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The aim of this study was to characterise possible histopathological and haemato-immunological changes after subclinical infection by S. agalactiae S13 serotype Ib. One hundred juveniles of Nile tilapia with average weight of 45 g were distributed in ten 90 L experimental units. After the acclimation period 25 fish were euthanised, and fragments of liver, spleen and posterior mid-intestine tissue were sampled to verify the integrity of the organs and blood samples taken to check the haematological profile. Fifty animals were used to verify the optimal dosage for the challenge. The remaining 25 fish were infected with S. agalactiae S13. After 96 h, tissue fragments from the liver, spleen and posterior mid-intestine and blood samples were collected. The analyses revealed that, 96 h after contagion, S. agalactiae S13 serotype Ib caused subclinical lesions in the liver and spleen that are not commonly described as pathognomonic, in addition to haematological alterations. These results allow a better understanding of sudden recurrent mortalities in Brazilian tilapia farms, since the serotype Ib of S. agalactiae causes inapparent infections and can remain lodged in internal organs and cause irreversible lesions and haemato-immunological alterations, therefore compromising physiological functions vital for the health of fish without revealing external clinical signs in the animals.

The study aimed to evaluate the oral infected-feed, intragastric-gavage, and intraperitoneal routes of the Streptococcus agalactiae infection in Nile tilapia (Oreochromis niloticus). For this purpose, 270 juveniles of Nile tilapia, with an average weight of 2 g, were distributed in 18 experimental units of 90 L, acclimatized, and raised for 55 days, until reaching 50 g (median weight). The experimental design was entirely randomized in six treatments, three of which were composed by bacterial infection routes: intraperitoneal 100 μL fish

This study evaluated the effects of dietary supplementation of organic acids blend (OAB) alone or in combination with essential oil, Lippia origanoides (OAE) for Nile tilapia fed supplemented diets for 30 days. Fish (1.1 ± 0.04 g) were fed control (Control), or OAB 0.5% or OAB 0.5% + essential oil 0.125% (OAE) respectively. At the end of the experiment, samples were collected for de hemato‐immunological, histological analysis of the intestine and liver, as well as microbiology of the intestine. The pH of the diets supplemented with OAB and OAE reduced 0.92 and 0.19 respectively. The growth and FCR were unaffected by the treatments, but survival was significantly higher in the OAB treatment. Fish fed the OAB diet showed reduced concentration of total heterotrophic bacteria and Pseudomonas sp. in the intestine. Increased glucose in fish fed OAB and high number of circulating monocytes in fish fed OAE diet were observed. The anterior intestine of fish fed OAE diet showed larger number of goblet cells and increased villi height. The diet supplemented with OAB, mainly, improved the intestinal health and survival of tilapia juveniles and can be used in juvenile production.

The aims of this study were to evaluate the inclusion of different concentrations of Lactobacillus plantarum in Nile tilapia diet and to verify histological effects on tissues of the animal organs, as well as to verify its effects on growth parameters and possible increase in the immune system. A total of 240 juveniles were distributed in 16 tanks arranged in a recirculation system. One control group and three treated groups (104, 106, and 108 colony-forming unit (CFU) g −1L. plantarum kg feed−1) were established in quadruplicate. After 35 days of supplementation, it was not possible to observe differences in growth rates and hematological parameters. However, in the kidney, there was a reduction in the presence of PAS-positive granular leukocytes (PAS-GL) between the collections (15 and 35 days). The liver had lower number of lesions related to loss of cordonal aspects of fish fed 108 CFU g−1 on day 15. Fish fed 104 and 108 CFU g−1 showed lower degree of congestion at day 35. The probiotic also provided a reduction in the number of melanomacrophage centers in the splenic tissue and an increase in the amount of goblet cells in the gut. The concentration 108 CFU g−1 of probiotic in diets increased the number of goblet cells, improved cordonal aspects, and reduced hepatic congestion, and indicated a possible improvement in the immunophysiological conditions of the fish.

Essential oils are obtained from vegetal material and present antibacterial activities, antioxidant, antiviral, antifungal properties and may replace the use of chemotherapeutics for treating and prophylaxis in fish farm. The objective of this study was to verify the influence of essential oil of Mentha piperita in the prevention of Streptococcus in Nile tilapia. A total of 300 fish with approximately 5 g were divided into 20 tanks with 15 fish each were fed diet supplemented with essential oil at concentrations of Mentha 0.075%; Mentha 0.125%; Mentha 0.25% and two controls (commercial feed and feed+cereal alcohol) in quadruplicate, during 50 days. At the end of the supplementation period, four fish from each experimental unit were collected for hemato-immunological analysis and the rest of the animals were challenged against Streptococcus agalactiae intraperitoneally. During seven days after infection, the fish were monitored every three hours for mortality registration. Zootechnical performance indexes were measured based in the biometries each 15 days along the experimente and did not present significant difference as well as the hematological parameters. Total plasmatic protein was higher in fish fed Mentha 0.125% than those fed Mentha 0.25%. After the challenge, unlike the animals whose diet did not contain essential oil, the animals that received supplemented ration maintained their alimentary activity. The supplementation with the essential oil increased the resistance of the fish after the challenge with S. agalactiae and survival was significantly higher in fish fed with Mentha 0.25%.

This study aimed to verify the effects of dietary supplementation with sodium butyrate and Lippia origanoides, combined and isolated, on the health and zootechnical performance of Nile tilapia juveniles Oreochromis niloticus. A total of 120 fish (5.38 ± 0.65 g) were randomly distributed in 12 experimental units and fed different experimental diets for 30 days, namely: commercial diet without supplementation (Unsupplemented); commercial diet supplemented with 0.5% sodium butyrate (Butyrate); commercial diet supplemented with 0.125% L. origanoides (Lippia) and commercial diet supplemented with a mixture of 0.5% sodium butyrate and 0.125% L. origanoides (Butyrate + Lippia). After preparing the experimental diets there was an increase in the pH of diet Butyrate when compared to the other diets. After 30 days the fish supplemented with Butyrate + Lippia showed reduction significate in the mean corpuscular haemoglobin, concentration of total heterotrophic bacteria in the intestine, and lymphocyte infiltrates in the liver. Besides that, the supplementation with Butyrate + Lippia promoted an increased number of intestinal villi compared to the fish Unsupplemented ones. Additionally, fish fed a diet containing only Lippia presented an increase in the villus perimeter in the posterior region of the gut and in the red blood cell number. Animals supplemented only with sodium butyrate demonstrated increased lactic acid bacterium in the gut and macrosteatosis in the liver, besides decreased melanomacrophages in the spleen. The use of sodium butyrate associated with essential oil had positive effects on the intestinal microbiota, intestinal structure, liver, and spleen integrity, suggesting a greater efficiency of the compounds when used together in the nutrition of Nile tilapia juveniles.

Fish may bioaccumulate contaminants from the aquatic environment and extend them to the food chain provoking risks to human health. This study evaluated the microbiological parameters of the pond´s water and trace elements concentrations in samples of water, sediment, feed and muscle of farmed Nile tilapia used for human consumption in southern Brazil. A total of 240 fish were collected from 12 tilapia farms. Sediment, tank water and dry ration used in the animals' diet were collected for analysis. Analysis were performed by Energy Dispersion X-ray Fluorescence (EDXRF), Inductively Coupled Plasma Mass Spectrometer (ICP-MS), Induced Coupled Plasma Optical Emission Spectrometer (ICP-OES), and Atomic Absorption Spectrometer (AAS-VGA). In addition, the microbiological analysis of the water was carried out. The concentrations of Se, I, Fe, Cu and Zn in fish muscle were higher than the recommended by the Brazilian legislation, considering the advised daily intake for adults. The arsenic element had concentrations above the limit stipulated by the present Brazilian legislation, observed in all samples of muscle, sediment and tank water highlighting a possible environmental and fish contamination by the toxic element. Moreover, the arsenic concentration in the water presented a positive correlation (ρ = 0.33) with arsenic in the muscle, suggesting that tilapia is a good environmental bioindicator, once they properly reflect the levels of arsenic in the water. It is suggested to perform an arsenic speciation for quantification of the inorganic form and accurate assessment of the degree of toxicity in the muscle samples and risks it can bring to human health. Regarding the other potentially toxic elements (Hg, Pb and Cd), and microbiological analysis of water it was verified that the consumption of the fish in question does not raise risks, since the values are within a quality benchmark established by law. The concentration of total and fecal coliforms in pond´s water in the facilities was in agreement with the microbiological indexes required by the legislation of CONAMA class II. Western region presented the lowest concentrations of fecal coliforms when compared to the other regions. There was no significant difference in the microbiological counts of total heterotrophic bacteria, Vibrio spp. and Pseudomonas spp. among the regions.

The present study evaluated the effect of pure and protected sodium butyrate with palm oil and buffered solution supplemented in the diet of Nile tilapia Oreochromis niloticus on the performance parameters, hematological parameters and disease resistance during sexual reversion. Initially, the minimum inhibitory concentration (MIC) of sodium butyrate (Na-butyrate) against Aeromonas hydrophila or Streptococcus agalactiae under three different pH to determine the concentration of inclusion of Na-butyrate in the diet were analyzed. After that a total of 3150 newly hatched post-larvae were distributed in 21 tanks with 100 L of capacity on six treatments and one control, in triplicate: fish fed unsupplemented diet (control); fish fed Na-butyrate supplemented diet (Pure 0.25% and Pure 0.5%); fish fed Na-butyrate coated with palm oil (Oil 0.25% and Oil 0.5%) and fish fed Na-butyrate coated with buffered solution (Buffer 0.25% and Buffer 0.5%). After 28 days of feeding, zootechnical parameters, hematological parameters and resistance against A. hydrophila were verified. The MIC results showed that Na-butyrate had a better inhibitory effect in vitro at pH 6 and 6.6 than at pH 7, regardless of the microorganism. The addition of Na-butyrate at different concentrations and forms did not influence the sexual reversal process of tilapia. Yield and biomass gain showed an increment in fish fed Buffer 0.5% and Oil 0.5%. Moreover, fish fed Oil 0.5% had a better feed conversion ratio than the other groups. An increase in the red blood cells (RBC) and monocytes were observed in fish fed Buffer 0.5% and Oil 0.25% when compared to control group, while those fed Pure 0.25% and Oil 0.5% showed the lowest monocytes number when compared to Buffer0.5% and Oil0.25%. After challenge by immersion in A. hydrophila solution, no difference was found among the treatments for 14 days of observation, except for the nonchallenged fish that showed no mortality ensuring the effectiveness of the experimental infection. The use of coated Na-butyrate either in buffer or oil showed to be feasible to improve the zootechnical parameters of Nile tilapia during the sexual reversion period.

This study evaluated the use in vitro and in vivo of Bixa orellana seed extracts on the hematological and biochemical parameters of Colossoma macropomum co-infected with bacterium and monogenean, Anacanthorus spathulatus. The extract presented antimicrobial and antiparasitic activity in vitro against the pathogens. Fish supported the toxicity test and in vivo assay used 180 fish distributed in six treatments in triplicate: non-parasitized fish non-injected with A. hydrophila; non-parasitized fish non-injected exposed to acetone 0.2%; parasitized fish injected non-treated with the extract; parasitized fish injected treated with 125 μg mL−1 of extract in 2 h bath for two consecutive days; parasitized fish injected treated with 250 μg mL−1 of extract in 2 h bath for two consecutive days; parasitized fish injected treated with 125 μg mL−1 of extract for 12 h. After last bath, the fish were examined. Acetonic extract showed minimal inhibitory concentration of 125 μg mL−1 against A. hydrophila in the in vitro test and 100% efficacy against monogenean with therapeutic baths in relation to control non-treated in the in vivo test. Aeromonas hydrophila infection did not cause mortality. The gross pathology analysis showed ascites and hemorrhagic liver, kidney and spleen. Increased hemoglobin concentration, mean corpuscular hemoglobin concentration and total number of erythrocytes was followed by a decrease in hematocrit percentage in non-treated fish compared to basal group. Lymphocytes from fish in the control group were higher than in the other groups. Glucose was higher in treated fish than that found in those of basal and control. The results demonstrated that B. orellana bath was an effective alternative to treat fish diseases.

The aim of this study was to evaluate the use of synthetic fibre as a biological support for the adhesion of nitrifying bacteria in an aquaculture recirculation system (RAS). It was developed from three assays over 120 days. In the first assay, the synthetic fibres used as biological support were introduced in tanks of biological filtration of the system for posterior respirometry analysis and scanning electron microscopy (SEM). Respirometry and SEM were performed 10 days after inoculation with nitrifying microorganisms. Water quality parameters were monitored daily, and the respirometry showed that the bacteria in this assay were consuming the following amounts of ammonium: concentrations [C1]35.369 mg NH3/L, R2 = 0.9912; [C2]51.628 mg NH3/L, R2 = 0.9883; [C3]79.494 mg NH3/L, R2 = 0.986; and [C4]215.225 mg NH3L, R2 = 0.9934. In the second assay, a 1920-L tank was stocked with 120 Nile tilapia, Oreochromis niloticus, with an initial weight 32.11 ± 7.6 g and a biomass of 3.8 kg. After 60 days, the tank and its contents were assessed to evaluate zootechnical parameters and physical–chemical parameters of water quality. From these results, a third assay was developed in which the biomass of fish was increased to challenge the recirculation system. The tank was stocked with 480 jundia Rhamdia quelen (initial weight 11.34 ± 2.4 g and biomass 5.4 kg) for 60 days. In both the tilapia and jundia assays, the fish were fed four times per day with a commercial diet of 35% crude protein and 42% crude protein, respectively, at 5% of each individual fish’s body weight. At the end of the zootechnical assays, the synthetic fibres used showed efficient biological support for bacterial growth, as confirmed by scanning electron microscopy. The fibres also demonstrated maintenance of the water quality, which allowed good fish growth in the recirculating aquaculture system, and the maintenance of up to 11.19 kg/m³ of biomass of fish.

Litopenaeus vannamei or Pacific white shrimp is one of the main shrimp species cultivated around the world. Despite its easy handling, there is no detailed description of its metabolic performance. This work developed a novel mathematical model for L. vannamei growth based on mass conservation and chemical equations for feed oxidation, allowing to calculate shrimp specific growth rate, specific rate of feed consumption, specific rate of ammonia nitrogen excretion, and oxygen specific consumption rate. Results, when compared to literature data, indicate a correlation higher than 99%, demonstrating that the proposed approach can successfully predict the growth based on the assessed parameters. Through this strategy it is possible to optimize the management of shrimp cultivation, especially in relation to dissolved oxygen, availability of feed and ammonia excretion, according to each stage of shrimp growth. Based on the environmental conditions maintained during the present study, the result of the present mathematical model can be a potential tool for reducing costs and environmental impacts in aquaculture shrimp farm.

Brazilian sardine is emerging as a promising species in Aquaculture. This study describes for the first time a case of parasitic infestation by Amyloodinium in Brazilian sardines Sardinella brasiliensis obtained from natural spawning in captivity. The sardines kept in nurseries were naturally parasitized by the amylodiniosis causative agente the dynoflagellate A. ocellatum with high mortalities above 50%. Fish presented clinical signs characteristic of amyloodiniosis which included easily perceived behavioral changes such as loss of appetite, scraping of the body against objects, walls and bottom, nursery pipes, agglomerations near the aerators and water inlets, presented with accelerated opercular beating and erratic swimming. For therapeutic treatment copper sulfate was used for 10 days. At the end of the treatment period the fish had no clinical signs or presence of the parasite on the body surface, indicating that the application of copper sulfate in concentration of 0.2 mg L−1 of Cu+ was effective to control this parasite, apparently without causing damage to Brazilian sardine.

Perkinsus spp. have been detected in various bivalve species from north-east Brazil. Santa Catarina is a South Brasil state with the highest national oyster production. Considering the pathogenicity of some Perkinsus spp., a study was carried out to survey perkinsosis in two oyster species cultured in this State, the mangrove oyster Crassostrea gasar and the Pacific oyster Crassostrea gigas. Sampling involved eight sites along the state coast, and oyster sampling was collected during the period between January 2013 and December 2014. For the detection of Perkinsus, Ray's fluid thioglycollate medium (RFTM) and histology were used, and for the identification of the species, PCR and DNA sequencing were used. Perkinsus spp. was found by RFTM in C. gigas and C. gasar from Sao Francisco do Sul. This pathology was also detected in C. gasar from Balneario Barra do Sul both, by RFTM and histology. Perkinsus marinus was identified in C. gigas and C. gasar from Sao Francisco do Sul and Perkinsus beihaiensis in C. gasar from Balneario Barra do Sul. This is the first report of P. marinus in C. gigas from South America. Results of this preliminary study suggest that both oyster species tolerate the species of Perkinsus identified, without suffering heavy lesions.

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This study aimed to assess the final body weight, weekly weight gain, yield, apparent feed efficiency, protein efficiency ratio, and feed intake of the Pacific white shrimp (Litopenaeus vannamei) fed four diets containing different levels of soy protein concentrate (SPC) as a replacement for fishmeal, reared in a super-intensive biofloc system. Diets consisted of replacing 209 g kg-1 fishmeal at 0, 33, 66, and 100% SPC. Shrimp were raised in a biofloc system using twelve experimental units stocked with 250 shrimp m-3 under constant aeration (O2>5mg L-1) and temperature (29±0.5 °C). No significant differences among treatments were observed based on water quality parameters. Shrimp fed diets with 0 and 33% substitution exhibited the highest weekly growth (1.88 and 1.79 g per week) and final weights (15.2 and 14.7 g) compared with shrimp fed the 66 and 100% replacement. A lower feed intake was observed for shrimp fed the 33% SPC diet (3.18 kg per experimental unit) compared with 0% replacement (3.62 kg). Shrimp fed the 33% replacement achieved a similar performance and lower feed intake than animals fed diet without replacement.

SOUZA, R. M. de et al. Lactobacillus plantarum como probiótico no desenvolvimento inicial de juvenis do robalo-peva. Arquivos de Ciências do Mar, Fortaleza, v. 50, n. 2, p. 72-80, jul./dez. 2017. With great potential for aquaculture, the fat snook need technologies for mass production of fingerling with high-quality for pre-ongrowing. One way of obtaining better results with healthy and resistant fish would be the use of probiotics. It was verified the influence of Lactobacillus plantarum supplementation to juvenile diet (56 days after eclosion) on growth, survival, activity of digestive proteases and resistance hypersaline stress. The test of 30 days was composed of three treatments, the first being exclusively fed with Artemia and the two feeding transition received for 15 days and Artemia feed with one of supplementation with L. plantarum and after exclusively the respective feed. The results indicate that bacterial supplementation during dietary transition resulted in increased alkaline protease activity in the digestive tract of fat snook juveniles, as well as increased resistance to salt stress, indicating fish better and healthier, assisting in production massive juvenile fat snook with high quality and ready for storage in pre-ongrowing system. Com grande potencial para a aquicultura, o robalo-peva necessita de tecnologias para a produção massiva de juvenis com alta qualidade para pré-engorda. Uma forma de se obter melhores resultados com peixes saudáveis e resistentes seria a utilização de probióticos. Foi verificada a influência da suplementação de Lactobacillus plantarum à dieta de juvenis (56 dias após a eclosão) sobre o crescimento, sobrevivência, atividade de proteases digestivas e resistência ao estresse hipersalino. O ensaio de 30 dias foi constituído por três tratamentos, sendo o primeiro alimentado exclusivamente com Artemia e os dois de transição alimentar receberam por 15 dias Artemia e ração sendo um destes com suplementação de L. plantarum e, após, exclusivamente as respetivas rações. Os resultados obtidos apontam que a suplementação bacteriana durante a transição alimentar resultou no aumento da atividade de protease alcalina no trato digestório de juvenis de robalo-peva, além da maior resistência ao estresse salino, indicando peixes de melhor qualidade e mais saudáveis, auxiliando na produção massiva de juvenis de robalo peva com alta qualidade e prontos para estocagem em sistema de pré-engorda.

Intensive culture of the hybrid surubim (Pseudoplatystoma corruscans × Pseudoplatystoma fasciatum) in Brazil is responsible for the occurrence of diseases and consequent economic losses. However, the causative agents are not well known. The objective of this study was to isolate and to characterize the pathogenic agent responsible for mortalities in cultured surubim and to demonstrate its virulence. Ten fish from a fish farm located in the Mato Grosso do Sul State (Brazil) were collected and 14 haemolytic bacteria characterized as Aeromonas hydrophila were isolated from the kidneys (eight) and brain (six). As an experimental challenge, fish weighing 98.1±23.6 g were injected with 1 mL of saline solution and 2 × 102, 2 × 104, 2 × 106 and 2 × 108 CFU A. hydrophila mL−1. Fish infected with 2 × 108 CFU showed increased external and internal symptoms and mortality of 50±12.5% after 96 h. Increased A. hydrophila concentration was responsible for a decrease in haematocrit percentage and erythrocyte number, lymphocytes and eosinophils, as well as an increase in monocytes, neutrophils, serum agglutination titre and serum antimicrobial activity. It was concluded that A. hydrophila was responsible for characteristic symptoms of bacterial haemorrhagic septicaemia as well as important haematological and immunological alterations, which led to surubim mortality.

The aim of this study was to assess the effect of a probiotic (Lactobacillus plantarum) supplemented diet on Nile tilapia (Oreochromis niloticus) in a polyculture system with marine shrimp (Litopenaeus vannamei) as regards culture performance, hematology, and gut bacterial microbiota. Ten 20-m² pens were arranged in one earthen pond and stocked with 2 fish (41.9 g) m−2 and 10 shrimp (2.3 g) m−2, in total of 40 Nile tilapias and 200 shrimp per experimental unit. Tilapia groups in five of the experimental units were fed a commercial diet supplemented with L. plantarum and the other five with an unsupplemented commercial diet (control). After 12 weeks of culture, the tilapia groups fed the probiotic-supplemented diet presented values 13.6, 7.5, and 7.1% higher for feed efficiency, yield, and final weight, respectively. Viable culturable heterotrophic bacteria counts were reduced, and the number of lactic acid bacteria was increased in the gut of fish and shrimp fed the probiotic-supplemented diet. Hematological analyses showed higher number of thrombocytes and leukocytes in tilapia fed the supplemented diet. L. plantarum utilized in this study colonized the gut of tilapia and shrimp and resulted in reduced number of total bacteria and increased tilapia final weight and feed efficiency.

The aim of this study was to evaluate the pathogenicity of Vibrio alginolyticus isolated from an outbreak of sea horse Hippocampus reidi reared in the State of Santa Catarina, Brazil, by experimental infection. Sea horses with necrosis on the mouth epithelium were collected from aquaria at the Aquaculture Department, UFSC and the bacterium isolated from the mouth, liver, heart and blood in tiosulphate citrate bilesalt sucrose agar broth. The strains were identified by API 20E kit with 99.1% probability as Vibrio alginolyticus. Twelve adult sea horses (9.63 ± 2.42 g and 15.12 ± 0.87 cm) were distributed in six aquaria of 10 L capacity with aerated sea water. Fish from three aquaria were submitted to an immersion bath in a solution containing 1.0 × 10(7) CFU of V. alginolyticus/mL for 15 minutes. Fish from the other three aquaria received the same procedure without bacteria. Twenty four hours after this challenge, 100% mortality was observed in the animals infected with V. alginolyticus. No mortality was observed in non-infected fish. Hyperplasia, displacement and fusion of secondary lamellae of the gills; leukocyte infiltration and necrotic foci in the kidney; hyperplasia, sinusoidal deformation and necrotic foci in the liver were observed in histopathological analysis. The V. alginolyticus isolated in this study was pathogenic to H. reidi and constitutes an important sanitary problem to its culture.

Aim The increment of decomposition of organic matter in sediment samples from Nile tilapia farms was evaluated with the introduction of Bacillus subtilis and B. licheniformis bacteria. Methods Sediment samples placed in 18L plastic boxes received single dose inoculum with the following concentrations: 1.21 x 106 CFU g-1 (equivalent to 75 g ha-1), 2.41 x 106 CFU g-1 (equivalent to 150 g ha-1), 4.82 x 106 CFU g-1 (equivalent to 300 g ha-1) and 1.61 x 107 CFU g-1 (equivalent to 1000 g ha-1), in addition to a control treatment with saline solution only. Organic matter content, total organic carbon (TOC) and oxidizable (OOC), total nitrogen (TN), ratios (TOC: N and OOC: N), clay content, pH in water, Shoemaker, McLean, Pratt index (SMP Index), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) contents, potential acidity (H + Al), cation exchange capacity (CEC) at pH 7.0, base saturation (V) and sum of bases (S). Results The values of OM showed significant difference, between the lowest values (treatments 75, 150 and 300 g ha-1) and the highest value, (control treatment). TOC, OOC, NT and their relationships (TOC: N and OOC: N) showed significant differences between the mean values of the control treatment and the other treatments. Conclusions The addition of Bacillus subtilis and B. licheniformis bacteria increased the decomposition rate of organic matter in sediments samples from Nile tilapia farms.