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Fish parasitic diseases impose a major economic concern on aquaculture. Identified parasites of Clarias gariepinus include one monogenean, Macrogyrodactylus clarii (gills), three digeneans Orientocreadium batrachoides, Eumasenia bangweulensis and Sanguinicola sp. (intestine), two cestodes Tetracampose ciliotheca and Monobothrioides chalmersius (intestine) and two nematodes Paracamallanus cyathopharynx and Procamallanus pseudolaeviconchus (intestine and stomach). Most nematodes, digeneans and cestodes occurred in all months of the study period. However, M. clarii and Sanguinicola sp. disappeared for 6 and 8 months of the year, respectively. The digenean group was the most dominant followed by the cestode and nematode groups, respectively. The nematodes attained the highest infection rate over the digeneans and cestodes while the monogenean M. clarii recorded the lowest infection rate. The infection level of examined parasites varied seasonally, but no overall significant pattern was detected. E. bangweulensis showed a highly significant difference for all parameters seasonally. A higher prevalence was obvious in males than females for most parasites, and the opposite for the mean intensity except for P. pseudolaeviconchus which was significantly different between females and males in the mean abundance. There were variations in the relationship between the host condition factor and helminth parasite infection levels. O. batrachoides, E. bangweulensis and P. cyathopharynx recorded the highest infection level in class II. The mean prevalence was highly significantly different between host classes for T. ciliotheca, M. chalmersius and P. pseudolaeviconchus. [ABSTRACT FROM AUTHOR]

We report the first record of Platyclarias machadoi Poll, 1977 since its original description. This species was sampled by electrofishing in rapids on the Kwanza River upstream of Capanda Dam in Angola. Morphometric and meristic data for the Kwanza River material were compared to published data from the Platyclarias type series. Osteology was compared between the Kwanza specimens and two Platyclarias paratypes using computed tomography (CT) scans. Prior to this discovery, the genus was known only from the Kwango River in Angola. [ABSTRACT FROM AUTHOR]

The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a "failure to diverge" phenomenon for G. transvaalensis. [ABSTRACT FROM AUTHOR]

Although the vast majority of fossil catfish material is isolated elements such as fin spines, a number of fossil catfishes (Siluriformes) have been named based on articulated crania from Palaeogene formations of Africa. The fossil taxa from marine sediments have been assigned to the extant marine family Ariidae, or have been assumed to have washed into marine sediments from freshwater habitats. The ability to assess the relationships of these fossils without reference to the nature of the geological sediments may provide insight into the history of these families. Most of the taxonomic work on the 11 catfish families found in Africa has focused on soft-tissues or DNA, which is problematic for the fossil material. Here we provide osteological features to distinguish families of African catfishes; eight of the families that are likely to be found in fossiliferous deposits can be distinguished based on a combination of skull features including the morphology of the cranial fontanelle, mesethmoid, and dermal ornamentation. We reassess the familial placement of the Palaeogene catfishes. We find that †Eomacrones wilsoni, from the Palaeocene of Nigeria, belongs in Bagridae s.s. This confirms that bagrids were in Africa much earlier than the Miocene. Because this catfish comes from Palaeocene marine sediments, the biogeographic history of Bagridae needs to be reassessed to consider marine dispersal in this taxon.

The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a “failure to diverge” phenomenon for G. transvaalensis.

The thyroid hormones (THs) play an important role in the regulation of the rate of metabolism, affect the growth and function of different systems in the organism. The aim of this study was to assess serum concentration of total triiodothyronine (T3), total thyroxine (T4) as well as T3/T4 ratio in serum from healthy fresh water fish from Salmonidae, Acipenseridae, Cyprinidae, and Clariidae families to determine species-specific reference intervals. Mean concentrations of T3 and T4 levels varied significantly among fish. Finally, the test results show clear differences in the serum concentration of the T3 and T4 and give new insight into the thyroid hormones reference values in some commercial fresh water fish species. [ABSTRACT FROM AUTHOR]

Abstract Background Monogenean flatworms are the main ectoparasites of fishes. Representatives of the species-rich families Gyrodactylidae and Dactylogyridae, especially those infecting cichlid fishes and clariid catfishes, are important parasites in African aquaculture, even more so due to the massive anthropogenic translocation of their hosts worldwide. Several questions on their evolution, such as the phylogenetic position of Macrogyrodactylus and the highly speciose Gyrodactylus, remain unresolved with available molecular markers. Also, diagnostics and population-level research would benefit from the development of higher-resolution genetic markers. We aim to offer genetic resources for work on African monogeneans by providing mitogenomic data of four species (two belonging to Gyrodactylidae, two to Dactylogyridae), and analysing their gene sequences and gene order from a phylogenetic perspective. Results Using Illumina technology, the first four mitochondrial genomes of African monogeneans were assembled and annotated for the cichlid parasites Gyrodactylus nyanzae, Cichlidogyrus halli, Cichlidogyrus mbirizei (near-complete mitogenome) and the catfish parasite Macrogyrodactylus karibae (near-complete mitogenome). Complete nuclear ribosomal operons were also retrieved, as molecular vouchers. The start codon TTG is new for Gyrodactylus and for Dactylogyridae, as is the incomplete stop codon TA for Dactylogyridae. Especially the nad2 gene is promising for primer development. Gene order was identical for protein-coding genes and differed between the African representatives of these families only in a tRNA gene transposition. A mitochondrial phylogeny based on an alignment of nearly 12,500 bp including 12 protein-coding and two ribosomal RNA genes confirms that the Neotropical oviparous Aglaiogyrodactylus forficulatus takes a sister group position with respect to the other gyrodactylids, instead of the supposedly ‘primitive’ African Macrogyrodactylus. Inclusion of the African Gyrodactylus nyanzae confirms the paraphyly of Gyrodactylus. The position of the African dactylogyrid Cichlidogyrus is unresolved, although gene order suggests it is closely related to marine ancyrocephalines. Conclusions The amount of mitogenomic data available for gyrodactylids and dactylogyrids is increased by roughly one-third. Our study underscores the potential of mitochondrial genes and gene order in flatworm phylogenetics, and of next-generation sequencing for marker development for these non-model helminths for which few primers are available.

The present study was carried out to analyse the effect of water temperature on two components: (1) growth performance, and (2) gastric emptying time (GET) of African catfish Clarias gariepinus fingerlings. After 70 days, it was observed that experimental temperatures had no significant effects on the growth performance parameters, except for food conversion ratio (FCR) and food conversion efficiency (FCE). GET observation through X-radiography denoted that the shortest GET (10 h) was observed in fish reared at 32 °C and the longest GET (16 h) was observed in fish reared at 26 °C. The rapid digestion rate coincides with the FCR and FCE obtained in this study. Considering the limited scope of our study, more extensive studies on the impact of water temperature on other fish physiological parameters should be pursued. A better understanding of this research topic would be beneficial for the growth of African catfish fingerling aquaculture.

In the present study, a possible nature immunostimulant and growth promoter—humic substances (HS) originating from Siberian leonardite mineraloid—were tested on juvenile Clarias gariepinus performance. Feed additive was applied onto commercial pelleted feed at four HS levels—0, 1, 3, and 6% w/w (HS0, HS1, HS3, HS6, respectively). Diets were tested in five repetitions (in total, n = 1800 individuals, mean body weight 28.1 ± 6.2 g) for 56 days. Growth and production parameters, fish condition and somatic indices, and overall mortality were evaluated after 14, 28, 42, and 56 days of exposure. Whereas, plasma samples were collected only after 0, 28, and 56 days, when fish health status was assessed with biochemical parameters (total proteins, TP; alanine aminotransferase, ALT; aspartate aminotransferase, AST; lactate dehydrogenase, LDH; cholesterol, CHOL; triglycerides, TAG) and fish antioxidant status with glutathione (reduced glutathione, GSH; oxidized glutathione, GSSG; glutathione ratio GSH/GSSG). Although a significantly positive effect of HS feed additive on growth performance was not found in the present study, moderately positive effects were found regarding biochemical parameters (ALT, AST, LDH, CHOL, and TAG) and antioxidants (GSH/GSSG ratio) that were improved especially in the HS3 group.

Các chỉ tiêu đo rất quan trọng trong việc phân tích hình thái trên cá. Tuy nhiên, việc đo đạc thường tốn nhiều thời gian, công sức và khó lặp lại khi kiểm tra sai số.Phương pháp phân tích hình ảnh đã và đang được ứng dụng rộng rãi trong việc đo các chỉ tiêu hình thái trên nhiều loài sinh vật. Nghiên cứu này nhằm mục đích kiểm nghiệm tính hiệu quả của phương pháp phân tích hình ảnh trong việc thực hiện các chỉ tiêu đo của hai nhóm hình thái cá (1) nhóm cá có dạng hình ống, đại diện là các loài cá trê (giống Clarias), (2) nhóm cá có hình dạng thân dẹp bên, đại diện là cá ba kỳ đỏ (Cyclocheilichthys apogon). Nguyên lý của phương pháp này là chuyển đổi dữ liệu hình ảnh ở đơn vị Pixel thành đơn vị đo thông dụng thông qua một tỉ lệ “SCALE” được xác định trên hình ảnh của mẫu cá được chụp cùng với thước đo. Các mẫu vật lần lượt được đo bằng phương pháp thông thường với thước vi cấp và được phân tích hình ảnh để xác định độ dài trên ứng dụng tpsDig. Phân tích tương quan (correlation) được thực hiện giữa các số liệu thu được từ hai phương pháp để so sánh sự tương đồng giữa hai phương pháp đo. Kết quả cho thấy đa số các chỉ tiêu đo (17 trên tổng số 25 chỉ tiêu) đều có hệ số tương quan cao (r>0,85), thể hiện tính chính xác cao của phương pháp phân tích hình ảnh trên cả hai dạng kiểu hình cá. Phương pháp phân tích hình ảnh có triển vọng ứng dụng cao trong các nghiên cứu hình thái cá để rút ngắn thời gian phân tích, giảm thiểu khả năng sai sót về dữ liệu hay kiểm tra lại việc đo đạc trong trường hợp xảy ra sai sót hay mất mẫu vật.

Trong nghiên cứu này, đặc điểm hình thái của một nhóm cá trê “lạ” thu ở huyện đảo Phú Quốc, tỉnh Kiên Giang được so sánh với các loài cá trê thuộc giống Clarias đã được định danh gồm cá trê trắng (Clarias cf. batrachus), cá trê vàng (C. macrocephalus), cá trê Phú Quốc (C. gracilentus) nhằm bổ sung thông tin thành phần loài trong giống Clarias. Tổng cộng 129 mẫu cá trê đã được thu thập và phân tích hình thái dựa vào 22 chỉ số sinh trắc hình thái (tỉ lệ số đo hình thái so với chiều dài chuẩn và chiều dài đầu). Về hình dáng bên ngoài, các nhóm cá trê có thể được phân biệt được với nhau bằng hình dạng thân, màu sắc, hình dạng đầu và đặc biệt là hình dạng gai vi ngực. Nhóm cá trê “lạ” có cạnh ngoài gai vi ngực với các răng to rõ và dễ dàng phân biệt với các nhóm khác. Tất cả các chỉ số sinh trắc đều khác biệt có ý nghĩa thống kê giữa bốn nhóm cá (p< 0,05). Kết quả phân tích thành phần chính (Principal Component Analysis- PCA) cũng thể hiện sự sắp xếp rõ ràng của bốn nhóm cá, trong đó nhóm cá trê vàng và nhóm cá “trê lạ” gần giống nhau hơn so với hai loài trê trắng và trê Phú Quốc. Hai thành phần chính (Principal Component - PC1 và PC2), giải thích lần lượt 46,3% và 22,6% sự khác biệt về số đo của bốn nhóm cá. Ngoài ra, phân tích nhóm còn cho thấy 100% các cá thể cá trê được xếp đúng vào từng nhóm ban đầu. Kết quả nghiên cứu này thống nhất với kết quả của nghiên cứu trước: cá trê “lạ” có thể không phải là con lai giữa cá trê vàng và cá trê Phú Quốc.

Background: Monogenean flatworms are the main ectoparasites of fishes. Representatives of the species-rich families Gyrodactylidae and Dactylogyridae, especially those infecting cichlid fishes and clariid catfishes, are important parasites in African aquaculture, even more so due to the massive anthropogenic translocation of their hosts worldwide. Several questions on their evolution, such as the phylogenetic position of Macrogyrodactylus and the highly speciose Gyrodactylus, remain unresolved with available molecular markers. Also, diagnostics and population-level research would benefit from the development of higher-resolution genetic markers. We aim to offer genetic resources for work on African monogeneans by providing mitogenomic data of four species (two belonging to Gyrodactylidae, two to Dactylogyridae), and analysing their gene sequences and gene order from a phylogenetic perspective. Results: Using Illumina technology, the first four mitochondrial genomes of African monogeneans were assembled and annotated for the cichlid parasites Gyrodactylus nyanzae, Cichlidogyrus halli, Cichlidogyrus mbirizei (near-complete mitogenome) and the catfish parasite Macrogyrodactylus karibae (near-complete mitogenome). Complete nuclear ribosomal operons were also retrieved, as molecular vouchers. The start codon TTG is new for Gyrodactylus and for Dactylogyridae, as is the incomplete stop codon TA for Dactylogyridae. Especially the nad2 gene is promising for primer development. Gene order was identical for protein-coding genes and differed between the African representatives of these families only in a tRNA gene transposition. A mitochondrial phylogeny based on an alignment of nearly 12,500 bp including 12 protein-coding and two ribosomal RNA genes confirms that the Neotropical oviparous Aglaiogyrodactylus forficulatus takes a sister group position with respect to the other gyrodactylids, instead of the supposedly 'primitive' African Macrogyrodactylus. Inclusion of the African Gyrodactylus nyanzae confirms the paraphyly of Gyrodactylus. The position of the African dactylogyrid Cichlidogyrus is unresolved, although gene order suggests it is closely related to marine ancyrocephalines. Conclusions: The amount of mitogenomic data available for gyrodactylids and dactylogyrids is increased by roughly one-third. Our study underscores the potential of mitochondrial genes and gene order in flatworm phylogenetics, and of next-generation sequencing for marker development for these non-model helminths for which few primers are available. [ABSTRACT FROM AUTHOR]

The study determined the variation in the morphological and meristic features among four populations of Clarias gariepinus Burchell, 1822 obtained from Owena Dam and River Oluwa in Ondo State and Rivers Omo and Ogbere in Ogun State, both in Nigeria. A total of ninety five (95) and one hundred and twenty (120) fish specimens collected from Ondo and Ogun states respectively were measured using standard procedures and the results were analysed using Analysis of variance and multivariate analyses. The results obtained from the ANOVA and Principal Component Analyses of Clarias gariepinus from the four populations revealed heterogeneity for most of their characters. Therefore, the morphological differences between the wild African catfish found in Ondo and Ogun state populations could be linked to genetic differences or environmental factors or a combination of both factors. Hence, this study concluded that the populations are different which could imply high genetic diversity if molecular marker techniques are employed in further studies. [ABSTRACT FROM AUTHOR]

Clariid catfish are favorite food fish especially in African and Asian continents. Recently there has been preference for particular species or hybrids of these species based on quality assurance and value addition. Consequently, this study aimed to evaluate the possible effect of different catfish species and their hybrids on proximate composition and sensory attributes. Catfish species, Clarias gariepinus ( CC), Heterobranchus bidorsalis ( HH), with their hybrid ( CH), and reciprocal hybrid ( HC) were evaluated for sensory variables - cognitive (sweet, salty, sour, bitter, and recent characteristic taste 'umami') and qualitative (texture, aroma, flavor, and color) tests; and nutritional variables - proximate composition (moisture, protein, ether/fat, and ash). A 5-point hedonic scale from 'neutral/neither like nor dislike' to 'excellent/like extremely' was employed in sensory testing. The results showed similar ( P > 0.05) high moisture contents (>70%) in all species and high but different ( P < 0.05) ash contents (11-14%) that suggested good sources of mineral elements. The parent species CC and HH had higher ash contents than CH or HC. The crude protein contents were high and similar ( P > 0.05) across species (>57%). Fat or ether extract was different ( P < 0.05) and tended to be higher for species with Clarias as the female parent than Heterobranchus. Sensory analysis showed the parent species, CC and HH, more favorably rated for sweet and umami than the hybrids, CH and HC. However, CH was less sour and bitter than all other species and HC better than CH for salty but similar to CC and HH. All fish species were very well liked for texture, but the parent species were superior in flavor than the hybrids. All species were very well liked for aroma, color, and overall acceptability except HC, which was moderately liked. HC rated inferior to the other species overall in sensory attributes. All the fish species did not rate 'excellent/like extremely' for any attribute. It can be concluded that the parent catfish species possess better sensory qualities than hybrids, but all species need exogenous enhancement to their natural sensory components. [ABSTRACT FROM AUTHOR]

L’examen de Clarias pachynema Boulenger, 1903 (Clariidae), Ctenopoma petherici Günther, 1864 (Anabantidae) et Parachanna obscura (Günther, 1861) (Channidae), capturés dans le bassin du Nkam au Cameroun, a révélé la présence de deux espèces nouvelles de Myxosporidies du genre Myxidium Bütschli, 1882, toutes parasites de la vésicule biliaire. Les espèces inédites sont : Myxidium nkamensis n. sp., parasite de Clarias pachynema; M. sangei n. sp., qui forme des spores dans la paroi de la vésicule biliaire de Parachanna obscura. Deux autres espèces, Myxidium petrocephali Fomena et Bouix, 1986 et M. distichodi Kostoïngué, Faye et Toguebaye, 1998, ont été retrouvées chez des hôtes nouveaux. Leur diagnose est complétée. La liste des espèces de Myxidium parasites des poissons d’eau douce d’Afrique est donnée.

L’étude des monogènes parasites branchiaux de trois espèces de poissons du genre Clarias Scopoli, 1777 (Clariidae) : C. pachynema, C. jaensis et C. camerunensis, pêchés dans le bassin du Nyong (Cameroun) a permis de récolter trois nouvelles espèces placées dans le nouveau genre Birgiellus, respectivement Birgiellus mutatus n. sp. chez Clarias pachynema, B. calaris n. sp. chez C. jaensis et B. kellensis n. sp. chez C. camerunensis. Le genre Birgiellus, voisin du genre Quadriacanthus, s’en distingue par la morphologie de la barre transversale ventrale formée d’une pièce unique (deux bras distincts chez Quadriacanthus) et par les uncinuli IV peu différents des autres (plus grands chez les Quadriacanthus). Birgiellus calaris diffère de B. mutatus par les anchors ventraux plus longs et plus épais, la morphologie de la barre transversale ventrale, la taille des pièces sclérifiées des appareils copulateurs mâle et femelle, avec la pièce accessoire mâle munie d’un talon, un manche trapézoïdal plus long et un crochet plus épais. Birgiellus kellensis, proche de B. calaris, s’en écarte par la taille plus faible des anchors dorsaux et ventraux, des barres transversales, du pénis, et de la pièce accessoire male, sans talon, mais avec une lame mince supplémentaire. En référence à l’article 8.5.2 du Code international de nomenclature zoologique (1999), le genre Birgiellus et les espèces B. mutatus et B. calaris remplacent respectivement le genre Claridectes et les espèces C. clarisa et C. alacris, initialement décrits par Birgi (1987), mais dont les spécimens n’ont jamais été déposés dans un musée. L’étude de la spécificité parasitaire de ces trois espèces montre qu’elle est du type oïoxène.

Clariidae is a group that includes many species that have great economic importance in both fisheries and fish culture. Monogenean parasites of fishes assigned to this family have been studied in Cameroon, but there have been no studies on Clarias submarginatus Peter, 1882, a fish that is traditionally consumed by the local people. The examination of 43 specimens identified as C. submarginatus from Lake Ossa (first record of this fish species in the Sanaga basin), revealed that some of them belong to Quadriacanthus and are new. Their identification was made based on the morphology and the size of sclerotized parts of the haptor and the male and female copulatory complexes. Quadriacanthus macruncus Bahanak, Nack & Pariselle sp. nov. and Quadriacanthus submarginati Bahanak, Nack & Pariselle sp. nov. are characterized by the morphology of their accessory piece, pointed, slightly curved and wider at medium level, equipped with two subterminal, symmetrical and similar spines for Q. macruncus sp. nov. and made up of one long tip flanked by a short spine and a bulb for Q. submarginati sp. nov., while Quadriacanthus ossaensis Bahanak, Nack & Pariselle sp. nov. is distinguished by the unique morphology of the penis, ending in a fork. The new species of Quadriacanthus are herein described and their host specificity is discussed. [ABSTRACT FROM AUTHOR]

This study was conducted to assess the effect of the water quality of Ogun River, on the African catfish Clarias gariepinus haematological indices. Samples of water and C. gariepinus were collected from Ogun River (Station I, Opeji and Station II, Lafenwa) to determine and compare effects of possible differences of water quality on hematological parameters of C. gariepinus. The results showed that higher values were recorded at the station II than Station I for almost all the physicochemical parameters and only sulphate values from Stations I and II were statistically significant (P < 0.05). [ABSTRACT FROM AUTHOR]

Qualitative and quantitative traits of the diet of Clarias buettikoferi (Siluriformes; Clariidae) in the Tanoe-Ehy swamp forest (Côte d'Ivoire). Feeding habits of the catfish Clarias buettikoferi Steindachner, 1894 were studied in the Tanoe-Ehy swamp forest (Côte d'Ivoire). Fishes were caught monthly using fyke nets and gillnets from March 2012 to February 2013. 208 fishes were collected, with standard length and weight ranging between 90 and 260 mm, and 7.3 and 132 g, respectively. Mean vacuity index (VI) was 14.4%. The seasonal average of VI was 40.4% and 8.4% for dry and rainy seasons, respectively. A total of 41 food items was recorded, including animals and vegetables. Main Food Index showed that insects were the principal prey category. Macrophytes were the secondary item, while mollusks, myriapods, crustaceans and arachnids were accessory prey. C. buettikoferi exhibited an omnivorous feeding behaviour with an insectivorous tendency. Significant variation of the diet was observed between seasons, showing different feeding behavior (pelagic or benthic feeding habits). C. buettikoferi is an opportunistic feeder, which mainly feeds on pelagic and floating insects during rainy months, while in dry season the preferential food items included mollusks and other benthic food resources. [ABSTRACT FROM AUTHOR]

Food habits of the eel catfi sh, Plotosus canius Hamilton 1822, were investigated in two localities, a mangrove estuary and a mudfl at, on the west coast of Peninsular Malaysia for approximately two years. The eel catfi sh is associated with mangrove estuaries, creeks, mudfl ats, and shallow coastal waters, and is a commercially valuable food fi sh that is exploited by artisanal fi shermen using hook and line, and commercial barrier nets operated on intertidal mudfl ats. Within the mangrove estuary Sungai [= river] Sementa Kecil, the gut contents of eel catfi sh consisted predominantly of crustaceans living in the mangrove shore or adjoining mudfl ats. The fi sh consumed an average of about 70% by volume of brachyuran crabs comprising of Sesarmidae, and penaeid prawns. At the Sungai Buloh mudfl at, 40% of its diet consisted of bivalves such as the blood cockle, Anadara granosa (L.), Xenostrobus and Placuna sp., while other items consumed include fi sh Stolephorus sp., and Glossogobius sp. The study indicates that eel catfi sh living in mangrove estuaries and mudfl ats consumes resident invertebrates thus utilising benthic resources of the intertidal zone. [ABSTRACT FROM AUTHOR]

Clarias gariepinus is a threatened highly prized species used for some elite ceremonies by the local communities. Artisanal fishers take advantage of this species annual breeding migration from the lower Cross River to the floodplain lakes in Mid-Cross River during the rainy season, and some migrant stocks are not able to spawn. Since there is a lack of information on this species population dynamics in the Mid-Cross area, this study aimed to evaluate the age, growth and mortality to support the development of effective management plans. For this, monthly overnight gill net catches (from 6 to 72mm mesh sizes) were developed between March 2005 and February 2007. Growth parameters were determined using the FiSAT II length-frequency distribution. A total of 1 421 fish were collected during the survey. The asymptotic growth (L∞) was 80.24cm, growth rate (K) was 0.49/year while the longevity was 6.12years. The annual instantaneous rate of total mortality (Z) was 2.54/year and the natural mortality (M) was 0.88. Fishing mortality (1.66/year) was higher than the biological reference points (Fopt=0.83 and Flimit=1.11) and the exploitation rate (0.66) was higher than the predicted value (Emax=0.64) indicating that C. gariepinus was over exploited in the Mid-Cross River-Floodplain ecosystem. Some recommended immediate management actions are to strengthen the ban of ichthyocide fishing, closure of the floodplain lakes for most of the year, restricted access to the migratory path of the fish during the flood period and vocational training to the fishers. In order to recover and maintain a sustainable harvest, I suggest that a multi-sector stakeholder group should be formed with governmental agents, community leaders, fishers, fisheries scientists and non-governmental organizations. These short and long term measures, if carefully applied, will facilitate recovery of the fishery. [ABSTRACT FROM AUTHOR]

Bacterial infection among the most common cultured mudfish Clarias gariepinus in Africa, has become a cause of concern, because it constitutes the largest economic loss in fish farms. In order to provide useful biological data of the pathogens for good management practices, samples were collected monthly between January 2008 and December 2009 in three monoculture nursery ponds, located in three different positions: upriver (A, grassland), mid-river (B, mixed forest and grassland) and downriver (C, rainforest) along 200km length of Cross River floodplains, Nigeria. A total of 720 fingerlings between 15.1 and 20.7g were analyzed to determine the degree of infection. The bacterial pathogens were taken from their external surfaces, and were isolated and identified by standard methods. The caudal fins of fingerlings from pond A had the highest bacterial load (5.8x10³cfu/g), while the least counts (1.2x103cfu/g) were identified on the head of fish from pond C, with Flexibacter columnaris as the major etiological agent. Pseudomonas fluorescens, Aeromonas hydrophila, Escherichia coli, Staphylococcus aureus and Micrococcus luteus were identified as co-isolates with P. fluorescens as dominant (0.7x10²cfu/mL) co-isolates in pond water. Clinical signs of five white spots with red periphery appeared on the external surface of infected fish. All the fish sampled, died after 4 to 9 days. There was no significant difference in the bacterial counts between different ponds, but the difference between fish organs/parts examined was significant. Fish from these ponds are therefore potentially dangerous to consumers and highly devalued, with the economic impact to producers. Preventive methods to avoid these infections are recommended. Rev. Biol. Trop. 59 (2): 751-759. Epub 2011 June 01. [ABSTRACT FROM AUTHOR]

Abstract: The question of whether or not pre-modern hominins were responsible for the accumulation of fish remains is discussed through analyses of remains recovered from two lacustrine facies (I-4 and I-5) from Area A of the Acheulian site of Gesher Benot Ya‘aqov (GBY) in the Jordan Rift Valley, Israel. The fish remains provide the first glimpse into the naturally accumulated fish assemblage from the fluctuating shores of a lake that had been continually exploited by early hominins some 780,000 years ago. Preliminary analysis of the remains show that thirteen of the seventeen species native to Lake Hula were identified at GBY. These represent three of the five freshwater fish families native to the lake: Cyprinidae (carps), Cichlidae (tilapini, St. Peter''s fish), and Clariidae (catfish). From a taphonomical perspective, a significant difference is found between the two lithofacies (Layers I-4 and I-5) in terms of species composition, richness, diversity, and skeleton completeness. It appears that the fish remains recovered from Layer I-4 (clay) are better preserved than those from Layer I-5 (coquina). In both lithofacies, Cyprinidae are highly abundant while Cichlidae and Clariidae are rare and under-represented, especially when compared to the Lake Hula fishery report from the 1950s. All of these identified species may have contributed significantly to the diet of GBY hominins. [Copyright &y& Elsevier]

A new proteocephalidean cestode is described from 2 catfishes, Clarias gariepinus (type host) and C. cf. anguillaris (Siluriformes: Clariidae), from Ethiopia (type locality), Sudan, Tanzania, and Zimbabwe, and a new genus, Barsonella, is proposed to accommodate it. The genus belongs to the Proteocephalinae because its genital organs (testes, ovary, vitellarium, and uterus) are situated in the medulla. Barsonella lafoni, the type and only species of the new genus, is characterized mainly by the possession of an additional opening of each sucker; circular musculature on the anterior margin of suckers, serving as a sphincter; a small thin-walled glandular apical organ; absence of well-developed osmoregulatory canals in mature, pregravid, and gravid proglottids; and a large strobila, up to 173 mm long and 3.2 mm wide. Species of Marsypocephalus Wedl, 1861 (Marsypocephalinae), other large-sized proteocephalidean tapeworms occurring sympatrically in African catfishes (Clarias and Heterobranchus) and also possessing a sphincter-like, circular musculature on the anterior part of suckers, differ from B. lafoni in the absence of an additional sucker opening and glandular apical organ, the cortical position of the testes, well-developed osmoregulatory canals throughout the strobila, and a large cirrus sac. Proteocephalus glanduligerus (Janicki, 1928), another cestode parasitic in Clarias spp. in Africa, is much smaller than B. lafoni (maximum length 15 mm), has suckers without additional opening and circular musculature on the suckers, a large-sized glandular organ, much larger than suckers, and well-developed osmoregulatory canals. Comparison of partial sequences of the 28S rRNA gene for 7 samples of B. lafoni from 2 different hosts and 4 localities in Ethiopia, Sudan, and Tanzania has shown a very low genetic variability. In a limited phylogenetic analysis, B. lafoni formed a clade with Corallobothrium solidum Fritsch, 1886 (Proteocephalidae: Corallobothriinae), an African electric catfish parasite. This clade was the sister group of almost all Neotropical taxa from pimelodid and other catfishes. [ABSTRACT FROM AUTHOR]

Specific fish species of the Okavango River, Botswana, partake in an annual intensive feeding migration as a response to the annual flood regime. Carnivorous fish species, such as the catfish species (Clarias gariepinus and C. ngamensis) (family: Clariidae) and the tigerfish (Hydrocynus vittatus) (family: Characidae) participate in a so-called "feeding frenzy ". The process of feeding is energy intensive and results in an increase in energy consumption. Energy -- required for growth, reproduction and metabolism -- will determine the net energy budget, and therefore serves as a measure of the general condition of fish. The cellular energy allocation (CEA) methodology is used to determine the net energy budget of fish species of different fish families (Characidae. Cichlidae, and Clariidae) at a cellular level. The method was applied to establish the effect that the feeding migration has on the energy allocation of the fish. This approach quantifies the energy reserves and energy consumed at cellular level and is integrated into a net energy budget to determine the energy status of the fish species. Cellular energy allocation as a biochemical endpoint of the energy budget of an organism, may provide information on the total amount of energy available for maintenance, growth, and reproduction. The difference between the energy available (EA) (total glycogen, lipid, and protein content) and the energy consumed (EC) (such as the electron transport activity in the mitochondria, which is directly linked to oxygen consumption) represents the net cellular energy allocation (CEA) or energy budget of an organism. A decreased energy budget is related to a reduction in energy available, an increase in energy consumption, or a combination of both. The condition factor (CF) and the hepatosomatic index (HSI) were determined to establish if a correlation between the CEA and the condition of the whole organism exists. The CF and HSI indices are used to give a general indication of the nutrient status of fish. A decline in the CF and HSI has been associated with a reduction in energy reserves, such as stored liver glycogen. The CEA was determined in the liver of the fish, since a large proportion of substrate transformation or changes in nutrient supply occur in this organ. The CEA technique gave a good indication of the energy allocation at cellular level in the fish. The total glycogen content of the different fish families was similar. The reduced lipid content in both Characidae and Clariidae contributed the most to the integrated energy available. Significant differences in the total protein content between the fish families were not apparent. The energy consumption which serves as an in vitro oxygen consumption measurement, did not affect the total CEA of the fish families in this study. The lower CEA in both Characidae and Clariidae compared to Cichlidae is possibly due to the involvement of Characidae and Clariidae in the intensive feeding migration. Individual fish from Characidae and Clarridae had significantly lower CF values compared to Cichlidae. Although the CF and HSI values differed among the fish families, no correlations were found between these indices and the CEA of the fish families. Changes in the energy budget or CEA of organisms provide a fast and sensitive response on a cellular level of biological organisation, however effects on the condition status (i.e. whole-organism level), will only manifest and become apparent after a few days or weeks. The feeding migration is probably associated with physiological adaptations in the fish families in relation to their energy allocation, which will be to the benefit of their general health status. It is recommended to collect fish during normal feeding periods to investigate the energy status of the fish families of the Okavango River, effectively. [ABSTRACT FROM AUTHOR]

The swimming, air-gaping, and agonistic behaviours of Heterobranchus longifilis (318 ± 67 mm) were examined while fish were in a fasted state under 12L:12D and variable group size (2, 5, 10 and 15 fish) in a 1000-L aquarium. Fish exhibited a predominantly nocturnal activity pattern independent of group size. A diurnal peak of activity occurred, however, at the usual feeding time. A reduction in frequency of agonistic interactions was observed in larger groups. Five fish were then observed under 72L:0D and 0L:72D. The nocturnal activity pattern remained, contrary to the diurnal peak, and was independent of the duration of illumination or darkness. These results suggest the absence of biological clock in H. longifilis, although fish may somehow be influenced by past feeding experience. Behavioural plasticity in this species may provide potential for aquaculture in northern latitudes. [ABSTRACT FROM AUTHOR]

In several water-breathing fish species, β-adrenergic receptor stimulation by noradrenaline leads to a decrease in plasma free fatty acid (FFA) levels, as opposed to an increase in air-breathing mammals. We hypothesised that this change in adrenergic control is related to the mode of breathing. Therefore, cannulated air-breathing African catfish were infused for 90 min with noradrenaline or with the nonselective β-agonist, isoprenaline. To identify the receptor type involved, a bolus of either a selective β1 antagonist (atenolol) or a selective β2-antagonist (ICI 118,551) was injected 15 min prior to the isoprenaline infusion. Both noradrenaline and isoprenaline led to an expected rise in glucose concentration. Isoprenaline combined with both the β1- and β2-antagonist led to higher glucose concentrations than isoprenaline alone. This could indicate the presence of a stimulatory β-adrenoceptor different from β1 and β2-adrenoceptors; these two receptors thus seemed to mediate a reduction in plasma glucose concentration. Both noradrenaline and isoprenaline led to a significant decrease in FFA concentration. Whereas the β1-antagonist had no effect, the β2-antagonist reduced the decrease in FFA concentration, indicating the involvement of β2adrenoceptors. It is concluded that the air-breathing African catfish reflects water-breathing fish in the adrenergic control of plasma FFA and glucose levels. [ABSTRACT FROM AUTHOR]

As a part of the general revision of anguilliform clariid genera and species, the status of Dolichallabes microphthalmus Poll, 1942, is reviewed, based on morphology and osteology of all available museum specimens. Dolichallabes microphthalmus, the most elongate species within the Clariidae, has been redescribed. Compared to Channallabes apus and Gymnallabes typus, D. microphthalmus is characterized by, in addition to some meristic differences, an elongate body, reduced skull ossification, with (1) one elongate fontanel, (2) antorbital and infraorbital 1V the only circumorbital bones present, (3) only one or two suprapreopercular bones on each side, and (4) a sphenotic bearing only one process. Osteological evidence suggests that D. microphthalmus could be considered a paedomorphic clariid. [ABSTRACT FROM AUTHOR]

Simple Summary: Fish are influenced by their surroundings. We investigated the effect of water temperature ranging from 26 °C to 32 °C on the growth performance and gastric emptying time (GET) of commonly cultured African catfish Clarias gariepinus fingerlings. Water temperatures between 26 °C and 32 °C were satisfactory for the growth of African catfish fingerlings, with GET observed between 10 and 16 h. Our experiment provides baseline data of the effects of water temperature on the culture of catfish. The present study was carried out to analyse the effect of water temperature on two components: (1) growth performance, and (2) gastric emptying time (GET) of African catfish Clarias gariepinus fingerlings. After 70 days, it was observed that experimental temperatures had no significant effects on the growth performance parameters, except for food conversion ratio (FCR) and food conversion efficiency (FCE). GET observation through X-radiography denoted that the shortest GET (10 h) was observed in fish reared at 32 °C and the longest GET (16 h) was observed in fish reared at 26 °C. The rapid digestion rate coincides with the FCR and FCE obtained in this study. Considering the limited scope of our study, more extensive studies on the impact of water temperature on other fish physiological parameters should be pursued. A better understanding of this research topic would be beneficial for the growth of African catfish fingerling aquaculture. [ABSTRACT FROM AUTHOR]

Simple Summary: Global aquaculture requires the development of new strategies to maintain the continuous growth of production, such as the development of aquafeeds with sustainable and functional components, ensuring better growth and health conditions of fish. Humic substances (HS) have the potential to become a functional additive for aquafeeds, as their growth-promoting and immunostimulant effects have been found in farm animals. Recently, there is limited knowledge on how different HS affects overall performance of various fish species. Therefore, in this study, the effects of four experimental Siberian leonardite HS diets (HS0, HS1, HS3, and HS6) on growth and production parameters, condition and somatic indices, overall mortality, health condition, and antioxidant status were assessed in juvenile Clarias gariepinus, which is well-known as a fast-growing and high-resistant fish species when reared at high stocking densities up to 500 kg m−3. In this study, growth and production parameters, condition, and somatic indices or mortality rate were not significantly affected by tested HS diets. On the other hand, moderately positive effects were observed regarding health status and good antioxidant parameters, especially in the HS3 group over the 56-day study. In the present study, a possible nature immunostimulant and growth promoter—humic substances (HS) originating from Siberian leonardite mineraloid—were tested on juvenile Clarias gariepinus performance. Feed additive was applied onto commercial pelleted feed at four HS levels—0, 1, 3, and 6% w/w (HS0, HS1, HS3, HS6, respectively). Diets were tested in five repetitions (in total, n = 1800 individuals, mean body weight 28.1 ± 6.2 g) for 56 days. Growth and production parameters, fish condition and somatic indices, and overall mortality were evaluated after 14, 28, 42, and 56 days of exposure. Whereas, plasma samples were collected only after 0, 28, and 56 days, when fish health status was assessed with biochemical parameters (total proteins, TP; alanine aminotransferase, ALT; aspartate aminotransferase, AST; lactate dehydrogenase, LDH; cholesterol, CHOL; triglycerides, TAG) and fish antioxidant status with glutathione (reduced glutathione, GSH; oxidized glutathione, GSSG; glutathione ratio GSH/GSSG). Although a significantly positive effect of HS feed additive on growth performance was not found in the present study, moderately positive effects were found regarding biochemical parameters (ALT, AST, LDH, CHOL, and TAG) and antioxidants (GSH/GSSG ratio) that were improved especially in the HS3 group. [ABSTRACT FROM AUTHOR]