A preliminary snapshot of the trophic model and ecosystem attributes of Kaptai reservoir ecosystem, Bangladesh

A mass-balanced Ecopath model presents a quantitative description of the trophic structure,fl ow of energy and trophic interaction among ecological groups of an ecosystem.The Ecopath with Ecosim(EwE)modeling program(Version 6.5)was used to develop a preliminary trophic model for a tropical freshwater reservoir.The total fi sh biomass was 6.245 t/km 2 and the highest trophic level of the reservoir was 3.362(for snakehead).The ecosystem is phytoplankton based because primary producers originated 68%and detritus originated 32%of the total fl ow from lower trophic level.The gross effi ciency of the fi shery was 0.004,suggesting the ineffi ciency of the system.The positive eff ect of phytoplankton and detritus on most of the other groups were evident from mixed trophic analysis while moderately higher ecotrophic effi ciency(EE)of phytoplankton shows the ecosystem’s potential bottom-up control.The competition for the same resources among diff erent groups was also obvious.The ratio of primary production/respiration(1.969)suggests that the ecosystem is at the developing stage and utmost contemplation should be given to concerned human activities.The low value of relative ascendancy(30.13)and overhead(69.87)reveals the stability of the ecosystem and some degrees of maturity.It also predicts the presence of signifi cant strength in reserve of the system to withstand or overcome any perturbation.However,ecologically sustainable resource management plans should be implemented to ensure the sustainability of this reservoir resources.

Effect of Plant Extracts on Seed Borne Fungi of Jute

The aim of this study was to determine the prevalence of seed-borne fungal pathogens of jute and their control with plant extract. The experiment was carried out in seed pathology centre, Bangladesh Agricultural University to obtain relevant information about the health of jute seeds and find out the efficacy of extracts as seed-treater. Two varieties viz., Deshipat (Corchorus capsularis) and Tossapat (Corchorus olitorius) were selected for this study and jute seeds were collected from two different locations of Bangladesh. The major predominant identified fungi were Colletotrichum corchori, Macrophomina phaseolina, Fusarium spp., and Botryodiplodia theobromae. Least seed-borne fungi were found in the variety of Tossapat. Low germination of seeds was found related to high prevalence of seed-borne fungal infections. Highest seed-borne infection was obtained in the variety of Deshipat. In this study, we evaluated some major plant extracts such as garlic clove (Allium sativum), neem leaves (Azadirachta indica), allamanda leaves (Allamanda cathartica L.) and marigold leaves (Tagetes spp.) for observing the action of these plant extracts on seed borne fungi of Jute. The study revealed that the extract of Garlic (Allium sativum), and Biskatali (Polygonum hydropiper) increased the germination of seeds and garlic?(Allium sativum) extract was also found to be most effective in controlling the seed-borne infection among all the treatments. Although the inhibiting capacity of the extracts of Allamanda (Allamanda cathartica L.) and Biskatali (Polygonum hydropiper) was found to be similar and Biskatali extract was found to have the second position among all the treated plant extracts in inhibiting the growth of isolated fungal pathogens.

Geochemical Color Maps of the Dhaka Water, Bangladesh—New Map Presentations for Toxic Metals and Isotopes

This research investigated the water qualities and distribution of heavy metals concentration in rain, river, ground and supply waters, providing a baseline in Dhaka Urban, Bangladesh, against which future changes can be assessed. The water sample was collected in the Dhaka central zone, from a site located in the center of the Bengal Delta plain between 23&#17640'N - 23&#17654'N latitude and 90&#17620'E - 90&#17631'E longitude which is affected by environmental pollution for high traffic, industrialization and because of its rapid urbanization. The water samples were analyzed for heavy metals by Inductively Coupled Plasma Mass-Spectrometry (ICP-MS), major ions by Ion-Chromatography (IC), water tracer (δ18O and δD) by Mass-Spectrometry (MS), following the standard techniques. Elevated EC and chloride (Cl-) are the markers of wastewater, providing an indication of impacts in the Buriganga River water. The relative concentrations of major ions were presented in the form of Piper and Stiff Diagram. The color maps were constructed to present ions distribution over the areas. The stream reaches directly in Buriganga River from leather industries which may reflect the naturally low dissolved oxygen (DO) 0.3 - 3.5 (mg/L), where aquatic life can’t survive. Uranium contents U238 (0.1 - 2.7 μg/L) are not exceeding the WHO guideline level of 30 μg&#183L-1. Significant portion of Cs133 (0.05 - 0.32 μg/L), Se (0.03 - 0.12 μg/L), B (50 - 2986 μg/L) and Cr (0.55 - 18.59 μg/L), could be increased in Buriganga River areas by the effect of local sources like leather industry. Zn (10 - 1466 μg/L) in the Dhaka Rain and Pb (4 - 6 μg/L) in Dhaka Water occur mainly in industrial and the high traffic areas, respectively. The isotopic (δ18O/δD) distributions have been evaluated for understanding of contaminant sources in groundwater and wastewater recharge from Buriganga River to adjacent depleted groundwater system. The results indicate that the magnitude of pollution problem depends on the size of the area affected, rapid groundwater depletion, polluted river water recharge and the type of the pollutant involved and finally that makes the complex in Dhaka Geochemical pattern.

Climate Change and Anthropogenic Interferences for the Morphological Changes of the Padma River in Bangladesh

This research aims to identify the morphological changes of the Padma River due to the effects of anthropogenic climate change. The morphological changes were measured by aerial satellite images and their historical comparison, terrestrial survey, sedimentation in the riverbed, water flow, water discharge, siltation, and erosion along the river, etc. The Padma River has been analyzed over the period from 1971 to 2020 using multi-temporal Landsat images and long-term water flow data. The climatic parameters data related to temperature and rainfall were collected from 21 metrological stations distributed throughout Bangladesh over a 50-year period (1965-2015) to evaluate the magnitude of these changes statistically and spatially. The Padma, traditionally considered as a dominantly meandering river, is switching over into a braided river due to its highly susceptible nature of erosion and deposition. Results reveal that the tidal range is high during the dry season and increases from upstream to downstream of the river. Climate change may bring changes upstream by changing rainfall intensity, flood severity, and extreme temperature. More inundation can occur due to sedimentation, and more bank erosion can occur at the same time. An exponential increase of morphological activity with increased river flow, water discharge, bank erosion might substantially increase in the future. The changes in the flow introduced by climate change would impact the morphology of the Padma River of Bangladesh during the monsoon. A major change has been observed in the location of the bank and channel, as well as bars, along with their geometry and morphology over time. It is also observed that the bank line is not stable and migrated continuously. The overall width of the Padma River is varied significantly during the last 50 years. Maps and Landsat images represented that the river channel is shifting abnormally. Both climatic parameters and anthropogenic activity play an important role in fish biology and production. From this study, it is hypothesized that this assessment’s findings might help understand the overall hydrodynamic and morphological nature of the Padma River. It will suggest possible future developmental works that might be implemented on this river.

Dynamic of Mangrove Associated Molluscs in Anthropized Areas of the Cameroon Coastline

Due to unabated anthropogenic exploitations, mangrove forests globally are constantly under pressure and degradation, which may result in the reduction of ecosystem functioning and biodiversity. Molluscan fauna, which is one of the main macroinvertebrates that play a major ecological role in nutrient dynamics in mangroves, are sensitive to the changes in their habitat. This survey aims to assess the impact of anthropogenic activities on the diversity of molluscs’ communities in the mangrove forest. Anthropogenic disturbances within 20 sampling sites were valued at six mangrove stands and patched scoring the degree of influence according to vegetation, structure, waste and trampling. Molluscs were caught by hand and counted within 1 × 1 m2 plots placed at three points distant of 50 m established using a straight line transect of 100 m. Upon the 20 sites investigated, five were slightly disturbed, eight moderately disturbed and seven sites were highly disturbed. The mean abundance of molluscs decreased from slightly disturbed areas (172.25 ± 73.09 Ind·m−2) to highly disturbed areas (100.57 ± 62.84 Ind·m−2). Highly disturbed areas have shown lower species richness (R = 1.09 ± 0.15) and diversity (H’ = 2.30 ± 0.31). Human activities in the mangrove forest could particularly have effects on the diversity of molluscs, however, feature potential conservation measures have to be in harmony with the needs of the local population.

Toxicity of organophosphorus pesticide sumithion on larval stages of stinging catfish Heteropneustes fossilis

Sumithion is widely used to control brittle in paddy fields and tiger bug in fish larval rearing ponds. The objective of this study was to elucidate the toxic effects of sumithion on larval stages of stinging catfish Heteropneustes fossilis. Larvae were exposed to two concentrations(150 and 250 μg/L) of sumithion with one control in three replicates of each. Larvae samples were collected at 20- and 24-h intervals followed by observation under a digital microscope. Exposures of stinging catfish larvae to sumithion produced deformities including irregular head shape, lordosis, yolk sac edema, body arcuation, tissue ulceration, etc. The mortality rates of larvae were significantly increased in response to increase in sumithion concentrations. Furthermore, around 30% of the total adult stinging catfish reared in sumithiontreated aquaculture ponds were found to be deformed permanently. These findings highlight that exposure of stinging catfish to sumithion at the critical and sensitive stages in their life cycle may significantly reduce the number of returning adults. Therefore, the use of sumithion for crop protection needs to be considered carefully and alternatives to sumithion should to be developed for controlling aquatic insects in aqua-ponds during larval rearing.

Integrated Rice-Based Shrimp and Crabs Farming: Adaptation to Climate Change and Potential Mitigation of Global Warming in the Coastal Wetlands of Bangladesh

Coastal agriculture is vulnerable to climate change, thereby may affect food production systems and food security in Bangladesh. Methane (CH4) emission from coastal wetlands rice farming is a major environmental concern due to its global warming potential. Therefore, field experiments were conducted at the southern coastal region of Shyamnagar, Satkhira, to investigate the feasibility of Rice-Shrimp and Rice-Crabs mixed farming for adaptation to the changing climate and sustaining food production system. The experimental treatments were designed on rice-based diversified farming systems such as rice sole cropping with no NPKS + no soil amendments (T1), rice sole cropping following farmers’ practice (FP) without soil amendment (T2), rice sole cropping following FP with phosphogypsum (PG) amendment (T3), Rice-Shrimp mixed culture with PG amendment (T4), Rice-Crabs mixed culture with PG amendment (T5), Rice-Shrimp mixed culture + PG amendment with Spirulina (Cyanobacteria) inoculation (T6), and Rice-Crabs mixed culture + PG amendment with Spirulina inoculation (T7). A closed chamber technique was followed to collect gas samples from the rice paddy field and samples were analyzed by Gas Chromatograph. It was found that Rice-Shrimp (T6) and Rice-Crabs mixed farming (T7) practices significantly decreased GWPs compared to the rice sole cropping system. In the dry boro season, the maximum GWPs 4175 kg CO2 eq. ha-1 was recorded from rice sole cropping (T2), which was decreased by 30% and 36.7% under Rice-Shrimp (T6) and Rice-Crabs (T7) mixed farming practices, respectively. Furthermore, in the wet aman season, maximum GWP 4525 kg CO2 eq. ha-1 was recorded from rice sole cropping (T2), which was decreased by 33.0% and 38.8% under Rice-Shrimp and Rice-Crabs mixed farming, respectively. Rice grain yield was low under rice sole cropping (3500 kg/ha), which was increased by 11.0% and 14.7% under Rice-Shrimp mixed farming amended with PG and Spirulina (T6) during wet aman and dry boro seasons, respectively. The postharvest soil properties, such as soil organic matter content, redox potential value (Eh), and exchangeable K+ and Ca2+, contents in soil increased significantly with Phosphogypsum and Spirulina applications, however, decreased Na+ content and electrical conductivity (EC) eventually improved rice plants’ tolerance to salinity and enhanced overall productivity of Rice-Shrimp and Rice-Crabs mixed farming. Conclusively, the conversion of wetland mono rice cropping into mixed Rice-Shrimp and Rice-Crabs farming would be a feasible strategy to sustain rice aquaculture-based farming, ensure food security and mitigate GWPs in coastal wetlands ecosystem.

Pervasiveness of microplastics in the gastrointestinal tract of some selected fish species from Turag River alongside the capital city of Bangladesh

Microplastics(MPs)are synthetic contaminants that have received global attention due to their ubiquitous occurrence,extreme durability,and capacity to harm ecosystems and human health.This study investigated the occurrence of MPs in three fish species(Channa striata,Puntius sophore and Anabas testudineus)collected from two locations(Ashulia Bridge and Mirpur Road)of the Turag River,which flows alongside the Dhaka city,Bangladesh.MPs abundance(items/individuals)was highest in Channa striata(3.8±0.6)from the Ashulia Bridge area and lowest in Puntius sophore(1.8±0.4)from the Mirpur Road area.Fiber was found to be the most dominant(89e93%)form of MPs followed by fragments(21 e35%),films(0e26%)and foams(0e5%).The dominant color of MPs was blue(69e83%),then red(20 e33%),black(11e14%),green(8e20%),and purple(6e8%).The majority(56e71%)of the MPs assessed were<0.5 mm in size,followed by 0.5e1.0 mm(29e33%)and 1e5 mm(38e53%).ATR-FTIR examination revealed three specific polymer varieties-PP(40%),PS(30%)and LDPE(30%).The results of this study provided a baseline of MPs pollution in one of the major protein sources freshwater fishes and raised concern on public health particularly who consume fishes from the urban waterways.

Problems and prospects of fish farming in the Chattogram Hill Tracts of Bangladesh:Community-based aquaculture might be a right choice

The study was carried out in Matiranga Upazila,Bandarban district,which is considered one of Bangladesh’s major hill tract regions.The study aimed to identify present farming conditions,prospects,and problems and suitable solutions to the problems of fish farming.Different participatory rapid appraisal tools such as focus group discussion,field visits,and farmers’interviews were used to collect relevant fish farming information in the study area.The polyculture method was the most practised aquaculture method.Among the selected farms,eleven fish species were identified as culture species.The transportation cost for seeds purchased from remote areas was high(11%of total seed cost).The average transportation-related mortality of fish fry and fingerlings was 7.2%and 2.8%.Feed cost was found as the major cost(58.4%)in aquaculture.Costs and revenue for fish production per decimal varied from BDT 311 to 3528 and BDT 23 to 1268.Utilization of vacant lake,youth and women engagement,integrated aquaculture,the desire of people to engage in aquaculture,and available human resources were found as significant prospects.The major problems identified were lack of hatchery,high feed cost,lack of stakeholder linkage,lack of capital for fish farming,and lack of proper knowledge,guidelines,and consultancy for fish culture.A community-based aquaculture model was proposed to overcome the present challenges and problems in the study area.The model may help to expand aquaculture and thus improve the livelihood and socio-economic status of the people of the hilly areas of Bangladesh.

Multi-species probiotics enhance survival,growth,intestinal microbiota and disease resistance of rohu(Labeo rohita)larvae

Multi-strain probiotics provide the most dependable approaches to improve health,immune response,and disease resistance in farmed fishes.In the present study,we examined the effects of multi-species probiotics on the survival,growth,immune response,and disease resistance of rohu(Labeo rohita)larvae.Newly hatched larvae from the day of first feeding(average weight of 0.003 g)were reared with multi-species probiotics having a combination of Bacillus subtilis(109 colony forming units(cfu)/mL)and Lactobacillus spp.(Lactobacillus plantarum,Lactobacillus buchneri-1011 cfu/mL)in water containing doses of 0(control-C),0.5 mL/L(treatment 1-T1),and 1.0 mL/L(treatment 2-T2)in triplicates for 90 days.After the experiment,a challenge test was performed to assess the fish's resistance to pathogenic Aeromonas veronii.Significantly higher survival was recorded in larvae of treated groups(87%in T2 and 79%in T1)compared to the control(62%).Significantly higher growth performance(weight gain and specific growth rate—SGR)was shown by the probiotic-treated larval groups compared to the control.Probiotic supplementation resulted in significantly higher counts of total viable colony(TVC)and lactic acid bacteria(LAB)in the intestine.Some immunological parameters(mucosal fold fattening,goblet cell abundance,expansion of lamina propria and enterocytes)of the gut were significantly better in probiotic-treated fish.The liver of treated fish showed irregular shape nuclei turning into regular shape and reducing spaces between the hepatic cells.Probiotic-treated fish had the highest post-challenge survival rate(90%)against A.veronii infection.The erythrocytes of challenged fish treated with probiotics had significantly lower frequencies of various nuclear and cellular abnormalities.These findings suggest that multi-species probiotic supplements could improve the survival,growth,health status,and immune response of rohu in the early stages of its development.

A review of potential conservation and fisheries benefits of breaching four dams in the Lower Snake River(Washington,USA)

Abundances of important and imperiled fishes of the Snake River Basin continue to decline.We assessed the rationale for breaching the four lower Snake River Basin dams to prevent complete loss of these fishes,and to maximize their likelihood of recovery.We summarize the science surrounding Sockeye Salmon(Oncorhynchus nerka),Chinook Salmon(O.tshawytscha),steelhead(O.mykiss),Bull Trout(Salvelinus confluentus),White Sturgeon(Acipenser transmontanus),and Pacific Lamprey(Entosphenus tridentatus).From this,we drew ten conclusions:(1)development of the Columbia River System(including the Snake River Basin)has converted mainstem rivers into reservoirs,altering fish behavior and survival;(2)most populations currently record their lowest abundance;(3)the Columbia River System dams reduce productivity of diadromous fishes in the highest-quality spawning grounds that could buffer against future climate dynamics;(4)past actions have done little to reduce impacts or precipitate recovery;(5)the Columbia River System constrains survival and productivity of salmon,steelhead and Bull Trout;(6)Snake River Basin salmon and steelhead remain at high extinction risk;(7)eliminating migration impediments and improving mainstem habitats are essential for maintaining genetic diversity and improving Bull Trout persistence;(8)the lower Snake River Basin dams preclude passage of adult White Sturgeon,constraining gene flow and recruitment;(9)the lower Snake River Basin dams impede dramatically passage of adult and juvenile Pacific Lamprey,and(10)Snake River Basin Pacific Lamprey is at high risk of extirpation.Breaching the four lower Snake River Basin dams is an action likely to prevent extirpation and extinction of these fishes.Lessons from the Columbia River System can inform conservation in other impounded rivers.

Biometrics of the rare fish Rhinomugil corsula(Hamilton,1822)(Mugiliformes:Mugilidae)in the Ganges,Northwestern Bangladesh

Objective:To investigate biometrics of the Rhinomugil corsula(Hamilton,1822)(R.corsula),including length-weight relationships(LWRS),condition factors(Allometric,K_(A);Fulton's,K_(F);Relative,K_(R);Relative weight,W_(R)),and sex ratio and length-frequency distributions in the Ganges(Padma River),Northwestern Bangladesh.Methods:Monthly sampling was conducted using traditional fishing gears during June to August 2012.Total length was measured to the nearest 0.01 cm using digital slide calipers,and total body weight was measured using an electronic balance with 0.01 g accuracy.The LWR was calculated using the expression:W=a×L_(b),where the W is the body weight,L is the total length,a and b are the parameters of the regression.Results:A total of 350 specimens ranging from 8.59-15.71 cm in total length and 9.57-32.59 g in body weight were analyzed during this study.The overall sex ratio was not significantly different from the expected value of 1:1(X^(2)=2.57,P>0.05),but there was significant difference in the length-frequency distributions between the sexes(P=0.03).The allometric coefficient b for the LWR indicated negative allometric growth(b=3.00)in males,female and combined sexes.Results further indicated that Kr was not significantly different between the sexes(P=0.57).However,the mean W_(R)of R.corsula showed significant differences from 100 for males(P=0.03)and females(P<0.001)in this study,indicating the imbalance habitat with food availability relative to the presence of predators.Conclusions:This study reported the first description of biometric relationships for R.corsula,which would be useful for the sustainable conservation of this rear fishery in Bangladesh and also neighboring countries.

Coastal set bagnet fishery in the Payra river,Bangladesh and its impact on fisheries and biodiversity

Objective:To assess the catch composition and seasonal variation in catch of set bagnet fishery from the coastal Payra river,to understand the importance and impact of set bagnet fishery on biodiversity and fisheries,and to find out feasible strategies to reduce the negative impact of set bagnet fishery.Methods:The research was conducted with selection of research area,preparation of gear survey and catch assessment form,sample collection,laboratory analysis and selection of analytical methods to achieve the objectives of the study.Results:A total of 52 species belonging to 23 families were recorded from set bagnet in the Payra river.Most important commercial fishes and their annual catch by set bagnet in the study area were 51.03 MT Ilish(Tenualosa ilisha),8.83 MT Rita(Rita rita),6.92 MT Air(Sperata aor),4.72 MT Chital(Chitala chitala),2.03 MT Boal(Wallago attu),1.84 MT Baghair(Bagarius bagarius),3.35 MT Foli(Notopterus notopterus)and 13.46 MT Golda chingri(Macrobrachium rosenbergii).All these species were mostly caught at initial stages of their life cycle,which usually move with the tidal current.Conclusions:Study suggested that set bagnet should be restricted to allowable limit with strong monitoring system for the protection and conservation of valuable fish species in the coastal areas of Bangladesh.

An overview of freshwater prawn fishery in Bangladesh:present status and future prospect

The freshwater prawn fishery plays an important role in the economy of Bangladesh.The fishery is mainly based on the culture of Macrobrachium rosenbergii.The culture fishery has been growing rapidly,thus,masking the dwindling capture fishery which is faced with serious environmental issues augmented by deleterious fishing methods.Despite the high prospects of the freshwater prawn aquaculture in Bangladesh,a lot of research is needed to ensure the sustainable development of the capture fishery which forms a key source of prawn aquaculture seed as well as provide a baseline for future appraisals.Freshwater prawn aquaculture in Bangladesh is based on traditional methods with continuous adaptations by the rural fishers.However,numerous constraints to its full development are evident at all stages of its production.Lack of quality brood stock,seed,feeds and poor technical knowledge at farmers level are but some of the impediments challenging the sustainability of this industry.This paper reviews the freshwater prawn fishery of Bangladesh over the last few decades and outlines approaches for the development of an ecosystem-based management of both the culture and capture sectors of this important fishery.

Probiotics ameliorate chromium-induced growth retardation and stress in Indian major carp rohu, Labeo rohita

Chromium(Cr)is one of the most prominent contaminants due to its cumulative negative effects on fish.Probiotics may be able to mitigate the unfavorable effects of Cr in fish.In this study,the rohu Labeo rohita(3.02±0.37 g)were exposed to Cr with or without probiotics,representing control(C;without Cr or probiotics),treatment one(T1;Cr at a dose of 4 mg/L),treatment two(T2;probiotics at a dose of 1 ml/L)and treatment three(T3;Cr at a dose of 4 mg/L+probiotics at a dose of 1 ml/L)for 42 days.The results showed that weight gain(WG)and specific growth rate(SGR)were inhibited significantly in T1,while those substantially increased in T2(probiotics)compared to C.On the other hand,WG and SGR were regained as compared to C in T3.The significantly lowest feed conversion ratio(FCR)was found in T2,and moderate FCR was recorded in C and T3,while it was significantly highest in T1.No mortality was observed in C and T2,while 20%mortality was recorded in T1,and decreased mortality was recorded in T3(10%).Exposure to Cr(T1)caused lower hemoglobin and higher glucose levels;however,the use of probiotics reversed these effects in T3(Cr+probiotics).The frequencies of nuclear(notched nuclei,nuclear bridges,and karyopyknosis)and cellular(tear drop shaped,fusion,and twin)abnormalities of erythrocytes increased in the Cr-exposed group(T1);however,these were recovered after probiotic administration(T3).The findings of the present study suggest that probiotics play a beneficial role in reducing the toxicities of Cr in rohu.

Aeromonas veronii isolated from climbing perch(Anabas testudineus)suffering from epizootic ulcerative syndrome(EUS)

Motile Aeromonads are responsible for various diseases in fishes that cause significant economic losses in aquaculture.Aeromonas spp.are also frequently isolated from fish suffering from Epizootic Ulcerative Syndrome(EUS).The present study was conducted to isolate and identify A.veronii from Vietnam climbing perch(Anabas testudineus)suffering from EUS,evaluate the pathogenicity of the isolates,and find out antibiogram profile and susceptibility of the isolates to medicinal plant extracts.Vietnam climbing perch(A.testudineus)suffering from EUS was collected from fish farms located at Savar,Dhaka and bacteria were isolated from the external ulcerative lesion,and kidney and liver of the infected fish on nutrient agar plates.Preliminary phenotypic identification of the bacterial isolates was performed following morphological,physiological and biochemical characterization tests.The 16S rRNA gene sequencing was accomplished for further molecular identification of five selected isolates.To evaluate the pathogenicity of the isolates in vivo artificial infection challenge test was conducted through immersion method.Another in vivo pathogenicity test was done at three different temperatures(18◦C,28◦C,and 37◦C)to examine the effects of temperature on the pathogenicity of the isolates.Ten commercial antibiotics were used to find out the antibiogram profile of the isolates.Finally,susceptibility of the isolates was screened against 19 medicinal plants extracts.A total of 38 out of 46 isolates isolated from Vietnam climbing perch(A.testudineus)suffering from EUS were phenotypically identified as Aeromonas sp.Five randomly selected isolates were further confirmed as A.veronii by analyzing the 16S rRNA gene sequence homology.The pathogenicity of the isolates was found moderate to high(41%-80%mortality)in the artificially challenged fish.The highest and lowest mortality was obtained in the fish challenged with the isolates BFKA33 and BFKA12,respectively.The isolates were found resistant to several antibiotics,including amoxicillin,ampicillin,penicillin-G,and vancomycin.Nevertheless,extracts of three medicinal plant(Allium sativum,Syzygium aromaticum,and Tamarindus indica)demonstrated antibacterial activity to the isolates(BFKA12,BFKA15,BFKA18,BFKA29,and BFKA33).