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.

Utilization of tempe dregs for the growth of tilapia fish (&lt;i&gt;Oreochromis niloticus&lt;/i&gt;)

The objective of this study is to determine the impact of feeding tempeh dregs at varying doses on tilapia growth and survival (Oreochromis niloticus). The study was conducted from March to May 2023 in Wataliku Village, Kabangka District, Muna Regency. The study employed a completely randomized design with four treatments that involved the administration of tempeh dregs in the diet. These were designated as follows: treatment A (control) was commercial feed; treatment B was 10% tempeh dregs; treatment C was 15% tempeh dregs; and treatment D was 20% tempeh dregs. Each treatment was replicated three times. The data were subjected to analysis of variance (ANOVA) at a confidence level of 95% (α0.05). The study results demonstrated that the highest specific growth was observed with the addition of 20% tempe dregs, with an average of 2.97% per day. This was followed by 15% tempe dregs (2.47% per day), 10% tempe dregs (2.28% per day), and commercial feed (2.00% per day). The highest absolute growth was observed in the treatment that included 20% tempe dregs, with an average of 1.04 g per individual. This was followed by the treatment that included 15% tempe dregs (0.87 g per individual), the treatment that included 10% tempe dregs (0.80 g per individual), and the treatment that included commercial feed (0.00 g per individual). It should be noted that survival was 100% in all treatments. Analysis of variance (α0.05) demonstrated that administration of tempe dregs at varying doses had a statistically significant impact on the specific and absolute growth of tilapia larvae (Oreochromis niloticus).

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.

Masculinization of Tilapia (Oreochromis Niloticus) by Oral Method Using Senggani Fruit Extract (Melastoma Malabathricum L.)

Introduction: Tilapia have different growth rates in male and female fish where the growth of male fish is faster than female. Therefore, in tilapia farming activities, the production of tilapia weighing &gt;100g/head is difficult to achieve due to uncontrolled spawning. Method: This study was designed using a completely randomized design (CRD) with 5 treatments and 4 replicates, namely treatment A (control), B (Senggani fruit extract 0.75 g/kg feed), C (extract 1.5 g/kg feed), D (extract 2.25 g/kg feed), E (extract 3 g/kg feed). The organisms used in the study were 7-day-old tilapia larvae. Tilapia larvae were given feed that had been added with Senggani fruit extract according to the treatment dose. Tilapia were reared for 62 days, and given artificial feed containing 41% protein, each feeding was given with a frequency of 3 times a day (morning, afternoon, evening). Results and Discussion: The results showed that the highest percentage of male sex was found in treatments A, B, C, D and E, which amounted to 50; 56.25; 57.5; 58.75; and 60%, respectively. Daily growth rate, survival and feed conversion ratio obtained during the study in each treatment amounted to 7.49, 7.45; 7.44; 7.46; and 7.40. for survival 73.75; 72.5; 72.5; 70; and 68.75 then the results of feed conversion ratio respectively 1.86; 1.88; 1.89; 1.86; and 1.91. The analysis showed that the highest percentage of male sex was found in the treatment of 3 g/kg feed which amounted to 60% (P&gt;0.05). Daily growth rate, survival rate and feed conversion ratio did not significantly affect the treatment given (p&gt;0.05). Conclusion: The results of water quality measurements obtained are still within the optimum limits for tilapia rearing. Conclusion: Feeding using Senggani fruit extract to masculinize tilapia did not have a significant effect (p&gt;0.05) on the percentage of male tilapia, daily growth rate and feed conversion ratio.

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.

Reduction of methyltestosterone concentration in feed during masculinization of Nile tilapia (Oreochromis niloticus) in biofloc system

Most larviculture of Nile tilapia is carried out in ponds with a large presence of live food, with temperature variations throughout the day and year, and feed leftoovers due to dissipation in the water. As a consequence, the masculinization process needs to be done with a high concentration of 17α-methyltestosterone (MT) in the diet. Production in closed systems, such as biofloc technology (BFT), allows controlling the water temperature, uses a smaller volume of water and generates less effluent, being an alternative system for the masculinization process. This study evaluated the masculinization rates of Nile tilapia in the BFT, with a controlled temperature (∼28 °C), using concentrations of MT in the feed lower than those recommended for masculinization in ponds and BFT (60 mg ∙ Kg−1 of feed). Tilapia larvae (post yolk sac absorption) were raised in BFT (2 larvae ∙ L−1 or 100 larvae ∙ tank−1) and submitted to different concentrations of MT in the diet (0, 30, 40, 50 and 60 mg ∙ Kg−1 of feed), which was offered five times a day for a period of 28 days. The experimental design was entirely randomized. After the hormonal treatment, the water in the tanks was completely replaced with new water, free of hormonal residues, where the fry remained until they reached a viable size for sexing. It was also tested to maintain the original water used during the hormonal treatment period, during the post-experimental period, where 30 mg ∙ Kg−1 of feed was used. The water quality variables (temperature, pH, dissolved oxygen, settleable solids, total suspended solids, alkalinity, nitrogen compounds, salinity, phosphate and organic carbon) and growth performance variables (final body weight and length, specific growth rate, condition factor and survival) did not differ between MT concentration in the diet (p > .05). The treatment without hormone (control) presented 73.6% of males and the treatments that received hormone showed masculinization rates >99%, significantly higher than control (p < .05), but did not differ from each other (p > .05). The percentage of male individuals in the control treatment was high and this may have occurred because of the temperature of 28 °C throughout the experiment. However, this percentage of males is not considered high enough for production, which requires higher rates close to 100% as possible. The MT was not detected in the water 12 h after the last feeding with feed containing hormone. Thus, it is feasible to use a lower concentration (30 mg of MT ∙ Kg−1 of feed) in BFT. Our study has a direct impact on the global tilapia production scenario, offering a new environmentally sustainable masculinization protocol, using less water and hormones in the process and avoiding the release of hormonal residues.

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.

Formation of Male Sex Tilapia Larvae (Oreochromis niloticus) Using Natural Methyltestosterone Hormone

Aims: Obtaining a productive tilapia, by changing the sex of the tilapia larvae into male monosex. This was achieved by determining the effect of the duration of administrating the natural methyltestosterone (MT) hormone on the male sex of tilapia using the Immersion method.&#x0D; Methodology: The study was conducted at the Northern Region Marine and Fisheries Service Branch, Wanayasa Freshwater Fish Seed Development Center, Purwakarta Regency, West Java Province, Indonesia. The experimental design used a completely randomized design (CRD) with 5 treatments and 3 replications. The study used the Immersion method where untreated tilapia and the four hormones tilapia. The treatments are as follows:&#x0D; A = untreated tilapia&#x0D; B = tilapia treated in 17a-MT (5h-100mg/L)&#x0D; C = tilapia treated in MT (5h-350mg/L)&#x0D; D = tilapia treated in MT (10h-350mg/L)&#x0D; E = tilapia treated in MT (15h-350mg/L)&#x0D; Results: Tilapia larvae used were aged 6 days after hatching and reared for 40 days, then the male and SR sex were observed. The results of this study showed that the duration of immersion of tilapia larvae using natural MT significantly affected the male tilapia which resulted in the highest male percentage at 15 h of immersion of 80.2%, then followed by 10-h immersion of 75.6% with the same SR value of about 90%.&#x0D; Conclusion: Administration of natural MT using cow testis meal by immersion method at different durations significantly affects male sexual development in 6-day-old tilapia larvae. Based on the obtained data analyses, the percentage of male tilapia in the 40-day experimental study shows the most effective duration in treatment E (15 h) with a measure of 350 mg/l, which is 80.2%. Further studies regarding the relationship between sex change and the growth of sex-changed fish as an effect of immersion duration.

Optimizing JICA Tilapia Larvae Production: Effect of Egg Density in Controlled Hatching at Jambi Peatland Hatchery

Sustainable aquaculture is crucial for environmental and economic stability in tropical regions. JICA tilapia (Oreochromis sp.) aquaculture development in Sumatran peatlands requires sustainable fry. This study aimed to analyze the optimal egg density to maximize larval production in a controlled hatchery environment. Utilizing a randomized experimental approach, we obtained eggs from naturally spawned tilapia, hatched in a funnel container (top diameter 30 cm; bottom diameter 15 cm; height 50 cm; water volume 10 L) within a 5 x 10 x 1 m3 tub filled with 90 cm of water using a recirculation system. We compared two densities: 2,000 eggs/L water and 3,000 eggs/L water. The findings of our study indicate that the difference in hatching rate between egg densities of 2000 eggs/L and 3000 eggs/L was not significant at the 95% confidence level (p&gt; 0.05). Increasing the egg density to 3000 eggs/L does not significantly reduce the hatching rate, making it possible to consider higher densities without significant risks to larval production. This offers a model that can be replicated in similar tropical peatland environments.

Toxicity of brilliant blue dye on development organ and survival rate of tilapia larvae (Oreochromis niloticus)

One of the most widely used textile dyes is brilliant blue. However, brilliant blue has a bad influence on the waters, namely the effect of carcinogenic, polluted air quality, cannot be degraded or non-biodegradable and affects fish life in the waters. The purpose of this research was to determine the effect of the toxicity of brilliant blue dye on organ development and survival rate of tilapia (Oreochromis niloticus) larvae. The stage of this research was a completely randomized design with the provision of brilliant blue dye to the larvae of tilapia (Oreochromis niloticus). The results showed that the highest concentration treatment (40 ppm) experienced the fastest organ development, the smallest yolk volume (0.14 mm3), the highest abnormality (20%), and the lowest larval survival rate (65%).

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).

Nutritional supplement of FOS enhances growth and immune system in tilapia larvae (Oreochromis niloticus)

Aquaculture is an essential economic activity worldwide, supplying the requirements of various nations. The larval stage is one of the most critical periods during the production cycle in aquaculture. To contribute to amplifying the knowledge related to viable methods to enhance this activity, the present study investigated the effects of prebiotic fructooligosaccharide (FOS) and the synthetic peptide GHRP-6 in the growth of fish, as well as its repercussions on a series of digestive enzyme activities and immune response parameters. Tilapias (Oreochromis niloticus) larvae were divided into three groups: group 1, fed with pre-formulated feed; group 2, fed with feed + FOS; group 3, fed with feed + GHRP-6. We measured the gain in size and weight at 72 and 87 days after starting the diets. At the end of treatment, we continue feeding the animals with a standard diet using the pre-formulated feed. We measured immune system parameters and digestive enzyme activities on larvae homogenate, focusing on lysozyme and antiprotease activity and α-amylase, trypsin and esterase activity, respectively. Results show a significant increment in size and weight in those fish fed with feed + FOS. Meanwhile, the primary enzyme activity was detected in those fish fed with feed + GHRP-6. On rough terms, both food combinations stimulated the immune system. Our study suggests that FOS and GHRP-6 could be desirable additives to incorporate into the tilapia larvae feeding and increase production efficiency. Keywords: aquaculture, digestive enzymes activity, FOS, GHRP-6, immune system, larvae

Glucocorticoid Receptor Mediates Cortisol Regulation of Glycogen Metabolism in Gills of the Euryhaline Tilapia (Oreochromis mossambicus)

In this study, we investigated the effects of cortisol on the regulation of the glycogen metabolism biomarkers glycogen synthase (GS) and glycogen phosphorylase (GP) in the glycogen-rich cells of the gills of tilapia (Oreochromis mossambicus). In the gills of tilapia, GP, GS, and glycogen were immunocytochemically colocalized in a specific group of glycogen-rich cells adjacent to the gills’ main ionocytes and mitochondria-rich cells. Cortisol plays a vital role in the regulation of physiological functions in animals, including energy metabolism, respiration, immune response, and ion regulation. However, no studies have elucidated the mechanisms regulating cortisol and glycogen-rich cells in the gills. Therefore, we treated tilapia larvae with exogenous cortisol and a glucocorticoid receptor (GR) antagonist to investigate the regulatory mechanisms between cortisol and glycogen-rich cells in the gills. Our results showed that cortisol promoted the expression of gill glycogen phosphorylase isoform (GPGG) mRNA via GR, whereas the GS gene expression remained unaffected. We also found that GR mRNA was colocalized with some glycogen-rich cells in the gills, further confirming our hypothesis that cortisol directly acts on glycogen-rich cells in the gills of tilapia and regulates glycogen metabolism by promoting GPGG mRNA expression.

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.

Counting tilapia larvae using images captured by smartphones

In this work, we propose a new way for automatically counting fish larvae in Petri dishes using images captured by a standard smartphone. A new tilapia larvae image dataset for training and validating machine learning models has been created and used to validate a recent machine learning approach based on multi-stage model refinement of confidence maps. A mean absolute error (MAE) of 1.43 has been achieved using the proposed automatic larvae counter, indicating that the proposed approach is promising for larvae counting, as the mean number of larvae per image is more than 20. The proposed approach also achieved precision, recall, and F-measure values of 0.98, 0.92, and 0.95, respectively, for larvae detection using a dataset containing images from more than 6,000 manually annotated larvae.

Probiotic Effectiveness in Artificial Feed Predigest on The Rearing of Tilapia (Oreochromis Niloticus) Larvae

Probiotic Effectiveness in Artificial Feed Predigest on The Rearing of Tilapia (Oreochromis Niloticus) Larvae

Pathogen identification, risk factor and preventive measure of a columnaris disease outbreak in Tilapia (Oreochromis niloticus) eggs and larvae from a tilapia hatchery

Flavobacterium columnare is the causative agent of columnaris disease and brings about huge damages to the aquaculture industry worldwide. First classified as one specie with several genomovars/genetic groups, then reclassified into four distinct species, F. columnare was well-known for its high genetic diversities among different isolates. In this study, six bacterial strains, designated as HNU-01 to HNU-06, were isolated from diseased Nile tilapia eggs and larvae in Hainan, China. Based on colony characteristics, physiological/ biochemical test and 16S rRNA gene analysis results, all isolated strains were identified as Flavobacterium davisii according to a recently published research (which correspond to genetic group 3 of F. columnare). Virulence test showed that among the isolates, HNU-01 was most virulent to tilapia larvae. The lethal doses of 7 days (LD50) of F. davisii HNU-01 to tilapia eggs and larvae were 7.29 × 107 CFU/ml and 1.56 × 106 CFU/ml, respectively. The antimicrobial susceptibility test indicated that the bacterium showed reduced susceptibility towards ampicillin and oxytetracycline. In the disinfection-infection experiment, compared with tilapia larvae hatched from untreated eggs, tilapia larvae hatched from disinfected eggs (treated with formalin, potassium permanganate and chloramine T) showed significantly higher mortality rates/F. davisii loads after challenging with F. davisii HNU-01. Salinity test showed that elevated hatching system water salinity decreased the mortality of tilapia larvae infected with F. davisii. The best protective effect was seen in water salinity of 4.0–10.0 ‰ . This is the first report of F. davisii (or genetic group 3 of F. columnare) infecting tilapia eggs and larvae. This study revealed that the virulence of F. davisii in tilapia varied at different fish developmental stages. In addition, disinfectant treatment of tilapia eggs increased the susceptibility of tilapia larvae to F. davisii, and regulation of water salinity is a potential effective measure to prevent columnaris disease in tilapia hatcheries.