Walking Catfish Research Articles

Farmer Friendly Low Cost Breeding and Seed Rearing Technology of Walking Cat Fish (Clarias Magur)

Farmer Friendly Low Cost Breeding and Seed Rearing Technology of Walking Cat Fish (Clarias Magur)

Effects of autochthonous bacteria and prebiotic supplementation on the growth and survival of Clarias batrachus

Studies were conducted to identify the autochthonous bacteria from the intestines of walking catfish, Clarias batrachus, and to evaluate the efficacy of the gut microbes supplementation on the growth and survival of the catfish under laboratory condition. Autochthonous bacteria were isolated from the intestines of experimental fish using Nutrient agar (NA) and de Man, Rogosa, and Sharpe (MRS) agar in duplicate. Primarily, 16 gut bacteria were isolated and three isolates were selected viz., Lactobacillus sp., Bacillus sp., and Lactococcus sp. after the phenotypic study. For biosafety evaluation of the selected bacteria, healthy C. batrachus fingerlings (average weight: 10.4 ± 0.8 g) were challenged with these bacteria at a dose of 107 CFU/mL by immersion technique for 7 days. Gut microbiota supplemented diets were prepared and analyzed for their proximate composition. A 3-week long feeding trial was conducted with ten 35 L capacity rectangular glass aquaria to evaluate the growth performance and survival of 96 C. batrachus fingerlings (average weight: 9.28 ± 1.5 g) fed with the above three gut microbiota supplemented diet and gut microbiota + prebiotic (molasses, yeast, and rice bran) supplemented diet. Morphometric measurements of the experimental fish and water quality parameters were determined weekly. The bio-safety evaluation revealed that the isolates were safe for C. batrachus with no clinical signs or mortalities during the challenge test. The study revealed better growth and survival of C. batrachus with gut bacteria supplemented diets but showed much better performance in the cases of all growth parameters while prebiotic was additionally supplemented. Thus, the above mentioned autochthonous gut probiotics and prebiotics could be recommended as an effective eco-friendly health management approach in C. batrachus culture. Further detail study is necessary to establish the fact.

On mating and function of associated electric pulses in Clarias macrocephalus (Günther 1864): probing an old puzzle, first posed by Charles Darwin

The Asian broadhead walking catfish (Clarias macrocephalus) generates weak electric monopolar pulses during spawning. Males emit a single pulse when attracting a female, and while in amplexus, only females emit a single burst of similar pulses. This burst is a necessary component in the mating ritual of C. macrocephalus. Release of milt occurs about 5 s prior to the onset of a burst, which is immediately followed by the release of eggs. Following sperm release, the male remains in tight embrace with the female. Though both male and female could perceive each other’s electric pulses via ampullary receptors (communication mode), we postulate that egg release can be facilitated by direct action of the female’s burst on the male’s neuromuscular system (contraction mode). Shedding light on the function of weak episodic electric emission, we propose that the modification of electrogenic structures evolved towards increasing the efficiency of direct bodily impact. As extant clariids exhibit intermediate features between non-electric and strongly electric catfishes, Clarias should be considered a “serviceable transition,” which Charles Darwin deemed a possible intermediate form between these two groups.

THE IMPACT OF CULINARY TOURISM ON THE ECONOMY OF COASTAL COMMUNITIES IN TIRAM BEACH NAGARI TAPAKIS SUB DISTRICT ULAKAN TAPAKIS PADANG PARIAMAN REGENCY WEST SUMATERA PROVINCE

This study aimed to utilize the fish bone waste from different types of fish, Pangasius sp., Clarias sp., Paraplotosus sp. as a high calcium of bone flour and determine the quality characteristics of fish bone flour which was produced. The method used was a non-factorial Completely Randomized Design (CRD), with different types of fish bones as treatments which consisting of 3 levels: Pangasius sp. bone (Tp), Clarias sp. bone (Tl), and Paraplotosus sp. bone (Ts) with 3 replications and 9 units of experimental units. The parameters tested were organoleptic, proximate analysis, calcium, phosphorus and whiteness degrees. The results showed that the Pangasius sp. bone flour (Tp) was the best treatment with characteristics of brilliant appearance, the distinctive aroma of fish was still felt, smooth and dry texture, as well as whiteness degrees that the best treatment in walking catfish bone flour with value 81.30%, referred to whiteness degrees of flour, it is below the range of 80-90%. Meanwhile the best proximate value was obtained in Paraplotosus sp. bone treatment (Ts) with moisture, ash, fat, protein, carbohydrate, calcium and phosphorus content was 5.71%, 54.60%, 2.57%, 25.21%, 10.83%, 38.4%, and 33.9%.

CHARACTERISTICS OF HYDROLYSATE PROTEIN FROM MALONG FISH (Congresox talabon) WHICH HYDROLIZED BY USING PAPAIN ENZYME

This study aimed to utilize the fishbone waste from different types of fish, Pangasius sp., Clarias sp., Paraplotosus sp. as high calcium of bone flour and determine the quality characteristics of fishbone flour which was produced. The method used was a non-factorial Completely Randomized Design (CRD), with different types of fish bones as treatments which consisting of 3 levels: Pangasius sp. bone (Tp), Clarias sp. bone (Tl), and Paraplotosus sp. bone (Ts) with 3 replications and 9 units of experimental units. The parameters tested were organoleptic, proximate analysis, calcium, phosphorus, and whiteness degrees. The results showed that the Pangasius sp. bone flour (Tp) was the best treatment with characteristics of brilliant appearance, the distinctive aroma of fish was still felt, smooth and dry texture, as well as whiteness degrees that the best treatment in walking catfish bone flour with value 81.30%, referred to whiteness degrees of flour, it is below the range of 80-90%. Meanwhile, the best proximate value was obtained in Paraplotosus sp. bone treatment (Ts) with moisture, ash, fat, protein, carbohydrate, calcium and phosphorus content was 5.71%, 54.60%, 2.57%, 25.21%, 10.83%, 38.4%, and 33.9%.

CHARACTERISTICS OF FISH BONE FLOURS QUALITY FROM DIFFERENT TYPES OF FISH (Pangasius sp., Clarias sp., Paraplotosus sp.)

This study aimed to utilize the fish bone waste from different types of fish, Pangasius sp., Clarias sp., Paraplotosus sp. as a high calcium of bone flour and determine the quality characteristics of fish bone flour which was produced. The method used was a non-factorial Completely Randomized Design (CRD), with different types of fish bones as treatments which consisting of 3 levels: Pangasius sp. bone (Tp), Clarias sp. bone (Tl), and Paraplotosus sp. bone (Ts) with 3 replications and 9 units of experimental units. The parameters tested were organoleptic, proximate analysis, calcium, phosphorus and whiteness degrees. The results showed that the Pangasius sp. bone flour (Tp) was the best treatment with characteristics of brilliant appearance, the distinctive aroma of fish was still felt, smooth and dry texture, as well as whiteness degrees that the best treatment in walking catfish bone flour with value 81.30%, referred to whiteness degrees of flour, it is below the range of 80-90%. Meanwhile the best proximate value was obtained in Paraplotosus sp. bone treatment (Ts) with moisture, ash, fat, protein, carbohydrate, calcium and phosphorus content was 5.71%, 54.60%, 2.57%, 25.21%, 10.83%, 38.4%, and 33.9%.

Optimal dietary lipid and protein level for growth and survival of catfish Clarias magur larvae

Large scale farming of Clarias magur (Indian walking catfish) is limited due to the non-availability of seed because of high mortality rate occurring during its larval rearing. The aim of the present study was to develop an optimal strategy based on the dietary lipids and proteins for enhancing the larval survival. A 3-week study from 14-35 day post hatching (dph) was conducted to elucidate the effects of dietary lipid and protein level on growth, survival and mRNA expression of growth related genes of C. magur larvae. Significantly (P < 0.05) high growth on average wet weight basis and survival rate was observed in 8% dietary lipid inclusion level followed by 10% and 12% lipid contents from 14-35 dph larval rearing phase. The effect of dietary lipid on the body composition was also reflected on the lipid content of larvae where a significant difference was observed. Similarly, growth-related genes like growth hormone (GH) and insulin-like growth factor I (IGF-I) exhibited a significantly high expression at 8% lipid level compared to 10% and 12% whereas, insulin-like growth factor binding protein3 (IGFBP3) showed a reverse trend. Based on the results, 8% dietary lipid along with the protein combination improved the performances significantly with regard to growth and survival. However, this experiment did not help to differentiate whether the differences observed at different time points are due to dietary protein level or the age of larvae. Hence, another experiment was conducted in which diets were formulated to contain different protein levels (55, 50 and 45%) with a constant 8% level of lipid in all the treatments along with commercial diet as control. The inclusion of 8% lipid and 55% protein was observed to show excellent performance with respect to growth, survival and the mRNA expression of important growth-related genes. Hence, a formulated diet with crude protein of 55% and 8% lipid can be suggested as the optimal microdiet for the larval rearing of C. magur.

Prevalence of trematode in wild fish from fishing in Ho Chi Minh City

A research on the prevalence of fishborne zoonotic trematodes (FZT), metacercariae stage, in wild fish from fishing in Nhieu Loc – Thi Nghe, Tau Hu – Ben Nghe and Thay Cai – An Ha canals was conducted in Ho Chi Minh City in the period of May 2017 and April 2018. The results showed that no metacercariae were found in fish in Nhieu Loc – Thi Nghe and Tau Hu – Ben Nghe canals. However, wild fish in Thay Cai – An Ha canal were infected with Haplorchis pumilio and Centrocestus formosanus. Metacecariae were infected in silver barb (80%), climbing perch (11.7%), snakehead (7.5%), and walking catfish (1.7%). The FZT prevalence in the wet season is significantly higher than in the dry season (P

Immune response of channel catfish (Ictalurus punctatus) against Ichthyophthirius multifiliis post vaccination using DNA vaccines encoding immobilization antigens

The channel catfish (Ictalurus punctatus) immune response against Ichthyophthirius multifiliis (Ich) after vaccination using plasmid DNA vaccines pcDNA3.1-IAg52a and pcDNA3.1-IAg52b, encoding Ich immobilization antigen genes was studied. Parasite infection level, serum anti-Ich antibodies level, fish mortality after theront challenge, and immune-related gene expression were measured. After in vitro transfection of walking catfish gill cells (G1b) with both pcDNA3.1-IAg52a and pcDNA3.1-IAg52b, antigens IAG52A and IAG52B were detected. During the vaccination trial, 76-fold increase in the Iag52b gene expression was observed in the vaccinated fish group h4 post vaccination. Administration of DNA vaccines by IM injection induced significant gene up-regulation in the head kidney, including immunoglobulin M (IgM), cluster of differentiation 4 (CD4), major histocompatibility I (MHC I), and T cell receptor α (TcR-α) from h4 to d5 post immunization. Fish vaccinated with DNA vaccines or theronts showed increased gene expression of the cytokine interferon (IFN-γ), complement component 3 (C3), and toll-like receptor-1 (TLR-1). Anti-Ich antibodies were detected in fish received pcDNA3.1-IAg52a, pcDNA3.1-IAg52b and the combination of both vaccines d10 post vaccination. Fish vaccinated with pcDNA3.1-IAg52b showed mild parasite infection level, partial survival (20%) and longer mean day to death (MDD) after theront challenge. By contrast, a heavy parasite load, 0% survival and short MDD were observed in the sham vaccinated control fish that received pcDNA3.1 (plasmid without genes encoding Ich immobilization antigen). Further research is needed to improve DNA vaccines for Ich that can induce strong protective immunity in fish. Suggested studies include improved transfection efficiency, use of appropriate adjuvants and including additional parasite antigen genes in the plasmid.

Expression and activity of key lipases during the larval development of walking catfish (Clarias magur).

The study was conducted to investigate the expression and activity of key lipolytic enzymes during the ontogenetic development of Clarias magur. After partial characterization, the messenger RNA (mRNA) expression analysis of lipoprotein lipase (LPL), pancreatic triacylglycerol lipase (PL), and bile salt-activated lipase (BAL) genes along with the specific lipase activity were performed in larvae from Day 1 after hatching till 34-day posthatch (dph). Heterogeneous patterns of mRNA expression were shown by the important lipolytic enzymes and were detected before first exogenous feeding during the yolk-sac stage. LPL started increasing from 13 dph and peaked at 16 dph followed by a declining trend till 34 dph. However, the PL observed to be peaking at 9, 22, and 30 dph. Similarly, BAL showed an increasing trend from 11 to 22 dph with a significantly high level of mRNA expression at 16 dph. Later, the specific lipase activity was evaluated which appears at Day 1 after hatching with a progressive increase from 7 to 16 dph and a further declining trend afterwards with a peak at 22 dph. The results indicated the development of exocrine pancreas at 16 dph. Furthermore, the transcript levels and the activity of lipases were regulated with the age. Hence, the present study can be helpful in devising different strategies containing optimum lipid levels at a suitable stage of development for improving the survival during larval rearing. Furthermore, the study could be a baseline for elucidating the optimized dietary lipid levels of this catfish during its larval rearing.

Preferences of Giant Gouramy (Osphronemus gouramy, Lac, 1801.), Walking Catfish (Clarias sp.) and Red Nile (Oreochromis sp.) on Natural Feed in Fish Culture

The aim of this study was to determine the preference for plankton as natural feed by giant gourami, walking catfish, and red nile on intensive aquaculture system. The study was designed using Completely Randomized Design (RAL), with two replications. Each fish was kept in six concrete tanks with dimension 2x2x1 m³ and 60 cm water level. Water source were from wells. Commercial pellet feed was given in three times daily ad libitum. Water samples were filtered and two individual fish were collected for plankton samples from pond water and alimentary canal, respectively, every two week, simultaneously with water quality measurements. Plankton samples were preserved using 5% formaldehyde and was observed under a compound light microscope with 100x magnification. The amount of plankton in the alimentary canal was converted to volume. Data were analyzed descriptively. The result showed that the volume contents proportion of plankton in the alimentary canal was less than 1%. The volume of plankton proportion in the alimentary canal of red nile were found the most than other fish. Each fish had the same preference of plankton of Lepocinclis and Scenedesmus, but different from other species of plankton. The plankton that utilized by giant gouramy were Crucigenia, Diadesmis and Navicula, whereas walking catfish was Pediastrum, and red nile was Microcystis. The plankton that preferred by giant gouramy were Crucigenia, Oscillatoria, Splirullina, and Synedra, walking catfish was Navicula, while red nile were Chrysamoeba and Tintinnidium.

Genome sequence of walking catfish (Clarias batrachus) provides insights into terrestrial adaptation

BackgroundWalking catfish (Clarias batrachus) is a freshwater fish capable of air-breathing and locomotion on land. It usually inhabits various low-oxygen habitats, burrows inside the mudflat, and sometimes “walks” to search for suitable environments during summer. It has evolved accessory air-breathing organs for respiring air and corresponding mechanisms to survive in such challenging environments. Thereby, it serves as a great model for understanding adaptations to terrestrial life.ResultsComparative genomics with channel catfish (Ictalurus punctatus) revealed specific adaptations of C. batrachus in DNA repair, enzyme activator activity, and small GTPase regulator activity. Comparative analysis with 11 non-air-breathing fish species suggested adaptive evolution in gene expression and nitrogenous waste metabolic processes. Further, myoglobin, olfactory receptor related to class A G protein-coupled receptor 1, and sulfotransferase 6b1 genes were found to be expanded in the air-breathing walking catfish genome, with 15, 15, and 12 copies, respectively, compared to non-air-breathing fishes that possess only 1–2 copies of these genes. Additionally, we sequenced and compared the transcriptomes of the gill and the air-breathing organ to characterize the mechanism of aerial respiration involved in elastic fiber formation, oxygen binding and transport, angiogenesis, ion homeostasis and acid-base balance. The hemoglobin genes were expressed dramatically higher in the air-breathing organ than in the gill of walking catfish.ConclusionsThis study provides an important genomic resource for understanding the adaptive mechanisms of walking catfish to terrestrial environments. It is possible that the coupling of enhanced abilities for oxygen storage and oxygen transport through genomic expansion of myoglobin genes and transcriptomic up-regulation of hemoglobin and angiogenesis-related genes are important components of the molecular basis for adaptation of this aquatic species to terrestrial life.

Susceptibility of important warm water fish species to tilapia lake virus (TiLV) infection

Tilapia lake virus (TiLV) is a novel orthomyxo-like virus that causes high mortality in tilapia and its hybrid species. Currently, no clinical infection of TiLV in other fish has been reported. In this study, a laboratory controlled TiLV infection was investigated in 10 warm water fish species consisting of giant gourami (Osphronemus goramy), snakeskin gourami (Trichogaster pectoralis), iridescent shark (Pangasianodon hypophtthalmus), walking catfish (Clarias macrocephalus), striped snake-head fish (Channa striata), climbing perch (Anabas testudineus), common carp (Cyprinus carpio), silver barb (Barbodes gonionotus), Asian sea bass (Lates calcarifer), and red hybrid tilapia (Oreochromis spp.). Our results revealed that only red hybrid tilapia and giant gourami developed clinical signs of infection including skin erosion, pale skin, exophthalmos and skin haemorrhage with a cumulative mortality rate of 60–100%. Amplification of TiLV using RT-qPCR confirmed the presence of the virus in the livers of challenged fish at 7 and 21 days post infection (dpi) with threshold cycle (Ct) values of 19.57 to 31.18, and 27.78 to ND (not detected) for red hybrid tilapia and giant gourami, respectively. Histopathological lesions were observed including hepatocellular necrosis and syncytial formation in the liver and lymphoid depletion in the anterior kidney of giant gourami and red hybrid tilapia. Moreover, the presence of TiLV in the brain and liver of giant gourami was further confirmed using in situ hybridization. A cohabitation challenge study indicated that the virus could be transmitted from infected red hybrid tilapia to naïve giant gourami with low mortality compared to an intraperitoneal injection. As polyculture systems are common practice in large parts of the aquaculture sector and multiple fish species share natural water resources, it is likely that direct and indirect contacts of infected fish could spread the disease in a farm with polyculture of multiple species. Therefore, the awareness of the spread of TiLV should be given. As such, biosecurity measures should be implemented if rearing tilapia with other fish species. Nevertheless, our study highlighted that most warm water fish species except giant gourami are resilient to TiLV infection.

Spawning and mortality of eggs and larvae produced by different brood sizes of Walking Catfish (Clarias batrachus L.)

An experiment was carried out on the spawning and mortality of eggs and larvae of Magur, Clarias batrachus collected from brood-stock pond during the study period.The lowest spawn production (3774 eggs) was recorded in the fish having 23 cm total length and 115 g total body weight and the highest spawn production (10102 eggs) was recorded in the fish having 26.4 cm total length and 230 g total body weight. The spawn production was found to increase with the increase of total length,standard length and total body weight following the equations, Y= –13921+833.7X, r= 0.685, Y= 13965+909.8X, r= 0.667 and Y= 1326+33.02X, r= 0.810, respectively. The relationships between spawn production with total length, standard length and total body weight of the fish were found to be linear and significant (p&lt;0.01). The lowest mortality rate (30.41%) was recorded in the fish having 26.4 cm total length and 224 g total body weight and the highest mortality rate (42.76%) was recorded in the fish having 23 cm total length and 125 g total body weight. The mortality rate of eggs and larvae was found to decrease with the increase of total length, standard length and total body weight of female brood following the equations, Y= 108.6–2.878X, r= –0.865, Y= 110.4–3.214X, r= –0.862 and Y= 54.99–0.108X, r= –0.970, respectively.The relationships between mortality rate of eggs and larvae with total length, standard length and total body weight of the fish were found to be linear and significant (p&lt;0.01).

Larval skipper frogs recognise kairomones of certain predators innately

Recognising potential predators is critical for the survival and reproduction of prey animals. However, prey animals may possess an innate ability to recognise the signature odours (kairomones) of only certain native, sympatric predators, while requiring learning to recognise others. Our observations have shown that larval skipper frogs (Euphlyctis cyanophlyctis) fail to recognise kairomones of dragonfly nymph, a common predator of amphibian tadpoles with a cosmopolitan distribution. Hence, we wanted to determine if larval skipper frogs totally lack an innate mechanism to recognise kairomones of all aquatic predators, or have an innate ability to recognise kairomones of only certain predators. In a series of experiments, we tested the antipredator response of larval skipper frogs to kairomones of dragonfly nymph (Bradinopyga geminata); walking catfish (Clarias batrachus); Mozambique tilapia (Oreochromis mossambicus); two species of predatory tadpoles, Indian bullfrog (Hoplobatrachus tigerinus) and Jerdon’s bullfrog (Hoplobatrachus crassus); and the checkered keel back snake (Xenochrophis piscator). The results clearly indicate that larval skipper frogs have the innate ability to recognise kairomones of the walking catfish, both species of larval bullfrog and checkered keel back snake. However, they lack the innate ability to recognise kairomones of dragonfly nymph and Mozambique tilapia. Prey choice of the Mozambique tilapia and gape-limitation of dragonfly nymphs could be responsible for the lack of innate responses of larval skipper frogs to them. The study provides empirical evidence for the notion that prey can innately recognise certain predators.

Expression and activity of trypsin and pepsin during larval development of Indian walking catfish (Clarias magur)

The gene expression of the trypsinogen and pepsinogen and activity of trypsin and pepsin in Indian walking catfish (Clarias magur) were investigated during the larval period to study the development of the digestive system. To this end, cDNA encoding the partial trypsinogen and pepsinogen were cloned and sequenced. Subsequently, the mRNA expression of genes was evaluated by quantitative polymerase chain reaction (qRT-PCR) along with the estimation of the activity of trypsin and pepsin. The mRNA expression pattern of trypsin appeared on 3rd-day post-hatching (dph) with a peak at 9 dph and 22 dph, while mRNAs of pepsin although detected at 4 dph but exhibited the significantly (P < 0.05) higher expression at 19 and 22 dph. The specific activity of trypsin increased from 11 dph onwards up to 16 dph. Similarly, the specific activity of pepsin enzyme showed a sudden increase from 13 to 19 dph. Based on these results, we suggest that the weaning time for C. magur larvae could be after 16 dph, as the activities were significantly increased after this stage which marks the functional development of the exocrine pancreas and stomach.

Immune defense of emodin enriched diet in Clarias batrachus against Aeromonas hydrophila

This study investigates the effect of emodin enriched diet on growth, hematology, and immune response in walking catfish, Clarias batrachus against Aeromonas hydrophila. The basal (control) diet supplemented with emodin at 0.0, 0.1, 0.2, or 0.4 g kg−1 was fed to the experimental groups for a period of four weeks. Feeding infected fish with 0.2 g kg−1 and 0.4 g kg−1 emodin enriched diets resulted in an overall weight gain, enhanced PER and FCR when compared to other diets. The survival rates were 98.3% and 96.7% in 0.1 g kg−1 and 0.4 g kg−1 emodin diet fed groups. Feeding with 0.2 g kg−1 diet the RBC level significantly elevated on week 1 and with 0.4 g kg−1 diet on weeks 2 and 4. The WBC, the percentage of globulin and neutrophils increased significantly with 0.2 g kg−1 diet only on week 4; however with 0.4 g kg−1 diet the increase was observed from week 1–4. The phagocytic activity increased significantly on being fed with 0.4 g kg−1 diet on week 2 while with 0.2 g kg−1 and 0.4 g kg−1 diets the increase manifested only on week 4; the respiratory burst activity also significantly increased on week 4 whereas increased the complement activity on weeks 2 and 4. The superoxide dismutase (SOD) activity was high on being fed with 0.4 g kg−1 diet on week 1; with 0.2 g kg−1 or 0.4 g kg−1 diets the increase was observed on weeks 2 and 4. The serum IgM level significantly increased when fed with 0.4 g kg−1 diet whereas the lysozyme activity was enhanced with 0.2 g kg−1 and 0.4 g kg−1 emodin diets on weeks 2 and 4. The percentage cumulative mortality was 10% with 0.1 g kg−1 or 0.2 g kg−1 diets while with 0.2 g kg−1 diet it was 15%. The results demonstrate that as a feed additive emodin acts as an immunostimulant enhancing the specific and nonspecific immune defense affording increased disease protection, enhances better growth and boosts hematology parameters in C. batrachus against A. hydrophila infection.

Integrated cage-cum-pond culture system with walking catfish (Clarias batrachus) in cages and tilapia (Oreochromis niloticus) in open ponds

An experiment was conducted for a period of 97 days at the Fisheries Field Laboratory Complex, Bangladesh Agricultural University, Mymensingh to determine the potential of the cage-cum-pond culture of walking catfish, as well as to assess the economic and environmental benefits of this system. The experiment had two treatments in triplicate. One treatment comprised walking catfish in cage and tilapia in open pond, and the other treatment comprised both walking catfish and tilapia stocked together in open ponds. Ponds of both treatments were stocked with walking catfish and tilapia at a stocking density of 10,000 and 20,000 ha-1, respectively. Fishes in both treatments were fed with commercial pelleted feed (26% crude protein) twice daily at the rate of 10% body weight of walking catfish. All ponds were fertilized with urea and TSP at a rate of 50 kgha-1 bi-weekly. Survival of catfish was very low in both treatments ranging from 8.33 to 21.33%. Specific growth rate of catfish was significantly higher (P&lt;0.021) in treatment-2 than in treatment-1 with a value of 2.42 and 1.69 g fish-1d-1, respectively. The net yield for catfish of treatment-1 and 2 were 49.67 and 43.45 kgha-1, respectively and there was no significant difference between the treatments. The survival rate of tilapia was 65.17 and 71.17% with daily weight gain of 2.31 and 2.22g fish-1 in treatment-1 and 2, respectively. Net yield were 817.00 and 790.63 kg ha-1, respectively and there were no significant difference in net yield of tilapia between treatments. Net profit obtained from integrated-cage-cum pond culture (Tk. 24,518 ha-197d-1) was higher than that of open pond (Tk 22,685 ha-197d-1).Res. Agric. Livest. Fish.4(3): 221-227, December 2017

Molecular Identification of Multiple Antibiotic Resistant Fish Pathogenic Enterococcus faecalis and their Control by Medicinal Herbs

The opportunistic fish pathogen, Enterococcus faecalis has been reported to cause mass mortality in several fish species in different countries. The objectives of this study were to (i) identify E. faecalis from the diseased fishes through molecular techniques; (ii) assess the antibiotic susceptibility profile of E. faecalis isolates; and (iii) control disease in tilapia fish by treatment with medicinal plant extracts. A total of 48 isolates were phenotypically identified as Enterococcus species from tilapia, stinging catfish and walking catfish cultivated in several fish farms in Gazipur. Ten randomly selected isolates were identified as E.faecalis by 16S rRNA gene sequencing. Artificial infection revealed that most of the isolates caused moderate to high mortality in fishes with characteristic disease symptoms. These isolates exhibited resistance to multiple antibiotics in vitro. Bioassay revealed that organic extracts of Tamarindus indica and Emblica officinalis leaves, Allium sativum bulb, and Syzygium aromaticum bud inhibited the growth of E. faecalis. Methanol extracts of A. sativum and methanol and acetone extracts of S. aromaticum significantly reduced the mortality of fish artificially infected with E. faecalis as both preventive and therapeutic agents. This is the first report on molecular identification, and herbal control of fish pathogenic E. faecalis in Bangladesh.

Conspecific vitellogenin induces the expression of vg gene in the Indian male walking catfish, Clarias batrachus (Linn.)

To understand the regulatory mechanism of Vg induced vitellogenin synthesis the vg gene expression in Indian male walking catfish, Clarias batrachus was investigated. Semipurified conspecific Vg containing Vg1 and Vg2 in a ratio of 2.7:1.0 was administered into male catfish and vg cDNA (1.1kb) was amplified from total RNA in liver by reverse transcriptase polymerase chain reaction (RT-PCR) using primers designed from published sequence of Clarias macrocephalus. The nucleotide and deduced amino acid sequence of the cDNA shared maximum similarities (98–100%) with the corresponding sequences of known E2-induced Vg of C. batrachus and C. macrocephalus in the database. A 0.178kb cDNA fragment nested within the 1.1kb DNA was then amplified by real time PCR to evaluate the role of Vg on relative expression of vg gene. The result revealed a significant upregulation (1.79 fold) of vg mRNA at 6h reaching maximum level (9.78 fold) at 24h post Vg injection as compared to the saline control. Similarly, E2-treatment also showed maximum mRNA expression (7.73 fold) at 24h post injection. The findings suggest that like E2, Vg itself can induce vg gene expression resulting in a significant increase in plasma Vg levels (9.11±0.73mg/ml for Vg1 and 3.02±0.28mg/ml for Vg 2) in male catfish where E2 is lacking. The work provides further opportunity to study the regulatory mechanism of vg gene expression by Vg.