Dualistic feeding pattern of Nile tilapia (Oreochromis niloticus,L.) reared under different self‐feeding system conditions

Nile tilapia (Oreochromis niloticus) is one of the most important cultured species worldwide. The research aims to clarify the feeding characteristics, such as daily feeding pattern of Nile tilapia using a self‐feeding technique. The feeding pattern was conducted under two rearing conditions, indoor treatments under a controlled light regime (LD 12:12) and constant water temperature (25°C), and outdoor treatments under natural conditions which consisted of duplicate trials with two periods each. The outdoor treatment was carried out from early summer through late autumn in Mie, Central Japan. Daily self‐feeding activity of Nile tilapia in indoor treatments was nearly daytime feeding pattern, synchronizing with the given photoperiod (24 hr). However, the self‐feeding activity in the outdoor experiments from early summer to early autumn was almost daytime feeding pattern, but it became less clear and shifted to a nighttime feeding profile in late autumn. The results revealed that Nile tilapia has a dualistic capacity for demand‐feeding both in light and dark phases. These results might have been caused by the seasonal change in light intensity and/or water temperature. Information obtained from the self‐feeding experiments enables us to identify the influence of environmental changes on the physiological condition of farmed fish through their expression of appetite.     

Effect of Arthrospira supplementation on Oreochromis niloticus gut microbiota and flesh quality

Supplementing fish feed with Arthrospira platensis has several beneficial effects, such as improved growth, survival and feed conversion, but little is known about how it affects gut microbiota or flesh quality. In this trial, feed with 3% A. platensis was given to Oreochromis niloticus (SPR, spirulina supplemented) over a period of 50 days and their gut microbiota and flesh quality were compared with controls (CTRs, no supplementation). Average daily growth was higher in SPR fish (p < 0.05). Regarding microbiota, a total of 5,470,272 readings (individuals) were obtained from 16 gut samples (n = 8 CTR, n = 8 SPR), with a gamma diversity of 1,563 species but no significant differences were found between treatments. Among the high inter‐individual variability found, some individual microbiota were dominated by Proteobacteria (36.6%) and Fusobacteria (32.9%) and others more by Actinobacteria (37%). Regarding flesh quality, significant differences were observed in flesh colour post‐mortem (a*, b* and chroma) (p < 0.05), with higher reflectance in the range of 470–500 and 620–670 nm in SPR tilapia, which corresponds with the reflectance range of β‐carotene and phycocyanin. However, rigor mortis was resolved earlier in SPR fish (p < 0.05), which suggests a shorter shelf life. Adding 3% of A. platensis in O. niloticus diet can improve growth and flesh colour and does not appear to modify intestinal microbiota.     

Moderate salinities enhance growth performance of Nile tilapia (Oreochromis niloticus) fingerlings in the biofloc system

The biofloc technology (BFT) has recently gained attention as an economic and environmentally sustainable system for aquaculture. The use of BFT with salinized water could be used to minimize the negative effects of nitrogenous waste and improve the growth performance of Nile tilapia. This work evaluated the growth performance, survival, gill lesions, and fillet composition of tilapia fingerlings (Oreochromis niloticus) reared during 70 days with different salinities (0, 4, 8, 12, and 16 g/L) in a biofloc previously developed. The results indicated that the use of mature bioflocs alone was sufficient to avoid fingerling mortality due to nitrite peaks. Moreover, the salinized water, especially between 4 and 8 g/L (maximum points around 6 g/L), can be recommended in BFT to improve the growth performance of tilapia in the initial culture phase. The salinity level that was evaluated did not affect fillet composition nor the occurrence of gill lesions. The total ammonia nitrogen concentration was lower in freshwater than in salinized water (p < 0.05). Nitrite peaks in salinities of 12 and 16 g/L appeared later and were higher in comparison to other treatments. Considering minimal water exchange in BFT, the use of salinized water in this system may be environmentally viable.     

Combined effects of temperature and salinity on yolk utilization in Nile tilapia (Oreochromis niloticus)

The combined effects of temperature and salinity on the yolk utilization of sac fry in Nile tilapia (Oreochromis niloticus) were investigated using central composite experimental design and response surface approach. Based on the preliminary trials, temperature was determined to range from 22 to 34°C, and salinity ranging from 2 ppt to 10 ppt. The utilization was mensurated in terms of yolk sac volume. Results showed that the linear effects of temperature and salinity on the yolk utilization was significant (P < 0.01); the quadratic effects of and the interaction between the two factors were significant (P < 0.05); temperature was more important than salinity in influencing the yolk utilization. The model equation of yolk sac volume towards temperature and salinity was established. From those high R² values, the model had excellent goodness of fit to experimental data and could be applied for predictive purpose. What with the production cost, it is suggested that the temperature/salinity combination, i.e. 28–30°C/4–6 ppt, be employed during the period of sac fry rearing, in which the yolk utilization was on average 98.6%.     

Determination of histological and genotoxic effects of formalin on Nile tilapia (Oreochromis niloticus L.)

Formalin (37–40% formaldehyde) is one of the most effective, widely used chemical in pisciculture for its antiparasitic, antifungal and prophylactic activities. It is used in paints, cleaning products and textile industry, as well. Genotoxic and histological effects of sublethal formalin exposure on Nile tilapia (Oreochromis niloticus) are investigated in this study. The semi‐static acute test was employed. One‐tenth, one‐fifth and half of the 96‐h LC₅₀ value, 148 mg L^?1, were used as sublethal exposure concentrations: 15, 30 and 75 mg L^?1 for 24, 48, 96 and 168 h respectively. The micronucleus test was applied to investigate the genotoxic effects on fish erythrocytes at the end of predetermined exposure periods and all tissues of the fish were sampled for histological examination. The micronucleus frequencies increased significantly in all exposure groups when compared with their control groups in a dose and time dependent manner (P < 0.05). Results of histological examination showed no histopathological findings in the gonads, heart, skeletal muscle, spleen and intestine tissues after sublethal formalin exposure. Passive hyperaemia of liver tissue in varying proportions, hydropic degeneration, fatty degeneration in high concentrations, branchitis on gill tissues in varying proportions, epithelial lifting, telangiectasia, bleeding in kidney and hyperaemia were found in Nile tilapia exposed to formalin at different concentrations and durations. As a result, it is thought that formalin leads to tissue damage and shows genotoxic effects even at 15 mg L^?1 concentration in O. niloticus.     

CD40 induces an antimicrobial response against the intracellular pathogen Streptococcus agalactiae in Nile tilapia,Oreochromis niloticus

Streptococcus agalactiae is a Gram‐positive facultative intracellular bacterium that leads to severe economic loss of tilapia worldwide. Previous studies demonstrated that CD40 contributes to host protection against intracellular injection. In this study, CD40 was characterized from Nile tilapia (Oreochromis niloticus), named OnCD40. Sequence analysis showed that open reading frame of OnCD40 was 933 bp, containing a single peptide, a transmembrane domain and four cysteine‐rich domains. The qRT‐PCR revealed that OnCD40 was expressed in all examined tissues with the most abundant ones in spleen and thymus. After S. agalactiae stimulation, the expression of OnCD40 was significantly induced in most of the detected organs. Moreover, OnCD40‐overexpressing fish elicited significant protection against subsequent S. agalactiae challenge; approximately 10000‐fold fewer bacteria were detected in spleen of OnCD40‐overexpressing fish in comparison with control fish. Thus, CD40 had protecting function in Nile tilapia against intracellular pathogens.     

Zingiber officinale and Glycyrrhiza glabra,individually or in combination,reduce heavy metal accumulation and improve growth performance and immune status in Nile tilapia,Oreochromis niloticus

This study evaluated the impact of dietary ginger and liquorice supplementation on growth performance, physiological and histopathological profiles and heavy metal accumulation in Nile tilapia fingerlings. Fish (n = 1,800, 17.5 ± 0.11 g BW) were randomly distributed into four treatment groups in triplicates and received no supplementation (control group), 5 ml aqueous ginger extract/kg feed (ginger group), 4 ml aqueous liquorice extract/kg feed (liquorice group) or 2.5 ml ginger plus 2 ml liquorice aqueous extracts/kg feed (mix group). The ginger‐liquorice mix supply improved the growth performance and feed efficiency (p < .05), increased the haematocrit and haemoglobin (p < .05), leucocytes (p = .108), neutrophils (p = .054), serum total protein (p < .05), albumin (p = .011) and globulin (p = .094) but decreased (p < .05) the blood urea nitrogen and creatinine than feeding liquorice or ginger lonely compared to the control. Heavy metal loads in pond water induced lamellar telangiectasis of gills and necrosis with sloughing of intestinal villi tips. These detrimental effects were alleviated, and the intestinal villus length (p = .041) and crypt depth (p = .069) were increased with liquorice supply. In all treatment groups, heavy metal contents in fish flesh were lower compared to the control. Thus, using ginger and/or liquorice aqueous extracts can decrease heavy metal accumulation in the fish flesh and exert positive effects on growth performance, metabolic profile and the intestinal and gill morphology of Nile tilapia.     

Dietary supplementation of Tribulus terrestris extract improves growth and reproductive performances of the male Nile tilapia (Oreochromis niloticus)

Effects of dietary supplementation of Tribulus terrestris (TT) and 17α‐methyl testosterone (MT) on growth performance and reproductive efficiency of male Nile tilapia, Oreochromis niloticus (N = 75, initial weight 60 ± 3.251 g), were evaluated. Five experimental treatments in triplicate were fed on basal diet (30% crude protein) (control group, CG), basal diet containing 60 mg MT (MT group) and basal diet containing 250, 500 and 750 mg/kg diet TT (TT250, TT500 and TT750 groups), respectively, for consecutive 45 days. Results revealed that the fish received TT in diet showed better growth performance (final body weight, weight gain, feed conversion ratio, specific growth rate, testes weight and gonadosomatic index) compared with MT and CG (p < .05), as well as for haemoglobin content and red blood cell count (p < .05). The highest level of testosterone, 11‐keto testosterone, sperm concentration and vitality was recorded in TT750 followed by TT500, TT250 and MT groups, while the lowest value was recorded in the CG (p < .05). The highest seminiferous tubule diameter was recorded in TT750 followed by TT500, TT250 and CG, while the lowest diameter was recorded in the MT group (p < .05). Fish received TT showed normal dilated seminiferous tubule filled with large amount of free sperms within their lumen in a dose related effect. In conclusion, male Nile tilapia dietary supplementation with different inclusions of Tribulus terrestris extract specially 500 and 750 mg/kg diet improves growth performance, health condition, semen quality and reproductive efficiency without any harmful effect on water quality.     

投喂鲍内脏多糖对罗非鱼肠道菌群结构的影响

利用PCR-DGGE和Illumina测序技术研究了罗非鱼(Oreochromisniloticus)肠道菌群结构及饲喂鲍内脏多糖后罗非鱼肠道菌群的动态变化。在罗非鱼肠道中检测到13个门的细菌,其中梭杆菌门(Fusobacteria,77.84%)为优势菌门,拟杆菌门(Bacteroidetes, 8.59%)、衣原体门(Chlamydiae, 6.18%)、变形菌门(Proteobacteria, 5.84%)和放线菌门(Actinobacteria, 1.20%)为次优势菌门,还检测到Saccharibacteria等8个菌门和一些未知类群。在属的水平上,优势菌属为鲸杆菌属(Cetobacterium)、Neochlamydia、邻单胞菌属(Plesiomonas)和不动杆菌属(Acinetobacter),分别占77.84%、5.796%、2.64%和1.13%,还有一个紫单胞菌科(Porphyromonadaceae)的未知属,占8.29%。此外还有分枝杆菌属(Mycobacterium)等6个菌属和一些未知属。投喂添加鲍多糖的饲料对罗非鱼肠道微生物的构成造成了明显影响,饲喂鲍多糖的处理组和饲喂普通饲料的对照组样品分别聚为两大类。投喂添加鲍多糖饲料后,放线菌门、Saccharibacteria、疣微菌门和TM6_Dependentiae的丰度显著下调;在属的水平上,邻单胞菌属、鲸杆菌属的丰度上调;Neochlamydia、不动杆菌属、分枝杆菌属、Alsobacter、Aquicella、假单胞菌属、气单胞菌属、Alpinimonas等属的丰度下调。其中分枝杆菌属、Alsobacter、Aquicella和邻单胞菌属的丰度与对照差异显著(P0.05)。在种水平上,一些潜在致病菌,如鲍曼不动杆菌(Acinetobabacterbaumannii)、龟分枝杆菌(Mycobacteriumabscessus)、Aeromonas sharmana、耐酪酸冢村菌(Tsukamurella tyrosinosolvens)、铜绿色假单胞菌(Pseudomonas aeruginosa)等的丰度下调,其中龟分枝杆菌和耐酪酸冢村菌与对照差异显著(P0.05),而鲸杆菌属等有益菌的丰度上调。本研究从肠道微生物的角度来研究鲍内脏多糖对宿主的影响,为海洋生物活性物质的功效评价提供了新思路,也为鲍内脏活性物质的开发利用、益生元的研制等奠定理论基础。     

Effects of putative dietary probiotics from the gut of milkfish (Chanos chanos) on the growth performance and intestinal enzymatic activities of juvenile Nile tilapia (Oreochromis niloticus)

Enzymes synthesized by the gut microbiome are recognized as vital for assisting host metabolism. This study was conducted to screen and identify bacterial isolates with enzyme-producing abilities from the intestine of milkfish Chanos chanos. Overall, 114 isolates were collected, of which 58% showed clear zones indicating various enzyme activities via plate-based assays. Specifically, 65 isolates were amylolytic, 1 isolate was cellulolytic, and 18 isolates exhibited both activities. The two most promising isolates—CC8 and CC27—were further subjected to spectrophotometric enzyme assays to determine their amylase, cellulase and protease activities. Results showed that amylase, cellulase and protease activities (6.00 ± 0.01, 0.52 ± 0.02 and 18.62 ± 0.16 U mg^?1 protein, respectively) were higher in CC8 than in CC27. Using 16S rRNA gene sequencing, the isolates were putatively identified as Vibrio sp. and Bacillus cereus respectively. At a suspension (mL) to feed (g) ratio of 3:25, dietary supplementation of putative probiotics was carried out to evaluate the growth performance, survival and enzymatic activities of juvenile Nile tilapia Oreochromis niloticus. Results revealed that probiotic-supplemented fish exhibited better growth performance—final average body weight, weight gain, specific growth rate and feed conversion ratio—along with increased intestinal enzymatic activities compared with the control (p < 0.05). Survival rates ranged from 80% to 90% and were statistically similar in all treatments (p > 0.05). This study concludes that the application of Vibrio sp. CC8 and Bacillus cereus CC27, supplemented either in monostrain or multistrain preparation, can promote growth and enzymatic activities in juvenile Nile tilapia.     

Evaluation of hydrolysed rubber seed meal as a dietary protein source for Nile tilapia Oreochromis niloticus L.

This study evaluated the use of hydrolysed rubber seed meal as a locally grown alternative feed ingredient to reduce the use of fishmeal within formulated feeds for tilapia. Five experimental diets were prepared by formulating different inclusion levels of hydrolysed rubber seed meal (0%, 25%, 50%, 75% and 100% of plant‐based protein contribution). Dried and defatted rubber seed meal was hydrolysed by adding rumen digesta liquid to the ingredient. For digestibility measurement, chromic oxide was added to each diet as an inert marker. The digestibility trial was conducted over a 14‐day period by collecting faecal matter from the rearing tanks. In addition, a growth trial was conducted over a period of 50 days using four replicates per dietary treatment. In both experiments, all fish were fed three times daily to apparent satiation. At the end of growth trial, the inclusion level of hydrolysed rubber seed meal up to 50% of plant‐based protein contribution did not give any significant difference compared to the control diet in terms of feed efficiency, specific growth rate and protein retention parameters. In the digestibility study, fish fed diets containing hydrolysed rubber seed meal up to a 50% of plant‐based protein inclusion level did not give any significant difference compared to the control diet in terms of protein and dry matter apparent digestibility. Based on the result of this growth and digestibility study, up to a 50% of plant‐based protein contribution of hydrolysed rubber seed meal can be used within formulated tilapia feeds without any adverse effect.     

Generation of mouse monoclonal antibodies specific to tilapia immunoglobulin using fish immunoglobulin/BSA complex for monitoring of the immune response in Nile tilapia Oreochromis niloticus

The simple immunoprecipitation method was used to isolate tilapia immunoglobulin (Ig) for immunization in order to produce monoclonal antibodies (MAbs) specific to tilapia Ig. First, the tilapia antiserum against bovine serum albumin (BSA) was prepared by peritoneal injection of BSA into tilapia, and the tilapia anti‐BSA antiserum was used to precipitate BSA to form the Ig/BSA immune complex. The Ig/BSA immune complex was then injected into Swiss mice for hybridoma production. After fusion, three hybridoma clones producing MAbs specific to the tilapia antibody were selected by dot blot and Western blot. All MAbs (101A, 59G, and 11A) were bound specifically to the heavy chain of immunoglobulin M (IgM). The MAbs 101A and 59G demonstrated twofold higher affinity than MAb 11A and the commercialized antibody. However, MAbs 11A could also bind to the heavy chain of IgM in Asian seabass, Lates calcarifer, as well. These MAbs can be used to monitor the immune responses of individual fish by indirect ELISA upon exposure to various antigens.     

Physiological responses and HSP70 mRNA expression of GIFT strain of Nile tilapia (Oreochromis niloticus) under cold stress

An investigation on the physiological responses and HSP70 expression under cold stress was conducted on Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia (Oreochromis niloticus). Tilapia were acclimated at 28°C as control and then the water temperature was reduced from 28°C to 15°C at a rate of 1°C h^?1, and serum biochemical indices, antioxidant enzymes and expression of HSP70 mRNA were analysed on days 0, 0.5, 1, 2, 3 and 5 after exposure to 15°C. The concentration of serum K, Na, Cl and Ca concentration showed instability during cold stress. Glucose rapidly increased on day 0 followed by a declining trend. Triglyceride, cholesterol, low density lipoprotein‐cholesterol signifi‐cantly decreased and high density lipoprotein‐cholesterol showed instability during cold stress. Aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase activities were prominently elevated under cold stress. Superoxide dismutase and catalase activities showed a remarkable rise on day 0.5 under cold stress, and gradually decreased thereafter. HSP70 mRNA level significantly increased both in liver and muscle under cold stress, especially on days 0.5 and 1. These results suggest that cold influences several physiological responses of tilapia, and the cold resistance and cold tolerance of tilapia will benefit from the enhancement of antioxidant enzymes activities and upregulated HSP70 mRNA expression.     

Utilization of Caridina nilotica (Roux) meal as a protein ingredient in feeds for Nile tilapia (Oreochromis niloticus)

The effects of replacing fish meal with Caridina nilotica as a protein ingredient on growth performance, nutrient utilization, carcass, proximate composition and economic benefits in Nile tilapia (Oreochromis niloticus) culture was evaluated. Replacement of the FM with C. nilotica was done at 25%, 50%, 75% and 100% (D25, D50, D75 and D100) and the substitution effects was compared with the control diet (D0, 0% C. nilotica). After 140 days of culture, the best growth performance, nutrient utilization and economic benefits occurred in fish groups fed diets with 25% C. nilotica inclusion. However, growth performance in fish fed diets D50 and D75 were comparable with the control (P > 0.05). At 100% substitution level of FM with C. nilotica, the growth performance and fish survival was lower than control. Protein and lipid contents in the fish and their digestibilities were highest in diet D25 and decreased with increasing levels of substitution of FM with C. nilotica. This study demonstrate that utilization of local protein sources (C. nilotica) can be effectively used to replace up to 75% of FM in the diets without compromising growth performance, survival, nutrient utilization and economic benefits in O. niloticus culture.     

Feed intake,growth and metabolism of Nile tilapia (Oreochromis niloticus) in relation to dissolved oxygen concentration

The objectives of the present study were to determine, for Nile tilapia of different body weights and fed to satiation, (1) the incipient dissolved oxygen (DO) concentration at which feed intake starts to level off and (2) the effect of DO on nitrogen and energy balances. Two successive experiments were conducted with two weight classes of male Nile tilapia (>200 g, Experiment 1, and <100 g, Experiment 2). Twelve aquaria were assigned to four DO levels in each experiment. Fish were fed to apparent satiation for 16 and 20 days in Experiments 1 and 2 respectively. The DO‐feed intake curve of fish<100 g appeared to level off at a DO of 3 mg L^?1, while that of fish>200 g continued to increase as DO increased from 2.6 to 6.0 mg L^?1. The latter curve suggests that the incipient DO for fish>200 g is about 5.5 mg L^?1. Fish tended to reduce the energy requirement for maintenance as DO declined. A DO reduction caused an increase in the apparent digestibility coefficient (ADC), but further declines in DO to levels below a critical level decreased ADC. The DO did not have a considerable effect on the metabolizable energy: digestible energy ratio of the diet.     

The sparing effect of cystine on methionine at a constant TSAA level in practical diets of juvenile Nile tilapia Oreochromis niloticus

The feeding experiment was conducted to evaluate the replacement effect of cystine on methionine at a constant total sulphur amino acid (TSAA) level in practical diets of juvenile Nile tilapia (Oreochromis niloticus). Soybean meal, cottonseed meal and rapeseed meal were used as the main protein sources in the diets containing 16.4 MJ kg^?1 gross energy and 301 g kg^?1 crude protein. Crystalline DL‐methionine (Met) to L‐cystine (Cys) were supplemented to fulfil various ratios of Met to Cys (60:40, 50:50, 40:60 and 30:70, based on an equimolar sulphur basis; and the analysed ratios were 53:47, 49:51, 34:66 and 31:69). Each diet was fed to triplicate groups of Nile tilapia juveniles (10.1 g mean initial weight) in a recirculation system for 8 weeks. The results showed that the growth performance and nutrient accretion were not affected by dietary methionine:cystine ratios (P > 0.05). However, the survival rates of fish tended to decrease with the decreasing methionine: cystine ratios. The only dietary treatment to achieve 100% survival was the 53:47 methionine: cystine treatment. And methionine digestibility decreased linearly with the decreasing methionine: cystine ratios (P < 0.05). Thus, it was concluded that cystine could replace up to approximately 47% of TSAA requirement on an equimolar sulphur basis without hampering growth performance in the practical diets of juvenile Nile tilapia.     

Attractability and palatability of liquid protein hydrolysates for Nile tilapia juveniles

The experiment was conducted with the aim of determining the attractability and palatability of liquid protein hydrolysates for Nile tilapia. Five experimental diets were formulated containing 5% inclusion of fishmeal (FPE; positive control), 5% inclusion of liquid protein hydrolysate of porcine mucosa (PHM), 5% inclusion of liquid protein hydrolysate of poultry (PHF), 5% inclusion of liquid fish oil (OPE) and a diet without fishmeal (negative control). Five juveniles (2.51 ± 0.13 g) were distributed in 10 L tanks, and the animals were fed five times a day, with a previous draw being made of the offered diets. The same amount of pellets was offered and the following feeding behaviours were evaluated with the aid of three‐minute footages per feeding: time to capture first pellet, number of rejections, number of approaches without capturing the pellet and number of consumed pellets. None of the observed parameters displayed significant differences (p > .05), and all diets presented negative palatability indexes in comparison to FPE. The SPE diet provided a attractability and palatability index of 6.17%, while OPE index was 2.87%, PHM 2.82% and PHF 2.74%. Both PHF and PHM reduced the final consumption of pellets in comparison to FPE in approximately 28% and 20%, respectively, although it did not present significant values.     

A new approach to fishery waste revalorization to enhance Nile tilapia (Oreochromis niloticus) digestion process

The main goal of this research was to analyse in vitro compatibility of Nile tilapia (Oreochromis niloticus) digestive proteinases and enzymes recovered from species comprising fishery waste as Pleoticus muelleri, Artemesia longinaris and Patagonotothen ramsayi. It evaluated the use of exogenous enzymes as feed supplements to increase digestion efficiency in tilapia fingerlings and juveniles (3.5 ± 0.11 g and 11.6 ± 1.5 g, respectively). We successfully have obtained proteinases from fishery waste as source of exogenous enzymes. P. muelleri and A. longinaris enzymes had more activity of acid and alkaline proteinases than P. ramsayi. SDS‐PAGE gels demonstrated that Nile tilapia digestive proteinases keep their activity when combined with each exogenous proteinase. Exogenous enzymes varied in their ability to enhance hydrolysis of different feed ingredients. P. muelleri by‐products are the best candidates to be employed as feed supplements for tilapia juveniles. Enzymes from this by‐product did not affect the activity and integrity of fish digestive enzymes, improved the hydrolysis of different protein sources (fish meal, squid meal, shrimp meal and soybean meal), and maintained its activity after being exposed to high temperatures and acid pHs. Our findings are applicable to other places where O. niloticus is raised utilizing local fishery waste, and also to different cultured species.