Different Species Of Fish Research Articles

МИКРОБИОЛОГИЧЕСКАЯ БЕЗОПАСНОСТЬ СВЕЖЕЙ РЫБЫ, ЗАРАЖЕННОЙ ТРЕМАТОДАМИ, С УЧЕТОМ САНИТАРНОГО СОСТОЯНИЯ ВОДОЕМОВ

The purpose of research is to study the relationship between the microbiological indicators of fish infected with diplostomosis and post-diplostomosis, and the indicators of veterinary and sanitary safety of water bodies involved in its cultivation. Objectives: determination of the main parasitological indicators of infected fish (intensity of invasion (II), extensiveness of invasion (EI), species predisposition of fish to pathogens of trematodes); conducting a microbiological analysis of the obtained fresh fish and the place of its cultivation, taking into account the degree of infestation of the fish by pathogens of diplostomosis and post-diplostomosis. The study was conducted in the conditions of the North Caucasus Zonal Research Veterinary Institute in the summer and autumn seasons of the year. The study material included fish of different species: Hypophthalmichthys molitrix (silver carp), Cyprinus carpio (carp), Ctenopharyngodon idella (grass carp), Abramis brama (Bream), both infected with trematodes and clinically healthy. The water of the fish catchment site, taken from the Nizhnedonsky canal, Veselovsky, Proletarsky and Tsimlyansky re¬servoirs, was studied. The lowest AI and EI were found in fish of the species Ctenopharyngodon idella (grass carp). AI in silver carp compared to grass carp was 11.3 times higher, in carp – 9.3 times, in bream – 6.6 times; EI was 11.3 times higher in silver carp and 11.0 times higher in carp; for bream – 3.3 times. In highly invasive fish of the species Hypophthalmichthys molitrix (silver carp), Cyprinus carpio (carp), mesophilic aerobes and facultative anaerobic microorganisms were found to be 14.7 and 4.24 times more, respectively, compared to healthy fish; according to the average value of detected coliform bacteria – 2.54 and 1.86; by the number of detected Staphylococcus sp. – at 24.3 and 33.15; Escherichia sp. – at 1.5 and 0.6; Klebsiella sp. – at 110 and 85; Salmonella sp. – 45 and 0.8 times more. A correlation was established between the total microbial number of water bodies and the number of mesophilic aerobes and facultative anaerobes in caught live fish (correlation coefficient 0.99).

Microplastic ingestion by fish with different feeding habits in the Ob and Yenisei Rivers

Microplastic particles in the size range 0.15 to 5.00 mm were quantified and characterised in the gastrointestinal tracts of three wild freshwater fish (n = 141) from the Ob and Yenisei rivers, including common ruffe (Gymnocephalus cernua L.), Siberian dace (Leuciscus baicalensis Dybowski) and European perch (Perca fluviatilis L.). Microplastics were found in the gastrointestinal tract of 62% of the fish examined, ranging from 18.5% in the Yenisei perch sample to 92.6% in the Ob ruffe sample. The vast majority of microplastics in all fish species were fibres (up to 99.7% of all particles detected in perch), followed by irregularly shaped fragments (up to 22.7% in ruffe), with no preference between the three species. Spheres and films were found exclusively in dace and ruffe, with proportions of 3.7% and 1.2% respectively. Particles consisted of polyethylene terephthalate, polypropylene, polyamide and other synthetic polymers with a significant proportion of highly degraded polymers. The mean MP content in fish GITs ranged from 0.44 ± 0.25 items per individual in Yenisei perch to 3.81 ± 0.55 items per individual in Ob ruffe. Particle burdens in fish were significantly higher in the Ob than in the Yenisei (p < 0.05), which may reflect the common level of plastic contamination in these two rivers. MP ingestion varied in species with different feeding habits as ruffe (benthivorous) > dace (omnivorous) > perch (hunter) in both rivers (p < 0.01). This study was the first to quantify MP consumption by freshwater fish of different species in the Ob and Yenisei rivers and to identify patterns associated with different feeding habits.

Radioecological monitoring of 90Sr and 137Cs accumulation in fish organisms in certain water bodies of the forest-steppe zone of Ukraine

The study aims to determine the radionuclide contamination formation patterns in ichthyofauna representatives of some Forest Steppe of Ukraine water bodies and to establish reference values for the specific activity of 90Sr and 137Cs in the fish body as of 2021. To determine the radionuclide pollution levels in the industrial ichthyofauna representatives in the water areas of the Kaniv Reservoir, the Kosivskyi, the Bila Tserkva Middle, and the Bohuslav Reservoirs on the Ros River and in the unregulated sections of the Ros River (above the city of Bila Tserkva) and Hnyliy Tikych (the village of Stavyshche) as of 2021, the following fish species were selected: red snapper - Rutilus rutilus L., flatfish - Blissa bjoerkna L., common bream - Abramis brama L., silver crucian carp - Сarassius gibelio (Bloch), bream - Alburnus alburnus alburnus L.; pike - Esox lucius L. (peaceful species); pike perch – Stizostedion lucioperca L.; European-Asian river perch – Perca fluviatilis fluviatilis L. (predatory species). The specific activity of 90Sr and 137Cs was determined in the entire fish body by generally accepted radiochemical and gamma spectrometric methods. In 2021, the registered average specific activity of 90Sr in fish of various species of the Kaniv Reservoir ranged from 0.6 to 1.3; 137Cs - from 2.4 to 13.2 Bq/kg. The average specific activity of 90Sr in fish of different species of the Kosiv Reservoir ranged from 0.1 to 0.5, that of 137Cs – from 0.2 to 2.1 Bq/kg, Bila Tserkva Middle ranged, respectively, from 0.2 to 0.8 and from 0.8 to 4.0, Bohuslav – from 0.1 to 0.5 and from 0.5 (bream) to 3.1 Bq/kg. The average content of 90Sr and 137Cs in the body of fish fished in unregulated sections of the Ros and Hnyliy Tikych rivers was 0.1–0.5 and 0.5–2.0 Bq/kg, respectively. The specific activity of 90Sr in peaceful and predatory fish of most of the studied reservoirs probably did not differ, and we can note only the tendency to the formation of higher levels of accumulation of the radionuclide by peaceful species. However, the values of the specific activity of 137Cs of predatory species exceeded the corresponding values that were registered in peaceful fish. The levels of fish radionuclide contamination in all the studied reservoirs, except for the Kaniv Reservoir, did not differ reliably. The increased content of radionuclides in the Kaniv Reservoir fish compared to other reservoirs of the Forest Steppe can be explained by the constant influx of radionuclides from the ecosystem of the Kyiv Reservoir through the Kyiv HPP dam. During the research period, 58–74% of the total activity of peaceful fish in forest-steppe reservoirs was formed by 137Cs, that of predatory species made 82–93%. The research results made it possible to determine reference and screening values in the specific activity of radionuclides in the fish of the forest-steppe reservoirs as of 2021. For peaceful fish, the value of the reference 90Sr activity in the studied reservoirs of the Forest Steppe is 1.0, the screening activity - 3.0, predatory fish - 0.5 and 2.0 Bq/kg, respectively. For 2021, the reference value of the specific activity of 137Cs in the body of peaceful fish of the Kaniv Reservoir makes 3.2, the screening value - 10.0, the Kosiv, Bila Tserkva Middle, Bohuslav reservoirs,the Ros and Hnyliy Tikych rivers are 2.0 and 6.0 Bq/, respectively kg; that of predatory fish of the Kaniv Reservoir - 12 and 36, respectively, Kosiv, Bila Tserkva Middle, Bohuslav Reservoirs, the Ros and Hnyliy Tikych rivers - 3.0 and 10.0 Bq/kg, respectively. Key words: water bodies of the Forest Steppe, fish, radionuclides.

Fish-Kills in the Urban Stretch of the Tiber River After a Flash-Storm: Investigative Monitoring with Effect-Based Methods, Targeted Chemical Analyses, and Fish Assemblage Examinations

In 2020 and 2021, fish-kills events occurred in the Tiber river in the city of Rome. These events, which caused the death of thousands of fish of different species (e.g., Barbus spp., Cyprinus carpio, Squalius spp.), were preceded the days before by severe flash-storms. Heavy rains in urban areas in recent years are linked to climate change and fish-kills events. With the aim to investigate the causes of these events, effect-based methods (EBMs) and targeted chemical analyses have been performed on a specific site of river Tiber in the center of the city. Additionally, examination and classification of the floating dead fishes have been performed. The chemical analysis performed on several groups of contaminants showed the presence of some pharmaceuticals, insecticides, and PFAS at up to ng/L. Results with the Fish Embryo Toxicity (FET) test confirmed lethal and sub-lethal effects, while acute effects were not detected with the Daphnia magna acute test. The fish-kills events probably can be generated by several factors as a consequence of an increasing human anthropization of the area with the contribution of different stressors together with chemical releases and emissions. This study shows that in multiple stressor scenarios characterized by heavy rainfall, droughts, and strong anthropogenic pressures, the application of EBMs, chemical analysis, and fish assemblage examinations can represent a useful support in the investigation of the causes of extensive fish-kills events.

Predation on pirarucu larvae by opportunistic fish species

ABSTRACT One of the constraints in pirarucu, Arapaima gigas farming is the reproduction in captivity, due to inconsistent number of spawning events per reproductive cycle, thus, unreliable availability of juvenile fish. This is a first-hand report on predation of pirarucu larvae by opportunistic fish species in a breeding pond. Fish samples were collected for stomach content analysis from a pirarucu-breeding pond with reported predation on the larvae. We obtained 61 fish of different species (Tetragonopterus sp., Astyanax bimaculatus, Moenkhausia intermedia, Hoplias malabaricus, and Apistogramma sp.). Tetragonopterus sp. stomachs had the highest frequency of occurrence of pirarucu larvae (83.3%), followed by A. bimaculatus (7.4%). The relationship between the feeding behaviour of these species and their predation upon pirarucu offspring is discussed.

NEW PREY ITEM IN THE DIET OF THE Orange-bellied swamp snake Tretanorhinus nigroluteus COPE, 1861 (DIPSADIDAE) IN THE SELVA LACANDONA, CHIAPAS, MEXICO

The orange-bellied swamp snake (Tretanorhinus nigroluteus) is considered a rare species in Mexico; there are few specific records of its presence in the country. They are known to feed on amphibians (anurans) and fish of different species (Families Gobidae and Poecilidae). We report the first record of freshwater snails (Pachychilus largillierti) as prey of T. nigroluteus.

Cryptokotyle lühe, 1899 (trematoda: heterophyidae): special characteristics of developmental biology and epizootiology

This review presents the scientific studies data on the special characteristics of developmental biology and epizo- otiology of Cryptocotyle trematodes, which belong to Heterophyidae family and pose a threat to the health of the endotherms, including humans, i.e., it is a typical zoonosis. These trematodes are predominantly widespread in the Mediterranean region, namely, in the western Mediterranean region and the Aegean province. The trematodes of Cryptocotyle genus are found in Europe, Asia, North and South America, and Antarctica. They are typical bio- helminths, i.e., they have a complicated life cycle, where the initial intermediate hosts are mollusks, the second ones – fish of different species, the definitive and final hosts are piscivorous birds, carnivorous animals (foxes, wolves, dogs, cats, etc.), and humans. Cryptocotylosis is remarkable for its seasonal prevalence, which depends on the climatic zoning of territories. For instance, in the territorial waters of Ukraine, the highest indices of crypto- cotylosis invasion among Agonidae fish are mainly observed in summer and autumn, but the peak of the invasion comes in autumn. The parasitizing of Cryptocotyle trematodes in the organism of mollusks impacts the reproduc- tion ability and behavioral specificities (motility) of the latter. The invaded fish have black pigment spots on the surface of their bodies – these are metacercariae. In the organism of definitive hosts, the agent is localized in the gastrointestinal tract and may cause inflammatory processes in the mucous membrane of the intestines and changes in parenchymatous organs, which demonstrates the toxic effect of the parasite on the host organism. The diagnos- tics of cryptocotylosis is based on detecting the agent in the host organism and its further taxonomic identification by its anatomic and morphological specificities. The pollution of the aqueous medium with organic and inorganic residues impacts the organisms of both hosts and parasites.

Activity of peptidases and glycosidases of the digestive tract in some species of bony fish of Vietnam

For the first time, the activity and pH dependence of digestive enzymes were studied in fish inhabiting the Mekong Delta: duskyfin glassy perchlet Parambassis wolffii, smallscale croaker Boesemania microlepis, catfish Pangasius macronema, and representatives of the family Cyprinidae. Significant interspecific differences were revealed in the level of peptidase and glycosidase activity providing hydrolysis of protein and carbohydrate food components. The greatest interspecific differences are characteristic of glycosidases: the level of enzymatic activity in Cyprinidae fish exceeds that in P. wolffii by 13.6 times. The differences in the level of peptidase activity in fish of different species are lower: in the case of the activity of stomach enzymes in P. wolffii, the values are 1.8 times higher than those in P. macronema, and in the case of total activity of stomach and intestinal enzymes in the same species, the values are 1.5 times higher. The data obtained confirm the concept that the digestive hydrolase activity depends on the fish feeding spectrum. The activity of intestinal enzymes decreases more significantly in the acidic pH zone than in the basic one. Consequently, acidification of the intestinal environment will negatively affect the digestive processes in these fish species.

Organophosphate esters in Great Lakes fish: An improved analysis to assess concentrations and human exposure via consumption

Organophosphate esters (OPEs) are flame retardant and plasticizer chemicals added to electronics, furniture, textiles, and other building materials and consumer products. In this study, fillets of fish often caught by anglers in the North American Great Lakes, Lake Trout (Salvelinus namaycush) across four Great Lakes and nearshore fish species near the large urban and industrial centers of Toronto and Hamilton, Canada, were analyzed for 22 OPEs. A rapid microextraction of homogenized tissues with methanol dramatically reduced preparation and sample handling time while achieving recoveries of 69–141%, and the optimized liquid chromatographic separation improved isomeric separations, including aryl-OPEs. Twelve of the 22 OPEs were detected, with frequencies of detection ranging from 8.3% to 98%, and five compounds were detected in >50% of the fish. The average ± standard deviation for the sum of 12 OPEs (ΣOPE12) ranged from 9.6 ± 0.9 (L. Erie 2017) to 74 ± 44 (L. Superior 2001) ng/g wet weight in Lake Trout, and 12 ± 2.7 to 35 ± 30 ng/g wet weight in nearshore fish species from the Toronto and Hamilton areas. The aryl-OPEs were dominant in Lake Trout, comprising 32–77% of total ΣOPE12 concentrations. In nearshore fish, the OPE patterns reflected the relative degree of exposure to run-off and wastewater inputs in the sampled receiving environments. The intake of OPEs via human consumption of Great Lakes Lake Trout and nearshore fish was estimated to range 6.5–31 ng/kg body weight/day, which is approximately 1–2 orders of magnitude lower than exposures via indoor air and ingestion/inhalation of dusts, and 3 orders of magnitude lower than estimated reference doses. The inclusion of additional OPE analytes enabled patterns of exposure and accumulation to be distinguished in fish of different species and location, and were related to source and food web influences.

Potential health risk index of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish species from Oguta Lake, Nigeria

ABSTRACT Polyaromatic hydrocarbons, polychlorinated biphenyls and organochlorine pesticides are among the ubiquitous and lipophilic persistent organic pollutants that pose environmental hazards to humans. In this study, four fish of different species; mochokidae, perpyroclanusalpha, cintharinidae and ciclidae, locally known as Okpo, Ubu, Ifuru and Egu, respectively, from Oguta Lake were analysed for poly aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and the data obtained were subjected to some chemometric assessments models. 10 g of each of the samples were subjected to soxhlet extraction using 100 mL of methanol for the extraction of the organic pollutants. The extracts were analysed for PAHs, PCBs and OCPs using Buck 530 Gas Chromatograph. PAHs, PCBs and OCPs were detected in all the samples, however, Ifuru had an equal level of PAHs followed by Ubu and Egu. The total mean for PAH were 18.367 mg/kg. The concentration of PCBs were in the order Okpo> ubu> ifuru > egu with a total mean of 0.0513 mg/kg. Ifuru recorded the highest level of OCPs while Ubu had the lowest with a total mean of 0.0666 mg/kg. Estimated dietary intake (EDI) showed higher in children than in adults for all the pollutants. Okpo showed equal EDI with Ifuru for PAHs followed by Ubu and Egu. EDI for PCBs were in the order Okpo> Ubu> Ifuru> Egu. EDI for OCPs were insignificant except for Ifuru. The health risk analysis showed that consumption of fish from Oguta Lake could pose a non-carcinogenic health hazard especially in children.

Occurrence and Safety Evaluation of Antimicrobial Compounds Triclosan and Triclocarban in Water and Fishes of the Multitrophic Niche of River Torsa, India.

Personal care product (PCP) chemicals have a greater chance of accumulation in the aquatic environments because of their volume of use. PCPs are biologically active substances that can exert an adverse effect on the ecology and food safety. Information on the status of these substances in Indian open water ecosystems is scarce. In this paper, we report the incidence of two synthetic antimicrobials, triclosan (TCS), including its metabolite methyl-triclosan (Me-TCS) and triclocarban (TCC) in Torsa, a transboundary river flowing through India. In water TCS and TCC were detected at levels exceeding their respective PNEC (Predictive No Effect Concentration). Both the compounds were found to be bioaccumulative in fish. TCS concentration (91.1-589µg/kg) in fish was higher than that of TCC (29.1-285.5µg/kg). The accumulation of residues of the biocides varied widely among fishes of different species, ecological niche, and feeding habits. Me-TCS could be detected in fishes and not in water. The environmental hazard quotient of both TCS and TCC in water indicated a moderate risk. However, the health risk analysis revealed that fishes of the river would not pose any direct hazard to human when consumed. This is the first report of the occurrence of these PCP chemicals in a torrential river system of the eastern Himalayan region.

Survey on ectoparasite occurrence of fish groupers sent to Fish Quarantine Agency for diseases inspection

A parasitology survey on fish groupers was conducted from January to April in 2016 in a Parasitology Laboratory belongs to Fish Quarantine and Inspection Agency, Makassar, to identify parasites from the fish groups. Previous data available at the institute did not distinguish between species of fish examined and the parasites that infect them, most of the fish from different species were only categorized as groupers, while many species of parasites are known to have high host specificity. Fifty-four grouper fish of different species were examined, includes; Cephalopholis sonnerati, C. argus, Plectropomus oligocanthus, P. leopardus, P. areolatus, P. maculatus. The fish species are common groupers that are exported alive to various countries. The fish were sent by exporter companies to the laboratory for disease inspection. The fish species were identified, length and weight were measured, then the whole body surface was visually examined for the presence of large parasites. Operculum was cut, and each gills were removed and placed on a petri dish contained saltwater. Observation of parasites presence was conducted under a stereomicroscope, and identification of parasite to genus level was conducted directly under a compound microscope. Species of parasites found were monogenean; Diplectanum sp., Pseudorhabdosynochus sp., Echinoplectanum leopardi, Echinoplectanum sp., Protozoa; Brooklynella hostilis., Cryptocaryon irritans., Crustacea; Hatschekia sp., Dissonus sp., copepod larvae. Diplectanum sp. was found from P. areolatus and C. sonnerati. The prevalence and mean intensity of the parasite in P. areolatus was 100% and 52.5, respectively, whereas the prevalence and mean intensity of the parasite in C. sonnerati was 50% and 69.6, respectively. Pseudorhabdosynochus sp. was only recorded from Cephalopholis spp. Echinoplectanum leopardi only occurred in P. leopardus. Echinoplectanum sp. was also recorded from P. oligocanthus, P. maculatus and C. sonnerati. Other species of parasites commonly found in the fish examined were B. hostilis., C. irritans, Hatschekia sp. and Dissonus sp. All the parasites are highly pathogenic and may complete their life cycle within a container. Therefore, their occurrence in aquaculture facilities may cause significant damage leading to mortality on fish without proper treatment.

Methylmercury Levels in Commercially Harvested Spiny Dogfish Captured off the Coast of Massachusetts

Abstract Spiny Dogfish Squalus acanthias are small sharks that are harvested for seafood, primarily off the Eastern Seaboard of the United States. For the purposes of establishing seafood consumption advisories with regard to methylmercury (MeHg) content, the U.S. Food and Drug Administration (FDA) classifies Spiny Dogfish as “sharks,” an overly broad taxonomic grouping with a mean MeHg content of 0.98 μg/g wet weight. Because the FDA mean includes fishes of different species that have been collected internationally over the last four decades, there is reason to believe that the FDA mean value is not reflective of the fish harvested in the Spiny Dogfish fishery. To evaluate how closely Spiny Dogfish match the values in the FDA’s generic shark category, we collected muscle samples from 102 commercially harvested Spiny Dogfish caught off Cape Cod, Massachusetts, during the 2018 fishing season. Among the fish we sampled, 100% had MeHg concentrations lower than the FDA mean for sharks and 77.5% had MeHg concentrations that the FDA considers safe for consumption at a frequency of once per week. The mean MeHg concentration in our samples was 0.378 μg/g wet weight, less than half of the value for the generic shark category. Moreover, through a comparison with data from the 1970s, we documented a 30% decline in MeHg concentrations for select size categories of Spiny Dogfish captured off the coast of New England. Exposure simulations indicated that to minimize risk, Spiny Dogfish should be consumed no more than twice per month by most people.

Дослідження зміни кислотного числа жирів та вмісту білків у пробах замороженої риби різних видів залежно від ступеня зміни органолептичних показників якості

Дослідження зміни кислотного числа жирів та вмісту білків у пробах замороженої риби різних видів залежно від ступеня зміни органолептичних показників якості

Parasitological diagnosis in food fish produced in a fish farm, in the Zona da Mata, Minas Gerais, southeastern Brazil.

This study identified the parasitic species in juvenile freshwater finfishes during the fattening stage, from a fish farm located in the Zona da Mata (MG), southeastern Brazil, and revealed both macro and microscopical lesions in fish gills. A total of 172 juvenile fishes of different species (Oreochromis niloticus, Ictalurus punctatus, Ctenopharyngodon idella, Cyprinus carpio, Astyanax bimaculatus and Brycon amazonicus) were transported to a laboratory in São Paulo city. The fish were sedated and then euthanized for parasitological analysis. All fish were infected by at least one parasite species. Ten different species of parasites were identified: Apiosoma sp., Epistylis sp., Ichthyobodo sp., trichodinids, Piscinoodinium pillulare, Ichthyophthirius multifiliis, Tetrahymena sp., monogeneans, Centrocestus formosanus metacercariae, and Dermocystidium sp. The best management practices and lack of sanitary control were also discussed.

Epizootic situation on fish invasion diseases in the waters of Ukraine

An important place in meeting the needs in food of the population has fisheries. The development of this industry, the increase in production and ensuring the high quality of fish as a food product greatly depend on the animal health of the farms and timely conducting veterinary and preventive measures – the basics of providing the mepizootic well-being. Fisheries in Ukraine engaged in more than 6 thousand individuals and legal entities. However, as evidenced by the practice of recent years and results of ichthyoparasitic studies, almost all fish planting and uterine young in the fish farms of Ukraine is infested by invaders of invasive diseases, including ichthyophthiosis, argulosis, lerneosis, fingerprinting, hydrodactylosis, diplozoonosis and others. Unfortunately, one of the disadvantaged regions of Ukraine with invasive fish diseases is west. In the pond farms of Rivne and Volyn regions it is wide the parasites were distributed: diplastomids and filometers, the larvae of which affect the muscle tissue and internal organs of the fish. In the ponds of Western Polissya of Ukraine has identified 23 species of parasites belonging to the classes of Monogenea, Hirudinea, Bivalvia and Crustacea. It should be noted that in most farms mainly mixed infestations are common in the western region. In the south of Ukraine, diplo- stomosis, metogonimosis, filometridosis, lerneosis and hepaticosis were registered. In the natural reservoirs of Mykolaiv invasiveness of fish of different species by P. ovatus metacercariae was revealed. Fishes of artificial and natural reservoirs of Kharkiv region were found 16 species of parasites belonging to the classes of Trematoidea, Cestoidea, Nematoda,Acanthocephala, Crustacea, Mastigophora, Infusoria and Monogenoidea. In the fish farms of Cherkasy, Zhytomyr and Kyiv areas in most cases the fish was struck by monogeneas. In the natural waters of Sumy region were registered trienophorosis and rafidoscaridosis. It is known that the infection of fish with parasites causes a delay in its growth and development, reduction of fatness, deterioration of product and taste, impaired reproduction and even death. Therefore regular monitoring of parasitofauna of fish in the pond farms of Ukraine is necessary because study of patterns of occurrence and spread of fish diseases, prediction of those diseases affect the efficiency of aquaculture breeding and preservation of fish products.

METACERCARIAE OPISTHORCHIDS IN COMMERCIAL CARP FISH FROM THE LOWER AND MIDDLE OB

This article shows the infection of commercial cyprinids from the Middle and Lower Ob with muscle trematodes that are dangerous to humans, collected in 2016, 2017 and 2018. From the point of view of human health, the study of carp fish infected with opistorchids is important. It is in the Ob – Irtysh basin that the world's largest opisthorchiasis is located. In the study of carp fish for infection with muscle trematodes, a compression method was used. Comparing the infection of carp fishes of different species with metacercariae opistorchids from different landscape-geographical zones, one can speak of the leading role of ide in maintaining the Ob - Irtysh center of opisthorchiasis.The role of the bream in maintaining the West Siberian focus of opisthorchiasis is gradually increasing due to the ever-growing herd of this fish. O. felineus and M. biliside infestation is most severe in Middle Ob, in the central taiga zone. In another subzone - the northern taiga (v. Hills) and the forest-tundra zone (v. Aksarka), the extensiveness of the O. felineus infection is either equal to 100% or approaches it. The intensity of infection in the ide from Middle Ob found maximum values. In other, more northern subzones, the intensity of infection with O. felineus metacercaria was significantly inferior to the infection of the Middle Ob’s ide. Based on the above, we can talk about the greatest infection of carp fish in Middle Ob. The center of the opisthorchiasis is situated exactly here.

Occurrence of diseases in fish used for experimental research.

The objective of the present study was to evaluate the occurrence of pathogens and diseases in laboratory fish over a 10-year period at the Centre for Experimental Fish Pathology of Sicily, University of Messina. This report also emphasizes the adverse effects of subclinical infections on research endpoints, as well as the importance of animal health with respect to welfare. Infections in fish used for research can alter experimental outcomes, increase the variability of data, and impede experimental reproducibility. For this purpose, 411 diseased fish of different species (out of a total of 2820 fish) that belonged to four marine species (Dicentrarchus labrax, Sparus aurata, Argyrosomus regius and Mugil cephalus) and to four fresh water species (Danio rerio, Carassius auratus, Xiphophorus variatus and Poecilia reticulata) were examined in this study. Our results showed that mycobacteriosis and myxosporidiosis were the most important diseases found in our research fish, and the results represent a useful tool to obtain wider knowledge on the incidence of various diseases in different fish species. Further studies in this field are necessary to improve knowledge on the state of the health of fish used for research.

Automatic fish detection in underwater videos by a deep neural network-based hybrid motion learning system

AbstractIt is interesting to develop effective fish sampling techniques using underwater videos and image processing to automatically estimate and consequently monitor the fish biomass and assemblage in water bodies. Such approaches should be robust against substantial variations in scenes due to poor luminosity, orientation of fish, seabed structures, movement of aquatic plants in the background and image diversity in the shape and texture among fish of different species. Keeping this challenge in mind, we propose a unified approach to detect freely moving fish in unconstrained underwater environments using a Region-Based Convolutional Neural Network, a state-of-the-art machine learning technique used to solve generic object detection and localization problems. To train the neural network, we employ a novel approach to utilize motion information of fish in videos via background subtraction and optical flow, and subsequently combine the outcomes with the raw image to generate fish-dependent candidate regions. We use two benchmark datasets extracted from a large Fish4Knowledge underwater video repository, Complex Scenes dataset and the LifeCLEF 2015 fish dataset to validate the effectiveness of our hybrid approach. We achieve a detection accuracy (F-Score) of 87.44% and 80.02% respectively on these datasets, which advocate the utilization of our approach for fish detection task.

The role of freshwater fish in the life cycle of Dioctophyme renale in Southern Brazil.

Brazil stands out by the diverse records of Dioctopphyme renale in different hosts; however, there is little information about the life cycle of the nematode in the region. This study aims to report on third-stage larvae infections in fish in southern Brazil. In this context, 324 fish of different species belonging to Characiformes, Cyprinodontiformes and Siluriformes were collected in an urban area of Rio Grande do Sul State, where domestic and wild hosts were reported with the nematode. Of the total fish examined, 25(7.7%) were found to be parasitized by third-stage larvae of D. renale which were found encysted in the stomach serous membrane and in the celoma cavity of Hoplosternum littorale (Siluriformes) with a prevalence of 53.2% (25/47) and mean intensity of infection of 4.4 larvae/host (1 to 13 larvae). The occurrence of larvae in H. littorale indicates the presence of parasitosis in the region; however, the contribution of this fish species as a source of infection for dogs in urban areas must be considered with caution given the difficulties these dogs may face in the capture and predation of the fish to the point of effectively maintaining the urban cycle of D. renale. In addition, the low level of larvae registered in the total sample of fish examined indicates that these hosts are unlikely to play an important role in the transmission of D. renale to domestic animals in the region of the study.