusk consumption, we adjusted the percent occurrence of mollusks from 26.6% to 54.1%, indicating that the previously reported incidences for bivalves (22.8%) and gastropods (16.5%) in the diet of wild Black Carp are likely to be underestimated. Based on percent occurrences in Black Carp, larger fish (>791 mm) had significantly higher fluke occurrence (42.6%) and fish captured from lentic habitats had significantly greater fluke-adjusted mollusk occurrence (87.5%). These diet-occurrence estimates, coupled with the presence of gravid A. conchicola and evidence of their continued viability in Black Carp intestines, indicate that these fish retain evidence of mollusk consumption for extended periods after evacuation of the gastrointestinal tract. Consequently, Black Carp has the potential to disperse this parasite to other mollusks.

Differential vulnerability of native and non-native mollusks to predation by juvenile black carp

Differential vulnerability of native and non-native mollusks to predation by juvenile black carp

Scenario analysis on optimal farmed-fish-species composition in China: A theoretical methodology to benefit wild-fishery stock, water conservation, economic and protein outputs under the context of climate change

Fish production from aquaculture and wild captures suffers from the rising risk of climate change. This impacts the livelihoods of fishers and fish farmers by shrinking wild fishery stocks, inland water scarcity, and consequent declines in economic and protein productions. China, feeding the most fish of the world with water-intensive crops, faces challenges of water scarcity but still be premature in developing strategies to adapt to climate change. Here, focusing on methodology development, we quantified the water footprint of fish-farming and economic and protein productions in the baseline year 2014. Then, 29 scenarios of farmed-fish-species composition (FFSC, i.e., tons of each farmed fish species) were developed for the target year 2020. The baseline 2014 shows that fish farming generates an average of 150 billion m3 of water footprint, 4.70 million tons of protein, and 263 billion RMB of economic output (~39 billion USD). Uncertainty optimizations were conducted to generate the optimal FFSC solutions that show a potential to increase fish production by 22%, economic and protein output by 18% and 29%, respectively and simultaneously lower water footprint by 22% to the maximum extent. Nine scenarios that lower wild fishery captures were further examined, with optimal FFSC solution that encourages aquaculture of Grass carp, Bighead Carp, and Silver Carp, and discourages Black carp, Tilapia, Crucian carp, Sea bass, and Wuchang bream. From a methodology aspect, this study pulls back policymakers from only focusing on the short-term economic interest of fish-farming and persuades them to rethink long-term adaptive strategies to climate change from multiple sustainable dimensions.

Grass Carp Reovirus VP56 Allies VP4, Recruits, Blocks, and Degrades RIG-I to More Effectively Attenuate IFN Responses and Facilitate Viral Evasion.

ABSTRACTGrass carp reovirus (GCRV), the most virulent aquareovirus, causes epidemic hemorrhagic disease and tremendous economic loss in freshwater aquaculture industry. VP56, a putative fibrin inlaying the outer surface of GCRV-II and GCRV-III, is involved in cell attachment. In the present study, we found that VP56 localizes at the early endosome, lysosome, and endoplasmic reticulum, recruits the cytoplasmic viral RNA sensor retinoic acid-inducible gene I (RIG-I) and binds to it. The interaction between VP56 and RIG-I was detected by endogenous coimmunoprecipitation (co-IP), glutathione S-transferase (GST) pulldown, and subsequent liquid chromatography-tandem mass spectrometry (LC-MS/MS) and was then confirmed by traditional co-IPs and a novel far-red mNeptune-based bimolecular fluorescence complementation system. VP56 binds to the helicase domain of RIG-I. VP56 enhances K48-linked ubiquitination of RIG-I to degrade it by the proteasomal pathway. Thus, VP56 impedes the initial immune function of RIG-I by dual mechanisms (blockade and degradation) and attenuates signaling from RIG-I recognizing viral RNA, subsequently weakening downstream signaling transduction and interferon (IFN) responses. Accordingly, host antiviral effectors are reduced, and cytopathic effects are increased. These findings were corroborated by RNA sequencing (RNA-seq) and VP56 knockdown. Finally, we found that VP56 and the major outer capsid protein VP4 bind together in the cytosol to enhance the degradation of RIG-I and more efficiently facilitate viral replication. Collectively, the results indicated that VP56 allies VP4, recruits, blocks, and degrades RIG-I, thereby attenuating IFNs and antiviral effectors to facilitate viral evasion more effectively. This study reveals a virus attacking target and an escaping strategy from host antiviral immunity for GCRV and will help understand mechanisms of infection of reoviruses.IMPORTANCE Grass carp reovirus (GCRV) fibrin VP56 and major outer capsid protein VP4 inlay and locate on the outer surface of GCRV-II and GCRV-III, which causes tremendous loss in grass carp and black carp industries. Fibrin is involved in cell attachment and plays an important role in reovirus infection. The present study identified the interaction proteins of VP56 and found that VP56 and VP4 bind to the different domains of the viral RNA sensor retinoic acid-inducible gene I (RIG-I) in grass carp to block RIG-I sensing of viral RNA and induce RIG-I degradation by the proteasomal pathway to attenuate signaling transduction, thereby suppressing interferons (IFNs) and antiviral effectors, facilitating viral replication. VP56 and VP4 bind together in the cytosol to more efficiently facilitate viral evasion. This study reveals a virus attacking a target and an escaping strategy from host antiviral immunity for GCRV and will be helpful in understanding the mechanisms of infection of reoviruses.

Black carp IKKε collaborates with IRF3 in the antiviral signaling

Interferon regulatory factor 3 (IRF3) is activated by IκB kinase ε (IKKε) and Tank-binding kinase 1 (TBK1), which plays a crucial role in the interferon signaling in vertebrates. However, the regulation of teleost IRF3 by IKKε remains largely unknown. In this study, the IRF3 homologue (bcIRF3) of black carp (Mylopharyngodon piceus) has been cloned and characterized. The transcription of bcIRF3 was detected to increase in host cells in response to different stimuli. bcIRF3 distributed predominantly in the cytosolic area; however, translocated into nuclei after virus infection. bcIRF3 showed IFN-inducing ability in reporter assay and EPC cells expressing bcIRF3 showed enhanced antiviral ability against both grass carp reovirus (GCRV) and spring viremia of carp virus (SVCV). Moreover, knockdown of bcIRF3 reduced the antiviral ability of the host cells, and the transcription of antiviral-related cytokines was obviously lower in bcIRF3-deficient host cells than that of control cells. The data of reporter assay and plaque assay demonstrated that bcIKKε obviously enhanced bcIRF3-mediated IFN production and antiviral activity. Immunofluorescent staining and co-immunoprecipitation assay revealed that bcIKKε interacted with bcIRF3. It was interesting that the nuclear translocation of bcIRF3 and bcIKKε was enhanced by each other when these two molecules were co-expressed in the cells, however, the protein levels of bcIRF3 and bcIKKε were decreased mutually. Thus, our data support the conclusion that bcIKKε interacts with bcIRF3 and enhances bcIRF3-mediated antiviral signaling during host innate immune activation.

DAK inhibits MDA5-mediated signaling in the antiviral innate immunity of black carp

Dihydroxyacetone kinase (DAK) functions as a negative regulator of melanoma differentiation-associated gene 5 (MDA5)-mediated interferon (IFN) production in human. To explore its role in teleost fish, DAK homologue of black carp (Mylopharyngodon piceus) has been cloned and characterized in this paper. The transcription of black carp DAK (bcDAK) variated in host cells in response to LPS, poly (I:C) and virus stimulation, and bcDAK was majorly distributed in the cytoplasm. Overexpressed bcDAK in EPC cells showed little IFN promoter-inducing ability in the reporter assay and no antiviral activity in plaque assay. When co-expressed with black carp MDA5 (bcMDA5) in EPC cells, bcDAK obviously inhibited bcMDA5-mediated IFN promoter transcription in reporter assay and the antiviral activity in plaque assay. The knockdown of bcDAK enhanced the antiviral activity of the host cells. The association between bcDAK and bcMDA5 has been identified through immunofluorescent staining and co-immunoprecipitation (co-IP) assay. Thus, the data generated in this study support the conclusion that black carp DAK interacts with MDA5 and negatively regulates MDA5-mediated antiviral signaling.

STATUS OF FISH HATCHERY AND NURSERY MANAGEMENT IN, DHANUSHA, NEPAL

The study was conducted to overview status of fish hatchery and nursery management. The main occupation of owners is hatchery business and 23% owners run as side business. 23% of respondents reared fifteen species including major seven species Rupchand, Puntius, Basai, Bhagi, Bata, Magur and Black carp. 30.8% respondents use brood stock from other hatchery of different place for cross breeding to reduce stress, inbreeding depression and to increase disease resistance, growth, performance and production. 61.53% respondents do not monitor the pond to check water quality pararameters like DO, pH and turbidity of water. The average hatchlings, fish fry and fingerling survivality was found 31.10%, 57% and 64% respectively. The problem encountered were flood, predator, unavailability of feed, hormone, fertilizer, skilled manpower and water shortage. The B/C ratio in private hatchery was 1.59 and 1.31 in government hatchery. Most of the respondents use motorcycle (53.8%) as means of transportation of fish seed. The main severe disease was learnaea followed by argulus. The inputs used in nursery management were less than that of recommended dose. High stocking density of fingerlings found (546.15kg/kattha). 69.23% of respondents sold fish, fry and fingerlings to distant market and 30.8% of fish farmers sold their fish seed products in local market. About 75%, 20% and 5% of hatchery fish seed production transferred through channel 1, channel 2 and channel 3 respectively. The problems faced in market were trader monopoly followed by open boarder, road inaccessibility, transportation loss and lack of market information

Spatiotemporal Variation in the Magnitude of Reproduction by Invasive, Pelagically Spawning Carps in the Illinois Waterway

AbstractThe relationship between the magnitude of reproduction and adult density of pelagically spawning carp (PSC) species (bigheaded carp Hypophthalmichthys spp., Grass Carp Ctenopharyngodon idella, and Black Carp Mylopharyngodon piceus) and the influence of environmental factors on this relationship are valuable information for management and control of these highly invasive cyprinids. Six years of standardized monitoring for PSC reproduction and adult density in navigation pools of the Illinois Waterway (IWW; the Illinois River and its connection to Lake Michigan through the Des Plaines River and Chicago Area Waterway System), in conjunction with removal efforts in the upper IWW, where there is limited fish movement between pools, provided an opportunity to deepen our understanding of factors affecting the reproductive productivity of this invasive assemblage. Reproductive activity most commonly occurred in May and June, with the magnitude of reproduction in June far exceeding that occurring in other months. The highest egg counts were found within a 72‐km zone containing the hydromorphological transition between the upper and lower Illinois River, with the majority of PSC larval drift occurring below this zone in the lower Illinois River. Magnitude of reproduction increased nonlinearly with adult PSC density, declining at high adult densities. Annual egg counts were also higher in years that combined more variable spring discharge with higher accumulated degree‐days through June. The density‐dependent reproduction exhibited by PSC implies that any stock–recruitment variation observed for these species needs to be interpreted cautiously before being ascribed to environmental factors affecting survival from hatching to juvenile stages. An increased understanding of which life stages of PSC are subject to density dependence can refine projections of how these species respond to harvest and other control measures.

RIPK3 collaborates with RIPK1 to inhibit MAVS-mediated signaling during black carp antiviral innate immunity

Both the activation and attenuation of MAVS/IFN signaling are critical for host defensing against viral infection and thus lead to an elaborate regulation of MAVS-mediated signaling. However, the regulatory mechanisms concerning MAVS/IFN signaling in teleost fish are not well understood. RIPK3 has been identified as a key regulator of necroptosis, apoptosis, and inflammatory signaling in human and mammals. Here we report the identification of the RIPK3 homologue from black carp Mylopharyngodon piceus (bcRIPK3) and describe its role in regulating MAVS/IFN signaling. qPCR results demonstrated that bcRIPK3 was transcriptionally activated in response to poly (I:C) or LPS stimulation. Immunoblot assay and immunofluorescent staining assay showed that bcRIPK3 was a cytosolic protein with molecular weights of 47 kDa. Like its mammalian counterparts, bcRIPK3 exhibited a conserved function in inducing cell death. The reporter assay and plaque assay showed that overexpression of bcRIPK3 restricted bcMAVS-activated transcription of the interferon promoters of black carp and zebrafish, and suppressed bcMAVS-mediated antiviral activity. Notably, EPC cells co-expressing bcRIPK3, bcRIPK1 and bcMAVS presented much attenuated antiviral activity than the cells co-expressing bcRIPK3 and bcMAVS; and the subsequent co-IP assay identified the interaction between bcRIPK3 and bcRIPK1. Our findings collectively elucidate for the first time in teleost that black carp RIPK3 interacts with RIPK1 to inhibit MAVS-mediated antiviral signaling.

Cloning, prokaryotic expression, purification, and functional verification of the insulin gene in black carp (Mylopharyngodon piceus)

In this paper, we studied the structure, expression and function of black carp insulin gene. The complete Mylopharyngodon piceus insulin (Mp-Ins) gene is 1,965 bp long and includes a 1,499 bp 5ʹ-untranslated region (UTR), a 139 bp 3′-UTR with a poly(A) tail, and an open reading frame (ORF) of 327 bp. The predicted molecular weight of the recombinant Mp-Ins(rMp-Ins) protein is 11.87 kDa. The mRNA expression of Mp-Ins is upregulated in the brain and liver. After the injection of rMp-Ins, Mp-Ins mRNA transcript abundance was significantly upregulated in the liver. The rMp-Ins protein could inhibit the concentration of glycogen phosphorylase (GP), growth hormone (GH), fatty acid synthase (FAS), and insulin-like growth factors-1 (IGF-1), and it also significantly increased the concentration of PI3K. Additionally, the injection of rMp-Ins did not have a significant impact on the glucose-6-phosphatase (G6Pase) content in blood. In situ hybridization results showed that the positive signal of the Mp-Ins gene was mainly concentrated in the cell nucleus of brain tissue and the cell membrane of liver tissue and muscle tissue. Together, these results demonstrated that Mp-Ins plays an important role in growth and metabolism in M. piceus.

Black carp TUFM collaborates with NLRX1 to inhibit MAVS-mediated antiviral signaling pathway

TUFM is a mitochondrial protein and serves as a regulator of antiviral signaling; nevertheless, the character of TUFM in teleosts remains unidentified. In this study, TUFM homologue of black carp (Mylopharyngodon piceus) has been characterized and its role in innate immunity has been explored. Black carp TUFM (bcTUFM) comprises 447 amino acids and shows the high similarity to human TUFM. bcTUFM was about 50 kDa in the Western blot assay and was determined as a cytosolic protein by immunofluorescent microscopy. Knockdown of bcTUFM by shRNA enhanced the antiviral ability of the host cells. The induction fold of interferon promoter transcription in the cells co-expressing bcTUFM and bcMAVS was much lower than that of the cells expressing bcMAVS alone. Our previous study has identified that bcNLRX1 interacted with bcMAVS and functioned as an inhibitor of bcMAVS. The interaction between bcTUFM and bcNLRX1, but not bcTUFM and bcMAVS, was detected through co-immunoprecipitation. The subsequent reporter assay and plaque assay demonstrated that the inhibition of bcMAVS-mediated interferon production and antiviral activity by bcNLRX1 was enhanced by co-expressed bcTUFM. Thus, our data suggests that bcTUFM cooperates with bcNLRX1 to inhibit bcMAVS-mediated antiviral signaling during host antiviral innate immune response against SVCV.

Effects of different drying methods on the quality and nonvolatile taste compounds of black carp

In this study, black carp was chosen as the subject. Effects of moisture content, hardness, color, microstructure, amino nitrogen content, ATP-related compounds, free amino acids, and equivalent umami concentration changes of black carp during hot air drying (HD) and vacuum drying (VD) process were studied. Results showed that the b* and hardness increased with the drying time extended and VD could effectively delay it. Whiteness, amino nitrogen content, ATP-related compounds, free amino acids, and equivalent umami concentration increased at first and decreased when arriving at a certain time. In HD, substances like protein and fat change more dramatically. In conclusion, color and hardness of VD are better than that of HD and microstructure was less damaged, but HD can obtain more umami substances. Practical applications As an effective method of food processing and preserving, drying not only improve the quality of the product, but also extend the shelf life. The reasonable drying will give food seductive color and unique flavor. The quality changes of black carp during drying for 12 hr were studied by measuring moisture, hardness, color, microstructure, nonvolatile taste compounds, and equivalent umami concentration. These results will provide benefit information for the quality control of black carp during the drying process.

NLK suppresses MAVS-mediated signaling in black carp antiviral innate immunity

Mammalian Nemo-like kinase (NLK) plays important roles in multiple biological processes including immune response; however, the roles of teleost NLK remain largely unknown. In the present study, the NLK homolog (bcNLK) of black carp (Mylopharyngodon piceus) has been cloned and characterized. The coding region of bcNLK consists of 1427 nucleotides and encodes 476 amino acid, including two low complexity region (LCR) domains at the N-terminus and a serine/threonine protein kinase catalytic (S-TKc) domain in the middle region. The transcription of bcNLK are promoted after spring viremia of carp virus (SVCV) infection and poly (I:C) stimulation in host cells, but not post LPS treatment. bcNLK exhibits weak impact on the transcription of interferon (IFN) promoter in the reporter assay, however, black carp MAVS (bcMAVS)-mediated IFN promoter transcription is remarkably dampened by bcNLK. The interaction between bcNLK and bcMAVS is detected through the co-immunoprecipitation assay. Accordingly, the plaque assay results show that bcMAVS-mediated antiviral ability is impaired by bcNLK. Moreover, knockdown of bcNLK in host cells leads to the enhanced antiviral ability against SVCV. All these data support the conclusion that black carp NLK associates with MAVS and inhibited MAVS-mediated antiviral signaling.

RNA-Seq Transcriptome Analysis of the Liver and Brain of the Black Carp (Mylopharyngodon piceus) During Fasting.

The black carp (Mylopharyngodon piceus) is an important carnivorous freshwater-cultured species. To understand the molecular basis underlying the response of black carp to fasting, we used RNA-Seq to analyze the liver and brain transcriptome of fasting fish. Annotation to the NCBI database identified 66,609 unigenes, of which 22,841 were classified into the Gene Ontology database and 15,925 were identified in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Comparative analysis of the expression profile between fasting and normal feeding fish revealed 13,737 differentially expressed genes (P<0.05), of which 12,480 were found in liver tissue and 1257 were found in brain tissue. The KEGG pathway analysis showed significant differences in expression of genes involved in metabolic and immune pathways, such as the insulin signaling pathway, PI3K-Akt signaling pathway, cAMP signaling pathway, FoxO signaling pathway, AMPK signaling pathway, endocytosis, and apoptosis. Quantitative real-time PCR analysis confirmed that expression of the genes encoding the factors involved in those pathways differed between fasting and feeding fish. These results provide valuable information about the molecular response mechanism of black carp under fasting conditions.

Acellular fish skin enhances wound healing by promoting angiogenesis and collagen deposition

Acellular matrix is a type of promising biomaterial for wound healing promotion. Although acellular bovine and porcine tissues have proven effective, religious restrictions and risks of disease transmission remain barriers to their clinical use. Acellular fish skin (AFS), given its similarity to human skin structure and without the aforementioned disadvantages, is thus seen as an attractive alternative. This study aims to fabricate AFS from the skin of black carp (Mylopharyngodon piceus), evaluate its physical and mechanical properties and assess its impact on wound healing. The results showed that AFS has a highly porous structure, along with high levels of hydrophilicity, water-absorption property and permeability. Furthermore, physical characterization showed the high tensile strength of AFS in dry and wet states, and high stitch tear resistance, indicating great potential in clinical applications. Cell Counting Kit-8 was used to test the viability of L929 cells when culturing in the extracts of AFS. Compared with the control group, there is no significant difference in optical density value when culturing in the extracts of AFS at days 1, 3 and 7 (*p > 0.05). In vivo wound healing evaluation then highlighted its promotion of angiogenesis and collagen synthesis, its function in anti-inflammation and acceleration in wound healing. Therefore, this study suggests that AFS has potential as a promising alternative to mammal-derived or traditional wound dressing.

TRIF-mediated antiviral signaling is differentially regulated by TRAF2 and TRAF6 in black carp

TRIF is an antiviral adaptor downstream of Toll-like receptors, the roles of teleost TRIF and their regulation remain largely unknown. In this study, a TRIF homologue (bcTRIF) of black carp (Mylopharyngodon piceus) has been cloned, and the transcription of bcTRIF in vivo and ex vivo increased in response to different stimuli. Overexpressed bcTRIF induced the transcription of interferon promoter in the EPC cells and enhanced protection of cells against infection of spring viremia of carp virus (SVCV). The previous study has identified that black carp TRAF2 (bcTRAF2) and TRAF6 (bcTRAF6) functioned positively in RIG-I/MAVS signaling. When co-expressed with bcTRAF2, bcTRIF-induced the transcription of interferon promoter in EPC cells was decreased, and the antiviral activity of bcTRIF was dampened accordingly. On the contrary, co-expressed bcTRAF6 enhanced both bcTRIF-mediated interferon promoter transcription and antiviral activity. The subsequent co-immunoprecipitation identified the interaction between bcTRAF2/6 and bcTRIF. Thus, bcTRIF-mediated antiviral signaling is up-regulated by bcTRAF6 and down-regulated by bcTRAF2.

Organic acid composition and consumer acceptability of fermented fish produced from black tilapia (Oreochromis mossambicus) and Javanese carp (Puntius gonionotus) using natural and acid-assisted fermentation

Ikan pekasam is an example of traditional fermented food products in Malaysia, prepared from freshwater fish such as black tilapia (Oreochromis mossambicus) and Javanese carp (Puntius gonionotus), salt and ground roasted rice, which is added as the only source of carbohydrate. However, some producers add tamarind (Tamarindus indica) pulp and/or dried slices of Garcinia atroviridis to assist the fermentation process. In this study, there was no correlation detected between pH value, titratable acidity (% lactic acid), salt concentration, organic acid composition and the consumer acceptability of ikan pekasam commercial samples made of black tilapia as well as Javanese carp. The organic acid composition in both natural and acid-assisted fermented ikan pekasam from black tilapia and Javanese carp were compared. The results obtained showed that lactic acid was the major organic acid detected, followed by succinic acid and acetic acid. The addition of tartaric and/or garcinia acids was proven to reduce the fermentation time. Therefore, the addition of acid has assisted the fermentation process by increasing the total organic acid content, mainly lactic acid. Moreover, the 9-point hedonic scale showed that ikan pekasam made of Javanese carp had higher overall acceptability due to tender flesh/muscle texture compared to black tilapia regardless of the fermentation process and organic acid content

Identifying threats from introduced and translocated non-native freshwater fishes in Croatia and Slovenia under current and future climatic conditions

Introduced and translocated non-native species are a major threat to biodiversity, especially in aquatic habitats. Efforts aimed at the mitigation of impacts and the implementation of preventative measures for the conservation of native biota must rely upon an accurate evaluation of the risks posed by non-native invasive species and are expected to be strengthened by international collaboration. In this study, 76 non-native freshwater fish species of which 48 extant (both introduced and translocated) and 28 horizon were screened for their risk of invasiveness in the neighbouring countries of Croatia and Slovenia under current and future climatic conditions. Using the Aquatic Species Invasiveness Screening Kit (AS-ISK), threshold scores for the Basic Risk Assessment (BRA) and for the combined BRA and Climate Change Assessment (BRA + CCA) allowed to distinguish with a high level of accuracy between low-, medium- and high-risk species – the latter representing ≈70% of the screened species. Brown bullhead Ameiurus nebulosus, round goby Neogobius melanostomus, topmouth gudgeon Pseudorasbora parva and Wels catfish Silurus glanis were the highest-scoring species for Croatia, and Ameiurus nebulosus, snakehead Channa argus and Pseudorasbora parva for Slovenia. There were discrepancies in medium- and high-risk rankings between Croatia and Slovenia for 12 species. Upon comparison of the BRA outcomes with those based on the Freshwater Fish Invasiveness Screening Kit (the predecessor of the AS-ISK), the risk changed for six species in Croatia and five in Slovenia. After accounting for predicted climate change conditions, the BRA + CCA risk scores increased for ≈50% of the species, with western mosquitofish Gambusia affinis, channel catfish Ictalurus punctatus and black carp Mylopharyngodon piceus achieving the highest score increment for Croatia, and round goby Neogobius melanostomus and Chinese (Amur) sleeper Perccottus glenii for Slovenia. The present outcomes will assist decision-makers in the implementation of appropriate measures for the management of extant non-native species and the potential introduction of horizon species. This is important for the regulation of pet trade and aquaculture as well as for management strategies aimed at the conservation of native biodiversity, which in the case of neighbouring countries/jurisdictions will benefit from joint efforts relying on a full risk assessment for the species classified at higher risk of invasiveness.

Swimming Performance of Four Carps on the Yangtze River for Fish Passage Design

Anthropogenic engineered structures alter the local ecological connectivity of river and survival habitat of native fishes. The swimming performance is critical for establishing fish passage or fish habitat. This study evaluated the swimming performance of four carps (black carp, grass carp, silver carp and bighead carp) with smaller body lengths (1.0–9.0 cm) in a swimming flume. The results showed that the critical and burst swimming speed (m/s) of the four carps increased with the increased body length, and the relative (critical and burst) swimming speed (the critical and burst swimming speed divided by the body length, BL/s) decreases with body length. The critical and burst swimming speed of each species at two individual length groups (1.0–5.0 cm, 5.1–9.0 cm) was significantly different (p &lt; 0.05), and the water velocities in fish passage should be less than the fish burst swimming speed. The results further provided the swimming performance data of juvenile carps and provided technical reference for the construction of fish passage and the restoration of ecological habitat.