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Motile aeromonad septicemia (MAS), caused by the Aeromonas species, has been a serious problem in fish health management, particularly in Nile tilapia (Oreochromis niloticus). This study characterized an Aeromonas species isolated from farmed tilapia fingerlings in Binangonan, Rizal, Philippines, and tested for its pathogenicity in tank trials. The isolate, designated as Aeromonas veronii DFR01 (Diseased Fish Rizal), was identified based on 16S rRNA phylogenetic analysis, 16S rRNA homology, and MALDI-TOF mass spectrometry. Its biochemical profile was generated from API and Biolog Gen III systems. A median lethal dose of A. veronii DFR01 was determined to be 107 CFU/mL in tank trials and was utilized as a whole-cell inactivated antigen for oral vaccine development. The immunized tilapia fingerlings produced elevated levels of immunoglobulin M (IgM) in the blood as determined by an enzyme-linked immunosorbent assay (ELISA). There was a significant increase in IgM levels 14 days post-vaccination. A quantitative polymerase chain reaction (qPCR) showed increasing levels of IgM gene expression after vaccination until 38 days of culture. Vaccinated fish showed 25–35% cumulative mortality after the challenge, while non-vaccinated-challenged fish showed 75% mortality. The findings of this research suggest that the fish oral vaccine may prove beneficial for farmed tilapia populations. The vaccine elicited improved immune responses in the fish and resulted in higher survival rates.

Ammonia is a respiratory gas that is produced during the process of protein deamination. In the unionised form (NH3), it readily crosses biological membranes and is highly toxic to fish. In the present study we examined the effects of unionized ammonia (UIA), on the resting oxygen consumption (MO2), ventilation frequency (fV), heart rate (HR) and heart rate variability (HRV) in Nile tilapia (Oreochromis niloticus). Fish were either exposed to progressively increasing UIA concentrations, up to 97 µM over a 5 h period, or to a constant UIA level of 7 µM over a 24 h period. For both treatment groups resting MO2, HR and fV were recorded as physiological variables. Relative to the control group, the fish groups exposed to the incremental UIA levels did not exhibit significant changes in their MO2, HR and fV at UIA concentrations of 4, 10, 35, or 61 µM compared to control fish. Exposure to 97 µM UIA, however, elicited abrupt and significant downregulations (p < 0.05) in all three responses, as MO2, HR and fv decreased by 25, 54 and 76 % respectively, compared to control measurements. Heart rate became increasingly irregular with increasing UIA concentrations, and heart rate variability was significantly increased at 61 and 97 µM UIA. Prolonged exposure elicited significant changes at exposure 7 µM UIA. Standard (SMR) and maximum metabolic rate (MMR) were significantly reduced, as was the corresponding fV and HR. It is evident from this study that Nile tilapia is tolerant to short term exposure to UIA up to 61 µM but experience a significant metabolic change under conditions of prolonged UIA exposures even at low concentrations.

High levels of dissolved carbon dioxide (CO2) occur nightly in earthen ponds characterized by high respiration rates. Exposure to high CO2 conditions (hypercapnia) leads to acidosis in fish, which can be compensated by an accumulation of HCO3− to recover intra- and extracellular pH levels, with a capacity that appears to be species-specific. For Nile tilapia, a freshwater tropical teleost traditionally produced in earthen ponds, little information is available on the tolerance to dissolved levels of CO2 and associated acid-base disturbances. Here, we investigated first the effects of acute and progressively increasing CO2, from normocapnic conditions to 60 mg CO2 L−1, on oxygen uptake rates (MO2). This was followed by exposure to three concentrations of CO2; 10, 30, and 60 mg L−1 (equivalent to pCO2 of 5.4, 16.2, and 32.4 mmHg) against a normocapnic control (pCO2 0.3 mmHg), to investigate acute (1 h) or prolonged (24 h) effects on standard (SMR) and maximum metabolic rates (MMR), haematology, and extra- and intracellular acid-base status in adult Nile tilapia (mean BM 435 ± 16 g ± SE). Acute exposure to hypercapnia led to concentration-dependent decreases in both SMR and MMR. Fish were able to fully or partially recover MMR and metabolic scope (MS) after 24 h, while depression of SMR persisted at all CO2 levels. Acute exposure to CO2 caused intra- and extracellular pH levels to decrease by up to 0.5 units in a concentration-dependent manner. Only the lowest hypercapnic treatment (pCO2 5.4 mmHg) was able to fully recover within 24 h. Changes in haematological variables appeared minor, being restricted to increasing haematocrit, haemoglobin concentration, and mean cell volume in the highest CO2 treatments after 24 h exposure. Although the Nile tilapia is generally considered a species able to

Tanzania is a country located in sub-Sahara Africa by the Indian Ocean. Tanzania's aquaculture sector is small but has the potential to grow. As the population grows, so does the demand for food. Nile tilapia is the most cultured fish in Tanzania due to its hardiness, fast growth and tolerance to many environmental conditions. Fish meal (FM) and soybean meal has traditionally been used as a protein source in fish feed. However, insects have been proposed as potential alternative protein sources to replace FM and soybean meal, which are expensive and negatively affects the environment and feed and food security. One of these insects is the black soldier fly (BSF) due to its high content of amino acids, lipids, vitamins and minerals. The objective of the current study is to examine and assess how a locally produced feed containing BSF meal will affect the growth performance of Nile tilapia. Physical feed quality and chemical composition were also evaluated. In addition, the environmental impact of using BSF larvae in tilapia feed was also evaluated by calculating the greenhouse gas (GHG) emissions from such a feed production system. The BSF diet was compared to a Control and commercially used diet at fish farms in Tanzania. Results show that growth performance could not be statistically evaluated due to variation in the different ponds used during the fish growth experiment. Nutritional composition and the chemical score showed low histidine, lysine, and methionine and a high phenylalanine content in the BSF meal compared to the FM. Physical feed quality showed that the BSF diet had the best water stability compared to other diets used in the experiment. However, the BSF diet had lower durability and hardness. GHG calculations showed that the BSF diet had the lowest emission of GHG.

The objective of the present study was to evaluate the effect of differentfeeding regimens on productive and economic performance, and on the proximal-chemicalcomposition of Nile tilapia. Four feeding regimens were designed considering the number ofdays fed per week, 7×0 (fed seven days a week), 6×1 (fed six days a week), 5×2 (fed fivedays a week) and 1×1 (alternating feeding, fed one day and not the next one). The periodof dietary restriction lasted 36 days and subsequently fish were re-feeding for 24 days sevendays a week. Growth was recorded every 12 days, estimating different productive parameters.An economic analysis taking into account the production costs was performed. Finally, themoisture, ash, lipid, protein and carbohydrate content of the Nile tilapia muscle was analyzed.At the end of the re-feeding period, a total wet weight compensation was observed for groups6×1 and 5×2, and total length for groups 6×1, 5×2 and 1×1. The economic analysisrecorded the highest increasing yields in group 5×2; while the group minimizing total variablecosts was 1×1. The reduction in costs per unit of production between groups 7×0 and 1×1was 15%. Chemical-proximal analysis revealed statistical differences for moisture content(7×0) and carbohydrate content (1×1). The groups 6×1 and 5×2 showed a total growthcompensation, without negatively affecting muscle quality and/or final economic performance.The compensatory growth observed in the Nile tilapia allows to design feeding strategies tomake its culture more efficient., El objetivo fue evaluar el efecto de diferentes regímenes alimenticios en eldesempeño productivo, económico y la composición química de la tilapia del Nilo. Seevaluaron cuatro regímenes alimenticios diseñados considerando el número de díasalimentados por semana, 7×0 (alimentados los siete días), 6×1 (alimentados solo seisdías), 5×2 (alimentados solo cinco días) y 1×1 (alimentación alternada, un día sí y undía no). El periodo de restricción alimenticia duró 36 días y posteriormente se realimentósiete días a la semana durante 24 días. Se registró el crecimiento cada 12 días, estimandodiferentes parámetros productivos. Se realizó un análisis económico en función de los costosde producción. Por último, se analizó el contenido de humedad, cenizas, lípidos, proteínasy carbohidratos del músculo. Se observó una compensación total del peso húmedo paralos grupos 6×1 y 5×2, y de longitud total para los grupos 6×1, 5×2 y 1×1. El análisiseconómico registró los mayores rendimientos crecientes en el grupo 5×2; mientras que elgrupo 1×1 minimiza los costos variables totales. La reducción en costos por unidad deproducción entre los grupos 7×0 y 1×1 fue de 15%. En el análisis químico se observarondiferencias significativas para el contenido de humedad (7×0) y de carbohidratos (1×1).Los tratamientos 6×1 y 5×2 permiten una compensación total del crecimiento, sin afectarnegativamente la calidad del músculo y/o el rendimiento económico final. El crecimientocompensatorio observado en la tilapia del Nilo permite diseñar estrategias alimenticias parahacer más eficiente su cultivo.

Within the thermal tolerance range of fish, metabolism is known to escalate with warming. Rapid thermic changes also trigger a series of physiological responses, including activation of the stress axis, producing cortisol. Fish have adapted to their environment by producing low level of plasmatic cortisol when unstressed (basal), so that thriving in their natural temperature should not impact their basal cortisol levels. Yet, surprisingly little is known on how temperature affects cortisol within and between fish species. Here, we conducted a phylogenetic meta-analysis to (1) test whether temperature can explain the differences in basal cortisol between species and (2) evaluate the role of temperature on differences in cortisol levels between individuals of a same species. To do so, we retrieved basal plasma cortisol data from 126 studies, investigating 33 marine and freshwater fish species, and correlated it to water temperature. Intra-species variability in basal plasma cortisol levels was further investigated in two species, the European sea bass Dicentrarchus labrax and the Nile tilapia Oreochromis niloticus. Factors such as life stage, sex and weight were also considered in the analyses. Overall, our phylogenetic analysis revealed a clear positive correlation between basal cortisol level and the temperature at which the fish live. The role of temperature has also been confirmed within D. labrax, while it failed to be significant in O. niloticus. In this paper, influence of habitat, life stage, sex and weight on basal plasma cortisol levels are also discussed. Since some abiotic parameters were not included in the analysis, our study is a call to encourage scientists to systematically report other key factors such as dissolved oxygen or salinity to fully depict the temperature-cortisol relationship in fishes.

The study aimed to assess Nile tilapia's (Oreochromis niloticus) growth performance and body chemical composition through varying levels of L-Glutamic acid supplementation. In the experiment, four different groups of feed were prepared; the control C (0% L-Glutamic acid), G1 (1% L-Glutamic acid), G2 (2% L-Glutamic acid), and G3 (3% L-Glutamic acid). Tilapia juveniles with an average initial weight of 4.86 g were stocked into 12 fiberglass tanks (450L) with 40 individuals and three replications under controlled conditions, and the experiment was continued for a period of 60 days. At the end of the experiment, for the G2 group final weight (FW, 19.31±0.59 g), specific growth rate (SGR; 2.30±0.05), feed conversion ratio (FCR; 1.02±0.03), daily growth rate (DGR; 4.95±0.20) protein efficiency ratio (PER 2.83±0.10) and net protein utilization (NPU; 61.62±3.39) were better than the other groups (P<0.05). Nutritional composition data showed that the groups differed between protein, dry matter, and lipid compositions. The G2 group exhibited the highest whole-body protein level, recording a value of 21.24±0.52, whereas the control group demonstrated the lowest protein level at 20.17±0.15. In conclusion, incorporating 2% L-Glutamic acid into the diet of juvenile Nile tilapia is advisable for both the growth and development of the fish and for enhancing their nutritional composition.

Muscle growth in teleosts is a complex biological process orchestrated by numerous protein-coding genes and non-coding RNAs. A few recent studies suggest that circRNAs are involved in teleost myogenesis, but the molecular networks involved remain poorly understood. In this study, an integrative omics approach was used to determine myogenic circRNAs in Nile tilapia by quantifying and comparing the expression profile of mRNAs, miRNAs, and circRNAs in fast muscle from full-sib fish with distinct growth rates. There were 1947 mRNAs, 9 miRNAs, and 4 circRNAs differentially expressed between fast- and slow-growing individuals. These miRNAs can regulate myogenic genes and have binding sites for the novel circRNA circMef2c. Our data indicate that circMef2c may interact with three miRNAs and 65 differentially expressed mRNAs to form multiple competing endogenous RNA networks that regulate growth, thus providing novel insights into the role of circRNAs in the regulation of muscle growth in teleosts

Tilapia are a group of originally freshwater species, some of which can be cultured in a wide range of salinities, e.g. in estuaries or in brackish water ponds in polyculture with shrimp. Although the physiological characteristics for osmoregulation have been studied extensively, it is less clear how selection results in adaptation to salinity stress. Here we studied the genomic architecture of one saline-tolerant strain, called “Sukamandi”, which was selected to grow well in brackish water. We also investigated the impact of selection for salinity tolerance on the genome. Since the Sukamandi strain is assumed to be derived from Nile tilapia (Orechromis niloticus) and blue tilapia (Orechromis aureus), we also searched for introgression signatures to understand their influence on salinity tolerance., Tilapia are a group of originally freshwater species, some of which can be cultured in a wide range of salinities, e.g. in estuaries or in brackish water ponds in polyculture with shrimp. Although the physiological characteristics for osmoregulation have been studied extensively, it is less clear how selection results in adaptation to salinity stress. Here we studied the genomic architecture of one saline-tolerant strain, called “Sukamandi”, which was selected to grow well in brackish water. We also investigated the impact of selection for salinity tolerance on the genome. Since the Sukamandi strain is assumed to be derived from Nile tilapia (Orechromis niloticus) and blue tilapia (Orechromis aureus), we also searched for introgression signatures to understand their influence on salinity tolerance.

Resilience can be defined as the capacity of an animal to be minimally affected by perturbations or to quickly recover to the state it had before the perturbation. When applied to production animals, resilience is defined as consistency in production over time. This consistency can be quantified by the variance of deviations from the expected trait level measured at multiple time points. The objectives of this study were to estimate genetic parameters for resilience in Nile tilapia, measured as consistency in growth. We used log-transformed variance of deviations (LnVar) of body weight measured five times during grow-out in either an aerated or a non-aerated pond. The hypothesis was that fish grown in non-aerated ponds are more challenged by environmental conditions, such that heritable variation in LnVar of body weight is more expressed showing larger differences between more and less resilient fish. The heritability for LnVar was 0.10 in aerated pond and 0.12 in the non-aerated pond. In aerated ponds the genetic correlation (rg) of LnVar with harvest weight (HW) was 0.36 ± 0.26, and with thermal growth coefficient (TGC) it was 0.47 ± 0.21. In the non-aerated pond, the rg with HW and TGC were close to zero (−0.01 ± 0.29 and − 0.08 ± 0.22). The genetic correlation for LnVar between both environments was 0.80. These estimates suggest that selection for HW or TGC in aerated ponds will increase LnVar in both environments. Increased LnVar may decrease resilience and this will be detrimental to performance. Selecting for more resilient fish would lead to more constant growth rates, which makes biomass estimation more accurate and could therefore result in more optimal feeding regimes and less feed waste. This would have a favorable effect on the feed efficiency in production units and on the environmental impact of fish farming. To improve resilience together with growth we recommend that fish breeding programs collect repeated records on body weight, preferably in chall

In aquaponics and circular multitrophic food production systems, dietary protein source, as well as fish species choice, particularly in cases of different nutritional physiology, could be factors affecting excreted nutrient profiles. Accordingly, growth performance, dissolved nutrient accumulation and feces nutrient profiles were evaluated for African catfish (Clarias gariepinus) reared in recirculating aquaculture systems (RAS) and fed single protein source diets based on black soldier fly larvae meal (BSF), poultry by-product meal (PM), poultry blood meal (PBM) and fish meal (FM) and the results were compared to previous findings for Nile tilapia (Oreochromis niloticus). All diets resulted in significantly different growth performances of African catfish, with FM producing the best growth performance, followed by PM, BSF and PBM. PM resulted in the highest soluble reactive phosphorus concentrations (SRP) in the RAS water; whereas, BSF resulted in the highest K, Mg and Cu concentrations. The highest feces nutrient density was recorded for PBM; whereas, FM and PM yielded the lowest feces nutrient density. Comparing African catfish to Nile tilapia revealed that the former showed significantly better growth performance with FM and PM, however, significantly weaker performance with BSF. Although dissolved K accumulation was similar between species across diets, significant differences were recorded for total inorganic nitrogen and SRP production per unit of feed for individual diets. Despite similar feces nutrient profiles, African catfish produce significantly less feces dry matter per unit of feed for each diet compared to Nile tilapia. Findings are discussed regarding their implications for aquafeed development in the context of circular multitrophic food production systems., the Federal Ministry of Education and Research/PtJ Project Management Agency as part of Agricultural Systems of the Future (CUBES Circle), Peer Reviewed

Tilapia cage farming in eutrophic lakes uses low stocking densities since tilapias can thrive mainly on natural food or minimal supplementary feeding. For semi-intensive Nile tilapia cage culture, feeding strategies to improve productivity are adopted based on technical viability and cost efficiency, as assessed in the present study. Tilapia fingerlings stocked in triplicate cages per treatment were reared in Laguna de Bay, Philippines for five months, one run each during the dry and wet seasons. The treatments were: I – UNFED or no feeding; II - FED, fish fed for the entire 155 days; III - D45, fish fed from day 45 to harvest; and IV - D75, or fish fed from day 75 to harvest. Average weight gain or AWG (153.18 g and 225.85g, for dry and wet seasons, respectively) were highest in FED. Growth parameters in all fed treatments were significantly higher (p<0.05) than in UNFED for both seasons. Survival rates were higher during the wet season (66-70%) compared to the dry season (35-37%). Moreover, in the wet season, when the lake’s primary productivity is low, full feeding can be done without compromising lake water quality. Results showed that it favored high AWG, survival, reasonable market price, and profit.

Tilapia cage farming in eutrophic lakes uses low stocking densities since tilapias can thrive mainly on natural food or minimal supplementary feeding. For semi-intensive Nile tilapia cage culture, feeding strategies to improve productivity are adopted based on technical viability and cost efficiency, as assessed in the present study. Tilapia fingerlings stocked in triplicate cages per treatment were reared in Laguna de Bay, Philippines for five months, one run each during the dry and wet seasons. The treatments were: I – UNFED or no feeding; II - FED, fish fed for the entire 155 days; III - D45, fish fed from day 45 to harvest; and IV - D75, or fish fed from day 75 to harvest. Average weight gain or AWG (153.18 g and 225.85g, for dry and wet seasons, respectively) were highest in FED. Growth parameters in all fed treatments were significantly higher (p<0.05) than in UNFED for both seasons. Survival rates were higher during the wet season (66-70%) compared to the dry season (35-37%). Moreover, in the wet season, when the lake’s primary productivity is low, full feeding can be done without compromising lake water quality. Results showed that it favored high AWG, survival, reasonable market price, and profit.

Standard metabolic rate (SMR) and maximum metabolic rate (MMR) were determined for Nile tilapia acclimated to six different experimental temperatures from 18 °C to 38 °C. SMR increased exponentially with temperature, from 79.8 mg O2 kg−1 h−1 at 18 °C, to 255.1 mg O2 kg−1 h−1 at 38 °C (Q10 = 1.79). The main increase in Q10 occurred within the highest temperature range, whereas in the lower temperature from 18 °C to 22 °C, temperature did not significantly affect SMR. MMR showed a hyperbolic correlation with increasing temperature, rising from 240.5 mg O2 kg−1 h−1 at 18 °C to a peak of 373.8 mg O2 kg−1 h−1 at 30 °C, before decreasing again at higher temperatures. Absolute aerobic scope (AAS) peaked at 26.0 °C, which we conclude to be the optimal temperature for Nile tilapia. The optimal temperature range, defined as the thermal range where 80% or more of the metabolic scope (MS) can be maintained, occurred between 19.5 and 32.1 °C. The lower (TCMIN) and upper (TCMAX) critical temperatures occurred at 13.1 °C and 38.8 °C. Nile tilapia showed a 4-fold scope for increasing ventilation frequency from 24 opercular beats min-1 (OB min−1) during SMR at 18 °C, to a maximum of 100 OB min−1 which occurred during MMR at 34 °C. fV during MMR increased with temperature, but above 30 °C became uncoupled with MO2, as fish were unable to sustain their rates of oxygen consumption despite a high fV. There was a strong correlation between fV and SMR (r2 = 0.83) across all temperatures indicating that fV is a good predictor of SMR. However, the correlation between MMR and fV was weak (r2 = 0.06), due to a strong interacting effect of temperature. When selecting data from the thermal optimum range, a good correlation between fV and MO2 was obtained (r2

Resident microbial communities that can support various host functions play a key role in their development and health. In fishes, microbial symbionts are vertically transferred from the parents to their progeny. Such transfer of microbes in mouthbrooder fish species has not been reported yet. Here, we employed Nile tilapia (Oreochromis niloticus) to investigate the vertical transmission of microbes across generations using a 16S rRNA amplicon sequencing approach, based on the presence of bacteria in different generations. Our analysis revealed that the core microbiome in the buccal cavity and posterior intestine of parents shapes the gut microbiome of the progeny across generations. We speculate that the route of this transmission is via the buccal cavity. The identified core microbiome bacteria, namely Nocardioides, Propionibacterium, and Sphingomonas have been reported to play an essential role in the health and development of offspring. These core microbiome members could have specific functions in fish, similar to mammals

A synthetic androgen 17-α methyltestosterone (MT) commonly used in the production of mono-sex fry of Nile tilapia (Oreochromis niloticus) during the first 21 days for sex reversal has been considered to suppress immunity thereby reduce survival. Present trial was conducted to evaluate whether vitamin C (L-ascorbic acid, AA) supplementation would benefit in terms of survival, growth, and stress resistance. Nile tilapia fry were fed with isonitrogenous (57.8±0.2% CP) diets formulated using Field cricket (Gryllus bimaculatus) meal (approx. 79%) and fish meal (approx. 20%) to use as control, and five other diets were prepared by supplementing 10, 20, 30 40 and 50 g of vitamin C (L-ascorbic acid per kg diet). Eighteen aquaria or glass tanks (100 L) were used having three replicates per treatment. Each aquarium was stocked with 300 fish (0.01±0.00 g). Fry were nursed for another 91 days to check their sex-ratio. Gonad histology showed increased number of spermatogonia when L-ascorbic dose was 30g/kg diet. At the end of the feeding trial results indicated significant increase (P<0.05) in growth, feed utilization and survival when fed with vitamin C at the dose of 10 g/kg diet during sex-reversal and nursing periods as compared to the control. Similarly, hematological information also showed 10 g vitamin C dose per kg diet. Polynomial regression showed that the optimum dietary ascorbic acid doses were calculated at 15.9, 10.0 and 12.0 g AA per kg diet for highest survival (83.5% max), weight gain and SGR, respectively, but the doses higher than 20 g of L-ascorbic acid/kg diet was not beneficial. Highest apparent digestibility (AD%) of protein (84.1%) was at 15.37g and AD% of lipid (91.4% max) was 17.8g of vitamin C/kg diet. Salinity challenge test also showed highest survival can be achieved at 15.8 g AA per kg diet. As the survival of fry is the most important parameter at these stages, the dose which resulted highest survival i.e., 15 g/kg diet is recommended.

The present study was carried out to compare between some freshwater food fish species and some other freshwater ornamental fish species commonly known in Egypt, concerning the haematological parameters, dressing percent, fillet (boneless meat) percentage, and chemical composition of the fish flesh on dry matter basis. Four food fish species (Nile tilapia, grass carp, catfish, and Tobara from Manzalah Fish Farm, Dakahlia governorate, General Authority For Developing Fish Wealth, Ministry of Agriculture, Cairo, Egypt) and two ornamental fish (Koi and Fan-tail (Goldfish), from local ornamental fish trade shops, Mansoura, Dakahlia governorate, Egypt) species all belonging to the freshwater fishes were sampled, three fishes from each. Body measurements of the individual fishes were recorded, blood samples were withdrawn, live body weight was recorded, fish were dressed (eviscerated) and filleted, the flesh were minced, dried, and sieved for chemical analysis. From the forgoing results, it could be concluded that the worthiness comparison among fish species for physical, biochemical and haematological parameters, and fish quality must be done between similar species, sex, size, physiological status, nutritional status, rearing system. These parameters are variable and influenced by genetically and environmental aspects.

The present study was carried out to compare between some freshwater food fish species and some other freshwater ornamental fish species commonly known in Egypt, concerning the haematological parameters, dressing percent, fillet (boneless meat) percentage, and chemical composition of the fish flesh on dry matter basis. Four food fish species (Nile tilapia, grass carp, catfish, and Tobara from Manzalah Fish Farm, Dakahlia governorate, General Authority For Developing Fish Wealth, Ministry of Agriculture, Cairo, Egypt) and two ornamental fish (Koi and Fan-tail (Goldfish), from local ornamental fish trade shops, Mansoura, Dakahlia governorate, Egypt) species all belonging to the freshwater fishes were sampled, three fishes from each. Body measurements of the individual fishes were recorded, blood samples were withdrawn, live body weight was recorded, fish were dressed (eviscerated) and filleted, the flesh were minced, dried, and sieved for chemical analysis. From the forgoing results, it could be concluded that the worthiness comparison among fish species for physical, biochemical and haematological parameters, and fish quality must be done between similar species, sex, size, physiological status, nutritional status, rearing system. These parameters are variable and influenced by genetically and environmental aspects.

Antioxidants are added to fresh and processed meat to prevent lipid oxidation, retard development of off-flavors, and improve color stability. Synthetic antioxidants have been confirmed for their toxicological and carcinogenic effects. Thus, the food industry now chooses natural products over synthetic ones. This study was carried out to investigate the effect of Rosemary extract (R.E.) and vitamin E on the quality of fried fillets of Nile tilapia (Oreochromis niloticus) during chilling and frozen storage. Fillets of Nile tilapia were treated with (R.E.)  0.1%, 0.2%, 0.3% and Vitamin E 0.1% then stored for 5,10 and 15 days at 4±1°C and for three months at -18±2°C. Then chemical tests including Peroxide value (PV), Thio-barbituric acid (TBA), Tri-methylamine-nitrogen (TMA-N) and Total volatile base-nitrogen (TVB-N) were done to evaluate the preservative effect of (R.E.) and vitamin E during storage. The TBA and PV increased in all treatments due to lipid peroxidation. Results showed that TMA-N,TVB-N, value of (R.E.) and vitamin E treated samples were significantly lower than those of the control samples (P<0.05). Results of our investigation revealed that R.E. retarded oxidative changes in chilling and frozen fried fillets of Nile tilapia whereas R.E. 0.1%, 0.2% and vitamin E 0.1% were not as effective as R.E. 0.3%  on oxidative stability. Best oxidation inhabitation results on chilling and frozen fried fillets of Nile tilapia was obtained when employing of R.E. The obtained results also showed that there was a significant (p<0.05) enhancement in sensory quality attributes of fried fillets of Nile tilapia; samples treated with R.E. and vitamin E. Conclusion, The tested R.E. had a high effectiveness as antioxidative and antimicrobial should be utilized for extending the shelf-life through retarded the spoilage and enhancing quality attributes of fried fillets of Nile tilapia during chilling and frozen storage.

In Bangladesh, aquaculture is critically important in terms of providing food and nutrition, sustainable livelihoods, income, and export earnings. Nevertheless, aquaculture in Bangladesh has faced recent concerns due to climate change. Aquaculture is vulnerable to a combination of climatic factors, such as global warming, rainfall variation, flood, drought, temperature fluctuation, and salinity change. Considering the vulnerability of fish production to the impacts of climate change, tilapia farming is one of the possible strategies for adaptation to climate change. The positive culture attributes of tilapia are their tolerance to low water levels and poor water quality with rainfall variation, temperature fluctuation, and salinity change. In fact, tilapia farming is possible in a wide range of water environments, including freshwater, brackish water, and saltwater conditions. We suggest that appropriate tilapia culture strategies with institutional support and collaboration with key stakeholders are needed for adaptation to environmental change.

Background Tilapia is one of the most abundant species in aquaculture. Hypoxia is known to depress growth rate, but the genetic mechanism by which this occurs is unknown. In this study, two groups consisting of 3140 fish that were raised in either aerated (normoxia) or non-aerated pond (nocturnal hypoxia). During grow out, fish were sampled five times to determine individual body weight (BW) gains. We applied a genome-wide association study to identify SNPs and genes associated with the hypoxic and normoxic environments in the 16th generation of a Genetically Improved Farmed Tilapia population. Results In the hypoxic environment, 36 SNPs associated with at least one of the five body weight measurements (BW1 till BW5), of which six, located between 19.48 Mb and 21.04 Mb on Linkage group (LG) 8, were significant for body weight in the early growth stage (BW1 to BW2). Further significant associations were found for BW in the later growth stage (BW3 to BW5), located on LG1 and LG8. Analysis of genes within the candidate genomic region suggested that MAPK and VEGF signalling were significantly involved in the later growth stage under the hypoxic environment. Well-known hypoxia-regulated genes such as igf1rb, rora, efna3 and aurk were also associated with growth in the later stage in the hypoxic environment. Conversely, 13 linkage groups containing 29 unique significant and suggestive SNPs were found across the whole growth period under the normoxic environment. A meta-analysis showed that 33 SNPs were significantly associated with BW across the two environments, indicating a shared effect independent of hypoxic or normoxic environment. Functional pathways were involved in nervous system development and organ growth in the early stage, and oocyte maturation in the later stage. Conclusions There are clear genotype-growth associations in both normoxic and hypoxic environments, although genome architecture involved changed over the growing period, indicating a transition in

The present study was carried out to compare between some freshwater food fish species and some other freshwater ornamental fish species commonly known in Egypt, concerning the haematological parameters, dressing percent, fillet (boneless meat) percentage, and chemical composition of the fish flesh on dry matter basis. Four food fish species (Nile tilapia, grass carp, catfish, and Tobara from Manzalah Fish Farm, Dakahlia governorate, General Authority For Developing Fish Wealth, Ministry of Agriculture, Cairo, Egypt) and two ornamental fish (Koi and Fan-tail (Goldfish), from local ornamental fish trade shops, Mansoura, Dakahlia governorate, Egypt) species all belonging to the freshwater fishes were sampled, three fishes from each. Body measurements of the individual fishes were recorded, blood samples were withdrawn, live body weight was recorded, fish were dressed (eviscerated) and filleted, the flesh were minced, dried, and sieved for chemical analysis. From the forgoing results, it could be concluded that the worthiness comparison among fish species for physical, biochemical and haematological parameters, and fish quality must be done between similar species, sex, size, physiological status, nutritional status, rearing system. These parameters are variable and influenced by genetically and environmental aspects.

The present study was carried out to compare between some freshwater food fish species and some other freshwater ornamental fish species commonly known in Egypt, concerning the haematological parameters, dressing percent, fillet (boneless meat) percentage, and chemical composition of the fish flesh on dry matter basis. Four food fish species (Nile tilapia, grass carp, catfish, and Tobara from Manzalah Fish Farm, Dakahlia governorate, General Authority For Developing Fish Wealth, Ministry of Agriculture, Cairo, Egypt) and two ornamental fish (Koi and Fan-tail (Goldfish), from local ornamental fish trade shops, Mansoura, Dakahlia governorate, Egypt) species all belonging to the freshwater fishes were sampled, three fishes from each. Body measurements of the individual fishes were recorded, blood samples were withdrawn, live body weight was recorded, fish were dressed (eviscerated) and filleted, the flesh were minced, dried, and sieved for chemical analysis. From the forgoing results, it could be concluded that the worthiness comparison among fish species for physical, biochemical and haematological parameters, and fish quality must be done between similar species, sex, size, physiological status, nutritional status, rearing system. These parameters are variable and influenced by genetically and environmental aspects.

DNA methylation is one of the main epigenetic mechanisms that regulate gene expression in a manner that depends on the genomic context and varies considerably across taxa. This DNA modification was first found in nuclear genomes of eukaryote several decades ago and it has also been described in mitochondrial DNA. It has recently been shown that mitochondrial DNA is extensively methylated in mammals and other vertebrates. Our current knowledge of mitochondrial DNA methylation in fish is very limited, especially in non-model teleosts. In this study, using whole-genome bisulfite sequencing, we determined methylation patterns within non-CpG (CH) and CpG (CG) contexts in the mitochondrial genome of Nile tilapia, a non-model teleost of high economic importance. Our results demonstrate the presence of mitochondrial DNA methylation in this species predominantly within a non-CpG context, similarly to mammals. We found a strand-specific distribution of methylation, in which highly methylated cytosines were located on the minus strand. The D-loop region had the highest mean methylation level among all mitochondrial loci. Our data provide new insights into the potential role of epigenetic mechanisms in regulating metabolic flexibility of mitochondria in fish, with implications in various biological processes, such as growth and development

Background: Tilapia is one of the most abundant species in aquaculture. Hypoxia is known to depress growth rate, but the genetic mechanism by which this occurs is unknown. In this study, two groups consisting of 3140 fish that were raised in either aerated (normoxia) or non-aerated pond (nocturnal hypoxia). During grow out, fish were sampled five times to determine individual body weight (BW) gains. We applied a genome-wide association study to identify SNPs and genes associated with the hypoxic and normoxic environments in the 16th generation of a Genetically Improved Farmed Tilapia population. Results: In the hypoxic environment, 36 SNPs associated with at least one of the five body weight measurements (BW1 till BW5), of which six, located between 19.48 Mb and 21.04 Mb on Linkage group (LG) 8, were significant for body weight in the early growth stage (BW1 to BW2). Further significant associations were found for BW in the later growth stage (BW3 to BW5), located on LG1 and LG8. Analysis of genes within the candidate genomic region suggested that MAPK and VEGF signalling were significantly involved in the later growth stage under the hypoxic environment. Well-known hypoxia-regulated genes such as igf1rb, rora, efna3 and aurk were also associated with growth in the later stage in the hypoxic environment. Conversely, 13 linkage groups containing 29 unique significant and suggestive SNPs were found across the whole growth period under the normoxic environment. A meta-analysis showed that 33 SNPs were significantly associated with BW across the two environments, indicating a shared effect independent of hypoxic or normoxic environment. Functional pathways were involved in nervous system development and organ growth in the early stage, and oocyte maturation in the later stage. Conclusions: There are clear genotype-growth associations in both normoxic and hypoxic environments, although genome architecture involved changed over the growing period, indicating a transition

The effect of feeding during off-flavour depuration on the elimination of geosmin from muscle tissue (fillet) and ovaries as a model for caviar was assessed in Nile tilapia (Oreochromis niloticus) (mean ± SD weight of 185 ± 15.0 g). The experiment had a 2 × 4 factorial design with feeding level (starved or fed) and depuration time (24, 48, 72 and 96 h) as factors with duplicates for each of the 8 treatment combinations. Fish were normally loaded with geosmin prior to the experiment. During off-flavour depuration geosmin levels in fillet and ovary declined over time in both fed and starved tilapia. In fed tilapia geosmin declined faster from the ovaries compared to starved fish (p = 0.018). The same trend of a faster decline was observed for the muscle tissue (fillets) of fed tilapia, though only numerically (p = 0.11). Because faster geosmin elimination paralleled with high blood lipids, we do not rule out that blood lipids are involved in geosmin transport via the circulatory system and that low blood lipid levels are limiting geosmin elimination in starved fish. No difference in geosmin elimination rate was detected between ovary and muscle tissue in Nile tilapia. Off-flavour depuration time is strongly reduced when farmers adopt a practice of feeding Nile tilapia during off-flavour depuration.

17 alpha, 20 beta-Dihydroxy-4-pregnen-3-one (DHP) is a maturation-inducing steroid in many teleost fish. Carbonyl reductase-like 20 beta-hydroxysteroid dehydrogenase (CR/20 beta-HSD) is a candidate enzyme responsible for DHP production during oocyte maturation in various fish, including Nile tilapia. However, a novel type of 17 beta-hydroxysteroid dehydrogenase, type 12-like (17 beta-HSD12L), is responsible for DHP production during oocyte maturation in masu salmon. 17 beta-HSD12 (presumably orthologous to salmon 17 beta-HSD12L) has been detected in Nile tilapia; however, its enzymatic activity and specific ability to convert the DHP substrate 17 alpha-hydroxyprogesterone (17OHP) have not been examined. This study aimed to determine whether CR/20 beta-HSD or 17 beta-HSD12 is responsible for DHP production during oocyte maturation in the Nile tilapia. Mammalian expression vectors containing tilapia hsd17b12 or CR/20bhsd were transfected into HEK293T cells, followed by incubation with 170HP. HEK293T cells transfected with hsd17b12 exhibited a strong ability to convert exogenous 17OHP to DHP (73.8% yield). Cells transfected with CR/20bhsd or the control vector converted only 7.4% and 7.5% of 17OHP to DHP, respectively. In addition, based on LC-MS/MS analyses, 17 beta-HSD12 did not convert any substrates other than 17OHP, including DHP, adrenosterone, androstenedione, estrone, testosterone, 11-ketotestosterone, and estradiol-17 beta. CR/20 beta-HSD showed strong 17 beta-HSD oxidoreductase activity especially with adrenosterone and androstenedione. Tissue-specific hsd17b12 expression analyzed by RT-PCR showed that hsd17b12 mRNA was strongest amplification in full-grown follicles. Finally, full-grown ovarian follicles were incubated with salmon pituitary extract (SPE, 100 mu g/mL) or human chorionic gonadotropin (HCG, 100 IU/mL) to induce 2013-HSD activity in vitro, and enzyme activity was assessed by co-incubation with 100 ng/mL 17OHP for 2, 4, 8, and 16 h. Conversion of

17 alpha, 20 beta-Dihydroxy-4-pregnen-3-one (DHP) is a maturation-inducing steroid in many teleost fish. Carbonyl reductase-like 20 beta-hydroxysteroid dehydrogenase (CR/20 beta-HSD) is a candidate enzyme responsible for DHP production during oocyte maturation in various fish, including Nile tilapia. However, a novel type of 17 beta-hydroxysteroid dehydrogenase, type 12-like (17 beta-HSD12L), is responsible for DHP production during oocyte maturation in masu salmon. 17 beta-HSD12 (presumably orthologous to salmon 17 beta-HSD12L) has been detected in Nile tilapia; however, its enzymatic activity and specific ability to convert the DHP substrate 17 alpha-hydroxyprogesterone (17OHP) have not been examined. This study aimed to determine whether CR/20 beta-HSD or 17 beta-HSD12 is responsible for DHP production during oocyte maturation in the Nile tilapia. Mammalian expression vectors containing tilapia hsd17b12 or CR/20bhsd were transfected into HEK293T cells, followed by incubation with 170HP. HEK293T cells transfected with hsd17b12 exhibited a strong ability to convert exogenous 17OHP to DHP (73.8% yield). Cells transfected with CR/20bhsd or the control vector converted only 7.4% and 7.5% of 17OHP to DHP, respectively. In addition, based on LC-MS/MS analyses, 17 beta-HSD12 did not convert any substrates other than 17OHP, including DHP, adrenosterone, androstenedione, estrone, testosterone, 11-ketotestosterone, and estradiol-17 beta. CR/20 beta-HSD showed strong 17 beta-HSD oxidoreductase activity especially with adrenosterone and androstenedione. Tissue-specific hsd17b12 expression analyzed by RT-PCR showed that hsd17b12 mRNA was strongest amplification in full-grown follicles. Finally, full-grown ovarian follicles were incubated with salmon pituitary extract (SPE, 100 mu g/mL) or human chorionic gonadotropin (HCG, 100 IU/mL) to induce 2013-HSD activity in vitro, and enzyme activity was assessed by co-incubation with 100 ng/mL 17OHP for 2, 4, 8, and 16 h. Conversion of

Chlorella vulgaris is a green, single-celled, spherical freshwater microalga belonging to the family Chlorellaceae of the division Chlorophyta. C. vulgaris is currently used as food supplement and medicinal agent due to its carotenoids, chlorophylls and proteins content. Chlorella vulgaris is incorporated in fish feed as a growth and immune stimulant. Tilapia is one of the most important cultured fish species with numerous advantages, contributing more than USD 10 billion to the world’s seafood market annually. Despite the important features of tilapia, disease outbreaks tend to cause massive mortalities in fish farms which impose serious negative impact to economies worldwide. Most tilapia mortalities were reported as a resultant stress due to overcrowding coupled with bacterial infection. Streptococcus agalactiae is one of the most virulent bacteria causing most of tilapia mortalities recently. The use of immunostimulants like microalgal supplementation in fish feed holds a promising future in mitigating tilapia fish disease. Nevertheless, the common amounts used (≥12%) in this practice is considered uneconomical by fish farmers, considering the high price of microalgal biomass procurement. In addition, scientific reports regarding the association of metabolites with pathways involved in the stimulation of immune system of tilapia fish (Oreochromis niloticus) exerted by consumption of C. vulgaris are still limited. Hence, the main aim of this study was to investigate the immunestimulating role of bioactive metabolites from C. vulgaris on the tilapia fish at lower concentrations using proton nuclear magnetic resonance (1H-NMR) metabolomics approach. The first part of the study dealt with the characterization of the metabolite composition of the cultured samples of C. vulgaris via 1H-NMR, gas chromatography mass spectrometry (GCMS) lipid analysis and liquid chromatography mass spectrometry (LC-MS/MS) analysis. 1H-NMR data obtained from six different organic solvent

17 alpha, 20 beta-Dihydroxy-4-pregnen-3-one (DHP) is a maturation-inducing steroid in many teleost fish. Carbonyl reductase-like 20 beta-hydroxysteroid dehydrogenase (CR/20 beta-HSD) is a candidate enzyme responsible for DHP production during oocyte maturation in various fish, including Nile tilapia. However, a novel type of 17 beta-hydroxysteroid dehydrogenase, type 12-like (17 beta-HSD12L), is responsible for DHP production during oocyte maturation in masu salmon. 17 beta-HSD12 (presumably orthologous to salmon 17 beta-HSD12L) has been detected in Nile tilapia; however, its enzymatic activity and specific ability to convert the DHP substrate 17 alpha-hydroxyprogesterone (17OHP) have not been examined. This study aimed to determine whether CR/20 beta-HSD or 17 beta-HSD12 is responsible for DHP production during oocyte maturation in the Nile tilapia. Mammalian expression vectors containing tilapia hsd17b12 or CR/20bhsd were transfected into HEK293T cells, followed by incubation with 170HP. HEK293T cells transfected with hsd17b12 exhibited a strong ability to convert exogenous 17OHP to DHP (73.8% yield). Cells transfected with CR/20bhsd or the control vector converted only 7.4% and 7.5% of 17OHP to DHP, respectively. In addition, based on LC-MS/MS analyses, 17 beta-HSD12 did not convert any substrates other than 17OHP, including DHP, adrenosterone, androstenedione, estrone, testosterone, 11-ketotestosterone, and estradiol-17 beta. CR/20 beta-HSD showed strong 17 beta-HSD oxidoreductase activity especially with adrenosterone and androstenedione. Tissue-specific hsd17b12 expression analyzed by RT-PCR showed that hsd17b12 mRNA was strongest amplification in full-grown follicles. Finally, full-grown ovarian follicles were incubated with salmon pituitary extract (SPE, 100 mu g/mL) or human chorionic gonadotropin (HCG, 100 IU/mL) to induce 2013-HSD activity in vitro, and enzyme activity was assessed by co-incubation with 100 ng/mL 17OHP for 2, 4, 8, and 16 h. Conversion of

The phenotype (body weight at five time points) from stocking to harvest during growing period of Nile tilapia. The genotype of all Nile Tilapia samples in the VCF format.

Handling or transporting fish can strongly affect physiology and behaviour, and anaesthesia is often used to minimize stress or injuries. The potential of propofol as an immersion anaesthetic for Nile tilapia (Oreochromis niloticus) was investigated in this study. Nile tilapia were divided into groups based on a body mass criteria of 10, 50, 100, 150 and 200 g, and subjected to different propofol concentrations (2.5, 5, 7.5, 10 or 12.5 mg L−1) using 3 individuals per size class for each prepared anaesthetic solution. Fish were placed in the prepared anaesthetic baths and times to lose reflex to mild touch as well as induction of full immobilisation recorded. Behavioural markers such as loss of the righting reflex and respiratory responses were also monitored. Following the induction of full anaesthesia, blood samples were drawn from each of the 200 g fish for haematological analysis. Induction times for deep anaesthesia (Stage IV) decreased significantly (p < 0.05) with increasing propofol concentrations for all size classes and increased as a function of increasing fish size. Recovery from anaesthesia was smooth in all size classes and exposure to higher doses of anaesthesia resulted in a general trend of prolonged recovery times. Larger fish showed a general trend of faster recovery times than smaller fish under the different propofol concentrations. Besides reporting the practicality of propofol as an immersion anaesthetic, this study has also demonstrated the importance of considering size when anaesthetizing Nile tilapia with propofol.

This study investigated whether dietary supplementation of phytogenic compounds limonene and thymol had synergistic or additive effects on growth and selected nutritional physiology pathways in Nile tilapia. A 63-day feeding experiment was conducted using fish of 1.5 ± 0.0 g (± standard error) fed on a commercial diet coated with either 0 ppm limonene and thymol (control), 400 ppm limonene (L), 500 ppm thymol, (T) or a combination of 400 ppm limonene and 500 ppm thymol (LT). Final fish weight (FW) was significantly improved to similar extents by diet LT (16.7 ± 0.3 g) and L (16.6 ± 0.4 g). Dietary thymol alone and the control did not enhance FW (15.0 ± 0.4 g and 13.7 ± 0.4 g respectively). Dietary thymol had shown a strong tendency to improve somatic growth (P = .052). The analysed candidate genes involved in the pathways of nutrient digestion, absorption and transport (muc), lipid metabolism (lpl), antioxidant enzymes (cat) and somatotropic axis growth (igfI) were also up-regulated to similar extents in Nile tilapia by diet L and LT (P < .05), above the regulation observed with the diet supplemented exclusively with thymol. This suggests lack of synergistic or additive effects on growth and nutritional physiology pathways when limonene and thymol are supplied in the diet.

Chlorella vulgaris is a green, single-celled, spherical freshwater microalga belonging to the family Chlorellaceae of the division Chlorophyta. C. vulgaris is currently used as food supplement and medicinal agent due to its carotenoids, chlorophylls and proteins content. Chlorella vulgaris is incorporated in fish feed as a growth and immune stimulant. Tilapia is one of the most important cultured fish species with numerous advantages, contributing more than USD 10 billion to the world’s seafood market annually. Despite the important features of tilapia, disease outbreaks tend to cause massive mortalities in fish farms which impose serious negative impact to economies worldwide. Most tilapia mortalities were reported as a resultant stress due to overcrowding coupled with bacterial infection. Streptococcus agalactiae is one of the most virulent bacteria causing most of tilapia mortalities recently. The use of immunostimulants like microalgal supplementation in fish feed holds a promising future in mitigating tilapia fish disease. Nevertheless, the common amounts used (≥12%) in this practice is considered uneconomical by fish farmers, considering the high price of microalgal biomass procurement. In addition, scientific reports regarding the association of metabolites with pathways involved in the stimulation of immune system of tilapia fish (Oreochromis niloticus) exerted by consumption of C. vulgaris are still limited. Hence, the main aim of this study was to investigate the immunestimulating role of bioactive metabolites from C. vulgaris on the tilapia fish at lower concentrations using proton nuclear magnetic resonance (1H-NMR) metabolomics approach. The first part of the study dealt with the characterization of the metabolite composition of the cultured samples of C. vulgaris via 1H-NMR, gas chromatography mass spectrometry (GCMS) lipid analysis and liquid chromatography mass spectrometry (LC-MS/MS) analysis. 1H-NMR data obtained from six different organic solvent

Two feeding trials were conducted to investigate the effects of dietary pH (pH 2.5, 3.7, 4.6, 5.7-control, pH 7.0, and pH 8.0) and dietary acid source (acetic acid, citric acid, hydrochloric acid and control-no acid) on growth rate and feed utilization efficiency of the Nile tilapia fry. In addition, attractability of the diets at different pH and dietary acid sources were determined. Results of the first feeding trial showed that the feed with pH adjusted to 4.6 resulted in significantly highest final average body weight (FABW), weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and most efficient food conversion ratio (FCR) in the Nile tilapia fry. Survival was 100% in diets with pH 3.7 up to 7.0; the diet with pH 2.5 exhibited significantly lowest survival followed by the pH 8.0 diet. In the second feeding trial, diets that contained hydrochloric, citric or acetic acids that were used to adjust the pH to the optimal 4.6 resulted in higher FABW, WG, SGR, and PER values but lower FCR values than did the control diet; these parameters were not significantly different among the dietary groups. This study demonstrated that the dietary pH promoted growth and efficiency in the Nile tilapia fry and that the three acids that were used were similar in their effects on growth and efficiency. Furthermore, it was demonstrated that either acidifying the diet to pH 4.6 by an inorganic acid such as HCl or the provision of a dietary acidifier such as citric acid or acetic acid could enhance growth, feed efficiency and survival of the Nile tilapia.

Imaging flow cytometry (IFC) is a powerful tool which combines flow cytometry with digital microscopy to generate quantitative high-throughput imaging data. Despite various advantages of IFC over standard flow cytometry, widespread adoption of this technology for studies in aquatic sciences is limited, probably due to the relatively high equipment cost, complexity of image analysis-based data interpretation and lack of core facilities with trained personnel. Here, we describe the application of IFC to examine phagocytosis of particles including microplastics by cells from aquatic animals. For this purpose, we studied (1) live/dead cell assays and identification of cell types, (2) phagocytosis of degradable and non-degradable particles by Atlantic salmon head kidney cells and (3) the effect of incubation temperature on phagocytosis of degradable particles in three aquatic animals-Atlantic salmon, Nile tilapia, and blue mussel. The usefulness of the developed method was assessed by evaluating the effect of incubation temperature on phagocytosis. Our studies demonstrate that IFC provides significant benefits over standard flow cytometry in phagocytosis measurement by allowing integration of morphometric parameters, especially while identifying cell populations and distinguishing between different types of fluorescent particles and detecting their localization.

A major problem in smallholder Nile tilapia (Oreochromis niloticus) farms is that the achieved production is much lower than under optimal management. One of the main environmental factors contributing to lower production is dissolved oxygen (DO), because the majority of Nile tilapia production takes place under smallholder farms with no aeration of ponds which leads to large DO fluctuations. On the contrary, breeding programs select fish in aerated ponds. Aerating ponds is currently not an option for smallholder farmers because either it is too expensive or they lack access to cheap electricity supply. Therefore, it is crucial to know the genetic correlation between aerated and non-aerated ponds to optimize breeding programs to select fish that perform well in ponds with fluctuating DO levels. The objectives of this study were 1) to investigate the presence of genotype by environment (GxE) interaction between aerated and non-aerated earthen ponds using a design that minimized common environmental effects and 2) the impact of (non-)aeration on genetic parameters. The experimental fish were mass-produced using natural group spawning and nursed in four 30m2 hapas. A random sample of fingerlings from each hapa was tagged and randomly distributed to aerated and non-aerated ponds for a grow-out period of 217 and 218 days. Body weight and photographs were taken on five consecutive time points during grow-out. Of the stocked fish, 2063 were genotyped-by-sequencing. A genomic relationship matrix was built using 11,929 SNPs to estimate genetic parameters with ASReml. No-aeration significantly reduced mean harvest weight (HW), survival and thermal growth coefficient (TGC) compared to aeration. Substantial heritabilities (0.14–0.45) were found for HW, TGC, surface area (SA) and body shape, expressed as ellipticity, and low heritabilities (0.03–0.04) for survival in aerated and non-aerated ponds. In both ponds, the environmental effect common to full sibs was not significant. G

Given the strong effects of behavioural hierarchies on growth in many cultured species and the key role of feed efficiency in aquaculture economics, understanding the nature of the interaction of these variables is important for the sustainability of aquaculture. The relationship between agonistic behaviour, growth and feed efficiency in Nile tilapia, Oreochromis niloticus, was studied by rearing 120 fish in eight aquaria. Fish were video-recorded to estimate the occurrence of agonistic behaviour during a fasting and a refeeding period. Growth, feed intake and feed conversion efficiency (FCE - calculated as the inverse of feed conversion ratio (FCR)) were subsequently measured individually for each fish. Fish showed 58% less agonistic traits during the fasting period compared to the feeding period, but generally, an aggressive fish during the fasting period was also aggressive during the refeeding period. The nature of agonistic behaviours between individuals was used to assess the presence of hierarchical relationships between fish. There were dominance hierarchies established in each experimental aquarium that despite minor shifts were maintained throughout the experiment. Agonistic behaviours were strongly correlated with each other, the aggression Index (AI) and with hierarchy rank. PCA analysis of the agonistic behaviours summarising the behavioural information showed little or no correlation between agonistic behaviour, fish growth or FCE. FCE was correlated with body weight gain (BWG). These results suggest that agonistic interactions in juvenile Nile tilapia do not have a large impact on growth and feed conversion efficiency.

The fenofibrate functions in mammals could be affected by many factors such as dietary nutrient levels and physiological status. However, this phenomenon has not been well studied in fish. The goal of our study was to investigate the effect of dietary protein contents on metabolic regulation of fenofibrate in Nile tilapia. An 8-week experiment was conducted to feed fish with four diets at two protein levels (28% and 38%) with or without the supplementation of fenofibrate (200 mg/kg body weight/day). After the trial, the body morphometric parameters, plasma biochemical parameters and qPCR data were examined. These results showed that fenofibrate significantly reduced the feeding intake and weight gain rate, increased the oxidative stress (increased plasma methane dicarboxylic aldehyde, MDA) and liver/body ratio (increased hepatosomatic index, HSI) in the LP (low protein)-fed fish. In contrast, fenofibrate exhibited a lipid-lowering (reduced hepatic lipid) effect and up-regulated the expressions of the genes related to lipid catabolism, transport and anabolic metabolism in the HP (high protein) fed-fish. The present study suggested that lipid-lowering effect of fenofibrate would be strengthened in the fish fed with HP diet containing high energy, but in the fish fed with the LP diet containing low energy, the fenofibrate treatment would cause adverse effects for metabolism. Taking together, our study showed that the metabolic regulation of fenofibrate in Nile tilapia was not only dependent on feed energy content, but also dependent on dietary nutrient composition, such as dietary protein and/or lipid levels. © The Author(s) 2019.

A feeding experiment was conducted to determine the optimum selenium requirement in juvenile Nile tilapia. Each of six purified diets with Se-methionine levels at 0.05, 0.21, 0.41, 0.57, 0.79 and 1.00 mg/kg was assayed in triplicate with initial body weight of 3.00 ± 0.01 g for 8 weeks. The growth of fish was obviously increased when the dietary Se was less than 0.57 mg/kg diet and reached a plateau when the dietary Se was ≥0.57 mg/kg. Serum and hepatopancreatic glutathione peroxidase (GPx) activity increased markedly when the dietary Se was less than 0.57 mg/kg, but then decreased when the dietary Se was higher than 0.57 mg/kg. The malondialdehyde contents in hepatopancreas were significantly decreased when the dietary Se was higher than 0.79 mg/kg. No significant differences were observed in hepatopancreatic total antioxidant capability (T-AOC) among the groups (p >.05). The results of this study indicated that Se addition as Se-methionine was essential, while both the deficiency and excess levels of dietary Se would cause negative effects on growth or antioxidant capability in juvenile Nile tilapia. Based on broken-line regression of WG and piecewise regression of liver GPx, the optimum requirement of Se for juvenile Nile tilapia is 0.57 mg/kg diet. © 2019 John Wiley & Sons Ltd

The fenofibrate functions in mammals could be affected by many factors such as dietary nutrient levels and physiological status. However, this phenomenon has not been well studied in fish. The goal of our study was to investigate the effect of dietary protein contents on metabolic regulation of fenofibrate in Nile tilapia. An 8-week experiment was conducted to feed fish with four diets at two protein levels (28% and 38%) with or without the supplementation of fenofibrate (200 mg/kg body weight/day). After the trial, the body morphometric parameters, plasma biochemical parameters and qPCR data were examined. These results showed that fenofibrate significantly reduced the feeding intake and weight gain rate, increased the oxidative stress (increased plasma methane dicarboxylic aldehyde, MDA) and liver/body ratio (increased hepatosomatic index, HSI) in the LP (low protein)-fed fish. In contrast, fenofibrate exhibited a lipid-lowering (reduced hepatic lipid) effect and up-regulated the expressions of the genes related to lipid catabolism, transport and anabolic metabolism in the HP (high protein) fed-fish. The present study suggested that lipid-lowering effect of fenofibrate would be strengthened in the fish fed with HP diet containing high energy, but in the fish fed with the LP diet containing low energy, the fenofibrate treatment would cause adverse effects for metabolism. Taking together, our study showed that the metabolic regulation of fenofibrate in Nile tilapia was not only dependent on feed energy content, but also dependent on dietary nutrient composition, such as dietary protein and/or lipid levels. © The Author(s) 2019.

Given the strong effects of behavioural hierarchies on growth in many cultured species and the key role of feed efficiency in aquaculture economics, understanding the nature of the interaction of these variables is important for the sustainability of aquaculture. The relationship between agonistic behaviour, growth and feed efficiency in Nile tilapia, Oreochromis niloticus, was studied by rearing 120 fish in eight aquaria. Fish were video-recorded to estimate the occurrence of agonistic behaviour during a fasting and a refeeding period. Growth, feed intake and feed conversion efficiency (FCE - calculated as the inverse of feed conversion ratio (FCR)) were subsequently measured individually for each fish. Fish showed 58% less agonistic traits during the fasting period compared to the feeding period, but generally, an aggressive fish during the fasting period was also aggressive during the refeeding period. The nature of agonistic behaviours between individuals was used to assess the presence of hierarchical relationships between fish. There were dominance hierarchies established in each experimental aquarium that despite minor shifts were maintained throughout the experiment. Agonistic behaviours were strongly correlated with each other, the aggression Index (AI) and with hierarchy rank. PCA analysis of the agonistic behaviours summarising the behavioural information showed little or no correlation between agonistic behaviour, fish growth or FCE. FCE was correlated with body weight gain (BWG). These results suggest that agonistic interactions in juvenile Nile tilapia do not have a large impact on growth and feed conversion efficiency.

Aquaculture is one of the major contributor of economic resources and food production in Malaysia and tilapia (Oreochromis spp.) was one of the highest value in import and export market. But the production was reported to decrease from 51, 554 MT to 35, 996 MT from 2012 to 2016 respectively due to streptococcosis. Streptococcosis was caused by Streptococcus sp. which is the etiological agent of diseases in human and animals which could lead to different pathological effects. It was suggested that the different pathological effects post infection was caused by genetically distinction of the bacterial strain. Thus, this study was conducted to determine the molecular serotyping, virulence genes profiling and pathogenicity of Streptococcus agalactiae isolated from cultured red hybrid tilapia in Malaysia. A total of 256 isolates of S. agalactiae, isolated from fish in Peninsular Malaysia. Genotype of the bacterial collections was determined using PCR based on the capsular polysaccharide gene clusters and multilocus sequence typing. Subsequently, two serotypes were identified, which were 11% and 89% for serotype Ia ST7 and III ST283, respectively. The profiles of virulence genes were constructed using m-PCR with different types of the various published primers involving 14 standard virulence genes (fbsA, fbsB, pavA, scpB, lmb, cylE, cfb, spb1, hylB, rib, bca, bac, cspA and pbp1A/ponA). Serotype Ia showed different pattern of virulence genes profile compared to serotype III, where it lacked the lmb, scpB, pavA, fbsB, cyl, bca, cspA and bac genes, thats differentiated the virulence level of the serotype. Median lethal dose 50 (LD50) of S. agalactiae in red hybrid tilapia for serotypes Ia and III were calculated at 8.7 x 103 CFU/mL and 6.3 x 103 CFU/mL, respectively. There was no significant difference (p > 0.05) between the rate of mortality of red hybrid tilapia for both serotypes following intraperitoneal challenge. Histopathological lesions included meningitis, necrosis

Given the strong effects of behavioural hierarchies on growth in many cultured species and the key role of feed efficiency in aquaculture economics, understanding the nature of the interaction of these variables is important for the sustainability of aquaculture. The relationship between agonistic behaviour, growth and feed efficiency in Nile tilapia, Oreochromis niloticus, was studied by rearing 120 fish in eight aquaria. Fish were video-recorded to estimate the occurrence of agonistic behaviour during a fasting and a refeeding period. Growth, feed intake and feed conversion efficiency (FCE - calculated as the inverse of feed conversion ratio (FCR)) were subsequently measured individually for each fish. Fish showed 58% less agonistic traits during the fasting period compared to the feeding period, but generally, an aggressive fish during the fasting period was also aggressive during the refeeding period. The nature of agonistic behaviours between individuals was used to assess the presence of hierarchical relationships between fish. There were dominance hierarchies established in each experimental aquarium that despite minor shifts were maintained throughout the experiment. Agonistic behaviours were strongly correlated with each other, the aggression Index (AI) and with hierarchy rank. PCA analysis of the agonistic behaviours summarising the behavioural information showed little or no correlation between agonistic behaviour, fish growth or FCE. FCE was correlated with body weight gain (BWG). These results suggest that agonistic interactions in juvenile Nile tilapia do not have a large impact on growth and feed conversion efficiency.

A feeding experiment was conducted to determine the optimum selenium requirement in juvenile Nile tilapia. Each of six purified diets with Se-methionine levels at 0.05, 0.21, 0.41, 0.57, 0.79 and 1.00 mg/kg was assayed in triplicate with initial body weight of 3.00 ± 0.01 g for 8 weeks. The growth of fish was obviously increased when the dietary Se was less than 0.57 mg/kg diet and reached a plateau when the dietary Se was ≥0.57 mg/kg. Serum and hepatopancreatic glutathione peroxidase (GPx) activity increased markedly when the dietary Se was less than 0.57 mg/kg, but then decreased when the dietary Se was higher than 0.57 mg/kg. The malondialdehyde contents in hepatopancreas were significantly decreased when the dietary Se was higher than 0.79 mg/kg. No significant differences were observed in hepatopancreatic total antioxidant capability (T-AOC) among the groups (p >.05). The results of this study indicated that Se addition as Se-methionine was essential, while both the deficiency and excess levels of dietary Se would cause negative effects on growth or antioxidant capability in juvenile Nile tilapia. Based on broken-line regression of WG and piecewise regression of liver GPx, the optimum requirement of Se for juvenile Nile tilapia is 0.57 mg/kg diet. © 2019 John Wiley & Sons Ltd

The fenofibrate functions in mammals could be affected by many factors such as dietary nutrient levels and physiological status. However, this phenomenon has not been well studied in fish. The goal of our study was to investigate the effect of dietary protein contents on metabolic regulation of fenofibrate in Nile tilapia. An 8-week experiment was conducted to feed fish with four diets at two protein levels (28% and 38%) with or without the supplementation of fenofibrate (200 mg/kg body weight/day). After the trial, the body morphometric parameters, plasma biochemical parameters and qPCR data were examined. These results showed that fenofibrate significantly reduced the feeding intake and weight gain rate, increased the oxidative stress (increased plasma methane dicarboxylic aldehyde, MDA) and liver/body ratio (increased hepatosomatic index, HSI) in the LP (low protein)-fed fish. In contrast, fenofibrate exhibited a lipid-lowering (reduced hepatic lipid) effect and up-regulated the expressions of the genes related to lipid catabolism, transport and anabolic metabolism in the HP (high protein) fed-fish. The present study suggested that lipid-lowering effect of fenofibrate would be strengthened in the fish fed with HP diet containing high energy, but in the fish fed with the LP diet containing low energy, the fenofibrate treatment would cause adverse effects for metabolism. Taking together, our study showed that the metabolic regulation of fenofibrate in Nile tilapia was not only dependent on feed energy content, but also dependent on dietary nutrient composition, such as dietary protein and/or lipid levels. © The Author(s) 2019.

Aquaculture is one of the major contributor of economic resources and food production in Malaysia and tilapia (Oreochromis spp.) was one of the highest value in import and export market. But the production was reported to decrease from 51, 554 MT to 35, 996 MT from 2012 to 2016 respectively due to streptococcosis. Streptococcosis was caused by Streptococcus sp. which is the etiological agent of diseases in human and animals which could lead to different pathological effects. It was suggested that the different pathological effects post infection was caused by genetically distinction of the bacterial strain. Thus, this study was conducted to determine the molecular serotyping, virulence genes profiling and pathogenicity of Streptococcus agalactiae isolated from cultured red hybrid tilapia in Malaysia. A total of 256 isolates of S. agalactiae, isolated from fish in Peninsular Malaysia. Genotype of the bacterial collections was determined using PCR based on the capsular polysaccharide gene clusters and multilocus sequence typing. Subsequently, two serotypes were identified, which were 11% and 89% for serotype Ia ST7 and III ST283, respectively. The profiles of virulence genes were constructed using m-PCR with different types of the various published primers involving 14 standard virulence genes (fbsA, fbsB, pavA, scpB, lmb, cylE, cfb, spb1, hylB, rib, bca, bac, cspA and pbp1A/ponA). Serotype Ia showed different pattern of virulence genes profile compared to serotype III, where it lacked the lmb, scpB, pavA, fbsB, cyl, bca, cspA and bac genes, thats differentiated the virulence level of the serotype. Median lethal dose 50 (LD50) of S. agalactiae in red hybrid tilapia for serotypes Ia and III were calculated at 8.7 x 103 CFU/mL and 6.3 x 103 CFU/mL, respectively. There was no significant difference (p > 0.05) between the rate of mortality of red hybrid tilapia for both serotypes following intraperitoneal challenge. Histopathological lesions included meningitis, necrosis

This study aimed to evaluate the effects of a high carbohydrate diet (HC) alone and HC supplemented with benfotiamine (HCB), a human anti-diabetic supplement, on the growth performance of Nile tilapia fry, Oreochromis niloticus. A total of 180 Nile tilapia fry (AWB=0.01g) were randomly distributed to 9 tanks and fed one of three experimental diets, namely, a control diet containing 15% carbohydrate; high carbohydrate diet (HC) containing 25% carbohydrate; and high carbohydrate diet (25%) supplemented with 0.02% benfotiamine (HCB) for 8 weeks. Increasing corn starch in the diet from 15% (i.e. control diet) to 25% (i.e. HC diet) did not have any effect on the growth performance nor feed efficiency of the Nile tilapia. In contrast, Nile tilapia fed the HCB diet exhibited significantly the highest final average body weight, weight gain, specific growth rate, feed intake and whole-body lipid content and the most efficient FCR among the treatments. Results of the attractability tests showed that the HCB diet significantly attracted the most percentage of fish. In conclusion, the findings indicated that the Nile tilapia efficiently utilized an increase of carbohydrate from 15% to 25% and that dietary benfotiamine significantly increased the utilization of this diet, enhancing further its growth performance and feed utilization; benfotiamine also increased the attractability of the diet.

[EN] Robustness has become a highly desirable breeding goal in the globalized agricultural market. Both genotype-by-environment interaction (G x E) and micro-environmental sensitivity are important robustness components of aquaculture production, in which breeding stock is often disseminated to different environments. The objectives of this study were (i) to quantify the degree of G x E by assessing the growth performance of Genetically Improved Farmed Tilapia (GIFT) across three countries (Malaysia, India and China) and (ii) to quantify the genetic heterogeneity of environmental variance for body weight at harvest (BW) in GIFT as a measure of micro-environmental sensitivity. Selection for BW was carried out for 13 generations in Malaysia. Subsets of 60 full-sib families from Malaysia were sent to China and India after five and nine generations respectively. First, a multi-trait animal model was used to analyse the BW in different countries as different traits. The results indicate a strong G x E. Second, a genetically structured environmental variance model, implemented using Bayesian inference, was used to analyse micro-environmental sensitivity of BW in each country. The analysis revealed the presence of genetic heterogeneity of both BW and its environmental variance in all environments. The presence of genetic variation in residual variance of BW implies that the residual variance can be modified by selection. Incorporating both G x E and micro-environmental sensitivity information may help in selecting robust genotypes with high performance across environments and resilience to environmental fluctuations.