Culture Tanks Research Articles

Chitosan Foam–Based Filter: Maintenance of Water Quality for Nile Tilapia Cultivation

The objectives of this research were to evaluate the maintenance of water quality when using chitosan foam filters in water recirculation systems during the cultivation of Nile tilapia and to verify the zootechnical performance and the hepatic and branchial histopathological changes, in comparison with the use of biological filter with bioballs. Two Nile tilapia cultivation trials were carried out (trial 1: 35-L tanks; trial 2: 130-L tanks), using six individual water recirculation systems, consisting of a culture tank, decantation tank, submerged pump for recirculation, aeration and external filter. The physical and chemical parameters related to water quality were evaluated every 48 h. At the end of each trial, the fish biometrics was performed to obtain final weight, feed conversion, and survival. In trial 2, the histopathological analysis of the hepatopancreas and gills was performed and the organ index was calculated. The daily averages of the physical and chemical parameters of the water quality, the zootechnical performance of the fish, and the organ indexes of the treatments of trials 1 and 2 were compared by the t test (p ≤ 5%). There were no significant differences in final weight, feed conversion, survival, or organ indexes between treatments (p > 0.05) in relation to the two trials. It was observed that the use of the filter with chitosan foam in the water recirculation systems resulted in lower or equal concentrations of total ammonia, nitrate, and dissolved orthophosphate, and maintained the same or higher alkalinity than in tanks with bioball biological filter. It is recommended to change the chitosan foam every 30 days of cultivation. The use of water recirculation systems with treatment using filters filled with chitosan foam during the cultivation of Nile tilapia is equally effective or better than the use of a biological filter with bioballs.

Lethal concentration of Cymbopogon citratus (Poaceae) essential oil for Dolops discoidalis and Argulus sp. (Crustacea: Argulidae).

This study investigated the acute toxicity (LC50-24hr ) effects of the essential oil of Cymbopogon citratus for adult Argulus sp. and Dolops discoidalis, before and during oviposition. In vitro acute toxicity (LC50-24hr ) was tested using 20, 40, 60, 80, 100, 120, 140 and 160μg/L of C.citratus essential oil, and two control groups (one with cultivation tank water and one with cultivation tank water+alcohol) were used. Specimens of Argulus sp. and D.discoidalis submitted to acute toxicity were evaluated using histological procedures. The major chemical compounds of C.citratus essential oil were geranial (47.5%), neral (35.6%) and myrcene (6.7%). The LC50-24hr for Argulus sp. adults was 67.97μg/L, while for D.discoidalis it was 59.55µg/L. In the oviposition of both species of argulids, maximum mortality began with treatments of 140μg/L, while the LC50-24hr for Argulus sp. and D.discoidalis was 83.98μg/L and 82.48μg/L, respectively. In both argulid species exposed to C. citratus essential oil, morphological alterations were observed only in the eyes, and they occurred in the ommatidium and rhabdomeres and were dependent on the concentration of C.citratus essential oil and the parasite species.

First Histopathological Description of Parasites and Shell Conditions of the Donkey's Ear Abalone Haliotis asinina (Linnaeus, 1758) Cultured in Marine Cages and Land-Based Tanks in the Philippines

This study is the first attempt to assess parasitic infestations in grow-out cage culture and land-based grow-out tanks of the donkey's ear abalone Haliotis asinina in the Philippines. This histopathological study of the parasites was conducted from 2010 to 2013. Using 30 samples of abalones collected monthly from two sites, samples were measured and fixed in 10% formaldehyde in seawater, and routine histological techniques were used to identify the parasites. Water temperatures of the grow-out floating sea cages and the abalone hatchery facilities whose abalones were collected measured 27.5°C–32.5°C and 26°C–29°C, respectively; salinity in the area of the sea cages was 32–34 ppt, whereas salinity of the abalone hatchery was 32–35 ppt. Examination of the shell from cage-cultured abalones revealed the presence of burrowing polychaetes belonging to the families Serpulidae (prevalence, 32.5%) and Dorvilleidae (prevalence, 30%); on the other hand, only Dorvilleidae (prevalence of 28.5%) was detected in abalones from the hatchery. Histological examination revealed the presence of unknown ciliates (prevalence, 37.5%), Nematopsis sp. (prevalence, 17%), and metacestode Tylocephalum sp. (prevalence, 8.5%) from the grow-out cage-cultured abalones, whereas unidentified ciliates (prevalence, 32.5%) and Nematopsis sp. (prevalence, 10.5%) were detected from hatchery stock. The data collected showed that there was low-intensity infection and prevalence of parasites in abalones from grow-out cages and hatchery. These records of parasites constitute baseline information for future research work on abalones.

Characteristics of Fluorescence Spectra, UV Spectra, and Specific Growth Rates during the Outbreak of Toxic Microcystis Aeruginosa FACHB-905 and Non-Toxic FACHB-469 under Different Nutrient Conditions in a Eutrophic Microcosmic Simulation Device

Microcystis aeruginosa is the dominant alga forming cyanobacteria blooms, the growth of which is limited by available nutrients. Thus, it is necessary to study cyanobacteria blooms and explore the growth of Microcystis aeruginosa under different nutrient conditions. In this paper, we take Microcystis aeruginosa, including toxic Freshwater Algae Culture of Hydrobiology Collection (FACHB)-905 and non-toxic FACHB-469 strains, into account. The strains were cultured using a simulation device under different nutrient conditions. Ultraviolet spectra, three-dimensional fluorescence spectra, and kinetic parameter indicators of the two species are studied. Compared to FACHB-469, the results show that the specific growth rate of FACHB-905 is much higher, in particular, FACHB-905 is the dominant species under low nutrient conditions. Furthermore, the UV spectral characteristics indicate that the molecular weight of dissolved organic matter in the culture tank of toxic FACHB-905 is greater than that of FACHB-469. Additionally, the humification index of toxic FACHB-905 is slightly higher as well, which suggests that it is more stable in the presence of dissolved organic matter during blooms. Therefore, the toxic Microcystis strain is more likely to become the dominant species in water blooms under lower eutrophic conditions and water blooms formed by the toxic Microcystis strain may be more difficult to recover from.

Essential oil of Lippia grata (Verbenaceae) is effective in the control of monogenean infections in Colossoma macropomum gills, a large Serrasalmidae fish from Amazon

This study investigated the efficacy of Lippia grata essential oil (EO) against monogeneans of Colossoma macropomum and effects on the haematology after immersion baths. In the in vitro assays, the efficacy of 100, 250, 350 and 700 mg/L of L. grata EO and two controls were tested, of which one control was with the cultivation tank water and the other was with the tank water and 70% ethyl alcohol. Composition of majority bioactive compounds in the EO was carvacrol (48.12%), p-cymene (24.39%) and γ-terpinene (2.49%). Anacanthorus spathulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni obtained of fish gills showed 100% immobilization in the in vitro assays when exposed to 700 and 350 mg/L after 30 min and 2 hr respectively. Fish showed tolerance to 700 mg/L of the EO, which was used in therapeutic in three consecutive baths, which caused lamellar hyperplasia in C. macropomum gills. The 700 mg/L of the EO in the therapeutic baths showed an efficacy of 95.1% against the monogeneans and caused decrease in haemoglobin, whereas control fish showed a reduction in mean corpuscular haemoglobin concentration. Results indicated that 700 mg/L of L. grata EO is a safe and effective concentration to treat C. macropomum infected with monogeneans.

Influence of inlet and outlet placement on the hydrodynamics of culture tanks for Atlantic salmon

The salmon farming industry has recently shifted to larger culture tanks with greater water flows to optimize the land-based production, but tanks approaching 1000 m3 in volume create challenging hydrodynamics. This paper presents a computational study of four combinations of inlet and outlet designs of a commercial land-based aquaculture tank. Windows-based OpenFOAM solvers are used to solve the conservation equations for tank hydrodynamics with an implicit unsteady second-order Eulerian (finite volume) technique on unstructured hybrid meshes. The model is validated by the velocity measurements at discrete locations in the tank using acoustic doppler velocimetry. To understand the dispersion of biosolids in the tank, 500 particles with a uniform size of 200 µm are tracked in the Lagrangian frame. While the tank's Reynolds number varies between 2E6 - 3.5E6 depending on the flow exchange rate, the local Reynolds number at the inlet pipe is about 2E5 which discovers the drag-crisis phenomenon. The effect of inlet and outlet placement on the velocity, vorticity and turbulence is addressed. The existing tank design could be improved using the bottom-drain and corner-inlet options, which strengthens rotational flow with better uniformity. Such design change is also proved to provide better particle removal and thus ensure the improved self-cleaning ability of the tank.

GROWTH PERFORMANCE AND POST-HARVEST QUALITY OF GIFT TILAPIA REARED IN TWO DIFFERENT CULTURE SYSTEMS

The growth performance, feed utilization, sensory evaluation, proximate and fatty acid composition of Genetically Improved Farmed Tilapia (GIFT) reared in different aquaculture systems (tank and cage culture in pond) were examined in a 126-day feeding trial. Throughout the feeding trial, fish were fed commercial tilapia feed twice a day at 3% of their body weight. Significantly higher final body weight, weight gain, daily growth rate, viscerosomatic and hepatosomatic indices were yielded in GIFT tilapia cultured in pond than in tank. In contrast, GIFT tilapia cultured in tank showed significantly higher survival rate than GIFT tilapia cultured in pond. Higher positive scores of sensory evaluation test were observed in both treatments, indicating the good acceptance of consumers towards GIFT tilapia. Meanwhile, higher contents of 20:5n-3 and 22:6n-3 of GIFT tilapia fillets from tank culture system than those cultured in cage were mainly influenced by significantly different size of fish and maturity factor during harvest. In general, it can be concluded that the performance of GIFT tilapia reared in pond culture system was better than those in tank culture system with benefits of early harvest and faster growth rate. On the other hand, tank culture system also has its own advantages in terms of higher survival rate and better fatty acid profile.

Molecular remedies against Cryptocaryon irritans Brown, 1951—Practical difficulties

This review paper deals with the immunological response in marine fish infected by Cryptocaryon irritans and discussed the practical difficulties in the development of potential molecular remedies. Browsing through the literature, it is understood that the development of molecular diagnostic tool to detect the early infection in fish by C. irritans is under progress. Once it is successfully established, the possible application of this technique could be suggested for even the non-specific treatments such as copper-based medications and bare-bottomed quarantine of culture tanks. However, prior protection of healthy fish from C. irritans could be accomplished through proper immunization by infective theronts. In this case, a well-suited in vitro culture technique is necessary to harvest theronts in large scale. Recent immunological and transcriptome studies predicted that the components related to local immune response are more effective against C. irritans than their systemic counterparts. However, in vivo experiments to prove the effect of these antiparasitic molecular components are meagre. Though molecular vaccines, developed from the well-characterized 34 kDa immobilization antigen (iAg), responded well, these remedies fail to have a uniform impact against antigenically different strains (serotypes). More research is recommended to identify common protective epitopes from different serotypes. Also, studying the adjuvant effects of various innate responsive components like cytokines is significant. The suggested studies would be immensely helpful to develop effective vaccines against C. irritans infection and thereby optimize the aquaculture practices.

Characterizing the water quality and microbial communities in different zones of a recirculating aquaculture system using biofloc biofilters

Recirculating aquaculture systems (RAS) using biofloc biofilters can address the high accumulation of nitrate (NO3−-N) and total suspended solids (TSS) in in-situ biofloc technology (BFT) aquaculture systems. A RAS was divided into the following four zones: reaction zones of the BFT biofilters, settling zones of the BFT biofilters, culture tanks, and a buffer tank. During the 95-day experimental period, the water quality parameters and microbial communities in different zones of the RAS were compared. The NO3−-N, nitrite (NO2−-N), total ammonia nitrogen (TAN), and TSS in the culture tanks were continuously controlled at average concentrations of 9.84 ± 5.15, 0.28 ± 0.15, 0.10 ± 0.18, and 96.92 ± 33.82 mg·L−1, respectively. Because denitrification produced alkalinity in the BFT biofilters, the alkalinity of the culture tanks reached an appropriate concentration of 109.40 ± 10.57 mg CaCO3·L−1 without intentional adjustment. The concentrations of NO3−-N, NO2−-N and TAN in the reaction zones were significantly lower than those in the influent (buffer tank) and culture tanks. However, there was no significant difference found for major water quality parameters between the reaction zones and the settling zones. There was also some removal of soluble reactive phosphate by the BFT biofilters, although there was no significant difference between the biofilters and influent. Microbial communities in the reaction zones were more diverse than those in the culture tanks, buffer tank and settling zones. Denitrifiers, nitrifying bacteria and important functional microbial populations for phosphorus removal were all present in the reaction zones, and at higher levels than those in other zones. Nitrogen and phosphorus removal were mainly achieved in the reaction zones of the BFT biofilters, and the microbial communities in the other three zones were similar. Besides, Scortum barcoo grew from an individual weight of 347.7 ± 73.0 to 472.1 ± 106.2 g, achieving a final stocking density of 32.81 kg·m−3 at the end of the experiment.

Design and development of a portable and streamlined nutrient film technique (NFT) aquaponic system

One pilot-scale portable Nutrient Film Technique (NFT) aquaponic system has been designed, developed, and tested at ICAR-CIFA, Bhubaneswar for a period of 90 days (October to December 2018) to study the efficiency of the new design. The experimental setup has three separate units, each consisting of four major components, such as Fibreglass Reinforced Plastic (FRP) round fish culture tank (ø2.15 × 0.9 m) with operational capacity 2800 L, biofilter unit made up of Polypropylene (PP) of 100 L capacity, FRP rectangular hydroponics tank (4 × 0.9 × 0.35 m) having 2.64 m2 plantation area and High-density Polyethylene (HDPE) sump (ø0.6 × 0.7 m) of 200 L capacity. Implementation of custom designed and calibrated automatic water recirculation system gives an average flow rate of 94.7 L/h for continuous flow of nutrients from fish culture tank to hydroponics tank. The designed system harnesses gravity flow in 75 % of the cycle. For performance assessment, the system was initially stocked with 54 numbers of fish fry/m3 (153.7 g/m3) of pangas (Pangasius hypophthalmus) in culture tank and 27 marigold (Tagetes erecta) plants/m2 in hydroponics tank. Length and weight gain of fish were by 77.04 % and 397.2 % from initial, respectively, and marigold plant harvested 107 number of flowers/m2. The Total Ammoniacal Nitrogen (TAN) reduction in biofilter was found to be 61.97 %.

The growth performance and genotoxicity effect of dietary Aloe vera on Oreochromis niloticus juveniles

Growth and all activities of fish depend significantly on the food they consume. However, with the rising price of conventional feedstuffs, there is a need to investigate less expensive and readily available plant source as an additive. This research is designed to study the effect of dietary Aloe vera on the growth performance of Oreochromis niloticus juveniles (41.71±0.78g) and its effect on genotoxicity (MN: Micronucleus; LB: Lobed; BD: Bud; BL: Blebbed; BN: Binucleated; NT: Notched). This research investigated the growth performance and genotoxicity activity of Oreochromis niloticus juveniles in a tank culture system. Aloe vera (fine powder) was used as a test ingredient in the feed formulation at five inclusion levels (T1 = 5g, T2 =10g, T3 =15g, T4 =20g, T5 =25g) and the Control diet (C0) without the test ingredient. Test diets were fed to Oreochromis niloticus juveniles, and each diet was assigned to the treatments and control overall in triplicates. Feeding with test diets was for twelve (12) weeks at 5% of their total body weight daily, which was divided into two and administered at 8 hrs and 16 hrs. The result showed that the highest growth rate (10.99 ± 5.49g) and the lowest FCR (0.68 ± 0.08) were recorded in the fish fed with the Control diet (C0). Better growth and nutrient utilization were achieved at low inclusion levels of Aloe vera, at 5g(T1) (8.98 ± 4.49) and 10g (T2) (6.73 ± 3.28) compared to the higher levels of incorporations of the test ingredient. The mean pH and temperature (°C) and dissolved Oxygen level mg/L are 6.50±0.30, 26.3±0.60 and 4.48±0.52mg/L respectively. The values of micronuclei for the cultured Oreochromis niloticus juveniles were recorded to be (T1 = 5.50 ± 0.50, T2 = 2.00 ± 1.00, T3 = 2.00 ± 0.00, T4 = 2.50 ± 1.50, T5 = 4.00 ± 1.00, and C0 = 7.00 ± 2.00). Nuclear abnormalities were recorded in T2 (BD = 1.00 ± 0.00), T3 (NT = 1.00 ± 0.00), T4 (BD = 1.33 ± 0.47, BN = 3.33 ± 0.47), and T5 (BN = 5.33 ± 0.47, LB = 3.00 ± 1.00, BL = 1.67 ± 0.47) . However, no abnormality was recorded in the fish fed with the Control diet (C0). This result showed that the slight addition of this Aloe vera to the diet of Oreochromis niloticus would enhance productivity.

Effects of irradiance, temperature, nutrients, and pCO2 on the growth and biochemical composition of cultivated Ulva fenestrata

Ulva fenestrata is an economically and ecologically important green algal species with a large potential in seaweed aquaculture due to its high productivity, wide environmental tolerance, as well as interesting functional and nutritional properties. Here, we performed a series of manipulative cultivation experiments in order to investigate the effects of irradiance (50, 100, and 160 μmol photons m−2 s−1), temperature (13 and 18 °C), nitrate (< 5, 150, and 500 μM), phosphate (< 1 and 50 μM), and pCO2 (200, 400, and 2500 ppm) on the relative growth rate and biochemical composition (fatty acid, protein, phenolic, ash, and biochar content) in indoor tank cultivation of Swedish U. fenestrata. High irradiance and low temperature were optimal for the growth of this northern hemisphere U. fenestrata strain, but addition of nutrients or changes in pCO2 levels were not necessary to increase growth. Low irradiance resulted in the highest fatty acid, protein, and phenolic content, while low temperature had a negative effect on the fatty acid content but a positive effect on the protein content. Addition of nutrients (especially nitrate) increased the fatty acid, protein, and phenolic content. High nitrate levels decreased the total ash content of the seaweeds. The char content of the seaweeds did not change in response to any of the manipulated factors, and the only significant effect of changes in pCO2 was a negative relationship with phenolic content. We conclude that the optimal cultivation conditions for Swedish U. fenestrata are dependent on the desired biomass traits (biomass yield or biochemical composition).

Evaluation of Growth and Fruit Quality of Cucumber (&lt;i&gt;Cucumis sativus L.&lt;/i&gt;) Irrigated with African Catfish Cultured Wastewater

This paper reports findings of an experiment carried out in a greenhouse to evaluate the growth and fruits quality of cucumber grown in plots irrigated with African catfish cultured wastewater compared with those irrigated with ordinary well water. Six circular African catfish culture tanks and six cucumber planter boxes were used for this experiment, three each for the fish cum cucumber integrated system and the control system of cucumber irrigated with ordinary well water. The results of the research indicated that fish cultured wastewater had a better influence on the plant height, the number, length, and diameterof leaves, as well as the diameter and length of the fruits. Six experts, each independently assessed fruits from the two treatments for juiciness, sweetness, taste and crispiness. The fruits were assessed by experts who though were aware of the purpose of the evaluation, did not know the identity of fruits they were assessing. The fish effluent fertigated cucumber fruits had a higher mean score in juiciness, sweetness, taste and crispiness. Wastewater from the African catfish production system thus exhibits the potential for reuse in the production of cucumber plants as it had no negative effect on the organoleptic quality of cucumber fruit produced.&#x0D; Keywords: Cucumis sativus, Fish, Growth, Yield, Wastewater.

Anthelminthic efficacy of Cymbopogon citratus essential oil (Poaceae) against monogenean parasites of Colossoma macropomum (Serrasalmidae), and blood and histopathological effects

This study investigated the in vitro and in vivo anthelminthic efficacy, histopathological and hematological effects of Cymbopogon citratus essential oil (EO) in Colossoma macropomum. The major compounds of the essential oil were geranial (45.7%) and neral (33.9%). Essential oil was assayed at concentrations of 100, 200, 300, 400 and 500 mg L−1 for in vitro efficacy against monogeneans Anacanthorus spathulatus, Mymarothecium boegeri and Notozothecium janauachensis of C. macropomum. Two controls were considered for in vitro assays, one with the use of cultivation tank water and the other with cultivation tank water +70% alcohol. The concentration of 500 mg L−1 of the EO in vitro assays showed 100% efficacy against the parasites within 5 min of exposure, causing structural damages to their tegument. The 400 and 300 mg L−1 concentrations were 100% effective with 10 min and 30 min of exposure, respectively. The 200 mg L−1 concentration in vitro assays was also 100% effective within 30 min and the 100 mg L−1 treatment was 100% effective within 100 min of exposure. Total parasite mortality in both control groups occurred within 7 h. Efficacy was 47.1% after therapeutic baths of 20 min for three consecutive days with 60 mg L−1 of this EO. In addition, 60 mg L−1 of EO was the highest concentration tolerated by the fish and it had an anesthetic effect, and it caused increase in plasma glucose levels and decrease in leukocytes and lymphocytes number, as well as hyperplasia, lamellar fusion, detachment and aneurysm in C. macropomum gills. A low efficacy against the monogeneans was shown perhaps due to the low concentration of this EO tolerated by C. macropomum and the strategy used for the therapeutic baths, which may be corrected with a lower concentration of EO and more consecutive days for therapeutic baths.

Mathematical model for goldfish recirculating aquaculture system (GRAS)

A mathematical model is framed for a goldfish recirculating aquaculture system based on unsteady-state mass balance for prediction of the concentration of total ammonia nitrogen (TAN), nitrite-nitrogen (NO2-N), nitrate-nitrogen (NO3-N), dissolved oxygen (DO) and total suspended solids (TSS). The goldfish were stocked at 100 numbers per m3 of rearing water volume of 5 m3 tank capacity in the years 2009 and 2010 and the model was calibrated and validated. The recirculation flow rate was fixed at 29,000 L/day. The model parameters were estimated as kTAN (mg of TAN generated per kg of feed): 20,000, M (mortality rate): 0.002 day−1, α (percentage of feed conversion to suspended solids): 23.8, koxy (mg of oxygen required for fish respiration per kg of feed applied in unit time): 300,000, kb (partial nitrification in the culture tank): 0.86 and the reaction rate constants, k1 and k2: 84.65 day−1 and 42.03 day−1 respectively and temperature growth coefficient (TGC): 5.00 × 10-5. The model efficacy was adjudged by estimation of the coefficient of determination (R2), root mean square error (RMSE), Nash-Sutcliffe modelling efficiency (ENS) and graphical plots between predicted and observed values.

Flocculation of Artemia induced by East Asian common Octopus octopus sinensis paralarvae under culture conditions

Artemia are potential food organisms for the mass culture of common octopus paralarvae but cause poor paralarval growth and mortality. To understand problems arising from Artemia use, we focused on Artemia flocculation in paralarval culture tanks; Artemia get caught up with each other, exhibit disrupted swimming, are deposited on the tank bottom and eventually die. To clarify whether paralarvae induce the flocculation of food organisms or not, we cultured newly hatched Artemia nauplii, 3-day-old metanauplii and decapod crustacean zoeae with or without paralarvae at different growth stages (weight). Flocculation occurred only when Artemia were cultured with paralarvae; metanauplii had a higher susceptibility for flocculation than nauplii. Flocculated Artemia proportion increased with increasing paralarval weight. Scanning electron microscopy revealed that flocculated metanauplii had deformed setules on their setae, with hook-shaped tips and adhesion of neighbouring tips, suggesting that flocculation may occur via a mechanism similar to the ‘hook-and-loop fastener’. As octopus paralarvae exhibit external digestion, digestive enzymes secreted by paralarvae may deform Artemia setules and result in flocculation. As flocculation did not occur when metanauplii were cultured in water in which paralarvae were cultured and then removed, causative enzymes were probably rapidly inactivated after secretion.

Chemical defense against microfouling by allelopathic active metabolites of Halymenia floresii (Rhodophyta)

During the experimental cultivation of the red alga Halymenia floresii under Integrated MultiTrophic Aquaculture (IMTA), the establishment of opportunist green algae and the colonization of sessile invertebrates, which were usually disturbing the cultivation, were not observed. The culture tanks were clean and the surface of the H. floresii was remarkably free from any fouling organisms. This phenomenon could reveal that the presence of H. floresii may prevent biofilm formation by releasing allelopathic active compounds that ultimately interfere with the settlement and growth of competitors. In order to understand this phenomenon, H. floresii was cultivated under controlled environmental conditions and analyzed for its surface chemical defense metabolites. The surface-associated metabolites were extracted using the DIP extraction method, using different solvents with increasing polarity and immersion periods. Using epifluorescence microscopy, n-hexane was found to be the suitable immersion solvent for H. floresii for a period of 10 to 60 s to extract surface metabolites. The whole cell metabolites were extracted exhaustively with the same solvent for a period of 24 h. The chemical profiling of the surface compounds was performed by liquid chromatography mass spectroscopy (LC-MS), followed by a Mass Bank search and compared with those obtained from the whole-cell extracts. The mean concentration of H. floresii surface metabolites was 600 ng cm−2 (c. 60 g of a fresh sample) whereas the whole-cell metabolite concentration was around 4.5 μg mg−1 (400 mg of the lyophilized sample). The bioactivity of the H. floresii surface extracts was studied by evaluating their quorum quenching behavior on the surface-associated bacteria. The cultivable bacteria isolated from the surface of H. floresii were identified as Vibrio owensii (B3IM), Alteromonas sp. (B7CC), Pseudoalteromonas arabiensis (B4BC), Ruegeria sp. (B4CC), Tenacibaculum sp.(B9BC), Maribacter sp. (B9IM) and Aquimarina sp. (B9.1CC). All the isolated strains belonged to Alphaproteobacteria, Gammaproteobacteria and Bacteroides. The results of this bioactivity proved that the surface-associated metabolite extract (DIP) interferes with the communication signals produced by the bacteria isolates with the reporter strain employed. According to the Mass Bank compound analysis, we hypothesized that flavonoids and/or halogenated compounds might have contributed to this activity. This work provides an understanding of the influence of surface-associated metabolites on the associated bacterial community and by which H. floresii manages to control the biofouling on its surface.

Cultivation of seaweed Kappaphycus alvarezii (Doty) doty ex silva using tissue–cultured seedlings in encircling tank culture system

The seaweed, Kappaphycus alvarezii, is the most widely cultivated commodity in Indonesia. The problem currently faced is seedling availability due annual seasonal variations such as heavy flooding This paper presents a study aimed at solving seedling scarcity: the first based on cultivating tissue-cultured seedlings in encircling tanks. The aim of the study was to determine the effect of different initial weight on growth and carrageenan yield of K. alvarezii using tissue – cultured seedlings. This research was conducted from March to June 2019 in the Shrimp Hatchery, Kendari, Indonesia. This study applied three treatments based on different initial weight and five replications. The treatments were 5g, B: 10g and 15 g initial weights (IW). The results showed that the daily growth rate (DGR) of all treatments tended not to differ significantly but the DGR of 5-g IW tended to be higher than those of the other two treatments. The means of DGR were 3.76±0.54%/day, 3.30±0.46%/day, and 2.84±0.27%/day for 5-, 10-, and 15-g IW, respectively. Healthy rates of all treatments were 90.28%, 94.45% and 87.47% for 5-, 10- and 15-g IW. The ratio of fresh weight (FW) and dry weight (DW of 5-, 10-, and 15-g IW were 9.51:1, 9.54:1, and 9.56:1, respectively. The ratio showed no significant differences among treatments. Furthermore, for carrageenan yield, 15-g IW treatment showed the highest yield (37.05±2.18%), but had no significant differences from the other two treatments. Furthermore, all water quality parameters, temperature, salinity, DO, pH, nitrat, phosphate and turbidity were within the normal range for cultivating the seedlings. In conclusion, 5-g initial weight is a prominent weight suitable to be used in cultivating the seedlings in the encircling tank.

The effects of density and artificial substrate on intensive shrimp Litopenaeus vannamei nursery production

Recirculating aquaculture systems (RAS) can be installed indoors, allowing year-round production of tropical animals in nearly any climate. A nursery phase is commonly used in Litopenaeus vannamei production since it allows for enhanced biosecurity and better quantification of animals while reducing space requirements. However, it is unclear whether animal density and inclusion of artificial substrate may improve shrimp performance during the nursery phase. In this experiment, we compared shrimp production parameters in two stocking densities with or without the use of an artificial substrate by creating four treatments: low-density LD; 1500 PL/m−3, low-density with substrate LDS, high-density HD; 3000 PL/m−3), and high-density with substrate (HDS). The LDS and HDS treatments included 0.46-m2 of high-density polyethylene 2.5-cm mesh as a substrate, which increased the tank surface area by 21 %. Each treatment was randomly assigned to four 160-l culture tanks, each with a biofilter. The shrimp had an initial weight of 4 mg and were grown for 50 days. The low-density treatments had significantly higher dissolved oxygen (DO) and pH than the high-density treatments (P ≤ 0.001). Specifically, LDS had the highest DO and pH followed by the LD, HD, and HDS treatments, respectively. High-density treatments had significantly higher NO2-N levels than low-density treatments during week 2 of the experiment when an unusually high concentration of nitrite was observed. FCR was significantly lower in both low-density treatments than in high-density treatments. At harvest, the total biomass (kg m−3) was significantly higher in high-density treatments than in low-density treatments (P ≤ 0.001), and the HDS treatment had a significantly greater biomass output than HD. Producers should consider artificial substrate and higher densities during nursery production to maximize shrimp production; however, the effects on water quality should also be taken into account.

Monitoring of growth, digestive enzyme activity, immune response and water quality parameters of Golden crucian carp (Carassius auratus) in zero-water exchange tanks of biofloc systems

A 56-day feeding trial was implemented to evaluate the effects of promoted biofloc on the water quality, growth performance, digestive enzymes activity, immune-related genes and antioxidant status of golden crucian carp in negligible exchange culture tanks. Four handred fifty healthy golden crucian carp juveniles (5.03 ± 0.22 g) were randomly assigned among 15 tanks. Five C:N ratios in triplicate tanks were tried: C/N = 5.48:1 with a commercial diet (Control), C/N = 10:1, C/N = 15:1, C/N = 20:1 and C/N = 25:1. Anhydrous glucose (99.97 %) was added to the commercial diet to maintain elevated carbon ratio in the three treatments. Uninterrupted 24 -h aeration was supplied during the test by using an air-stone connected to an air pump to develop the biofloc in the water column. The results demonstrated that BFT significantly reduced ammonia nitrogen (TAN), nitrite (NO2−-N), total phosphorus (TP) concentration and water transparency (Secchi depth) in C/N 15–25 than control (p < 0.05), wheras the chemical oxygen demand (COD) and nitrate nitrogen (NO3−-N) concentration gradually increased over time. Apart from, weight gain (WG), specific growth rate (SGR), and protein efficiency ratio (PER) were considerately elevated in C/N 20 and C/N 25 than control (p < 0.05).This was coincidental with the higher activities for protease, lipase and amylase in liver. Significant increases in lysozyme (LSZ), acid phosphatase (ACP) and alkaline phosphatase (AKP) activities of golden crucian carp were found in the C/N 20 group than control (p < 0.05), and regulating the expression of immune-related genes including IL-1β, TNF-α and HSP70 after a 56-day feeding trial. Comparing the antioxidant capacity of golden crucian carp from the five experimental groups, the activity of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), catalase (CAT) activity and glutathione peroxidase (GSH-PX) activity of juveniles in the C/N 20 and C/N 25 groups were significant higher (p < 0.05), and the content of malondialdehyde (MDA) was much lower (p < 0.05) than in the control under this experiment condition. Overall, this findings suggest that BFT not only can enhance golden crucian carp growth performance, elevate digestive enzymes activity, and strengthen antioxidant status but also upgrade immune response.