Nile Tilapia Larvae Research Articles

Comparative effect of proviron and 17 α-methyltestosterone on sex ratio of Nile tilapia (Oreochromis niloticus Linnaeus, 1758) fry

ABSTRACT The present study investigated the effect of the proviron, oral anabolic steroid on undifferentiated Nile tilapia (Oreochromis niloticus) larvae sex reversal and to compare its effect with that of 17 α-methyltestosterone. Thus, doses of 25 mg, 50 mg and 75 mg proviron versus 60 mg/kg for 17 α-methyltestosterone were incorporated in the diet of 10-days-post-fertilization old larvae for 28 days. At the end of the treatment and after pre-growth until 90 days post-fertilization, we carried out sexing. Results displayed male rates ranged from 65.7 ± 3.1% to 96.7 ± 1.1% for treatments with 25 mg and 75 mg proviron, respectively and was 99 ± 0.1% for that with 17 α-methyltestosterone. However, no significant difference (p > .05) was found between the average male rate of larvae fed the feed containing 75 mg of proviron and that of larvae fed the feed that containing 17 α-methyltestosterone.

Exploring the nutritional potential of Monoraphidium littorale and enriched copepods as first feeds for rearing Nile tilapia (Oreochromis niloticus) larvae

One of the challenges in the aquaculture industry is providing nutritionally balanced and environmentally sustainable live food for fish larvae. Therefore, the rearing techniques of fish larvae with preferred starter food should be given importance for obtaining optimal hatchery production. Nile tilapia, Oreochromis niloticus larvae just after yolk absorption (body length 0.950 ± 0.004 mm; body weight 6.00 ± 0.02 mg) were reared in laboratory conditions for 16 days, feeding with 6 different diets to know their effect on survival and growth. The diets were live Monoraphidium littorale (T1), live enriched copepods with M. littorale (T2), powdered M. littorale (T3), powdered enriched copepods (T4), live M. littorale + live enriched copepods (T5), and powdered M. littorale + powdered enriched copepods (T6). The proximate composition, amino acid profile and fatty acid content of both M. littorale and copepods were analyzed. The biochemical analysis of the dried powder of enriched copepods and M. littorale revealed that both of them are excellent sources of protein, amino acids, and lipids, especially with monounsaturated and polyunsaturated fatty acids. The O. niloticus larvae fed the T2 diet exhibited the most favourable outcomes, with significantly higher larval gain in weight and percent weight gain, in comparison to the larvae fed other diets (p < 0.001 for all comparisons). The LG% and SGR of the larvae were also significantly higher in T2 in comparison to the T1, T3, T4, and T6 (p < 0.001 for all comparisons) except T5. In addition, the highest percent survival rate of the larvae was observed in T2 (95 %) followed by T4 (93 %), T6 (93 %), T3 (82 %), T5 (73 %) and then T1 (43 %). Based on the present findings, it is recommended that live copepods enriched with M. littorale can be utilized as a starter food for the rearing of Nile tilapia, O. niloticus larvae in hatcheries because of its enriched nutritional profile.

Use of zooplankton prey in aquaculture production of Nile Tilapia (Oreochromis niloticus Linnaeus, 1758) in Daloa, Côte D'Ivoire

The aim of the study carried out at the Ouattara N'golo fish farm in Daloa was to contribute to the improvement of fish production in Côte d'Ivoire through the production of Nile tilapia fed on zooplankton prey. Larvae of the Brazilian strain of Oreochromis niloticus, with an initial weight of 0.03 ± 0.01 g and an initial total length of 1.7 ± 0.1 cm, were distributed in triplicate in three plastic tanks. Fish in BAC 1 were fed only low-grade rice flour (LSRF), while those in BAC 2 were fed LSRF and live zooplankton (LSRF + ZOO). Fish in BAC 3 were fed mainly live zooplankton (ZOO). The main results show that fish fed with low-grade rice flour and live zooplankton (FBR + ZOO), and those fed mainly with live zooplankton (ZOO) recorded the highest survival rates (95.25 ± 0.0025% and 97.5 ± 0.005% respectively). Furthermore, weight and length growth at the end of the experiment were greater in fish fed with low-grade rice flour and live zooplankton (2.66 ± 0.01 g and 6.8 ± 0.1 cm) than in those fed with low-grade rice flour only (2.46 ± 0.02 and 5.8 ± 0.1 cm) and those fed mainly with live zooplankton (1.93 ± 0.03 and 5.5 ± 0.1 cm). The involvement of zooplankton prey in the diet of Nile tilapia larvae confers better survival and growth performance on these small fish, while at the same time reducing the expense of producing them.

Ontogeny of daily rhythms in the expression of metabolic factors in Nile tilapia (Oreochromis niloticus) kept at two different temperature regimes: Thermocycle and constant temperature

The daily variations of temperature are one of the main synchronizers of the circadian rhythms. In addition, water temperature influences the embryonic and larval development of fish and directly affects their metabolic processes. The application of thermocycles to fish larvae has been reported to improve growth and the maturation of the digestive system, but their effects on metabolism are poorly understood. The aim of the present study was to evaluate the effect of two different temperature regimes, cycling versus constant, on the daily rhythms of metabolic factors of Nile tilapia (Oreochromis niloticus) larvae. For this purpose, fertilized eggs were divided into two groups: one reared in a 31 °C:25 °C day:night thermocycle (TCY) and another group maintained in a constant 28 °C temperature (CTE). The photoperiod was set to a 12:12 h light/dark cycle. Samples were collected every 4 h during a 24-h cycle on days 4, 8 and 13 post fertilization (dpf). The expression levels of alanine aminotransferase (alt), aspartate aminotransferase (ast), malic enzyme, glucose-6-phosphate dehydrogenase (g6pd), phosphofructokinase (pfk) and pyruvate kinase (pk) were analyzed by qPCR. Results showed that, in 13 dpf animals, most of the genes analyzed (alt, ast, malic, g6pd and pfk) showed daily rhythms in TCY, but not in the group kept at constant temperature, with most acrophases detected during the feeding period. An increase in nutrient metabolism around feeding time can improve food utilization and thus increase larval performance. Therefore, the use of thermocycles is recommended for tilapia larviculture.

Optimisation of plasma-activated water: Plasma DBD technology and application in recirculating aquaculture system for Nile tilapia larval culture

Plasma-activated water (PAW) is a useful tool for producing pathogen-free seed fish. This study aimed to apply dielectric barrier discharge (DBD) plasma to reduce the microbial population in the water of a recirculating aquaculture system (RAS) for Nile tilapia larval culture. Initially, a PAW system prototype was developed and found to effectively reduce bacterial populations in both stagnant and circulating water. Additionally, a slight increase in water temperature was observed in the circulating water. Subsequently, the optimisation of PAW conditions in the circulating water was performed. The PAW system, with a copper anode distance of 2 cm and a 1 cm distance between the copper tip and the water surface, combined with a non-spaced cathode pad, exhibited the highest bactericidal effect. Using the optimised PAW conditions, for Experiment I, Nile tilapia larval culture was established in the RAS, supplemented with a bacterial suspension (Bacillus subtilis, Streptococcus agalactiae and Aeromonas hydrophila) to assess the bactericidal effects. Three treatments were applied: 1) control (no PAW or antibiotics), 2) PAW, and 3) antibiotic treatment for Nile tilapia larvae cultured in the RAS system for 672 h. The results demonstrated that both PAW and antibiotic treatments significantly reduced the bacterial populations in the water in relation to the control (P < 0.05). Moreover, a substantial reduction in bacterial population was observed in the whole body of the fingerlings in both the PAW and antibiotic groups in relation to the control fingerlings (P < 0.05). In Experiment II, Nile tilapia larval culture in the RAS was conducted under three different conditions: 1) control (no PAW or antibiotic), 2) PAW, and 3) antibiotic treatment, to evaluate the antimicrobial effects of PAW on waterborne bacterial populations for 672 h. Similar to Experiment I, both antibiotic and plasma treatments significantly reduced the bacterial populations in the water and whole-body fingerlings in relation to the control (P < 0.05). Notably, the growth performance and whole-body composition (moisture, crude protein, crude fat, and ash) of the fingerling fish appeared comparable among the experimental groups (P > 0.05), suggesting that PAW had no detrimental effects on long-term fish culture. Therefore, PAW can be employed to effectively reduce bacterial populations in water, thus minimising bacteria-related issues in fish without adverse impacts on fish growth.

Efisiensi Pakan Larva Ikan Nila (Oreochromis Niloticus) Hasil Maskulinisasi Madu Hutan

Nile tilapia is a superior commodity that has been developed with high production. Male nile tilapia has a growth rate of 2 times faster than female nile tilapia, so the cultivation of male nile tilapia (monosex) is far more profitable. The masculinization using honey will produce monosexual male nile tilapia, through immersion method using honey. Honey contain flavonoids which function to direct male genitals. Honey also contains potassium which triggers steroid hormones in protein metabolism, brings glucose into cells and stimulates the hypothalamus, so that it can trigger appetite in animals and influence the level of consumption and feed efficiency. This study aims to determine the best type of honey in nile tilapia larvae for consumption and feed efficiency. Honey used in this study were; forest honey (from Bontocani, Selayar, Sumbawa) and livestock honey with a dose of 0.2% of the total volume of solvents, through the immersion method. The seven days old nile tilapia larvae were immersed in the treatments for 24 hours, then they were reared for 60 days. Completely Randomized Design (CRD) with 3 replications per treatment was used in this experiment. The results showed that honey from Bontocani forest produced highest feed consumption and forest honey (from Bontocani, Selayar and Sumbawa) produced highest feed efficiency.

First Investigation of the Optimal Timing of Vaccination of Nile Tilapia (Oreochromis niloticus) Larvae against Streptococcus agalactiae.

To investigate early immune responses and explore the optimal vaccination periods, Nile tilapia at 1, 7, 14, 21, 28, 35, and 42 days after yolk sac collapse (DAYC) were immersed in formalin-killed Streptococcus agalactiae vaccine (FKV-SA). A specific IgM was first detected via ELISA in the 21 DAYC larvae (0.108 g) at 336 h after vaccination (hav), whereas in the 28-42 DAYC larvae (0.330-0.580 g), the specific IgM could be initially detected at 24 hav. qRT-PCR analysis of the TCRβ, CD4, MHCIIα, IgHM, IgHT, and IgHD genes in 21-42 DAYC larvae immunized with the FKV-SA immersion route for 24, 168, and 336 hav revealed that the levels of most immune-related genes were significantly higher in the vaccinated larvae at all DAYCs than in the control larvae (p < 0.05) at 336 hav. Immunohistochemistry demonstrated stronger IgM signals in the gills, head kidney, and intestine tissues at 21, 28, and 35 DAYC in all vaccinated larvae compared with the control. Interestingly, at all DAYCs, FKV-SA larvae exhibited significantly higher survival rates and an increased relative percent survival (RPS) than the control after challenge with viable S. agalactiae, particularly in larvae that were immunized with FKV-SA at 168 and 336 hav (p < 0.05).

Utilization of rotifers as natural feed in the rearing of saline nile tilapia (Oreochromis niloticus) larvae

After the yolk sac of fish larvae is absorbed, they will utilize external food sources such as natural phytoplankton and zooplankton. Specifically, one of the zooplankton species used is the small-sized rotifer Brachionus sp., which matches the mouth opening of the larvae. The purpose of the experiment was to examine the effects of providing live rotifer in combination with artificial feed on the survival rate and growth of Nile tilapia (Oreochromis niloticus) larvae in high salinity conditions. The Nile tilapia larvae used in the experiment were the offspring of Red Nifi strain breeders raised in freshwater and still containing yolk sacs. Feeding commenced after the yolk sacs were absorbed, and the salinity was gradually increased to 25-30 ppt. The larvae were fed with rotifers for seven days (P-1), 14 days (P-2), and then continued with another type of artificial feed. There was also a control group that only received artificial feed without rotifers. The stocking density of the fish larvae was 25 individuals per liter, and the total water volume used was 15 liters. The rotifer dose was maintained at 10-20 individuals per milliliter of water per day during the 4-week rearing period. The results showed that providing rotifers in water salinity between 10-15 ppt during the first seven days resulted in a survival rate of &gt; 80%, whereas the control group achieved &gt; 90% survival. However, the survival rate of the larvae started to decline from the second seven-day period with the increase in salinity between 15-25 ppt, and it continued to decrease to &lt; 60% until the fourth week for all treatments.

Salinidade da água durante a masculinização de tilápia-do-nilo em sistema de bioflocos

Abstract The objective of this work was to evaluate the effect of different water salinity levels on the growth performance, survival, and masculinization rate of Nile tilapia (Oreochromis niloticus) larvae in a biofloc technology (BFT) system. Seven salinity levels (0, 2, 4, 6, 8, 10, and 12 g L-1) were tested during four weeks in the masculinization period after the absorption of the yolk sac in a matured biofloc system. The water quality variables were within the recommended range for Nile tilapia farming. However, the nitrite peaks were higher at higher salinity levels and were associated with the lower survival of fish at salinity levels equal to or higher than 6 g L-1. There was no difference between treatments for average final body weight and masculinization rate. Final biomass and survival decreased, and the feed offered as a proportion of final biomass showed the worst results because of the increase in salinity. Therefore, since higher masculinization rates are not obtained at slight and moderate levels of saline water, salinity should be kept close to 0 g L-1 for the masculinization protocol of Nile tilapia in a BFT, for a better survival and higher biomass of the fish, as well as a lower waste of the offered feed.

Microencapsulated dietary supplementation coupled with sexual inversion improves the immune and antioxidant response of Nile tilapia larvae under stressful conditions

In tilapia aquaculture, the cultivation of single-sex animals is extremely widespread, as it allows for the standardization of lots, in addition to improving the general performance of the animals. However, it is possible that hormonal inversion interacts with other factors, such as environmental and nutritional management, and modulates the immune response and antioxidant system of animals in a distinct manner. In order to test this hypothesis, an experiment was carried out using Nile tilapia larvae six days after hatching, divided into four experimental groups: NI (non-inverted animals), I (sexual inverted animals), NI + M (non-inverted supplemented with microencapsulated products) and I + M (sexual inverted and supplemented with microencapsulated products; half of which were subjected to transportation-related stress after 28 days of the experiment. At the end, the survival rate was evaluated; the gene expression of heat shock protein (HSP70), interleukin 1 beta (IL-1β) and cyclooxygenase-2 (COX 2) via RT-PCR; also evaluated were the activity of catalase (CAT) and superoxide dismutase (SOD) enzymes, as well as the total antioxidant capacity by 2,2-diphenyl-1-picryl-hydrazyl (DPPH). Animals from the I and I + M groups had the highest survival rate (p < 0.001) regardless of transportation stress. The highest expressions of HSP70 were found in the NI group (p < 0.001, with and without transportation). For the IL-1β gene, there was an increase in expression for animals belonging to groups NI and NI + M (no transportation); and NI (p < 0.0001, with transportation). Increased COX 2 expression was observed for all groups after transportation (p < 0.0001). The highest SOD activities were observed in groups I and I + M (without transportation, p = 0.0004), and I (with transportation, p < 0.0001). The transportation decreased the total antioxidant capacity of DPPH in all treatments (p < 0.001). Finally, when evaluating all of the results together, we came to a conclusion that sex inversion improves the immune response and antioxidant profile of animals under stressful conditions when associated with microencapsulated dietary supplementation.

Addition of microalgae Nannochloropsis sp. and Isochrysis sp. in the feed of Nile tilapia larvae

Microalgae added to feed can increase the quality, production, and welfare of fish, although they contain antinutritive factors and allelopathic compounds that can be harmful. The aim of this work was to compare the effect of five feeds: Basic feed and enriched with two levels of Nannochloropsis sp. and Isochrysis sp. lyophilized (15 and 30 kg-1 of feed) in larval rearing of Nile tilapia. The larvae fed with Isochrysis sp. (15 and 30 g kg-1) had some yield parameters slightly lower than those of the larvae fed with the basal feed. For larvae fed with Nannochloropsis sp., all yield parameters were similar to those of the control group, except for the weight and stress resistance of larvae fed with the 15 g kg-1 enriched feed, which were lower than those of the control group. Since the main objective of juvenile fish producers is survival rate, which was high and stable in larvae fed with Nannochloropsis sp. (30 g kg-1), it is recommended that this feed should be used for rearing Nile tilapia larvae. The inclusion of Isochrysis sp. in the feed should be better evaluated.

Hormônios naturais e sintéticos impactam as características zootécnicas e morfológicas da tilápia do Nilo (Oreochromis niloticus)

ABSTRACT This work aimed to investigate the effects of the endocrine disruptors 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) on Nile tilapia (Oreochromis niloticus) development, emphasizing the zootechnical and morphological aspects. The concentrations of E2 and EE2 tested were 250, 500, and 1,000 μg·L−1. The evaluated compounds were capable of producing intersex individuals and causing zootechnical damage in Nile tilapia, with a significant decrease in the condition factor as the concentrations increased. Besides, these concentrations were also able to induce the development of morphological anomalies without any significant difference between them. E2 and EE2 exposure were shown to be lethal for Nile tilapia larvae, having no effect on the incubation time and the percentage of larvae hatching. Morphological anomalies such as head shape malformation, oral malformation, operculum malformation, belly retraction, distended abdomen with fluid accumulation (ascites), exophthalmos, signs of bleeding in the belly, and curved pectoral fin radii, were also observed, which impaired the fish development.

All-male Nile tilapia larvae production using high-temperature and low dose of MT combination treatment

Previous studies have shown that high-temperature treatment during thermosensitive periods (TSPs) induces >70% Nile tilapia to become pseudomales (XX phenotypic males) in all-XX families mainly by downregulating the 17β-estradiol (E2) levels. Commercially, methyltestosterone (MT) is used to induce the sex reversal of XX individuals in Nile tilapia and produce all-male larvae. In order to reduce the dosage of methyltestosterone (MT), it is very necessary to investigate the possibility of obtaining all-male Nile tilapia larvae using combination treatment with high-temperature and low dose of MT. In this study, three families were developed by crossing XX females with XY males and were used for subsequent analysis. The results demonstrated that the male ratio in T + 0 MT (36 °C high-temperature treatment and 0 μg/g MT in diet) was higher than in the C + 0 MT (28 °C culturing water temperature and 0 μg/g MT in diet) or C + 2 MT (28 °C culturing water temperature and 2 μg/g MT in diet) group and lower than in C + 10 MT. The lowest MT concentration achieving a 100% male ratio was 10 μg/g in the high-temperature-treated group and 20 μg/g in the control group. High-temperature and MT combination treatment further downregulated E2 levels compared to the control and various MT-treated groups. High-temperature treatment significantly increased 11-KT levels in XX Nile tilapia trunks, and 11-KT levels in T + 0 MT were significantly higher than in C + 0 MT or C + 2 MT and were not significantly different from that in XY. Interestingly, 11-KT levels in the XX Nile tilapia trunk in the C + 10 MT, C + 20 MT, T + 10 MT and T + 20 MT groups were significantly higher than in the XY group. High-temperature treatment significantly downregulated mRNA and protein expression levels of Cyp19a1a in 21 dpf (days post fertilization) XX Nile tilapia gonads (T + 0 MT). High-temperature and MT combination treatment further downregulated mRNA and protein expression levels of Cyp19a1a in 21 dpf XX Nile tilapia gonads (T + 10 MT) to levels similar to those in the XY group. In contrast to Cyp19a1a, high-temperature and MT combined treatment significantly upregulated expression levels of Dmrt1 in 21 dpf XX Nile tilapia gonads (T + 10 MT), and expression levels of Dmrt1 in T + 10 MT were higher than in XY. Furthermore, we found that high-temperature and low dose of MT combined treatments synergistically promote the growth of Nile tilapia. These results illustrated the potential applicability of high-temperature and low dose of MT combined treatment for all-male production of Nile tilapia larvae used in aquaculture industry.

Effect of rearing systems and dietary probiotic supplementation on the growth and gut microbiota of Nile tilapia (Oreochromis niloticus) larvae

The establishment of the early-life gut microbiota plays an important role in fish development and influences the host's health status and growth performance. Different rearing conditions can impact the initial colonization of the gut microbiota, while the addition of probiotics may also affect such colonization. However, how this may affect fish larvae survival and growth remains largely unexplored. In this study, 3-day old Nile tilapia embryos were hatched until 9 days post fertilization (dpf) in three systems, including one flow-through system (FTS) and two identical recirculating aquaculture systems (RAS). When feeding started at 10 dpf, tilapia larvae in the FTS and one of the RAS were fed with a control diet, while larvae in the second RAS were fed with the control diet coated with B. subtilis spores (RASB). The feeding trial lasted 26 days, from larvae to fry stage, during which the survival, growth performance and gut microbiota were analyzed. The larvae reared in FTS showed significantly lower survival than those in RAS and RASB, while no differences were observed in fish growth and apparent feed conversion ratio between treatments. Different rearing systems resulted in different gut microbiota compositions, which strongly correlated with the survival rate and standard body length at harvest. Cetobacterium was enriched in RAS and RASB, while was barely detected in the gut of FTS-reared tilapia fry. Probiotic supplementation increased the relative abundance of beneficial Bacillus in fish gut. Our findings indicate that rearing fish larvae in RAS supports better survival compared to FTS, while dietary probiotic supplementation further modulates the gut bacterial composition and stimulates presence of beneficial bacteria during early life.

Toxic effect of lead (Pb) on hatching rate and larvae abnormalities of Nile Tilapia (Oreochromis niloticus)

Like other fish, Nile tilapia (Oreochromis niloticus) is one species that potentially exposed to pollutants, including lead (Pb). However, the impact of Pb exposure on hatching rate and larvae development of Nile tilapia is still not investigated. Therefore, this study aimed to examine the toxic effect of Pb exposure on hacthing rate and larvae abnormalities of Nile tilapia. A total of 2,400 fertilized eggs of Nile tilapia was distributed to control and 3 treatment group namely: treatment A (0.21 mg/L PbCl2), treatment B (0.42 mg/L PbCl2) and treatment C (0.63 mg/L PbCl2) with triplicate. The exposure period lasted for ten days. Cumulative hatching rate, survival rate, malformation rate, heart rate, body length, total lead content and deformities of larvae were analyzed. The results showed that increasing Pb concentration significantly increased malformation rate, heart rate, and total Pb content in Nile tilapia larvae. The highest malformation rate, heart rate and total lead content observed in treatment C were 3.4%, 115.6 beats/minute and 4.80 mg Pb/kg, respectively. Furthermore, Pb was affect several deformities of Nile tilapia larvae including lordosis, kyphosis, and curved tail. Otherwise, exposed to lead up to concentration 0.63 mg/L PbCl2 have no significant effect on cumulative hatching rate, survival rate and body length in Nile tilapia.

Mortality rate of newly hatched larvae of Nile tilapia (Oreochromis niloticus) submitted to different photoperiods

ABSTRACT: Fish farming is a growing area in the aquaculture industry. Brazil is among the five largest tilapia producers in the world, with a production of 283 thousand tons in 2017. Tilapia has been intensively cultivated and improved through more efficient cultivation techniques. In this sense, the objective was to evaluate the mortality rate of newly hatched larvae of Nile tilapia reared three photoperiods (12Light:12Dark, 18L:06D, and 24L:0D) during 9 days of cultivation. For this purpose, a recirculation system with 9 water tanks was set up, with 3 boxes per group containing 930L of freshwater. After the embryos hatched, the larvae were transferred to nurseries (2 trays per tank, n = 64 larvae/tray), with 384 larvae per photoperiod. Water quality parameters were monitored and remained in the ideal ranges between treatments. However, temperature (p=0.004) and pH values (p= 0.009) for the 18L:06D photoperiod were lower than those observed for the 24L:0D photoperiod. A high mortality rate was observed in the first days of culture, specifically on the second day, for all photoperiods. However, there was a decrease in mortality throughout the experiment, with little variation in the mortality rate for the remainder of the experiment. In this context, it appears that the influence of the photoperiod on the survival of the fish seems to be related to the age of the animal. KEYWORDS: Tilapia farming, Survival, Light stimulation.

Risk assessment and acute toxicological effects of atrazine on Nile tilapia larvae after stress

The present study aimed to evaluate the risk assessment, median lethal concentration LC50-96h, development, and mortality of Nile tilapia Oreochromis niloticus larvae exposed to atrazine after stress management. An LC50-96h trial was carried out using fish (n = 147; 8.5 ± 1.0 mg; seven larvae/aquarium), which were allocated randomly in 21 aquaria (1 L) and exposed to five concentrations of atrazine: 2, 4, 8, 16, and 32 mg L−1 plus one control (without herbicide) and a control with a solubility adjuvant (acetone). Temperature, pH, dissolved oxygen, conductivity, and total ammonia were measured daily. In addition, a stress test was performed with fish (n = 150; 17.9 ± 1.7 mg; 10 larvae/aquarium) submitted to air exposition (five minutes) and posteriorly distributed randomly in 15 aquaria (1 L), and exposed to atrazine at 0.18, 6, 12, and 18 mg L−1. The LC50-96h of atrazine for Nile tilapia larvae was 17.87 mg L−1. Significant differences (P < 0.05) were found for weight and final length, pH, and dissolved oxygen that was responsive to the increased levels of herbicide. Larvae mortality post-stress was registered to 6, 12, and 18 mg L−1 of atrazine, and was more critical at 24 h. The increased doses of atrazine used in LC50-96h test depressed the development of Nile tilapia larvae. Fish submitted to stress (air exposition) and exposed to sub-lethal doses of atrazine showed significant mortality, indicating that stressors may increase the toxic effect of atrazine for Nile tilapia larvae. On the other hand, based on risk assessment atrazine can be classified as herbicide with low toxicity for Nile tilapia larvae and low toxicological risk.

Acute Toxicity and Risk Assessment of Florfenicol for Nile Tilapia Larvae

The aim of this study was to determine the median lethal concentration (LC50-96h), effective concentration (EC50-96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mgL-1 plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC50-96h of FF for Nile tilapia larvae was 349.94 mgL-1. The EC50-96h of FF was 500 mgL-1 for weight reduction and was 1040 mgL-1 for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.

Growth performance of tilapia (Oreochromis niloticus Linnaeus, 1758) larvae with feeding Tubifex tubifex (Müller, 1774) from different fermentation of animal manures

Tubifex tubifex is a natural feed for many fish species, which still relies on natural catches. High nutrient contents culture media is needed to increase the availability and quality of T. tubifex. The aim of this study was to investigate growth performance of Nile tilapia (Oreochromis niloticus) larvae fed with T. tubifex cultured using different animal manures. Some profiles of T. tubifex nutrition (N, P, and K), Nile tilapia composition (proximate, essential amino acids, and fatty acids) fed with T. tubifex, Relative Growth Rate (RGR), Survival Rate (SR), biomass, feed intake, protein efficiency ratio, and water quality were analyzed. The results showed that tilapia fed with T. tubifex which cultured using various animal manures had a significant effect (p 0.05). The best treatment was obtained at T. tubifex cultured using 50 g/L of quail manure + 100 g L-1 of rice bran + 50 g L-1 of tofu waste (T2).

Toxicity of palm oil mill effluent on the early life stages of Nile tilapia (Oreochromis niloticus, Linnaeus 1758).

Harmful effects of several pollutants have been reported on early life stages of fish. However, the effects of palm oil mill effluent (POME) on fish early life stages are still unexplored. Therefore, the objective of this present study was to elucidate the impact of POME on the early life stages of Nile tilapia (Oreochromis niloticus). Fertilized eggs of Nile tilapia were exposed to four concentrations of POME (0, 1.565, 2.347, and 3.130mg/L) in 20 plastic funnels. Each of the control and treatment groups was maintained in five replicates. The cumulative hatching rate, malformation rate, body length, and deformities of larvae were analyzed. Results showed that hatching rate and survival rate of Nile tilapia larvae significantly decreased with increasing concentrations of POME. In contrast to, malformation rate and heart rate were significantly increased. Furthermore, results showed several malformations of Nile tilapia larvae including lordosis, kyphosis, and curved tail when exposed to 1.565mg/L, 2.347mg/L, and 3.130mg/L of POME concentrations. Further research is required to understand the physiological mechanisms of different endpoints in the early stages of Nile tilapia induced by the toxicity of POME.