Zoonotic human liver flukes,a type 1 biocarcinogen,in freshwater fishes:genetic analysis and confirmation of molluscan vectors and reservoir hosts in Bangladesh

Background Opisthorchiid flukes,particularly Opisthorchis viverrini,Opisthorchis felineus,Clonorchis sinensis,and Metorchis spp.are the most common fish-borne zoonotic human liver flukes(hLFs).Liver fluke infections are more prevalent in resource-deprived and underprivileged areas.We herein estimated the prevalence of the metacercariae(MC)of major hLFs in common large freshwater fishes(lFWF)marketed for human consumption from some selected areas of Bangladesh along with detection of their molluscan vectors and reservoirs.Methods The current status of fish-borne zoonotic hLF infections in lFWF was investigated along with their molluscan vectors and mammalian reservoir hosts in Mymensingh and Kishoreganj in Bangladesh from July 2018-June 2022 using conventional and multiple molecular techniques,such as PCR,PCR-restriction fragment length polymorphism(RFLP),sequencing,and bioinformatic analyses.The infection rate of fishes was analyzed using the Z-test and the loads of MC were compared using the chi-squared(χ^(2))test.Results The MC of C.sinensis,Opisthorchis spp.,and Metorchis spp.were detected in 11 species of common and popular lFWF.In lFWF,the estimated prevalence was 18.7%and the mean load was 137.4±149.8 MC per 100 g of fish.The prevalence was the highest(P<0.05)in spotted snakehead fishes(Channa punctata,63.6%).The highest rate of infection(P<0.05)was observed with the MC of C.sinensis(11.8%).Metacercariae were almost equally(P>0.05)distributed between the head and body of fishes.The infection rate was slightly higher in cultured(19.6%)fishes.The MC of C.sinensis,O.felineus,O.viverrini,and Metorchis orientalis in fishes were confirmed using PCR,PCR-RFLP and bioinformatics.The cercariae of opisthorchiid(Pleurolophocercus cercariae)flukes were only recovered from Bithynia spp.(3.9%,42 out of 1089).The ova of hLFs from dogs(4.3%,5 out of 116)and cats(6.0%,6 out of 100),and adult flukes(M.orientalis)from ducks(41.1%113 out of 275)were detected.Conclusions The MC of hLFs are highly prevalent in fresh water fishes in Bangladesh.Reservoir hosts,such as street dogs,cats,and ducks carried the patent infection,and residents of Bangladesh are at risk.

Helminth parasites of freshwater fishes from Cuatro Ciénegas,Coahuila,in the Chihuahuan Desert of Mexico:inventory and biogeographical implications

As part of an ongoing inventory of the helminth parasites of freshwater fishes in Mexico, 570 individual fish were collected between Apr 2008 and Oct 2011 in 26 localities along the Cuatro Ciénegas region in Coahui­la State, northern Mexico. Seventeen species of hosts, mostly corresponding to Nearctic freshwater elements, were studied. A total of 8324 individual worms were collected during this survey, representing 25 species of helminths, of which 9 were digeneans, 3 monogeneans, 3 acanthocephalans, 9 nematodes and 1 cestode. Most of the records in this checklist represent new host or locality records. The information provided in this checklist may be helpful for our understanding of the biodiversity and historical biogeography of this host-parasite sys­tem, because in the Cuatro Ciénegas region occur a Nearctic freshwater fish fauna, along with Neotropical and endemic elements, and from a biogeographical point of view, this may represent a transitional area.

Length-weight relationships for six freshwater fish species in Iran

The aim of this study is to report the length-weight relationship parameters （a and b） for some economically important fish species from Iranian freshwaters. The length-weight relationships （LWR） are calculated for six freshwater fish species collected during 2006 and 2007 in Iran. The values of the exponent b in the LWR （W=aL^b） vary between 2.985 and 3.543. The LWR with high correlation coefficient （r^2） is significant for all the species. These parameters axe of great importance to evaluate the relative condition of populations, biology, species management and their fisheries and stock assessment. The application of the length-weight relationships presented here should be limited to the observed length ranges.

Bioaccumulation and depuration of chromium in the selected organs and whole body tissues of freshwater fish Cirrhinus mrigala individually and in binary solutions with nickel

Contamination of aquatic ecosystems with heavy metals has been receiving increased worldwide attention due to their harmful effects on human health and other organisms in the environment. Most of the studies dealing with toxic effects of metals deal with single metal species, while the aquatic organisms are typically exposed to mixtures of metals. Hence, in order to provide data supporting the usefulness of freshwater fish as indicators of heavy metal pollution, it has been proposed in the present study to investigate the bioaccumulation and depuration of chromium in the selected organs of freshwater fingerlings Cirrhinus mrigala, individually and in binary solutions with nickel. The results show that the kidney is a target organ for chromium accumulation, which implies that it is also the ＂critical＂ organ for toxic symptoms. The results further show that accumulation of nickel in all the tissues of C. mrigala is higher than that of chromium. In addition, the metal accumulations of the binary mixtures of chromium and nickel are substantially higher than those of the individual metals, indicating synergistic interactions between the two metals. Theoretically the simplest explanation for an additive joint action of toxicants in a mixture is that they act in a qualitatively similar way. The observed data suggest that C. mrigala could be suitable monitoring organisms to study the bioavailability of water-bound metals in freshwater habitats.

Development of Intermediate Foodstuff Derived from Freshwater Fish in China

According to the three-dimensional contour maps showing the gel-forming properties of surimi derived from freshwater fish, 8 species of surimi were classified into two types. The-valley type surimi （silver carp, big-head carp, Chinese snake head and blunt snout bream） shows easy setting, low resistance to gel collapse, high enhancement ability with two-step heating, and narrow optimum heating temperature and time area, which are of the same characteristics as the walleye pollack surimi. In contrast, the Plateau type surimi （tilapia, grass carp, mud carp and common carp） exhibits difficult setting, high resistance to gel collapse, no enhancement ability with two-step heating, and wide optimum heating temperature and time area. There are seasonal changes of gelling properties of silver carp surimi, and the setting ability of surimi gel is higher in winter and lower in summer. The marine fish meat gels and the freshwater fish meat gels have the same acceptability for inland Chinese according to the sensory evaluation results. A slight increase in sensory scorings of kamaboko gels occurred when the extract from walleye pollack muscle was added, especially in the odor scoring of silver carp kamaboko gels.

BIODIVERSITY AND CONSERVATION OF FRESHWATER FISH IN HONG KONG, CHINA

We surveyed the distribution, composition and diversity of freshwater fish in Hong Kong, China from 2002 to 2004. Sites surveyed were mainly streams, marshes and estuaries. There are ponds for aquaculture and reservoirs in Hong Kong but no large natural water bodies. From the 220 sites surveyed, 114 species of 37 families were found. Gobiidae (with 24 species) and Cyprinidae (21 species) were the dominant families. This survey has increased the number of freshwater fish species recorded in Hong Kong to 167. Among these, 71 (42.5%) are primary freshwater fish, 44 are brackish and 46 are vagrants. The remaining 6 species are diadromous. In Hong Kong, freshwater fish are conserved by a combination of measures. About 38% of Hong Kong’s land area is designated as country parks and/or special areas, and is managed for nature conservation and educational purposes. In addition, another 5% of land area is zoned for conservation in the statutory land use zoning system to protect them from development and incompatible land uses. Major development projects have to go through the statutory environmental impact assessment process to ensure that they will not have adverse impact as far as practicable. There are conservation action plans for important species. For example, captive-bred individuals of the endemic Hong Kong Paradise Fish Macropodus hongkongensis have been released to suitable and secure sites inside country parks and their populations are regularly monitored. Other measures such as wetland creation, restoration and enhancement programmes are also implemented for freshwater fish conservation.

Strategic Conception for Sustainable Development of Massive Freshwater Fish in China

[ Objective] To propose strategic conception for sustainable development of massive freshwater fish in China. [ Method] The current development status of massive freshwater fish industry in China was analyzed. On this basis, strategic conception for sustainable development of massive freshwater fish in China was proposed. [Remlt] In order to solve the present problems in the massive freshwater fish industry in China, basic strategies were proposed to develop the massive freshwater fish industry in China. The fishery resources should be capitalized to promote sustainable development of resources. Consumer demand of end-market should be used to drive stable development of the whole industry chain. Consumer demand should be guided to enhance the industrial market position. Processing and distribution channels should be constructed to promote sustainable development of seed and farming industries. Consumer demand at different levels should be used to promote multi-level multi-media health culture. Brand building and operating should be performed to enhance the competitive position of the industry in international and domestic markets. [ Condusion] The study has great theoretical and practical significance for promoting development of the massive freshwater fish industry in China.

Distribution and Relationships of Seven Trace Elements （Cr, Fe, Mn, Ni, Co, Cu and Zn） in Freshwater Fish from Five French Fishing Areas

The concentrations of seven essential trace elements in 149 freshwater fish from eight fish species （European eel, bream, common carp, European catfish, roach, perch, pike and pikeperch） from five different French fishing areas from contaminated and control sites were measured by inductively coupled plasma mass spectrometry after microwave digestion under pressure. Differences in the concentration of elements in the muscles of these species were examined and the mean levels were compared for each species with previous French and European studies. The condition factor and the differences between the control and contaminated sites and between predatory and non-predatory groups, with respect to the concentration of these elements, were also studied.

The Relationship between the Area of Aquaculture Pond and Purification Pond in Water Circulation Aquaculture System

The establishment of water circulation aquaculture system realized the hi- erarchical use of nitrogen, phosphorus and other eutrophic substances in aquaculture wastewater and the recirculation use of water resource. However, no research has been reported on the detailed calculation of the relationship between the area of aquaculture pond and purification pond. In this study, referring to the absorption ability of aquatic plants to pollutants in aquaculture wastewater and pollutant generation and discharge coefficient in aquaculture pond, based on the general rules of water quality management in freshwater aquaculture system, a calculation mode was es- tablished to investigate the relationship between the area of aquaculture pond and purification pond in freshwater recirculation aquaculture system, which was feasible to explain related cases and would provide theoretical basis to reduce the economic costs in the construction of water circulation aquaculture system and realize the bal- ance between the ecological benefits and the economic benefits.

Discovery of Tanichthys albonubes Lin 1932 (Cyprinidae) on Hainan Island,and Notes on Its Ecology

A wild population of the globally restricted and highly threatened freshwater fish Tanichthys albonubes Lin was recently discovered on Hainan Island, China. Prior to the present study, native populations were only known from isolated pockets in Guangdong Province of China and Quang Ninh Province of Vietnam; the Hainan record thus represents the first insular and southernmost distribution of this little-known species. Thus far it is known only from a single site in Hainan, despite repeated surveys of similar habitats throughout the island. The Hainan population occurs in a clean, sluggish coastal stream with abundant hydrophytes, and is sympatric with 20 fish species. Due to the unique geographic distribution of the Hainan population, and the conservation significance of the species, studies of its phylogenetic relationships with conspecifics populations elsewhere are underway. The exact locality of the newly discovered Hainan population cannot be revealed, but relevant government authorities have been notified and we are working to protect the site.

The effects of season on fatty acid composition and ω3/ω6 ratios of northern pike(Esox lucius L.,1758) muscle lipids

In the present study, the effects of season on fatty acid composition, total lipids, and ω3/ω6 ratios of northern pike muscle lipids in Klzlhrmak River （Klrlkkale, Turkey） were investigated. A total of 35 different fatty acids were determined in gas chromatography. Among these, palmitic, oleic, and palmitoleic acids had the highest proportion. The main polyunsaturated fatty acids （PUFAs） were found to be docosahexaenoic acid, eicosapentaenoic acid, and arachidonic acid. There were more PUFAs than monounsaturated fatty acids （MUFA） in all seasons. Similarly, the percentages of ω3 fatty acids were higher than those of total ω6 fatty acids in the fatty acid composition. ω3/ω6 ratios were calculated as 1.53, 1.32, 1.97, and 1.71 in spring, summer, autumn and winter, respectively. Overall, we found that the fatty acid composition and ω3/ω6 fatty acid ratio in the muscle of northern pike were significantly influenced by season.

The Microflora of Gills, Gut and Skin of European Eels （Anguilla anguilla） in Lakes of Latvia

The microbial contamination of fish is the most important factor in assurance of food safety. The microflora on the surface of skin, gills and gut of fish is constantly under the influence of the water environment and this may cause colonization of microorganisms on fish. The goal of this study was to evaluate the bacterial contamination level on the skin, gills and gut of the European eel （Anguilla anguilla）, i.e., detecting total bacteria count （TBC） and Enterobacteriaceae counts, as well as Listeria spp, and Salmonella spp. in freshly caught fish. Among the three lakes, TBC on skin, gills and gut varied from 0.66 CFU/cm2 to 4.93 CFU/cm~, from 0.40 CFU/cm2 to 5.51 CFU/cm2 and from 0.30 CFU/cm2 to 6.37 CFU/cm2, respectively. Enterobacteriaceae count on skin, gills and gut was from 0 CFU/cm2 to 4.30 CFU/cm2, from 0 CFU/cm2 to 2.47 CFU/cm2 and from 0 CFU/cm2 to 1.72 CFU/cm2, respectively. The highest mean count of TBC on gills, skin and gut was found in samples from Sivers lake, while the lowest was in samples from Aluksne lake. Values among the lakes were significanty （P 〈 0.05） different. Also the highest mean counts of Enterobacteriaceae were found on gills and skin of eels from Sivers lake, but the highest count on gut was found in Usma lake. All tested samples were Listeria monocytogenes and Salmonella spp. negative. TBC and Enterobacteriaceae counts of skin, gills and gut were typical for wild fish in fresh water. Foodborne pathogens, such as Salmonella spp. and L. monocytogenes, have not been found in the present study, indicating that fish are safe for human consumption.

Whole Chia Flour as Yield Enhancer, Potential Antioxidant and Input of n-3 Fatty Acid in a Meat Product

In this paper, the effect of the addition of whole chia flour and water at cooked fish burgers on yield, water and fat retention, n-3 fatty acids content and oxidative stability were studied. The results showed that 94% of yield, 92% of water retention and 97% of fat retention were achieved with the addition of 5.92 g of whole chia flour and 15 g of water per 100 g of burger. The n-3 fatty content increased from 704.57 ± 21.66 mg to 1551.71 ± 47.71 mg/100g of cooked burger when the chia flour was added, enhancing nutritional quality indices of lipid. A good oxidative stability, with minimum formation of conjugated dienes, hydroperoxides and thiobarbituric acid reactive substances during 30 days frozen storage was obtained too, probably due to the presence of polyphenolic compounds with antiradical activity and reducing power in the fibrous fraction of the flour chia. The results from the present study highlight remarkable technological applications of whole chia flour as food ingredient in the design of healthier fish meat commodities.

Estimation of Mercury Intake from Consumption of Fish and Seafood in Russia

Data on the mercury concentration in freshwater and marine fish and seafood on the territory of Russia are presented. The level and pattern of the fish and seafood consumption in various regions of Russia are found from the analysis of open statistics. Regions with the maximum and minimum consumption of fish products are established. Mercury intake from these products in a human organism is calculated. It is shown that at the current level and pattern of the diet in Russia fish cannot be a source of high mercury concentrations in a human organism.

Arsenic speciation in freshwater fish:challenges and research needs

Food and water are the main sources of human exposure to arsenic.It is important to determine arsenic species in food because the toxicities of arsenic vary greatly with its chemical speciation.Extensive research has focused on high concentrations of arsenic species in marine organisms.The concentrations of arsenic species in freshwater fish are much lower,and their determination presents analytical challenges.In this review,we summarize the current state of knowledge on arsenic speciation in freshwater fish and discuss challenges and research needs.Fish samples are typically homogenized,and arsenic species are extracted using water/methanol with the assistance of sonication and enzyme treatment.Arsenic species in the extracts are commonly separated using high-performance liquid chromatography(HPLC)and detected using inductively coupled plasma mass spectrometry(ICPMS).Electrospray ionization tandem mass spectrometry,used in combination with HPLC and ICPMS,provides complementary information for the identification and characterization of arsenic species.The methods and perspectives discussed in this review,covering sample preparation,chromatography separation,and mass spectrometry detection,are directed to arsenic speciation in freshwater fish and applicable to studies of other food items.Despite progress made in arsenic speciation analysis,a large fraction of the total arsenic in freshwater fish remains unidentified.It is challenging to identify and quantify arsenic species present in complex sample matrices at very low concentrations.Further research is needed to improve the extraction efficiency,chromatographic resolution,detection sensitivity,and characterization capability.

Genetic diversity and population structure of Prochilodus costatus and Prochilodus argenteus preceding dam construction in the Paraopeba River,Sao Francisco River Basin,Minas Gerais,Brazil

Curimat?-pioa (Prochilodus costatus) and curimat?-pacu (Prochilodus argenteus) are migratory fish species endemic to the S?o Francisco River Basin in Brazil. Both species play important roles in local fisheries and ecology in the Paraopeba River. A dam was recently constructed on this river and to help in the development and conservation programs, we characterized the genetic variation of both species before dam construction. Complex hypervariable repeats micro-satellite was used to asses genetic variation for both species within and between the five collection sites in order to detect population substructuring. Nucleotide substitutions and insertion/deletion polymorphisms (indels) resulted in 35 P. costatus haplotypes (sample size = 89) and 22 P. argenteus haplotypes (sample size = 32). Significant genetic diversity and population differentiation was detected between five sampling sites for both species. Therefore, each of the five sites should be regarded as a group comprising significant genetic differences in species conservation and maintenance plans. Comparing these results to genetic diversity measures after dam construction will be critical for future management in this region.

The dynamic changes of arsenic biotransformation and bioaccumulation in muscle of freshwater food fish crucian carp during chronic dietborne exposure

Dietary uptake is the major way that inorganic arsenic(iAs)enters into benthic fish;however,the metabolic process of dietborne i As in fish muscle following chronic exposure remains unclear.This was a 40-day study on chronic dietborne i As[arsenite(AsⅢ)and arsenate(AsⅤ)]exposure in the benthic freshwater food fish,the crucian carp(Carassius auratus),which determined the temporal profiles of iAs metabolism and toxicokinetics during exposure.We found that an adaptive response occurred in the fish body after iAs dietary exposure,which was associated with decreased As accumulation and increased As transformation into a non-toxic As form(arsenobetaine).The bioavailability of dietary AsⅢwas lower than that of AsⅤ,probably because AsⅢhas a lower ability to pass through fish tissues.Dietary AsⅤexhibited a high potential for transformation into AsⅢspecies,which then accumulated in fish muscle.The largely produced AsⅢconsidered more toxic at the earlier stage of AsⅤexposure should attract sufficient attention to human exposure assessment.Therefore,the pristine As species and exposure duration had significant effects on As bioaccumulation and biotransformation in fish.The behavior determined for dietborne arsenic in food fish is crucial for not only arsenic ecotoxicology but also food safety.

Sequence analysis and typing of Saprolegnia strains isolated from freshwater fish from Southern Chinese regions

Saprolegniasis,caused by Saprolegnia infection,is one of the most common diseases in freshwater fish.Our study aimed to determine the epidemiological characteristics of saprolegniasis in Chinese regions of high incidence.Saprolegnia were isolated and identified by morphological and molecular methods targeting the internal transcribed spacer(ITS)ribosomal DNA(rDNA)and building neighbor-joining(NJ)and maximum parsimony(MP)phylogenetic trees.The ITS sequences of eight isolated strains were compared with GenBank sequences and all strains fell into three clades:CLADE1(02,LP,04 and 14),CLADE2(S1),and CLADE3(CP,S2,L5 and the reference ATCC200013).Isolates 02 and LP shared 80%sequence similarity with S.diclina,S.longicaulis,S.ferax,S.mixta,and S.anomalies.Further,isolates 04 and 14 shared 80%similarity with S.bulbosa and S.oliviae.Finally,extremely high ITS sequence similarities were identified between isolates S1 and S.australis(100%);CP and S.hypogyna(96%);and S2,L5,ATCC200013 and S.salmonis(98%).This research provides insights into the identification,prevention and control of saprolegniasis pathogens and the potential development of effective drugs.

The effects of two free-floating plants (Eichhornia crassipes and Pistia stratiotes) on the burrow morphology and water quality characteristics of pond loach (Misgurnus anguillicaudatus) habitat

Loach exhibit conspicuous drilling behaviors in the mud of shallow waters,yet their burrow morphology and the factors affecting this behavior have received little attention.We characterized the burrow morphology and water quality of the pond loach Misgurnus anguillicaudatus in three scenarios:in tanks without plants,tanks with the free-floating plant water hyacinth Eichhornia crassipes,and tanks with water lettuce Pistia stratiotes.Water hyacinth effectively removed water TN,COD,NO3-N and NH4-N,and water lettuce removed water TP and NH4-N.Water hyacinth and water lettuce markedly reduced water turbidity and DO,increased TOC and EC.Water hyacinth purified water more effectively than water lettuce,providing a suitable habitat for loach feeding,living and burrowing.The burrow structures were V-shaped,Y-shaped,inverted L-shaped,or complicated dendritic networks composed of multiple V shapes.The hyacinth treatment was characterized by the greatest burrow volume,length,depth,and structural complexity,but the opening size was reduced by dense root mat coverage.Burrows in the water lettuce treatment were characterized by intermediate volume,length,branches and sinuosity,but they had the largest opening and pit size.The control treatment had a flat bottom with the smallest,shortest burrows.This study indicates that free-floating plants improve habitat suitability and change burrow morphology and may be used to improve loach breeding methods。

Intensity of parasitic infestation in silver carp,Hypophthalmichthys molitrix

Silver carp,Hypopthalmichthys molitrix is one of the most economically valuable fish species in Bangladesh.However,its production is often hindered by parasite-induced mortality.The present study reports the intensity of parasitic infestation in 216 specimens of H.molitrix collected from different fish markets in Rajshahi City,Bangladesh.Nine different parasite species (Trichodina pediculatus,Dactylogyrus vastator,Ichthyophthirius multifilis,Gyrodactylus elegans,Lernaea sp.,Apiosoma sp.,Myxobolus rohitae,Camallanus ophiocephali,and Pallisentis ophiocephali) were recovered from the gill,skin,stomach,and intestine of host fish.The highest level of infection was observed for host skin,while lower levels were observed for host gill,stomach,and intestine.The results also revealed that the intensity of parasite infection in different organs of H.molitrix varied with the season.In particular,the highest levels of infection were recorded during the winter period (November-February),when fish are most susceptible to parasites.The findings of the study will help in the management and conservation of H.molitrix.