Impact of transportation in freshwater and brackish water on Nile tilapia (Oreochromis niloticus) resistance.

BACKGROUND: Oreochromis niloticus has great economic value and potential for farming and development. Transportation of fish was done for breeding or trading purpose and it is a challenging aspect of aquaculture. This study aimed to investigate the effect of transportation in freshwater and brackish water on the resistance of O. niloticus as well as transportation stress mitigation effect of NaCl. Four equal groups were used; each of 50 fish, the 1st group served as the control (P 1), while the 2nd group (PT 2) was transported in water without salt, the 3rd (PT 3) and 4th (PT 4) groups were transported in water containing 5 gL- 1 and 10 gL- 1 salt respectively. PT 2, PT 3 and PT 4 were transported for 5 h without any rest or sedative drugs. RESULTS: The serum cortisol of O. niloticus significantly increased at 0 h and then decreased at 12 and 24 h post transportation in the PT 2 group and non-significantly increased at all point times in the PT 3 and PT 4 groups comparing to P 1 group. Mucin2 gene (MUC2) expression was non-significantly up regulated in the PT 2 group and down regulated in the PT 3 and PT 4 groups at 0 h comparing with P 1 group, but at 12 and 24 h it was significantly up regulated in the PT 2, PT 3 and PT 4 groups. The ß Defensin-1 (ß D1) and 2 (ß D2) genes expression was non-significantly down-regulated in the PT 2 group and significantly up regulated in the PT 3 and PT 4 groups at 0 h., while at 12 and 24 h was significantly down regulated in the PT 2 group and non-significantly down regulated in the PT 3 and PT 4 groups, it significantly down regulated in the PT 2 and PT 3 group and non-significantly down regulated in the PT 4 group at 24 h. Non-significant up regulation in interleukin - 1ß (IL-1ß) gene expression was reported in the PT 2 group and non-significant down regulation in the PT 3 and PT 4 groups at 0 h. However, significant up regulation was recorded in the PT 2, PT 3 and PT 4 groups at 12 and 24 h. The Tumor necrosis factor-alpha (TNF-α) gene expression was non-significantly up regulated in the PT 2 group and non-significantly down regulated in the PT 3 and PT 4 groups at 0 h. However, it was significantly up regulated in the PT 2, PT 3 and PT 4 groups at 12 and 24 h. CONCLUSION: The results of this study confirmed the stressful effect of transportation on O. niloticus as well as the transportation stress mitigation effect of NaCl.

Replicated Functional Evolution in Cichlid Adaptive Radiations.

AbstractAdaptive radiations highlight the mechanisms by which species and traits diversify and the extent to which these patterns are predictable. We used 1,110 high-speed videos of suction feeding to study functional and morphological diversification in 300 cichlid species from three African Great Lake radiations of varying ages (Victoria, Malawi, and Tanganyika) and an older, spatially dispersed continental radiation in the Neotropics. Among African radiations, standing diversity was reflective of time. Morphological and functional variance in Lake Victoria, the youngest radiation, was a subset of that within Lake Malawi, which itself was nested within the older Tanganyikan radiation. However, functional diversity in Neotropical cichlids was often lower than that in Lake Tanganyika, despite being much older. These two radiations broadly overlapped, but each diversified into novel trait spaces not found in the youngest lake radiations. Evolutionary rates across radiations were inversely related to age, suggesting extremely rapid trait evolution at early stages, particularly in lake radiations. Despite this support for early bursts, other patterns of trait diversity were inconsistent with expectations of adaptive radiations. This work suggests that cichlid functional evolution has played out in strikingly similar fashion in different radiations, with contingencies eventually resulting in lineage-specific novelties.

Interactive effects of water temperature and dietary protein on Nile tilapia: growth, immunity, and physiological health.

Optimizing fish performance depends on several factors, with dietary protein levels and rearing temperature playing important roles. In this study, Nile tilapia fingerlings (Oreochromis niloticus) weighing an average of 20.00 ± 1.26 g were divided into nine groups (in three replicates). Each group was subjected to different water temperatures (26 °C, 28 °C, and 30 °C) and received one of three dietary protein levels (20%, 25%, and 30%) for two months. Our findings indicate that higher temperatures, particularly at 30 °C, increased water electrical conductivity and total dissolved salts, especially noticeable in fish fed 25% or 30% crude protein (CP). Lower total ammonia nitrogen levels were observed at 28 °C with 25% CP, 30 °C with 30% CP, and 26 °C with 30% CP. Hepatic growth hormone receptor 1 and insulin-like growth factor 1 expression gradually rose with higher dietary CP percentages in fish at 26 °C but declined in those at 30 °C, albeit remaining higher than in the 28 °C groups with 25% CP. Fish at 28 °C showed the best final body weights and growth performance when fed 20% or 25% CP, with no significant difference between these groups. Hepatic leptin expression did not differ significantly among groups, but hepatic fatty acid binding protein expression notably increased in fish fed 30% CP at both 26 °C and 30 °C compared to those at 28 °C with 25% CP. Within the same temperature group, fish fed 30% CP exhibited higher globulin levels, particularly thriving at 28 °C or 30 °C. Hepatic mucin-like protein expression significantly increased across all groups, especially in fish at 30 °C with 30% CP compared to those at 28 °C with 25% CP. Hepatic lysozyme expression also increased notably in fish at 30 °C with 30% CP. Notable changes in superoxide dismutase, catalase, and glutathione peroxidase expression were observed, with the highest serum superoxide dismutase and catalase activities recorded in fish at 30 °C with 25% CP. Overall, dietary protein levels of 25% and 30%, combined with temperatures of 28 °C and 30 °C, yielded favorable outcomes, particularly favoring 28 °C with 25% protein.

The regulatory effects of water probiotic supplementation on the blood physiology, reproductive performance, and its related genes in Red Tilapia (Oreochromis niloticus X O. mossambicus).

Probiotics are becoming increasingly popular as eco-friendly alternatives in aquaculture. However, there is limited research on their impacts on the reproductive efficiency of Red Tilapia (Oreochromis niloticus x O. mossambicus) broodstock. Therefore, this experiment aimed to explore the combined effects of selective probiotics Bacillus subtilis and B. licheniformis (BSL; 1:1) added to water on blood hematology, serum metabolites, gonadal histology, reproductive performance, and reproductive associated genes in Red Tilapia broodstock. Tilapia broodfish weighing 140-160 g were stocked in four treatment groups: control (T0), and the other three groups were added different levels of BSL to the water as follows: T1 (0.01 g/m3), T2 (0.02 g/m3), and T3 (0.03 g/m3), respectively. Results indicate that BSL administration significantly improved RBCs, hemoglobin, hematocrit, MCH, and MCHC, with the highest improvement seen in the T3 group (P < 0.05). BSL added to the fish water significantly enhanced serum protein fractions (total protein, albumin, and globulins), while AST, ALT, ALP, creatinine, uric acid, and glucose were significantly diminished in a dose-dependent way (P < 0.05). Adding 0.02-0.03 g/ m3 of BSL resulted in higher antioxidant status (superoxide dismutase and catalase) compared to other groups (P < 0.05). Testosterone levels were higher in T3 than in other groups (P < 0.05). All female hormones (LH, FSH, estradiol, and progesterone) were substantially augmented by the addition of BSL. Additionally, the BSL groups exhibited higher GSI, HSI, VSI (male only), egg diameter (mm), mean number of fry/fish, and mean fry weight (g) compared to the control group (P < 0.05). Expression of reproductive-associated genes (vasa, nanos1a, nanos2, dnd1, pum1, AMH, and vtg) were significantly up-regulated in the gonads of fish in the 0.03 g/m3 treatment. The histological gonadal structure exhibited that BSL improved gonad maturation in both genders of Tilapia fish. Overall, adding a mixture of B. subtilis and B. licheniformis (0.03 g/m3 water) can accelerate reproductive performance in Red Tilapia through up-regulation of reproductive genes and enhance the health profile.

Behavioral dysregulation in Nile tilapia (Oreochromis niloticus, GIFT) post-Streptococcus agalactia infection: Role of the microbiota-gut-brain axis.

In the aquatic farming industry, understanding the factors affecting fish behavior is crucial, particularly in response to infections that compromise welfare and productivity. Swimming performance is a key life history trait critical to their ecology. This study explores the swimming behavior imbalance in Nile tilapia (Oreochromis niloticus, GIFT) post-infection with Streptococcus agalactiae (GBS), a common pathogen responsible for significant losses in aquaculture. We focused on how the microbiota-gut-brain axis influences the behavioral response of tilapia to GBS infection. Behavioral changes were quantified by measuring collision times and swimming speeds, which decreased significantly following infection. This behavioral downturn is mediated by alterations in the microbiota-gut-brain axis, evidenced by increased levels of monoamine neurotransmitters (serotonin, norepinephrine, and dopamine) in the brain and intestinal tissues. The study utilized pharmacological agents, the 5-HT1A receptor agonist (8-OH-DPAT) and antagonist (WAY-100635), to investigate their efficacy in mitigating these behavioral and biochemical changes. Both agents partially restored normal behavior by adjusting neurotransmitter concentrations disrupted by GBS infection. Additionally, a notable increase in the relative abundance of Streptococcus within the gut microbiota of infected fish highlights the potential role of specific bacterial populations in influencing host behavior. This research provides novel insights into the complex interactions between pathogen-induced gut microbiota changes and Nile tilapia's behavioral outcomes, highlighting potential avenues for improving fish health management through microbiota-targeted interventions.

A pheromone receptor in cichlid fish mediates attraction to females but inhibits male parental care.

Reproductive behaviors differ across species, but the mechanisms that control variation in mating and parental care systems remain unclear. In many animal species, pheromones guide mating and parental care. However, it is not well understood how vertebrate pheromone signaling evolution can lead to new reproductive behavior strategies. In fishes, prostaglandin F2α (PGF2α) drives mating and reproductive pheromone signaling in fertile females, but this pheromonal activity appears restricted to specific lineages, and it remains unknown how a female fertility pheromone is sensed for most fish species. Here, we utilize single-cell transcriptomics and CRISPR gene editing in a cichlid fish model to identify and test the roles of key genes involved in olfactory sensing of reproductive cues. We find that a pheromone receptor, Or113a, detects fertile cichlid females and thereby promotes male attraction and mating behavior, sensing a ligand other than PGF2α. Furthermore, while cichlid fishes exhibit extensive parental care, for most species, care is provided solely by females. We find that males initiate mouthbrooding parental care if they have disrupted signaling in ciliated sensory neurons due to cnga2b mutation or if or113a is inactivated. Together, these results show that distinct mechanisms of pheromonal signaling drive reproductive behaviors across taxa. Additionally, these findings indicate that a single pheromone receptor has gained a novel role in behavior regulation, driving avoidance of paternal care among haplochromine cichlid fishes. Lastly, a sexually dimorphic, evolutionarily derived parental behavior is controlled by central circuits present in both sexes, while olfactory signals gate this behavior in a sex-specific manner.

Disruption in cortisol synchrony and pair-dissolution in the serially monogamous convict cichlid (Amatitlania nigrofasciata).

Endocrine synchronization is a biological process often associated with social bonding. The mechanisms that mediate this process have been well studied in many vertebrate clades with evolved complex social behaviors. However, studies focusing on such processes in the less neurologically complex teleost clade are surprisingly lacking. In this study, we investigated the hypothesis that mated pairs of convict cichlids (Amatitlania nigrofasciata) perform cortisol synchronization and that the disruption of this might accompany pair-bond instability. Mated pairs were subjected to both behavioral and non-invasive waterborne hormonal assays to better understand the biological complexity of endocrine synchrony and its role in pair-bonding. Baseline cortisol assays indicated a positive correlation between male and female cortisol levels. Individuals that were subjected to a prolonged separation from their mate exhibited a negative correlation in cortisol synchrony after being reunited with their mate. Cortisol synchrony was disrupted, but pairs did not show a significant variance of intrapair aggression after initial pair reunion. However, more than half of the pairs that received the stressor exhibited significantly higher levels of intrapair aggression than their time matched controls approximately 1-7 days following this reunion, indicating pair-dissolution. Concurrently, pairs who underwent the stressor but maintained their bonds did not display an increase in intrapair aggression and also re-synchronized their cortisol levels. Not only does this study provide crucial insights in regard to the role of cortisol synchrony in serially monogamous systems, but it also suggests that the mechanisms that mediate the synchronization of endocrine through the formation of social bonds are more evolutionarily conserved than originally thought.

Tissue-specific effects of temperature and salinity on the cell cycle and apoptosis in the Nile Tilapia (Oreochromis niloticus).

The Nile Tilapia (Oreochromis niloticus) evolved in warm, freshwater rivers, but possesses a broad physiological tolerance to a range of environmental conditions. Due to this hardiness and resilience, this species has been successfully introduced to regions widely outside of its native range. Here, we examine the impact of temperature and salinity variation on this species at the sub-lethal level. Specifically, Nile Tilapia were exposed to two temperatures (21 °C or 14 °C) and three salinities (0, 16, 34 ppt) for 1-h. Given their native habitat, the 21 °C / 0 ppt exposure was considered the control condition. Both cell cycle arrest and apoptosis represent sub-lethal but deleterious responses to environmental stress. Flow cytometry was used to assess the percentage of cells in a given stage of the cell cycle as a metric of cell cycle arrest in spleen and liver. Percentage of apoptotic cells were also quantified. Spleen was more sensitive to cold stress, demonstrating an increase in cells in the G2/M phase after experimental treatment. Liver, however, was more sensitive to salinity stress, with a significant increase in cells stalled in G2/M phase at higher salinities, which is in keeping with the freshwater evolutionary history of the species. A modest apoptotic signal was observed in liver but not in spleen. Together, these findings demonstrate that even short, acute exposures to cold temperatures and elevated salinity can cause sub-lethal damage in a species that is otherwise tolerant of environmental stress at the whole organism level.

Status-dependent metabolic effects of social interactions in a group-living fish.

Social interactions can sometimes be a source of stress, but social companions can also ameliorate and buffer against stress. Stress and metabolism are closely linked, but the degree to which social companions modulate metabolic responses during stressful situations-and whether such effects differ depending on social rank-is poorly understood. To investigate this question, we studied Neolamprologus pulcher, a group-living cichlid fish endemic to Lake Tanganyika and measured the metabolic responses of dominant and subordinate individuals when they were either visible or concealed from one another. When individuals could see each other, subordinates had lower maximum metabolic rates and tended to take longer to recover following an exhaustive chase compared with dominants. In contrast, metabolic responses of dominants and subordinates did not differ when individuals could not see one another. These findings suggest that the presence of a dominant individual has negative metabolic consequences for subordinates, even in stable social groups with strong prosocial relationships.

Toxicological insight of metiram: immuno-oxidative, neuro-behavioral, and hemato-biochemical changes during acute exposure of Nile tilapia (Oreochromis niloticus).

BACKGROUND: The inappropriate use of pesticides including fungicides creates severe biological hazards that can endanger fish health and impede sustainable aquaculture. OBJECTIVE: This study investigated the negative impacts of metiram (MET), a fungicide on the health status of Nile tilapia (Oreochromis niloticus) for a 96-hour duration as an acute exposure in a static renewal system. METHODS: Three hundred fish (average body weight: 37.50 ± 0.22 g) were assigned into six groups (50 fish/group) with five replicates (10 fish/replicate). Fish were exposed to various six concentrations (0, 1.5, 3, 4.5, 6, and 7.5 mg/L) of MET as a water exposure to for 96-hour without water exchange. The fish's behavior, clinical signs, and mortalities were documented every day of the exposure period. Additionally, MET's impact on blood profile, stress biomarkers, hepato-renal functions, immune-antioxidant status, and brain biomarker were closely monitored. RESULTS: The lethal concentration (LC50) of MET estimated using Finney's probit technique was 3.77 mg/L. The fish's behavior was severely impacted by acute MET exposure, as clear by an increase in surfacing, loss of equilibrium, unusual swimming, laterality, abnormal movement, and a decline in aggressive behaviors. The survivability and hematological indices (white and red blood cell count, differential white blood cell count, hematocrit value, and hemoglobin) were significantly reduced in a concentration-dependent manner following MET exposure. Acute exposure to MET (1.5-7.5 mg/L) incrementally increased stress biomarkers (nor-epinephrine, cortisol, and glucose), lipid peroxides (malondialdehyde), and brain oxidative DNA damage biomarker (8-hydroxy-2-deoxyguanosine). A hepato-renal dysfunction by MET exposure (4.5-7.5 mg/L) was evidenced by the significant increase in the alanine and aspartate aminotransferases and creatinine values. Moreover, a substantial decline in the immune parameters (lysozyme, complement 3, serum bactericidal activity, and antiprotease activity) and antioxidant variables (total antioxidant capacity, superoxide dismutase, and glutathione peroxidase) resulted from acute MET exposure. CONCLUSION: According to these findings, the 96-hour LC50 of MET in Nile tilapia was 3.77 mg/L. MET exposure triggered toxicity in Nile tilapia, as seen by alterations in fish neuro-behaviors, immune-antioxidant status, hepato-renal functioning, and signifying physiological disturbances. This study emphasizes the potential ecological dangers provoked by MET as an environmental contaminant to aquatic systems. However, the long-term MET exposure is still needed to be investigated.

Historical Field Records Reveal Habitat as an Ecological Correlate of Locomotor Phenotypic Diversity in the Radiation of Neotropical Geophagini Fishes.

AbstractPhenotypic macroevolutionary studies provide insight into how ecological processes shape biodiversity. However, the complexity of phenotype-ecology relationships underscores the importance of also validating phenotype-based ecological inference with direct evidence of resource use. Unfortunately, macroevolutionary-scale ecological studies are often hindered by the challenges of acquiring taxonomically and spatially representative ecological data for large and widely distributed clades. The South American cichlid fish tribe Geophagini represents a continentally distributed radiation whose early locomotor morphological divergence suggests habitat as one ecological correlate of diversification, but an association between locomotor traits and habitat preference has not been corroborated. Field notes accumulated over decades of collecting across South America provide firsthand environmental records that can be mined for habitat data in support of macroevolutionary ecological research. In this study, we applied a newly developed method to transform descriptive field note information into quantitative habitat data and used it to assess habitat preference and its relationship to locomotor morphology in Geophagini. Field note-derived data shed light on geophagine habitat use patterns and reinforced habitat as an ecological correlate of locomotor morphological diversity. Our work emphasizes the rich data potential of museum collections, including often-overlooked material such as field notes, for evolutionary and ecological research.

Respiratory and muscular effort during pre-slaughter stress affect Nile tilapia fillet quality.

Nile Tilapia (Oreochromis niloticus) management procedures are directly linked to the final quality of the product. The aim of this study was to evaluate the effect of pre-slaughter density and different stunning methods on biochemical, respiratory and muscle injury parameters associated with quality and sensory characteristics of Nile tilapia fillets. Fish with an average weight of 762±105 g were used, first collected called the control group. The experiment was conducted in a 2 × 2 factorial scheme, with two densities (50 and 300 kg of live weight m-3) and two stunning methods thus totaling four treatments, with 15 repetitions per treatment totaling 75 fish sampled. Blood gas analysis, evaluation of biochemical parameters, analysis of meat quality and sensory analysis were carried out. For blood gas, biochemical and enzymatic parameters, the highest values were obtained for the density of 300 kg m-3 and asphyxia method: partial pressures of CO2; glucose and lactate, the highest values presented were 268.98 and 11.33 mg dL-1 respectively. As well as enzymatic activities, Creatinine kinase (CPK); Creatinine kinase isoenzyme (CKMB) showed higher values (768.93 and 1078.98 mg dL-1 respectively) in the higher density and asphyxia method. Conversely, when evaluating the quality parameters, the highest values were observed for lower density and thermonarcosis. High depuration density (300 kg m-3), combined with the asphyxiation stunning method, promotes changes in respiratory dynamics and provides greater stress, less firm fillet texture and greater weight loss due to cooking, as well as changes in creatine kinase (CK) and its CK-MB isoenzyme, demonstrating greater muscle damage. On the other hand, the density of 50 kg m-3 during pre-slaughter, combined with the method of stunning by thermonarcosis, provide a longer period of permanence in pre rigor mortis, which will result in fillets with a better sensory profile.

Sexual selection may support phenotypic plasticity in male coloration of an African cichlid fish.

The expression of sexually selected traits, such as ornaments or body coloration, is often influenced by environmental conditions. While such phenotypic plasticity is often thought to precede evolutionary change, plasticity itself can also be a target of selection. However, the selective forces supporting the evolution and persistence of plasticity in sexual traits are often unclear. Using the cichlid fish Astatotilapia burtoni, we show that variation in the level of mate competition may promote plasticity in body coloration. In this species, males can change between yellow and blue colour. We found that experimentally increased competition over mating territories led to a higher proportion of males expressing the yellow phenotype. The expression of yellow coloration was found to be beneficial because yellow males won more staged dyadic contests and exhibited a lower level of oxidative stress than blue males. However, females were more likely to spawn with blue males in mate choice experiments, suggesting that expression of blue coloration is sexually more attractive. The ability to adjust colour phenotype according to the local competitive environment could therefore promote the persistence of plasticity in coloration.

Nile tilapia and gilthead seabream dietary self-selection of alternative feeds.

Classical assessments of new fish feeds are anthropocentric, focusing mainly on growth. Although this methodology is accurate, it does not consider the fish' perspective. This study aimed to investigate the behavioural responses and feed preferences of Nile tilapia (Oreochromis niloticus) and gilthead seabream (Sparus aurata) through a self-selection trial using self-feeders. Both species were offered three feeds: a control (PD) commercial-like feed and two diets (ORG1 and ORG2) formulated with different inclusions of alternative ingredients to address some of the current environmental concerns and/or ethical issues often associated with commercial formulations. Three groups of tilapia with an average weight of 163.0 g ± 4.3 g (mean ± SD) and four groups of seabreams with 174.7 g ± 27.0 g were tested. Tilapia exhibited a preference for ORG2 (46.5%), influenced by the sensory properties of the feed and post-ingestion signals. Seabream did not show a preference for any feed. These findings highlight the effectiveness of self-selection experiments in allowing fish to express their feeding behaviour and preferences. Therefore, this approach should be considered in the initial screening and design of new aquaculture feeds and ingredients.

Low temperature inhibits food intake via TRPA1 channel activation in Nile tilapia (Oreochromis niloticus).

Low temperatures significantly influence feeding behavior in ectothermic vertebrates, but the underlying mechanisms remain elusive. This study investigated the role of transient receptor potential ankyrin 1 (TRPA1) channels in mediating the appetite-suppressing effects of low temperature in Nile tilapia. TRPA1 was found to be highly expressed in the hypothalamus and co-localized with neuropeptide Y (NPY) neurons. Exposure to low temperatures reduced feeding frequency and increased TRPA1 expression. In vitro experiments demonstrated that low temperature and TRPA1 agonists induced calcium influx, which was blocked by a TRPA1 inhibitor. TRPA1 expression exhibited post-prandial increases and was downregulated by fasting. TRPA1 activation dose-dependently inhibited food intake, while its inhibition restored feeding suppressed by low temperature. TRPA1 activation downregulated orexigenic factors and upregulated anorexigenic factors through Ca2+/calmodulin-dependent pathways. These findings suggest that TRPA1 plays a crucial role in sensing low temperatures and regulating feeding behavior in tilapia.

Sexually dimorphic control of aggression by androgen signaling in a cichlid.

Innate social behaviors like aggression are modulated by sex steroid hormones such as androgens and estrogens. However, we know little about how the same hormone regulates similar behaviors in both sexes. We investigated the role of androgenic signaling in the regulation of aggression in Astatotilapia burtoni, a social fish in which males and females perform similar aggressive behaviors. We used androgen receptor (AR) α knockout (KO) animals for this study since this gene was recently shown to be required for male-typical aggression and mating. Surprisingly, ARα KO females did not show deficits in aggression. We also determined that females lacking the other AR, ARß, showed normal levels of aggression. Blocking both ARs pharmacologically confirmed that neither AR is necessary for aggression in females. However, ARα KO males showed clear deficits in attacks. Thus, in A. burtoni there appears to be a sexual dimorphism in the role of ARα in the control of aggression.

Optimizing nutrient utilization, hydraulic loading rate, and feed conversion ratios through freshwater IMTA-aquaponic and hydroponic systems as an environmentally sustainable aquaculture concept.

Water quality in land-based fish production can be controlled through either instantaneous water exchange or costly wastewater treatment followed by recirculation. Agricultural-aquaculture integration is an excellent alternative technique for reducing nutrient discharge levels, boosting profitability, and converting fish culture wastewater into valuable products. The current study employed a solar energy system to power two separate IMTA-aquaponics systems (Nutrient Film Technique, NFT, and Floating Raft Systems, FRS) for the cultivation of Nile tilapia, African catfish, thin-lipped grey mullet, freshwater crayfish, freshwater mussels, and a variety of vegetables. Tilapia and catfish were fed exclusively on diets under the IMTA system. All wastewater from tilapia and catfish ponds, both dissolved and solid, flows sequentially to ponds containing other cultivated species. The water then flows through the IMTA system's terminal point to the NFT and FRS systems before returning to the tilapia and catfish ponds, allowing complete control of the nutrient flow throughout this entire circular system. Two 147-day production cycles were concluded. The results from the second production cycle are reported. Total biomass gain for aquatic species in the IMTA system was 736.46 kg, compared to 145.49 kg in the tilapia and 271.01 kg in the catfish monoculture systems. The current IMTA system had a cumulative feed conversion ratio (FCR) of 0.90, while the FCRs for tilapia and catfish were 1.28 and 1.42, respectively. Nile tilapia and catfish consumed 571.90 kg of feed containing 25.70 kg of nitrogen (N) and 9.70 kg of phosphorus (P), reflecting, and gaining 11.41 and 3.93 kg of dietary N and P, representing 44.40 and 40.46% dietary N and P retention, respectively. In the IMTA system, the addition of mullet and prawn as detrivores aquatic animals improves dietary N and P utilization efficiency to 59.06 and 51.19%, respectively, while the addition of mussels as herbivore animals improves dietary N and P utilization efficiency to 65.61 and 54.67%, respectively. Finally, using FRS and NFT as hydroponic systems increased dietary N and P efficiency to 83.51% N and 96.82% P, respectively. This study shows that the IMTA-Aquaponic system, as a bio-integrated food production system, can convert the majority of fish-fed residues into valuable products suitable for desert, rural, and urban areas in impoverished and developing countries.

Arthrospira platensis nanoparticles dietary supplementation improves growth performance, steroid hormone balance, and reproductive productivity of Nile tilapia (Oreochromis niloticus) broodstock.

This study evaluates the impact of dietary supplementation of the blue-green alga Arthrospira platensis NIOF17/003 nanoparticles (AN) on the growth performance, whole-body biochemical compositions, blood biochemistry, steroid hormonal, and fry production efficiency of Nile tilapia (Oreochromis niloticus) broodstock, during the spawning season. After a 21-day preparation period to equip the females and ensure that their ovaries were filled with eggs, mating between the mature females and males took place in a 3:1 ratio during a 14-day spawning cycle. A total of 384 tilapia broodstock 288 females and 96 males with an initial body weight of 450.53±0.75, were divided into four groups; AN0: a basal diet as a control group with no supplementation of Arthrospira platensis, and the other three groups (AN2, AN4, and AN6) were diets supplemented with nanoparticles of A. platensis at levels of 2, 4, and 6 g kg─1 diet, respectively. The results found that fish-fed group AN6 showed the highest significant differences in weight gain (WG), final weight (FW), feed conversion ratio (FCR), protein efficiency ratio (PER), and feed efficiency ratio (FER). Females fed the AN6 diet showed the highest significant fat content. Compared to the AN0 group, fish fed on the supplemented diets showed significant improvement (p < 0.05) in triglyceride, glucose, and aspartate aminotransferase (AST). A gradual increase in AN inclusion level resulted in a gradual increase in the concentrations of luteinizing hormone (LH), and follicle-stimulating hormone (FSH), testosterone, progesterone, and prolactin. The rates (%) of increase in fry production for females fed supplemented diets were 10.5, 18.6, and 32.2% for AN2, AN4, and AN6, respectively, compared to the control group. This work concluded that the inclusion levels of 6 g kg─1 of A. platensis nanoparticles in the diet of Nile tilapia broodstock significantly improved the growth performances, steroid hormone concentrations, and increased the fry production efficiency by 32.2%, respectively. These findings revealed that A. platensis nanoparticles resulted in a significantly enhanced female' reproductive productivity of Nile tilapia broodstock.

Investigating the optimum stocking density of tilapia (Oreochromis niloticus) for intensive production focused to in-pond raceway system.

The primary objective of this trial was to study the effects of stress caused by stocking density in tilapia (Oreochromis niloticus) cultured in the in-pond raceway system (IPRS). Fingerlings (Initial body weight = 30.00 ± 1.20 g) were reared at different stocking densities i.e. low stocking density (n = 13,000; 1.77 kg/m3), medium stocking density (MSD) (n = 17,000; 2.32 kg/m3), and high stocking density (HSD) (n = 21,000; 2.86 kg/m3), all confined within the raceways of the IPRS. Each group was studied in triplicates. The observed growth revealed a regression in the HSD treatment, evident in its reduced weight gain per fish per day, in contrast to other treatments. Survival rate across all treatments was above 99%. Notably, the HSD treatment exhibited an elevated level of cortisol; however, this intensified crowding stress did not significantly undermine the nutritional value of the fish in HSD and other experimental treatments. Furthermore, an elevation in the levels of superoxide dismutase, catalase, and glutathione peroxidase was noted within the HSD treatment in comparison to the other treatments to reduce the damage caused by reactive oxygen species. As the trial proceeded, functions of digestive enzymes like amylase, protease, and lipase diminished consistently across all treatments. This could possibly signify a deliberate redirection of energy resources toward stress alleviation rather than the usual digestive processes. In summation, it can be reasonably deduced that a stocking density of approximately 2.32 kg/m3 (MSD) emerges as the optimal threshold for effectively cultivating tilapia within an intensive aquaculture framework.