Silurus Glanis Research Articles

Reappraisal of Goezeella Fuhrmann, 1916 (Cestoda: Proteocephalidae), parasites of Neotropical catfishes (Siluriformes), with description of a new species from Pimelodella cristata (Heptapteridae)

The cestode genus GoezeellaFuhrmann, 1916 is reviewed on the basis of taxonomic evaluation of type and newly collected material from pimelodid and heptapterid catfishes (Siluriformes) in the Amazon River basin, South America, and its generic diagnosis is amended. The genus is typified by the exclusively ventral position of the cortical vitelline follicles, the inner longitudinal musculature formed by dense individual muscle fibres, rather than forming bundles as in other proteocephalids, a well-developed metascolex and biloculate suckers. The type species, G. siluriFuhrmann, 1916, is redescribed based on its syntype from Cetopsis coecutiens (type-host) (Cetopsidae) and specimens from Pinirampus pirinampu (Pimelodidae). The validity of G. danbrooksi de Chambrier, Rego & Mariaux, 2004 from Ageneiosus pardalis (Auchenipteridae) is confirmed and some erroneous morphological traits are corrected based on examination of its holotype. A new species, Goezeella mariae sp. nov., is described from the heptapterid catfish Pimelodella cristata (Heptapteridae). The new species differs from congeners by its overall size (much smaller compared to G. siluri), morphology of the scolex (strongly wrinkled metascolex and weakly developed interlocular septum of suckers) and number of the testes. This is the third proteocephalid cestode described from a heptapterid catfish in South America and the first helminth parasite reported from P. cristata. Goezeella is unusual among other Neotropical proteocephalids by its occurrence in catfishes of as many as four families; all species of the genus are known only from the Amazon and Orinoco River basins. Molecular data on two of the three valid species and a key to their identification are provided.

Back-Calculation of Fish Size in Diet Analysis of Piscivorous Predators: A New Index for the Alien Silurus glanis

The wels catfish Silurus glanis has been constantly spreading in many European basins, outside its native range. Being a voracious predator, it is considered to have a severe impact on local fish communities. In the Ticino River (Northern Italy), bones of S. glanis were found in feces from the top predator Lutra lutra. To estimate the control capability of L. lutra for this species and to back-calculate S. glanis’ size from its bone remains, whole skeletons from 27 differently sized S. glanis specimens were analyzed. A double pharyngeal element and all caudal vertebrae emerged as significant items for species identification. The mean length of the pharyngeal element was directly related to fish mass, while for vertebrae, a K-index was proposed to identify the position of each vertebra along the spine and, from this, to calculate the original fish mass. This methodology allowed us to establish that the length of the preyed S. glanis was 85–435 mm, and the ages were between 0+ and 2+ years. The proposed methodology opens new perspectives for more detailed studies on the efficiency of predation by piscivorous species on allochthonous ones.

A confirmed record of the European catfish Silurus glanis L., 1758 (Actinopterygii: Siluriformes: Siluridae) from the southern marshes of Iraq, with a new anatomical set of characters to separate S. glanis and S. triostegus

Investigations conducted in the southern Iraq freshwater systems allowed the authors to collect the European catfish, Silurus glanis L., 1758. These are the first confirmed records of S. glanis from the freshwater systems in Lower Mesopotamia, based on 13 adult specimens, each 325–525 mm in total length. Furthermore, a new set of anatomical characters of S. glanis and S. triostegus from Chibayish marsh area, south of Iraq, was examined to reveal similarities and differences between the two Silurus species. In addition to the traditional separation of the two species of Silurus by number of barbels, these two species can now be recognised based on a new set of morphological and osteological features.

Seasonal changes in depth position and temperature of European catfish (Silurus glanis) tracked by acoustic telemetry in the Danube River

AbstractThe giant European catfish, Silurus glanis (total length = 200 cm; total weight ≈ 80 kg) was caught downstream of Iron Gate II hydropower dam (Danube River, 863 rkm) and tagged with an ultrasonic transmitter (V16TP; Vemco Ltd.) equipped with depth and temperature sensors. Changes in catfish diving behavior and temperature exposure were monitored over a period of roughly 2 years. Transmitter detections were recorded by nine autonomous receivers (VR2W, installed in 2015 between Serbia and Romania, as well as near Romanian shiplock and upstream Romanian turbines). The first signals were recorded on April 28, 2015 and the last on February 13, 2017. Altogether 59,355 and 59,175 detections of the catfish depth and water temperature were recorded, respectively. The greatest number of signals were recorded by the two receivers closest to the location where the catfish was caught, 72.3% and 27.1%, while only 0.6% of signals were recorded by other receivers. The mean catfish depth was 8.4 m, while minimum and maximum depths were 1.2 and 16.2 m. Results obtained showed that this catfish exhibited high site fidelity, while changes in depth at certain periods are possibly related to its search for prey and upstream migration during the spawning period. Hydropower dam and shiplock were obstacles on its migration upstream and telemetry studies could ensure habitat requirements and meet the development of restoration and conservation strategies for the fish resources in the future.

Potential of corn distiller’s dried grains with solubles (DDGS) in the diet of European catfish (Silurus glanis)

Two experiments were conducted to evaluate the suitability of corn DDGS as a protein source for European catfish (Silurus glanis). The first experiment consisted of an in vivo digestibility assessment to determine apparent digestibility coefficients for protein, lipid, phosphorus and amino acids available in DDGS. One hundred twenty juveniles (average weight, 154.29 ± 2.73 g) were distributed in recirculation water system equipped with six 1m3 fiberglass tanks (20 fish per tank), which were allotted to two experimental group in triplicates. Juveniles were fed either of the two diets, with or without DDGS (DDGS diet or reference diet) ad libitum till saturation 3 times per day for two weeks. Apparent digestibility coefficient of dry matter, crude protein, crude fat and phosphorus of DDGS ingredient for Europeean catfish were found 49.42 %, 73.39 %, 77.38 % and 87.98 % respectively. The second experiment was conducted for eight weeks to evaluate the effect of corn DDGS on growth, nutrient utilization and metabolism of European catfish. Two hundred forty juveniles of European catfish (average weight, 272.7 ± 37.8 g) were stocked in 1000 L glass fibre tanks in a recirculation system in triplicates. Juveniles were fed with either of the four iso-nitrogenous and iso-caloric (37 % crude protein and 6 % crude fat) experimental diets formulated with the inclusion of 0, 10, 20 and 30 % corn DDGS with partial replacement of soybean and wheat. No significant differences were found between the experimental groups regarding growth performance and plasma biochemical parameters. The liver histopathological observations showed that 20 and 30 % DDGS groups had less vacuolized hepatocytes than the other groups. Both experiments conclude that apparent digestibility of corn DDGS is auspicious for European catfish and 30 % DDGS can be included in the diet of European catfish without compromising the growth performance and nutrient utilization.

EDNA metabarcoding survey of fish communities in the Danube and its tributaries

In complement to the JDS4 traditional fish survey (TFS, mainly by electrofishing), a fish eDNA metabarcoding-based survey has been implemented within the framework of the monitoring program organized by DNAqua-Net and in collaboration with the INTERREG "MEASURES" program. Water samples were collected at 29 sites from the source to the mouth of the Danube River, and at 18 tributaries. Two water samples (mean volume 29 L per sample) were collected at each site and the water filtered in situ. Twelve PCR replicates were performed per sample using teleo primers. In total, 80 taxa were detected, of which 19 corresponded mainly to farmed fish or food fish due to eDNA release in waste waters, most often downstream of large cities. Of the remaining 61 taxa, 50 taxa were identified at the species level, six taxa at the genus level, and five taxa at a higher taxonomic level. Concerning the Danube river itself, 69 and 57 species/markers were detected along the Danube River by TFS and eDNA surveys, respectively. 50 of these taxa were detected by both methods. Nine species were captured by TFS alone, mainly due to gaps in reference librairies and too colosely related barcodes. Eight species were only detected by eDNA. Except for the Salvelinus group, these were all benthic species, which are difficult to catch by electrofishing in large rivers (Acipenser ruthenus, Acipenser stellatus, Benthophilus sp., Romanogobio uranoscopus, Sabanejewia balcanica, Umbra krameri). The species richness tended to increase from upstream to downstream and the relative number of DNA sequences per taxa showed a clear succession of species along the river. Barbatula barbatula, Cottus gobio, Hucho hucho, Lampletra planeri, Phoxinus phoxinus and Thymallus thymallus were restricted to the Upper Danube whereas A. ruthenus, Neogobius fluviatilis, S. balcanica and Scardinius erythrophtalmus were detected from Vienna to the Danube river mouth. Abramis brama, Alburnus alburnus, Cyprinus carpio, Silurus glanis, Sander spp, Zingel streber were detected all along the river course; Alosa spp. and Syngnathus abaster downstream from the Iron Gate; A. stellatus and U. krameri only on the most downstream site (Danube delta). The calculation of a fish index, based on the common metrics used to intercalibrate national fish assessment methods on a European scale, classified most of the sites as being in moderate ecological status. Comparison of the indicative ecological status calculated using the same assessment method based on TSF and eDNA data at the common Danube sites showed a similar classification for six of the 13 sites and a difference of one class for the remaining seven sites.

Seasonal variability in the diet of juvenile European catfish, Silurus glanis, in the Arno River (Italy) in Florence

Abstract While approaches for assessing the impact of invasive species are advancing, fundamental autoecological information such as feeding preferences is often unavailable for many invasive species. The European catfish, Silurus glanis, is a well-known, high-impact invasive predator; however, there remain considerable gaps in knowledge about its feeding preferences and biotic interactions that limit ecological impact predictions for this predator. This study is an investigation of seasonal variability in this predator’s diet during the juvenile life stage using the Arno River, Italy as a model system. This study identified significant differences across seasons, provided further information on the dietary spectrum of this species, and raised important questions for further study.

Length-weight relationship of European catfish (Silurus glanis L.) fry reared at different stocking densities under controlled conditions

Abstract. The present paper investigates the body length and weight, and the size-weight variations of one-month-old European catfish reared at 4 variants of stocking density: Variant 1 – 5 spec/l; Variant 2 – 10 spec/l; Variant 3 – 15 spec/l and Variant 4 – 28 spec/l. The experiment is carried out at the Institute of Fisheries and Aquaculture, Plovdiv for a period of 16 days, using a production system consisting of tubs with continuous water flow (0.7 l/min). At the end of the experiment, the fish from each variant are sorted in three size-weight groups: A – large, B – medium and C – small. The number of fish in each group is established. From the group of the medium- and small-sized fish, 150 speciments are measured, while from the group of the large specimens, which are the smallest in number, all specimens are measured for the biometric parameters body weight (BW, g) and total body length (TL, cm). The results from the study show small variations in the length and weight of the fish reared at the lowest stocking density (Variant 1). As the density increase, the size-weight differences between the specimens from Group A also increased, while of those from Group B they decrease. The number of the medium-sized fish decrease (p≤0.001) while the number of large specimens (p≤0.01) and small fish increase (p≤0.001).

Records of Invasive European Catfish Silurus Glanis (Linnaeus, 1758) in the Neretva River Delta (Croatia): Social Media as Information Source

Abstract Records of European catfish Silurus glanis in the Neretva River delta (Adriatic Sea basin) in Croatia are reported. The first occurrence of this non-native species was reported via social network which led to its timely detection by researchers. Origin of introduction is unknown but it is most likely the case of human-mediated introduction. The importance of social networks as a useful tool for the timely detection of non-native fish species, as well as the importance of raising awareness about the impacts of biological invasions, is discussed in this paper.

Microsatellite genetic differentiation between two populations of European catfish (Silurus glanis) in Iran

Microsatellite genetic differentiation between two populations of European catfish (Silurus glanis) in Iran

Evaluation of body weight and color of cultured European catfish (Silurus glanis) and African catfish (Clarias gariepinus) using image analysis

Two cultured catfish species (European catfish Silurus glanis, and African catfish Clarias gariepinus) were evaluated for their weight estimation and colors by image analysis. A total of 60 whole fish from each species were first weighed, and then their pictures taken by a digital camera in a light box. Length, weight and color of all fish were determined by image analysis and results were compared between the two fish. Fish weight ranged from 7.4 to 39.61 g and 25.71 to 93.91 g for European and African catfish, respectively. Weight (W) vs length (L) data were fitted linear (W = A + BL), power (W = A LB) and second order polynomial equations (W = C0 + C1 L + C2 L2). The R2 values ranged from 0.835 to 0.974. For the W vs view area (V) relationship, the same equations were used. The R2 values for these equations ranged from 0.927 to 0.972. No significant difference was found between the average color values according to the L*, a* and b* distributions for both fish species (P > .05). Image analysis can easily determine length, view area, and color of fish and help in developing W vs L, and W vs V relationships.

Plastic ingestion by the Wels catfish (Silurus glanis L.): detailed chemical analysis and degradation state evaluation.

Plastic ingestion by various organisms within different trophic levels, including humans, is becoming a serious problem worldwide. Plastic waste samples are often found concentrated in an organism's digestive tract and can be degraded and further translocate to the surrounding tissue or circulatory systems and accumulate in food chains. In the present work, we report a detailed chemical analysis and degradation state evaluation of a relatively large piece of plastic waste found in the gastrointestinal tract of a Wels catfish (Silurus glanis L.) caught in the Bodrog River (Danube River basin), eastern Slovakia. Chemical analysis by surface-sensitive X-ray photoelectron spectroscopy (XPS) was performed to identify the surface composition of the digested plastic piece. Micro-Fourier transform infrared (μFTIR) spectroscopy showed that the plastic waste was oxidized low-density polyethylene (LDPE), with some nylon fibers adhered on the surface. Glyceraldehyde adhered onto LDPE was also detected, which might come from the carbohydrate metabolism of that fish. A morphology study by digital optical microscopy indicated solid inorganic particles attached to the surface of LDPE. A degradation study by differential scanning calorimetry (DSC) showed considerable oxidation of LDPE, leading to fragmentation and disintegration of the plastic waste material.

Theoretical and practical aspects of domestication of common catfish (Silurus glanis, L.)

The article discusses some aspects of the domestication of common catfish (Silurus glanis) in the conditions of cyprinid fish farms. Under the pressure of selection and directed cultivation in pond conditions of carp fish farms, changes in ethological, morphological, and physiological indicators are observed. The variability of the majority of morphological indicators and development indices (8–14%) indicates a high degree of consolidation of the resulting breeding offspring and indicates the completion of the first stage of domestication in the conditions of fish-breeding carp farms. Physiological and biochemical assessment of different age categories of catfish showed low variability of physiological indicators. it Can be assumed that the decrease in the coefficient of variability is a consequence of domestication. Studies of the immunological status have shown its optimal level, which allows us to accept the obtained indicators as indicative standards for evaluating brood flocks and their offspring. There was a significant increase in the body weight of commercial three-year-olds of the 4th breeding generation, compared with the first generation. It is established that the reproduction of catfish planted in carp summer-fallow ponds is more successful than in natural reservoirs, since ponds of this category are often small, well-warmed, which contributes to the rapid maturation of producers and the development of caviar. When growing in pond conditions for 2–3 generations, changes in behavioral reactions were noted — there was a decrease in aggressiveness and the development of conditioned reflexes to the specified food objects. The level of food availability affects the metabolism and maturation period, so along with the use of the natural feed base of the pond, it is recommended to use additional feeding and directed formation of the natural feed base.

Risk of invasiveness of non-native aquatic species in the eastern Mediterranean region under current and projected climate conditions

Human-induced biological introductions pose a major threat to global biodiversity, and this is especially frequent in the eastern Mediterranean region, which is a globally important biodiversity hotspot area of high conservation value. To predict at which level introduced species in this region might become invasive under current and projected climate conditions, 232 non-native aquatic organisms were screened using the Aquatic Species Invasiveness Screening Kit. Based on receiver operative characteristic curve analysis, thresholds were identified to distinguish between low, medium and high risk species. The “top invasive” (very high risk) species identified were: brown bullhead Ameiurus nebulosus, blue crab Callinectes sapidus, gibel carp Carassius gibelio, Philippine catfish Clarias batrachus, Chinese mitten crab Eriocheir sinensis, bluespotted cornetfish Fistularia commersonii, silver carp Hypophthalmichthys molitrix, silver-cheeked toadfish Lagocephalus sceleratus, half-smooth golden pufferfish Lagocephalus spadiceus, Suez pufferfish Lagocephalus suezensis, signal crayfish Pacifastacus leniusculus, fathead minnow Pimephales promelas, channeled applesnail Pomacea canaliculata, red swamp crayfish Procambarus clarkii, devil firefish Pterois miles and European catfish Silurus glanis. The risk of being invasive of more than half of the screened species increased after taking global warming predictions into account, and several species considered to be globally invasive (cf. high risk) were classified as posing only a medium risk for the eastern Mediterranean region. Region-specific risk screenings, as implemented in this study, are therefore essential for setting priorities in preventative management for the conservation of key biodiversity hotspots and the optimal allocation of resources in view of full risk assessment for the species identified as (very) high risk.

Improving the biotechnology of growing Silurus Glanis L., Clarias Gariepinus, Pangasius Hypophthalmus catfish (Siluroidea) in the waters of energy facilities

The modern biotechnologies of reproduction and cultivation of European catfish, African clary catfish and pangasius are considered. The development of biotechnology led to the development of a technology for its reproduction by the method of hormonal injection with preservation of life of the females and the euthanasia of the males for the collection of pure sperm. Further development of biotechnology is associated with the expansion of species diversity and the inclusion of African clary catfish and pangasius into aquaculture in warm waters.

Pupil size variation as a response to stress in European catfish and its application for social stress detection in albino conspecifics.

Hormonal changes such as increased cortisol level in blood plasma in response to stress and social environmental stimuli are common among vertebrates including humans and typically accompanied by other physiological processes, such as changes in body pigmentation and/or pupil dilatation. The role of pupil size variation (PSV) as a response to stress have yet to be investigated in fish. We exposed albino and pigmented European catfish to short-term stress and measured changes in pupil size and cortisol level. Albinos showed lower pupil dilatation and higher cortisol levels than did pigmented conspecifics. A clear positive relationship between pupil dilatation and cortisol concentrations was observed for both pigmented and albino specimens, suggesting that PSV can be used as a stress indicator in fish, irrespective of albino’s inability to express social communication by coloring. During the follow-up, we investigated whether a penultimate contest between albino individuals would impact contestants’ social stress during subsequent contact. We observed PSV during the contact of unfamiliar albino catfish with different penultimate experiences (winner (W) and/or loser (L)). Then, the following treatment combinations were tested: WW, WL and LL. Twenty-four-hour contact of two unfamiliar catfish resulted in higher pupil dilatation among individuals with previous winner experience. Among treatment combinations, a WL contest displayed the highest pupil dilatation for winners. PSV reflected socially induced stress in individuals that was accompanied by the “winner” experience and dominancy in albinos. To conclude, the present study validates pupil dilatation as a non-invasive method to evaluate stress level in pigmented as well as albino fish in various contexts.

Yayın Balığı (Silurus glanis L., 1758)’nın Otolit Morfometrisi

The relationships between dimensions of the asteriscus and lapillus and fish length for Wels catfish, collected from Sıddıklı Dam Lake between September 2015 and August 2016, are presented. No significant differences were noted between the dimensions of the left and right otoliths, and between otolith dimensions of male and female. For analyses, the right-side data of otoliths were used regardless of sex. The strongest correlation coefficient was obtained from the linear model for all relationships. Thus, a linear model was used for determining relationships. The r2 values of relationships between asteriscus dimensions and total length were more appropriate than relationships between lapillus dimensions and total length. Asteriscus height was more suitable than other otolith dimensions for predicting the length of Wels catfish. Results provided the first information on relationships between total length and otolith dimensions of Wels catfish. These relationships from this study can provide a reliable tool to reconstruct the predator diet, and to estimate the size of the prey, as well as also provide support to paleontologists in their research on fish fossils.

Eltérő típusú tartástechnológiák hatása a szürke harcsa (Silurus glanis) termelési paramétereire, valamint a víz és az üledék minőségére

A kísérlet célja annak a megállapítása volt, hogy két eltérő tartástechnológia (monokultúra (M), intenzív-extenzív tavi rendszer (I-E)) milyen hatással van a szürke harcsa (Silurus glanis) termelési paramétereire, valamint a tavak vízminőségére és az üledék kémiai összetételére. Kísérletünket, mely 153 napig tartott, kétnyaras szürke harcsa és ponty (Cyprinus carpio) állománnyal végeztük. A vizsgálat kezdetén a szürke harcsa átlagos testtömege 485,7±3,4 g, a ponty átlagos testtömege 348,9±2,5 g volt. A kísérlet végén az átlagos testtömegek 1932,9±194,5 g és 2266,9±87,6 g (ponty) voltak. A termelési paraméterek között szignifikáns különbséget nem találtunk. A növekedési sebesség (SGR) mind a két kezelés esetében nagyon alacsony értékeket (0,9±0,1 %/nap) mutatott. A vízminták adatainál a nitrát-N, nitrit-N, ortofoszfát-P és az összes lebegőanyag esetében szignifikáns különbséget kaptunk a kezelések között. Az üledékminták Kjeldahl-N és foszfor tartalmában jelentős csökkenést figyeltünk meg az intenzív és extenzív technológiát kombináló kezelés esetében. Mindez arra enged következtetni, hogy a kombinált rendszerben a haltermelés tápanyag transzformációja meghaladta a monokultúráét, jelentős mennyiségű szerves N és P vegyület került kivonásra és akkumulálódott a kiegészítő pontyhozamban.

First Record of the Ichthyofaunal Diversity of Bhagar Oxbow Lake, in Dumraon, South Bihar, India

Fishes are very important food resources in developing countries, due to high protein content and its nutritional value. The present study deals with Ichthyofaunal diversity of Bhagar oxbow Lake, in Dumraon, District, Buxar. Total of 44 freshwater fish species were listed that belonging to 30 genera, 16 families and 7 orders, described in the present study from February, 2018 to January, 2020. Among them Cypriniformes was the dominant order in term of species diversity that represent (16 species) while the Puntius is the most dominant genus, and held a major portion of the lake. Siluriformes (11 species), Perciformes represented with 6 species, Channiformes (4 species), whereas Mastacembeliformes & Clupeiformes represented (3 species) each and Tetraodontiforme represented only (1 species). Fish of the family Cypriniformes was the most abundant 37.20% of the total fish species followed by the family Siluridae 25.58% and Perciformes 13.95% were reported. Order Channiformes represent 9.30%, followed by the family Clupeiformes 6.97%, Mastacembliformes, 4.3% and Tetrodontiform represented with 2.32% of the total fish species. In the Bhagar oxbow lake, a large number of fish species have edible as well as ornamental and medicinal values. The species composition of ichthyofaunal diversity can also be better understand by this paper. This is the first ever study on the fish diversity and would help in explore the fish fauna and to develop a sustainable fishery practices need to Bhagar oxbow lake in Dumraon.

Level of in vitro storage of the European catfish (Silurus glanis L.) eggs at different temperatures.

European catfish (Silurus glanis) is a commercially important freshwater fish originating from Eastern Europe. The objective of this study was to examine the short-term storage of its eggs especially in relation to maintaining a low level of malformation in newly hatched fry. The eggs from freshly spawned individuals were stored separately in cell incubators at 17 and 22°C under aerobic conditions. Changes in fertilization, hatching, and malformation were examined in eggs stored at 1, 3, 5, and 7h post-stripping. The sperm used for fertilization showed very good motility rates (84-90%) and curvilinear velocity (110-125μm/s), and straight-line velocity did not drop below 77μm/s. For all females, a temperature of 17°C was better than 22°C for egg storage in vitro. Egg fertilization and total hatching decreased rapidly after 7h storage at 17°C. The storage time of eggs in vitro to fertilization should therefore not exceed 5h at 17°C. In all females, there was no difference in the total number of eggs hatching between 1 and 3h of egg storage at 17°C. The storage time of eggs did not correlate with the level of malformations of the fry. However, the level of hatching and malformations was clearly affected by the storage temperature of eggs when it was > 17°C. Analysis showed that the storage time of eggs, temperature of storage, and individual females had a significant influence on fertilization and total hatching rates. Regression analysis confirmed a low correlation of fertilization and hatching rates with storage time of eggs.