Application of simple dynamic response analysis to a recirculating aquaculture system — A preview

This paper describes the application of dynamic response analysis to a simple first order recirculating aquaculture system and demonstrates how the distribution of ammonia throughout the system may be predicted following dynamic changes. The approach is validated by experimental data obtained for a recirculating system under controlled conditions of mixing and disturbance.It is concluded that unsteady state predictive methods have significant potential application in the context of aquaculture, subject to further refinement in the modelling of biochemical kinetics and liquid mixing.     

Long Term Rearing of Cuttlefish in a Small Scale Facility

Cephalopods are arguably the most complex and fascinating aquatic invertebrate taxa. Except for a few well known exceptions, this group of organisms has been a challenge to study primarily due to difficulties in rearing and maintaining these animals in a small laboratory setting. Our knowledge about cephalopod rearing comes mainly from large marine centers, with much less known about small scale rearing facilities. This paper describes a bench top (ca. 450 litre) aquarium system that is relatively inexpensive, easy to maintain, and suitable for long term rearing of cuttlefish in the laboratory. This closed aquarium system uses artificial sea water and a biological filter to remove/recycle nitrogenous wastes. The simple design of this system can be easily replicated by inland researchers interested in studying cuttlefish but who have been thwarted by the lack of suitable housing facilities. This revised version was published online in August 2006 with corrections to the Cover Date.     

Acclimation Induced Responses of SDH Activity of Tilapia (Oreochromis mossambicus) Following Introduction in a New Pond Habitat

Responses of the major mitochondrial respiratory enzyme succinate dehydrogenase (SDH) activity in gill and muscle tissue of tilapia (Oreochromis mossambicus) were investigated upon their transfer to a new pond habitat. Sixty healthy adult fish were procured from each of the three ponds used and were distributed in three cages in equal numbers; the cages were placed in each of the other two ponds as well as into original rearing pond. Four fish were removed from each cage every week and were sacrificed for the assay of SDH activity in gills and muscles. Transfer of fish from a stress condition to a benign environment and vice versa resulted in an increase and decrease in SDH activity of fish, respectively. The intensity of increase upon transfer was again dependent upon the amount of stress in the new habitat. In general, the SDH activity of the test fish strongly correlated with the ammonia concentration (P?<?0.05) of water regardless of habitats. Time required for the introduced fish to acclimatize with new environmental conditions was dependent upon the environmental milieu of both its initial and final place of rearing and hence their physiological states. Differences in water quality, especially ammonia concentration, between its original place of rearing and the place of transfer were found to be responsible for the differences in acclimation period of two or three weeks. Relatively less difference in ammonia (2.68 for gills and 3.20 for muscles) between the initial place of rearing and new habitat resulted in acclimation of the fish one week earlier (second week) than the relatively wide difference (4.46 for gills and 5.62 for muscles) for third week. It may be reasonable to conclude that the varied responses of the mitochondrial respiratory enzyme of exogenously introduced fishes with the differences in the water quality—especially the ammonia concentration of ambient water between the original fish holding pond and growout pond—can be used to predict the time that will be required for the exogenously introduced fish to fully acclimatize with the new habitat.     

Evaluating the Rearing condition of Rainbow Trout (Oncorhynchus Mykiss) Using Fuzzy Inference System

Rainbow trout (Oncorhynchus mykiss) is one of the most popular aquacultured species in the world. Sustainable production of this fish at commercial scale is very important but requires maintaining good water quality throughout the total rearing period. The present study aimed to develop a rainbow trout production index in order to raise awareness about the conditions of the rearing environment, enhance production, and reduce losses. For this purpose, an intensive rainbow trout production system was selected as the study system. In this system, there were seven stations including (a) 3000 5-g fish, (b) 3000 25-g fish, (c) 3000 50-g fish, (d) 3000 100-g fish, (e) 3000 220-g fish, (f) 2000 350-g fish, and (g) 2000 830-g fish. The fuzzy inference system was used to develop the target rearing index. Water quality parameters involved in the variation in the rainbow trout rearing conditions were classified into three groups including un-ionized ammonia, nitrite, and nitrate, Alkalinity and phosphate, along with dissolved oxygen and linear velocity. For each group and condition of rearing, a separate fuzzy inference system was defined and the output of each fuzzy system was named I₁, I₂, I₃. Finally, I₁, I₂, and I₃ were considered as the inputs to a fuzzy system in order to evaluate their effects on the index of general rearing conditions (I). The results indicated that un-ionized ammonia, nitrite, nitrate, and phosphate had negative effects while dissolved oxygen, linear velocity, and alkalinity positively affected water quality and rearing index. Most of the decline in the rainbow trout rearing index was related to the effect of un-ionized ammonia, nitrite, and nitrate due to food decomposition. Therefore, intelligence feeding based on fish appetite through reducing food conversion rate and water pollution can improve rainbow trout production in this system. The index of rainbow trout production conditions reflects the type, amount, and effect of water quality pollutants on rearing conditions. Producers can use this information to reduce the negative environmental effects and improve the product quality.     

Biocontrol of ammonia pollution in the rearing water of fish by inducing a heterotrophic bacterial-based food chain in the medium

In intensive aquaculture, one of the main problems confronted by the farmers is the ammonia pollution and subsequent disease outbreaks, high costs of quality protein feed, and the labor for periodic water exchange. Ammonia is a major metabolic waste product from fish, which is excreted across the gill membranes and in the urine. Controlling the inorganic nitrogen by manipulating the carbon/nitrogen ratios seems to be a practical and inexpensive means of reducing the accumulation of ammonia. At high carbon to nitrogen (C/N) ratios, bacteria will assimilate nitrogen, i.e., ammonia, from water and produce new cell protein. The experiment was designed by adding 0, 10, 20, and 30 g of carbohydrate (rice flour) for each gram of total ammonia nitrogen (TAN) released as a result of feeding metabolism and feed waste decomposition. The ammonia built up in the rearing water showed a drastic decrease in all the carbohydrate added tanks. The heterotrophic bacterial growth was significantly higher in the same. The biochemical constituents and growth rate were higher in fishes in the tanks having C/N ratio 10 and 20. Percentage weight gain was 100% for T₃₀, protein efficiency ratio (PER) was high for T₂₀ and T₃₀ (4.048). The C/N ratios of 20 and 30 worked more effectively. Shifting the aquatic ecology from autotrophic to heterotrophic bacterial-based community can improve water quality and recycle the toxic ammonia waste to heterotrophic bacterial flocs, which in turn can be consumed by the fish, thereby reducing the feed protein demand and subsequently the reduction of feed cost.     

Selection for improved stress tolerance in rainbow trout (Oncorhynchus mykiss) leads to reduced feed waste

The magnitude of the cortisol response to a standardised stressor is a heritable trait in salmonid fishes, and selection for stress responsiveness induces differences in both behaviour and neuroendocrine function. For instance, in laboratory studies, fish with a high cortisol response show a greater propensity for stress induced anorexia. Some authors have, however, commented that controlled studies encompassing relatively small groups of fish hold little or no relevance to practical aquaculture. This notion may be flawed, since understanding the mechanisms behind the behaviour of individuals is a proviso to predict behaviour in groups even with the caveat that some behaviors may be modified by group size. As an example, optimal feeding regimes should be easier to predict in a population consisting of individuals whose appetite is relatively less affected by external stressors. In a fluctuating and potentially stressful environment, such a population should also generate less feed waste, if kept on fixed rations. In the present experiment, we tested this hypothesis by monitoring feed waste and feed conversion efficiency in lines of rainbow trout selected for a low (LR) or high (HR) cortisol response to stress. The study was carried out after fish had been transported between rearing sites in the United Kingdom and Norway. There was significantly more feed waste from rearing units containing HR fish, and these fish also showed lower feed efficiency (growth per unit feed consumed). The difference in feed waste became more apparent with increasing time after transport, as rations increased. Simultaneously, size was more variable and growth was slower in HR rearing units. These results suggest that there are several potential benefits of selection for low stress responsiveness in aquaculture.     

Strategies for ammonium and nitrite control in Litopenaeus vannamei nursery systems with bioflocs

In biofloc technology (BFT) rearing systems, nitrogen compounds, specially ammonia and nitrite, have to be controlled by microbial pathways, mainly through the activity of heterotrophic and chemoautotrophic bacteria. The objective of this work was to assess different water preparation strategies (heterotrophic, chemoautotrophic and mature) in BFT system for nursery of Pacific white shrimp (Litopenaeus vannamei). A 35-day study was conducted with post-larvae shrimp (0.08 g) stocked in twelve 300 L tanks at a stocking density of 2000 shrimp m⁻³. The water preparation strategies for shrimp rearing that were evaluated in this study included: i) Heterotrophic treatment, where the water received sugar as a carbon source; ii) Chemoautotroph treatment, where ammonium and nitrite salts were added to the water; and iii) Mature treatment, which was created by the addition of a significant amount of water containing mature biofloc from another established BFT system. In both mature and chemoautotrophic treatments, the nitrification process was able to keep toxic nitrogen compounds (ammonia and nitrite) at low levels without the addition of carbohydrates. In contrast, heterotrophic system showed peaks of ammonia and nitrite during the rearing cycle, and the level of these compounds were found to be higher in this treatment (relative to the mature and chemoautotrophic treatments). The chemoautotrophic system exhibited a lower abundance of bacteria from the family Vibrionaceae in the beginning of the experiment compared to the heterotrophic and mature treatments. The combination of low Vibrionaceae abundance and good water quality resulted in improved growth performance in this treatment. These findings demonstrate the importance of manipulating the environment of BFT systems to induce an enrichment of nitrifying bacteria before stocking shrimp. We have also found that the addition of a carbon source to BFT systems is necessary only in emergency situations, when ammonia spikes need to be controlled.     

Comparison between traditional methods and artificial neural networks for ammonia concentration forecasting in an eel (Anguilla anguilla L.) intensive rearing system

One of the main problems in the management of fishfarms with water recirculating system is the forecasting and control of ammonia concentration in order to minimise the fish stress status. This paper examines methodologies of prediction in a real-time environment for an eel intensive rearing system. Approaches based on linear multiple regression, univariate time series models (exponential smoothing and autoregressive integrated moving average (ARIMA) models) and computational neural networks (ANNs) are developed to predict the daily average ammonia concentration in rearing tanks with water recirculating. The models are established using actual data from an eel fishfarm in southern Spain. The input variables used in the models (multiple regression, Holt smoothing model, ARIMA models and ANN models) are the ammonia concentration of previous days. In ANN models, the training method used is a standard back-propagation variation known as extended-delta-bar-delta (EDBD). Different neural architectures, whose learning is carried out by crossvalidation and controlling several threshold determination coefficients, are compared. Globally, the nonlinear ANN model approach is shown to provide a better prediction of daily average ammonia concentration than linear multiple regression and univariate time series analysis when the correlation between data series is low and when the models were obligated to predict in a situation for which specifically had not been calibrated. The best results were obtained by 5:10s:15s:1l ANN model in the pre-growth series.     

A case study of biofilter activation and microbial nitrification in a marine recirculation aquaculture system for rearing Atlantic salmon (Salmo salar L.)

Marine recirculation aquaculture system (RAS) is a prominent technology within fish farming. However, the nitrifying bacteria in the biofilter have low growth rates, which can make the biofilter activation a long and delicate process with periods of low nitrification rates and variations in water quality. More knowledge on the microbial development in biofilters is therefore needed in order to understand the rearing conditions that favour optimal activation of the biofilters. In this case study, we investigated the activation of two biofilters in a marine RAS for Atlantic salmon post‐smolt associated with either high or low stocking densities of fish by monitoring the microbial communities and chemical composition. The results showed that the microbial communities in both biofilters were similar during the first rearing cycle, despite variations in the water quality. Nitrifying bacteria were established in both biofilters; however, the biofilter associated with low stocking density had the highest relative abundance of ammonia‐oxidizing Nitrosococcus (1.0%) and nitrite‐oxidizing Nitrospira (2.1%) at the end of the first rearing cycle, while the relative abundance of ammonia‐oxidizing Nitrosomonas (2.3%–2.9%) was similar in both biofilters. Our study showed that low fish stocking density during the first rearing cycle provided low and steady concentrations of ammonium, nitrite and organic load, which can stimulate rapid development of a nitrifying population in new marine RAS biofilters.     

A technical solution to the mass-culturing of larval turbot

A 1000 litre recirculation system of eight cylindrical rearing tanks has been tested in three 40-day periods to determine its capacity for rearing larval turbot (Scophthalmus maximus L.).The larvae were fed on rotifers and Artemia nauplii, as well as mixed marine algae. Continuous artificial light of 1500–2000 lux was applied at the surface. The applied algae served a dual function; keeping rotifers and Artemia at a high nutritional level as well as effectively removing the released ammonia. The combination of upwelling water and light at the surface maximized the contact surface between larvae, food items and algae.With this system, using a stocking density of 16 larvae litre^?1 in the rearing tanks, a survival total of 40% at Day 40 was achieved, giving a production of 6·4 larvae litre^?1 or 3000 larvae metre^?2 of the surface of the rearing tanks.     

A technique for maintaining water quality in fish tanks containing eels and fish larvae

Abstract. A technique which uses electrodes at the mouths of meshless water outlets of fish tanks is described. The electrical field generated by the electrodes was effective in discouraging fish from approaching the open outlet, and allowed free discharge of debris-laden water without the usual blockage of the outlets by faeces and uneaten food. The system was found to be particularly effective for the rearing of eels (from the glass eel stage on) which typically cause a rapid deterioration in water quality due to their feeding behaviour. It was also found very useful for rearing other fish larvae in tanks.     

Ammonia reduction in seawater by Yucca schidigera extract: efficacy analysis and empirical modelling

Yucca schidigera is a plant native to southwestern USA and Mexico. Its extract has been used in the livestock industry to control ammonia accumulation in animal holding facilities, and to reduce ammonia concentration in animal excreta. This study investigated the potential and effectiveness of Y. schidigera extract (YUPE) for ammonia reduction in seawater. A dose–response experiment was conducted to determine the effect of different concentrations of YUPE at 0, 18, 36, 72 and 108 mg L⁻¹ on total ammonia nitrogen (TAN) at 1, 3 and 9 mg L⁻¹. At a higher YUPE dosage rate, higher TAN reduction was observed, and TAN reduction was highest during the first 12 h, and decreased thereafter. A stepwise multiple linear regression that included the initial TAN, YUPE concentration and time was developed, which accurately predicted empirical TAN concentrations. Applications of this model for ammonia management strategies were formulated for hypothetical tiger prawn (Penaeus monodon) rearing conditions. YUPE's efficacy for ammonia reduction, natural origin and safety make YUPE a potentially suitable compound for water quality management in mariculture.     

Effects of feeding frequency on the enzymes and genes involved in oxidative stress in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson) exposed to ammonia

Optimal feeding strategies improve fish growth and health but may be affected by ammonia stress in closed rearing systems such as tanks or ponds. This study aimed to evaluate the effects of feeding frequency and ammonia levels in rearing water on the enzymes and genes involved in oxidative stress of yellow catfish. Experiment (ammonia exposure) and control groups were randomly assigned to one of three feeding frequencies (1, 2 and 4 times daily) for 8 weeks. Weight gain increased as feeding frequency increased from 1 to 4 times daily, but feed conversion ratio values decreased. The highest survival in ammonia group was found when fish was fed 2 times daily. Glutathione peroxidase activity and total antioxidant capacity in liver and brain of fish exposed to ammonia increased as feeding frequency increased from 1 to 4 times daily. Liver malondialdehyde content in control group decreased as feeding frequency increased from 1 to 4 times daily. The lowest liver malondialdehyde content in ammonia group was observed when fish was fed 2 times daily. Liver mRNA expression of superoxide dismutase and catalase in control group increased as feeding frequency increased from 1 to 4 times daily, but the highest superoxide dismutase and catalase expression in ammonia group were observed when fish were fed 2 times daily. This study indicates that higher feeding frequency of yellow catfish exposed to ammonia could result in oxidative stress and poor survival. The optimal feeding frequency of yellow catfish exposed to ammonia is 2 times daily.     

Productive performance of juvenile freshwater prawns Macrobrachium rosenbergii in biofloc system

The aim of this study was to compare two rearing systems for freshwater prawn Macrobrachium rosenbergii: one with use of a recirculating aquaculture system with biofilters (RAS) and another with use of microbial flocs (F). Thirty postlarvae of freshwater prawn with an initial average weight of 0.13 ± 0.05 g were randomly stocked in six experimental units with 0.20 m² and volume of 50 L. The experiment lasted thirty days. Dissolved oxygen, temperature and pH were monitored daily; ammonia concentration was determined three times per week; nitrite concentration, alkalinity and hardness were measured weekly. For the formation of microbial floc, molasses was used to keep the ammonia concentrations within safe levels for prawn farming. The variables of water quality remained within the suitable range for the production of the species, except for ammonia concentrations at the F treatment, which exceeded the safe levels. At the end of the experiment, the following parameters were evaluated: survival, specific growth rate, weight gain and feed conversion rate. Differences were found only in feed conversion rate with better values on RAS treatment. The microorganisms present in the RAS and F treatment were also evaluated. The densities of rotifers, amoebas and total bacteria were higher at the F treatment although the same organisms were found at the RAS treatment. The results of this study showed the possibility of rearing M. rosenbergii in biofloc system technology.     

Performance of a closed recirculating system with foam separation, nitrification and denitrification units for intensive culture of eel: towards zero emission

The development of a closed recirculating aquaculture system that does not discharge effluents would reduce a large amount of pollutant load on aquatic bodies. In this study, eel were reared in a closed recirculating system, which consisted of a rearing tank, a foam separation unit, a nitrification unit and a denitrification unit. The foam separation unit has an inhalation-type aerator and supplies air bubbles to the rearing water. The growth of eel, which were fed a commercial diet, was satisfactory, with gross weight increases of up three times in 3 months. The survival rate under the congested experimental conditions was 91%. The foam separation unit maintained oxygen saturation in the rearing water at about 80%. Furthermore, fine colloidal substances were absorbed on the stable foam formed from eel mucus and were removed from the rearing water by foam separation. Ammonia oxidation and the removal of suspended solids were accomplished rapidly and simultaneously in the nitrification unit. The ammonia concentration and turbidity were kept at less than 1.2 mg of N per litre and 2.5 units, respectively. When the denitrification process was operated, nitrate that accumulated in the rearing water (151 mg of N per litre) was reduced to 40 mg of N per litre. The sludge was easily recovered from the nitrification and denitrification tanks, and the components were found suitable as compost. Based on these results, the intensive aquaculture of freshwater fish such as eel can be achieved using a closed recirculating system without emission.     

中华绒螯蟹温室育苗的水处理

通过对生物净化系统处理前后育苗水质指标变化情况的测定,初步探讨了生物净化系统在河蟹育苗过程中对水质的处理效果和应用价值。与传统的育苗工艺相比,应用生物净化系统有机物降解速度快,脱氮效果显著。ＣＯＤ、总氨氮的平均去除率分别为３３．２％,５５．５％。整个育苗过程ｐＨ稳定,溶氧丰富,池底无氧债和黑臭。     

Dynamics of ammonia excretion in juvenile common tench, Tinca tinca (L.), during intensive rearing under controlled conditions

This paper presents the first data on ammonia excretion by fed and starved juvenile common tench. The aim of the study was to determine the amount of ammonia excretion by juvenile common tench Tinca tinca (L.), fed with a commercial feed under intensive rearing conditions. Rearing was conducted for a period of 4 weeks at a water temperature of 27 °C. On the test day, the amounts of ammonia excreted by starved fish (over 12 h: control group) and fish fed with a morning feed dose (3 % of biomass: experimental group) were determined at 1, 3, 5, 7, 9 and 11 h after feeding. Ammonia excretion measurements were taken in 7-day intervals. Despite the increased growth rate in successive weeks of experiment, the amount of ammonia excreted by the fish was always at a similar level within the control (maximum 0.26 mg g^?1) and the experimental group (maximum 0.39 mg g^?1). This paper presents for the first time reliable amount of ammonia excreted by fed and starved juvenile common tench. The obtained results may also increase the effectiveness of intensive rearing procedures (taking into account stocking density and feeding regime) and allow to design the most effective biofiltration capacity of recirculating aquaculture systems for the commercial production of this species.     

A closed water recirculation system for ecological studies in marine fish larvae: growth and survival of sea bass larvae fed with live prey

This paper describes the suitability of a closed recirculation system to study the development of fish larvae in a strictly controlled environment, where only feeding was varied (fed, starved, delayed and late fast treatments). The system served both as an incubator and hatchery. The time variation of physical and chemical parameters together with survival and growth of reared sea bass larvae (Dicentrarchus labrax) were studied over the first month of life. The recirculation design allowed for the maintenance of levels of ammonia, nitrite and nitrate below those cited as responsible for mortality or decreased feeding ability in other marine fish larvae. Almost no larval mortality occurred in the fed larvae from day 9 after hatching. The starved group of larvae showed a sharp decline in survival after 16 days of food deprivation. Larvae for which feeding was delayed until day 13 ceased dying 4 days after food was supplied. Fast feeding on days 24 and 25 had no effect on larval survival. Growth in length was similar during the first 2 weeks of larval life regardless of feeding treatment. Two days of late fast had no effect on larval growth. Growth patterns of fed larvae in this study were similar to those reported for larvae reared in flow through systems. We believe that survival and growth of the reared larvae was a direct function of diet, and that the type of rearing system did not adversely affect these parameters. The rearing design and the results obtained suggest that future nutritional studies of field-collected larvae will benefit from this kind of rearing experiment.     

Stringed bed suspended bioreactors (SBSBR) for in situ nitrification in penaeid and non-penaeid hatchery systems

For establishing nitrification in prawn (non-penaeid, salinity 10–15 ppt) and shrimp (penaeid, salinity 30–35 ppt) larval production systems, a stringed bed suspended bioreactor (SBSBR) was designed, fabricated, and validated. It was fabricated with 5 mm polystyrene and low density polyethylene beads as the substrata for ammonia and nitrite oxidizing bacterial consortia, respectively, with an overall surface area of 684 cm². The reactors were activated in a prototype activator and were transported in polythene bags to the site of testing. Performance of the reactors activated with the nitrifying bacterial consortia AMONPCU-1 (ammonia oxidizers for non-penaeid culture) and NIONPCU-1 (nitrite oxidizers for non-penaeid culture) was evaluated in a Macrobrachium rosenbergii larval rearing system and those activated with AMOPCU-1 (ammonia oxidizers for penaeid culture) and NIOPCU-1 (nitrite oxidizers for penaeid culture) in a Penaeus monodon seed production system. Rapid setting up of nitrification could be observed in both the static systems which resulted in a higher relative per cent survival of larvae.     

纳米材料净化海水育苗水体的实验研究

设计纳米功能滤料及涂料试验,应用于海水育苗水体的净化。通过对实验水体的温度、盐度、pH、溶氧、氧化还原电位、氨氮、亚硝酸盐氮、硝酸盐氮、菌落总数、水质线幅半高宽值测定,以及育苗（青蛤苗）成活率统计,对比纳米材料净化海水育苗水体的功效。结果表明：试验组降解有机物能力均优于对照组,并获良好抑菌效果;功能涂料、功能粉体试验组均能促进蛤苗增长,其成活率分别较对照组均值提高31．3％、9,1％：