Silver Catfish Research Articles

Extraction of Oil From Solid Fat of Silver Catfish (Pangasianodon hypophthalmus) Waste by Centrifugation

Oil extracted from fish waste could be a source of valuable fatty acids such as saturated (SFAs), monounsaturated (MUFAs), and polyunsaturated fatty acids (PUFAs). In this study, the solid fat from silver catfish (Pangasianodon hypophthalmus) waste was used to extract oil by centrifugation using different extraction solvent (distilled water, 70% ethanol, 70% acetone and 70% cyclohexane), rotation time (15, 25, 35 & 45 min), rotational speed (2000, 4000, 6000, 8000 & 10000 r.p.m) and rotational temperature (5, 10, 15, 20 & 25 °C). The compositions of fatty acids in the extracted oil were determined by gas chromatography-mass spectrometry (GC-MS) analysis. The highest oil yield of 156.7 ± 16.7 mg/g was achieved by centrifugation at 10000 r.p.m, 25 °C for 15 min using 70% acetone. The extracted oil contains 0.0223 mg/g palmitic acid, 0.0216 mg/g steric acid, and 0.0262 mg/g oleic acid. However, the essential PUFAs such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) could not be detected by GC-MS analysis. This study found that the fish oil extracted from the solid fat of the silver catfish waste can be used as a potential source of palmitic acid, stearic acid, and oleic acid.

Dietary Supplementation with R-(+)-Limonene Improves Growth, Metabolism, Stress, and Antioxidant Responses of Silver Catfish Uninfected and Infected with Aeromonas hydrophila.

R-(+)-limonene is a monoterpene from plants of the genus Citrus with diverse biological properties. This research evaluated the effects of dietary supplementation with R-(+)-limonene on growth, metabolic parameters in plasma and liver, and the antioxidant and stress responses in silver catfish, Rhamdia quelen, challenged or not with Aeromonas hydrophila. Fish were fed for 67 days with different doses of R-(+)-limonene in the diet (control 0.0, L0.5, L1.0, and L2.0 mL/kg of diet). On the 60th day, a challenge with A. hydrophila was performed. R-(+)-limonene in the diet potentiated the productive performance of the fish. The metabolic and antioxidant responses indicate that R-(+)-limonene did not harm the health of the animals and made them more resistant to the bacterial challenge. Histological findings showed the hepatoprotective effect of dietary R-(+)-limonene against A. hydrophila. Igf1 mRNA levels were upregulated in the liver of fish fed with an L2.0 diet but downregulated with bacterial challenge. The expression levels of crh mRNA were higher in the brains of fish fed with the L2.0 diet. However, the L2.0 diet downregulated crh and hspa12a mRNA expression in the brains of infected fish. In conclusion, the results indicated that R-(+)-limonene can be considered a good dietary supplement for silver catfish.

Diets with soybean oil and l-carnitine alter lipid metabolism and improve the growth and reproduction of Rhamdia quelen females

This study aimed to evaluate the reproduction, growth, biochemical parameters of blood, hepatic and gonadal redox parameters, hepatic and gonadal histology, and lipid metabolism of silver catfish females (Rhamdia quelen) fed diets containing l-carnitine and different lipid sources. Females were fed for 223 days with eight (08) isoproteic (282 g of digestible protein kg of ration−1) and isoenergetic (13.34 MJ of digestible energy kg of ration−1) diets, containing 0.00, 0.15, 0.45, and 0.75 g l-carnitine kg−1 of feed, and soybean or marine fish oils. Feeding the females diets containing l-carnitine and the different oils resulted in an interactive effect (p < 0.05) that improved the growth and reproduction of the fish. Females fed soybean oil and 0.45 g l-carnitine kg−1 had the highest growth rates, the largest ovaries, and produced the most fertile oocytes, which resulted in the highest hatching rates. These females also showed higher levels of total cholesterol and high-density lipoprotein (HDL) cholesterol, and alterations in the levels of alanine aminotransferase in the blood, in addition to greater activity of hepatic superoxide dismutase and a greater amount of saturated fatty acids in the liver. The ovaries of these females also had the highest amount of docosahexaenoic fatty acid (DHA), highest amount of polyunsaturated fatty acids and fatty acids from the n-3 and n-6 series, and the lowest crude protein content. The interaction between l-carnitine and the lipid source of the diets promoted hepatic protection and regulated lipid metabolism and the fatty acid profile in the liver and ovaries of silver catfish females. The benefits of these interactions improved the growth and reproduction of females fed diets containing soybean oil and 0.45 g l-carnitine kg−1.

A Study on the Bagrid Catfish (Chrysichthys nigrodigitatus) from Itapaji Water Reservoir, Ekiti State, Nigeria

The Silver catfish, Chrysichthys nigrodigitatus is a highly valued food fish included among the dominant commercial catches exploited in major rivers of Africa. To obtain biological data for management and to contribute to their ecological knowledge some aspects of biology were studied on 120 samples of C. nigrodigitatus collected from Itapaji dam reservoir in Ekiti State, Nigeria between the months of June 2021 to September 2021. The specimens were transported to Zoology and Environmental Biology Post-graduate laboratory of Ekiti State University, where they were examined, relevant data recorded and analysed. The data was analysed using MS excel 2010, PAST and IBM SPSS Statistics 22. Results obtained from the male and female in the same population showed significant differences (P &lt; 0.05) in 19 of these morphometric features. The males had a mean standard length of 21.36cm (21.20 to 34.8 cm) while the mean standard length in females was 18.52cm (20.50 to 29.40cm). The mean condition (K) values were 0.90, 0.98 and 0.94 for males, females and sexes combined respectively indicating that they are indeed in good condition. The gonado-somatic index (GSI) peaks in June for both sexes. Hepatosomatic index (HSI) was higher in females than in males. The sex ratio of 1M: 1.5F was in favour of females. The ingested food items of C. nigrodigitatus were evaluated by occurrence and numerical abundance methods in which algae and diatoms are dominant. The mean weight of the internal organs for male was (10.15g) and for female it was (11.65g). The histopathology studies show they are in good condition. Absolute (individual) fecundity of the fish ranged from 2500 eggs (TL of 19.5cm and body weight of 90g) to 6500 eggs (TL of 27.3cm and body weight of 246g) Mean fecundity ranged between 1857 and 4652eggs. Hence this study provides useful information for culturing and improvement of this fish species.

Experimentally exposed toxic effects of long-term exposure to environmentally relevant concentrations of CIP in males and females of the silver catfish Rhamdia quelen

Ciprofloxacin (CIP) is an antibiotic commonly used in human and veterinary medicine. It is present in the aquatic environment, but we still know very little about its effect on non-targeted organisms. This study aimed to evaluate the effects of long-term exposure to environmental CIP concentrations (1, 10, and 100 μg.L−1) in males and females of Rhamdia quelen. After 28 days of exposure, we collected the blood for the analysis of hematological and genotoxic biomarkers. Additionally, we measured 17 β-estradiol and 11 keto-testosterone levels. After the euthanasia, we collected the brain and the hypothalamus to analyze acetylcholinesterase (AChE) activity and neurotransmitters, respectively. The liver and gonads were assessed for biochemical, genotoxic, and histopathological biomarkers. At 100 μg.L−1 CIP, we observed genotoxicity in the blood, nuclear morphological changes, apoptosis, leukopenia, and a reduction of AChE in the brain. In the liver was observed oxidative stress and apoptosis. At 10 μg.L−1 CIP, leukopenia, morphological changes, and apoptosis were presented in the blood and a reduction of AChE in the brain. Apoptosis, leukocyte infiltration, steatosis, and necrosis occurred in the liver. Even at the lowest concentration (1 μg.L−1), adverse effects such as erythrocyte and liver genotoxicity, hepatocyte apoptosis, oxidative stress, and a decrease in somatic indexes were observed. The results showed the importance of monitoring CIP concentrations in the aquatic environment that cause sublethal effects on fish.

Fish sperm cryopreservation using biodegradable containers: New low-cost and environment-friendly methodology.

The containers used in cell cryopreservation are essential to maintain cell integrity and viability after thawing. This paper reveals the methodology of using biodegradable containers for fish sperm cryopreservation. Cryopreserved sperm in biodegradable containers showed high fertility capability. Biodegradable capsules could be alternative containers to plastic straws for sperm cryopreservation. Containers used to cryopreserve sperm are made with non-biodegradable plastic compounds, having a high monetary and environmental cost. Therefore, the development of biodegradable alternative containers for cell cryopreservation is necessary. Thus, this study aimed to evaluate the efficiency of hard-gelatin and hard-hydroxypropyl methylcellulose (HPMC) capsules as low-cost and biodegradable alternative containers for sperm cryopreservation. Sperm from 12South American silver catfish Rhamdia quelen were individually cryopreserved in plastic straws 0.25 mL (as control), hard-gelatin, and hard-HPMC capsules. The quality of post-thaw sperm cryopreserved in the different containers was checked by measuring spermatozoa membrane integrity, kinetic parameters, mitochondrial activity, fertilization, hatching, and normal larvae rates. The samples cryopreserved in straws showed a higher percentage of membrane integrity (68%) than those frozen in hard-gelatin (40%) and hard-HPMC capsules (40%). However, we did not observe differences between the samples stored in straws and hard capsules for the rest of the tested sperm parameters. Thus, based on the high sperm fertility capability, both capsules were efficient as cryopreservation containers for maintaining sperm functionality.

L-threonine requirement of silver catfish (Rhamdia quelen): growth performance, body composition, plasma and liver metabolites

ABSTRACT A feeding trial was performed to evaluate the effects of dietary L-threonine supplementation on growth and body composition of fingerlings Rhamdia quelen (initial weight: 4.47 ± 0.39 g). Five diets (370 g/kg crude protein and 14.23 MJ / kg of digestible energy) containing levels of L-threonine (16.0, 22.0, 28.0, 34.0, 40.0 g threonine/kg protein) were fed to quadruplicate groups of fishes for 10 weeks. The analysed variables were influenced by the threonine levels. Fish fed with diet containing 16.0 g threonine/kg of CP showed lower growth and body deposition of nutrients. In addition to unsatisfactory performance, the fish subjected to lower levels of threonine presented higher hepatosomatic index scores and changes in the concentrations of some plasmatic metabolites. To determine the ideal level of threonine in the diet, the weight gain, specific growth rate and feed conversion ratio were subjected to broken-line and quadratic regression. The results showed indicate that a diet containing inadequate levels of threonine causes insufficient growth. Dietary threonine requirement of R. quelen was estimated between 24.5 and 32.5 g threonine/ kg of crude dietary protein, corresponding to 9.1 and 12.0 g/ kg threonine in the diet for the initial growth of silver catfish.

Impact of dietary supplementation with Cinnamomum cassia essential oil on silver catfish (Rhamdia quelen): Toxicological effects and muscle antioxidant and fatty acid profiles

ABSTRACT The aim of this study was to determine the biological effects of dietary supplementation with 0.05% and 0.1% cinnamon essential oil extracted from Cinnamomum cassia on silver catfish (Rhamdia quelen). The final body weight, weight gain, and specific growth rate were significantly higher in fish supplemented with 0.05% cinnamon essential oil than in the control(untreated) group. Muscle reactive oxygen species and lipid peroxidation levels were significantly lower in fish supplemented with 0.05% cinnamon essential oil but higher at the 0.1% concentration. Muscle antioxidant capacity against peroxyl radicals (ACAP) and superoxide dismutase activity were significantly higher in fish supplemented with 0.05% cinnamon essential oil, while ACAP levels were lower in fish supplemented with 0.1%. The total saturated fatty acid content was significantly higher in the muscle of supplemented fish than in controls, while the total monounsaturated fatty acid content was significantly higher only in fish fed 0.1% cinnamon essential oil. Finally, the total content of polyunsaturated fatty acids was significantly lower in fish fed 0.1% essential oil. Thus, data demonstrated that 0.05% C. cassia essential oil improves fish health by improving performance and muscle oxidant/antioxidant status. Higher doses of cinnamon essential oil produced oxidative stress in muscle, suggesting toxicity at the 0.1% level. Although this cinnamon essential oil diet exerted positive health effects, this diet impaired the muscle fatty acid profile, suggesting adverse impacts on human health.

Effect of Extraction Time on the Extractability and Physicochemical Properties of Pepsin—Soluble Collagen (PCS) from the Skin of Silver Catfish (Pangasius sp.)

The current study aimed to determine the effects of extraction time on the extractability and physicochemical properties of collagen from the skin of silver catfish (Pangasius sp.). Pepsin soluble collagen (PSC) was extracted for 24 and 48 h and analysed in terms of chemical composition, solubility, functional group, microstructure, and rheological properties. The yields of PSC at 24 h and 48 h extraction time were 23.64% and 26.43%, respectively. The chemical composition exhibited significant differences, with PSC extracted at 24 h showing better moisture, protein, fat, and ash content. Both collagen extractions indicated the highest solubility at pH 5. In addition, both collagen extractions exhibited Amide A, I, II, and III as fingerprint regions for collagen structure. The morphology of the extracted collagen appeared porous with a fibril structure. The dynamic viscoelastic measurements of complex viscosity (η*) and loss tangent (tan δ) decreased as temperature increased, and the viscosity increased exponentially as the frequency increased, whereas the loss tangent decreased. In conclusion, PSC extracted at 24 h showed similar extractability to that extracted at 48 h but with a better chemical composition and shorter extraction time. Therefore, 24 h is the best extraction time for PSC from silver catfish skin.

Some Aspects of the Biometry of the Silver Catfish, Chrysichthys nigrodigitatus from Freshwater and Brackish water Environment in Nigeria.

Some Aspects of the Biometry of the Silver Catfish, Chrysichthys nigrodigitatus from Freshwater and Brackish water Environment in Nigeria.

Influence of the rearing system on phagocytic indexes and weight gain of the silver catfish (Rhamdia quelen, Quoy & Gaimard, 1824)

Influence of the rearing system on phagocytic indexes and weight gain of the silver catfish (Rhamdia quelen, Quoy & Gaimard, 1824)

Stress response of Rhamdia quelen to the interaction stocking density – Feeding regimen

This study aimed to verify the effect of different feeding and stocking conditions during 14 days on the gene expression of several hormones and enzymes related to the stress cascade and metabolic parameters in silver catfish Rhamdia quelen under the following experimental conditions: 1) fed at low stocking density (2.5 kg m−3, LSD-F); 2) fed at high stocking density (32 kg m−3, HSD-F); 3) food-deprived at LSD (LSD-FD); and 4) food-deprived at HSD (HSD-FD). Fish from LSD-F and HSD-F groups were fed daily (1 % of their body mass), while fish from food-deprived groups (LSD-FD and HSD-FD) were not fed during the experimental time. Plasma metabolic parameters (glucose, lactate, triglycerides, and proteins) and hepatosomatic index (HSI) were evaluated. In addition, mRNA expression of genes related to the stress axis (crh, pomca, pomcb, nr3c2, star, hsd11b2 and hsd20b), heat shock protein family (hsp90 and hspa12a), sodium-dependent noradrenaline transporter (slc6a2), and growth axis (gh and igf1) were also assessed. Specific growth rate and HSI decreased in food-deprived fish regardless of stocking density. The HSD-FD group showed weight loss compared to the HSD-F, LSD-F, and LSD-FD groups. Plasma glucose and triglycerides were reduced in food-deprived groups, while lactate and protein levels did not change. The expression of key players of the stress response (crh, pomca, pomcb, hsd11b2, nr3c2, and hsp90b) and growth (gh and igf1) pathways were differently regulated depending on the experimental condition, whereas no statistical difference between treatments was found for hsd20b, scl6a2, hspa12a, and star mRNAs expression. This study suggests that LSD acts as a stressor affecting negatively the physiological status of fed fish, as demonstrated by the reduction in growth rates, altered metabolic orchestration, and a higher crh mRNA expression. In addition, food deprivation also increased mRNA expression of other assessed genes (nr3c2, hsp90b, pomca, and pomcb) in fish from the HSD group, indicating higher responsiveness to stress in this stocking density when combined with food deprivation.

Occurrence, source delineation, and health hazard of polycyclic aromatic hydrocarbons in tissues of Sarotherodon melanotheron and Chrysichthys nigrodigitatus from Okulu River, Nigeria.

Polycyclic aromatic hydrocarbons (PAHs) are mistakenly consumed by people through their diet, including food and water. The occurrence, source, and health hazards of 16 PAHs in 36 tilapia (Sarotherodon melanotheron) and silver catfish (Chrysichthys nigrodigitatus) samples from Okulu River, Nigeria were investigated in this study. The total PAH concentration ranged from 11.70-24.20 to 13.40-19.60µg/kg, being statistically different between the two species. The values were higher than the European Commission limits of 12µg/kg and within the World Health Organization limit of 20µg/kg. The 16 PAHs were detected in both fish species. The diagnostic ratio revealed that petroleum, fossil fuel, and incomplete combustion of biomass wastes were the sources of PAHs in the fishes. Pearson's correlation showed that the PAHs can come from diverse sources. The non-carcinogenic risk quotients (HQs) and hazard index (HI) in both fish species were 1, an indication of no adverse health effects. Among the 9 PAHs that were used to calculate the HI, BaP and BgP accounted for 31% and 62%, respectively, for Chrysichthys nigrodigitatus, and 25% and 69%, respectively, for Sarotherodon melanotheron. The carcinogenic hazard of the 7 PAHs assessed was within the acceptable range of 10-6-10-4. But the sum of the carcinogenic hazard was on the order of 10-3 in both species of fish, an indication of carcinogenic health effects. 79% and 75% of the total carcinogenic risk for Chrysichthys nigrodigitatus and Sarotherodon melanotheron, respectively, are from DaA and InP. The consumption of PAHs by residents of the study area and other population groups through fish foods from the studied river underlines the importance of checking PAHs in aquatic foods for health concerns on a frequent basis.

Consumers' preference and willingness-to-pay for GAqP-compliant farmed fish produce: Evidence from Malaysia

The practice of GAqP among Malaysian aquaculture farmers is not widespread because farmers believe that this scheme is too complex and expensive, has no obvious premium prices for GAqP-compliant products, and less profitable compared to non-GAqP producers. The study's objective is to assess consumers' preference for farmed fish and their willingness-to-pay (WTP) for GAqP-compliant produce toward the introduction of premium prices for such products. This study is based on a survey conducted using the Contingent Valuation Method (CVM). Descriptive analyses using frequency and cross-tabulations were used to describe consumers' preference toward farmed fish. Binary logistic regressions were used to estimate the influence of consumer characteristics, product characteristics, and market environment factors on consumers' WTP for GAqP-compliant produce. Results showed that seabass was the most preferred brackish water farmed fish, while African Catfish the most preferred freshwater farmed fish; the least preferred fish was silver catfish. The findings also revealed consumers' spending on farmed and captured fish to be comparable, with consumers allocating an average of RM130.45 and RM140.03 for captured and farmed fish, respectively. The average WTP calculated using CVM and open-ended model were approximately 114% and 43% higher than non-compliant GAqP produce, indicating a strong preference for GAqP-compliant fish. The elderly, the educated, those with higher income, those with aquaculture knowledge, and those interested in sustainability issues were more likely to pay a premium price for GAqP-compliant product.

Trace metal concentration in common fishes from the Lagos lagoon, Southwestern Nigeria

Due to trace metals’ toxicity, accumulative tendency, and non-biodegradability, we assessed their levels in six fish species: Chrysichthys nigrodigitatus (Silver Catfish), Sarotherodon melanotheron (Blackchin Tilapia), Scomber scombrus (Atlantic Mackerel, locally known as Titus), Sardinella maderensis (Sardine), Dentex canariensis (Canary dentex), and Pseudotolithus typus (Croaker) commonly available in the Lagos lagoon. Samples of various sizes and maturity were selected, and their tissues (fillets, gills, and intestines) were examined for trace metal concentrations. Fe was the most concentrated metal in all the tissues (1.64–8.61 mg/kg), albeit below the WHO permissible limits (100 mg/kg). Others were Pb (0.05–8.2 mg/kg), Zn (0.48–4.88 mg/kg), Cu (0.08–2.51 mg/kg), and Cd (0.03–1.95 mg/kg), with only Zn and Cu entirely below WHO permissible limits of 100 and 30 mg/kg, respectively. Specifically, the toxic metals were more concentrated in the intestines (mean = 4.36 ± 1.02 mg/kg), reaching 8.61 mg/kg, followed by the gills (mean = 1.50 ± 0.77 mg/kg; max = 3.17 mg/kg), while the fillet was the least toxic metal-laden (mean = 0.55 ± 0.08 mg/kg; max = 2.01 mg/kg). Further, Fulton condition factor assessment (body weight–length relationship) identified Sarotherodon melanotheron as “good” (1.74) and Dentex canariensis as “moderately good” (1.33), while others were “poor” Overall, Scomber Scrombus, Psuedotolithus typus, and Dentex canariensis exhibited the least toxic metal accumulations. Therefore, having considered WHO’s permissible limits for the metals in edible fishes, these three species seem suitable for human consumption, provided other environmental and human conditions are favorable.

Flow cytometry evaluation of phagocytosis and respiratory burst in silver catfish (Rhamdia quelen) leukocytes exposed in vitro to atrazi

Flow cytometry evaluation of phagocytosis and respiratory burst in silver catfish (Rhamdia quelen) leukocytes exposed in vitro to atrazi

BIOACCUMULATION OF COMMONLY DETECTED METALS IN THE SILVER CATFISH (CHRYSICHTHYS NIGRODIGITATUS) COLLECTED FROM MAKOKO RIVER, LAGOS NIGERIA

This study investigated the bioaccumulation of selected essential and non essentialmetals in the silver catfish (Chrysichthys nigrodigitatus) collected from Makoko River,dead end of the Lagos Lagoon. Concentrations of Iron (Fe), Lead (Pb) and Calcium(Ca) were found to be higher in liver of Chrysichthys nigrodigitatus with mean valuesof 34.52± 6.52 mg kg-1, 1.02± 0.16 mg kg-1and 63.45± 8.62 mg kg-1respectivelycompared to concentrations detected in its gills with mean values of 32.64± 5.71 mgkg-1, 0.10± 0.01 mg kg-1 and 41.58± 6.56 mg kg-1 respectively. While concentrationsof Copper (Cu), Manganese (Mn) and Magnesium (Mg) were found to be higher in itsgills with mean values of 2.09±1.61 mg kg-1, 1.79±1.84 mg kg-1, and 12.84±11.90 mgkg-1respectively compared to concentrations detected in its liver with mean values of0.74±0.53 mg kg-1, 1.79±0.94 mg kg-1 and 8.36± 4.67 mg kg-1 respectively. Theconcentrations of the metals in the tissues were found to be higher than respectiveconcentrations detected in water or sediments of the fish habitat indicative ofbioaccumulation. Concentrations of light metals Ca and Mg were also observed to behigher than concentrations of heavy metals Fe, Pb, Cu and Mn in the tissues of thefish species. Bioaccumulation of metals in tissue of edible fish species can havedeleterious effects on nutritional values of the fish and also pose a public healththreat to final consumers. The need for continuous monitoring of levels of harmfulpollutants in water bodies and edible aquatic species supported.

Performance and carcass yield of silver catfish raised in monosex and mixed-sex systems

Abstract - An experiment lasting 180 days was carried out to evaluate the influence of sex on the performance and production of silver catfish (Rhamdia quelen) when reared in closed recirculation systems using only males, only females, or with both genders. A total of 300 fish (41.49 ± 6.82 g and 16.53 ± 0.95 cm) were used, comprising 150 females and 150 males distributed in an experimental structure consisting of three closed water recirculation systems coupled to a 20,000 L culture tank and a 20,000 L biofiltration tank connected by a 3,500 L h-1 water pump. The first system contained 100 females, the second, 100 males, and the third, 50 females and 50 males. High fish weight variations were observed regardless of sex. Female weight gains and specific growth rates were 41.51 % and 28.94 % higher compared to males, respectively, exhibiting greater growth than males raised monosexually or in mixed rearing systems, with no effect on chemical composition or trunk yield. The findings thus indicate that both male and female silver catfish exhibit wide weight variations and females that gain more biomass than males reared monosexually or in mixed-sex systems.

KELANGSUNGAN HIDUP DAN PERTUMBUHAN IKAN PATIN (Pangasius djambal) YANG DIPELIHARA PADA SISTEM BUDIKDAMBER DENGAN PADAT TEBAR BERBEDA

This study aimed to examine the effect of application of different stocking densities in budikdamber system on the survival rate and growth of silver catfish (Pangasius djambal). The non-factorial Complete Randomized Design (RAL) used in this study consisted of four treatments and three tests. The treatments studied were the application of a stocking density of 5 fishes/container (P1), 10 fishes/container (P2), 15 fishes/container (P3), and 20 fishes/container (P4). The silver catfish used in this study was 6-8 cm in size. The maintenance period of silver catfish in this study was in 40 days. The research parameters that measured in this study were survival rate, absolute weight growth, absolute length growth, specific growth rate and water quality. The results of analysis of variance (ANOVA) showed that different stocking densities on rearing media with the “Budikdamber” system had no significant effect for survival rate, absolute weight growth and specific growth rate of silver catfish (Pangasius djambal), but had a significant effect on absolute length of silver catfish (Pangasius djambal). The best stocking density to increase the absolute length growth of silver catfish is 15 fishes / container (P3) in number 7.36 cm.

Expression of Ion Transporters and Na+/K+-ATPase and H+-ATPase Activities in the Gills and Kidney of Silver Catfish (Rhamdia quelen) Exposed to Different pHs

Exposure to acidic and alkaline pHs results in an ionic imbalance. Cellular responses involved in osmoregulation in silver catfish exposed to different pHs (5.5, 7.5, and 9.0) for 24 h were evaluated. The gills and kidney were collected to measure Na+/K+-ATPase (NKA) and H+-ATPase (V-ATPase) activities and to evaluate the expression of ion transporter-related genes: NKA (atp1a1), H+-ATPases (atp6v0a1b, atp6v0a2a, atp6v0a2b), Na+/H+ antiporter (slc9a3), K+/Cl− symporters (slc12a4, slc12a6, slc12a7a, slc12a7b), Na+/K+/2Cl− symporter (slc12a2), and ammonium transporter Rh type b (rhbg). The gills presented greater responses to pH changes than the kidney. The pH alterations changed the atp1a1 gene expression and NKA activity, whereas the H+-ATPase activity increased in the gills in alkaline water, probably to maintain ionic balance. The slc9a3 and slc12a2 genes play more prominent roles in the ion uptake at acidic pH than H+-ATPase. The slc12a7a was the only isoform of this transporter affected by pH. The rhbg is apparently related to ammonia excretion through the gills and kidney (minor scale). Exposure to alkaline pH seems to be battled by impairment of NKA and H+-ATPase activities in the gills, whereas the expression of some ion transporters in silver catfish changes during both acidic and alkaline pHs.