Optimal Stocking Density Research Articles

A Study on Nitrogen and Phosphorus Budgets in a Polyculture System of Oreochromis niloticus, Aristichthys nobilis, and Cherax quadricarinatus

Polyculture is an effective way to achieve efficient utilization of nutrient resources in high-density intensive aquaculture systems. In order to study the optimal culture mode of Oreochromis niloticu, Aristichthys nobilis, and Cherax quadricarinatus, the budget of nitrogen and phosphorus in various polyculture systems (CH, CHC1, CHC2, CHC3) was studied with land-based enclosures. The results showed that all the three polyculture systems had higher total yields of cultured animals than the control group (two polyculture systems) (p < 0.05). The co-cultured organisms absorbed artificial feed or organic matter (such as plankton and sediment) from the polyculture system to different degrees. Feed was the main input of nitrogen (98.22–98.33%) and phosphorus (99.43–99.56%) in all systems. Considering the N and P outputs, 46.64–64.58% and 81.60–84.79%, respectively, accumulated in the sediment, and 34.43–52.55% and 14.89–17.30% of the N and P outputs, respectively, were harvested by aquaculture organisms. The pollution production coefficients of TN and TP in the O. niloticus polyculture ponds were 5.35–6.26 g/m2 and 1.17–1.61 g/m2, respectively. The TN production coefficients of O. niloticus and the ternary polyculture groups (CHC1, CHC2, and CHC3) were lower than that of the control group (CH). The TP production coefficients showed the opposite pattern. The N and P utilization efficiencies in the group with the optimal ratio of O. niloticus, A. nobilis, and C. quadricarinatus (4, 0.15, and 3 ind/m2, respectively) were 2.56–12.82% and 6.62–11.03% higher, respectively, compared with those of the other groups. The N utilization efficiency was effectively improved in this group with the optimum stocking density for the polyculture systems, resulting in improved ecological efficiency and economic benefits.

Optimizing zebrafish rearing-Effects of fish density and environmental enrichment.

Despite its popularity in research, there is very little scientifically validated knowledge about the best practices on zebrafish (Danio rerio) husbandry, which has led to several facilities having their own husbandry protocols. This study was performed to expand knowledge on the effects of enrichment and fish density on the welfare of zebrafish, with hopes of providing a scientific basis for future recommendations and legislations. Zebrafish were reared at three different stocking densities, (1, 3 or 6 fish/L), in tanks with or without environmental enrichment. Agonistic behavior was observed twice a week for 9 weeks directly in the housing tanks. Aspects of welfare is known to be reflected in neuroendocrine stress responses. Thus, cortisol secretion in response to lowering the water level was analyzed for each group. In addition, we assessed cortisol secretion in response to confinement and risk-taking behavior (boldness) using the novel tank diving test for individual fish. At termination of the experiment fish were subjected to stress by transfer to a novel environment and brain tissue was sampled for analysis of brain monoaminergic activity. Fish kept at the lowest density (1 fish/L) showed a significantly higher level of aggression than fish kept at 3 or 6 fish/L. Moreover, fish kept at this low density showed significantly higher cortisol secretion on a group level than fish kept at the higher stocking densities, when subjected to lowering of the water level. Keeping fish at 1 fish/L also had effects on brain monoamines, these fish showing higher brain dopamine concentrations but lower dopamine turnover than fish kept at higher densities. Neither stocking density or enrichment had any clear effects on the behavior of individual fish in the novel tank diving test. However, fish kept at high densities showed lower and more variable growth rates than fish kept at 1 fish/L. Taken together these results suggest that zebrafish should not be kept at a density of 1 fish/L. The optimal stocking density is likely to be in the range of 3-6 fish/L.

Effects of Stocking Density on the Growth Performance, Physiological Parameters, Antioxidant Status and Lipid Metabolism of Pelteobagrus fulvidraco in the Integrated Rice-Fish Farming System.

Pelteobagrus fulvidraco is a freshwater fish commonly raised in rice fields, yet the optimal stocking density for this species remains unknown. Therefore, this study aimed to investigate the appropriate stocking density of P. fulvidraco in integrated rice-fish farming systems. Three different stocking densities--low density (LD, 125 g/m2), middle density (MD, 187.5 g/m2), and high density (HD, 250 g/m2)--were set up to evaluate P. fulvidraco's growth performance, stress indices, immune function, antioxidant status, and lipid metabolism after 90 days of farming. The results indicated that HD treatment had a detrimental effect on P. fulvidraco's growth parameters. HD treatment led to an increase in cortisol (Cor) and lactate (La) levels, but a decrease in glucose (Glu) content in serum. After 90 days of farming, an immune response accompanied by the increase of complement 3 (C3), C4, and immunoglobulin M (IgM) was observed in the HD group. Meanwhile, HD treatment induced oxidative stress and altered antioxidative status evidenced by the levels of catalase (CAT), glutathione peroxidase (Gpx), glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) in serum or liver. Additionally, the lipid metabolism-related genes including lipoprotein lipase (lpl), peroxisome proliferators-activated receptor (pparα), carnitine palmitoyltransferase-1 (cpt-1), and sterol regulatory element binding protein-1 (srebp-1) were markedly downregulated in the HD and/or MD group after 90 days of farming. In conclusion, this study contributes to a better understanding of P. fulvidraco's response to different stocking densities in integrated rice-fish farming systems. We suggest that the appropriate stocking density for P. fulvidraco in these farming systems should be below 250 g/m2, considering both fish growth and physiological responses.

Effect of Stocking Density on Culture Efficiency and Physiological Indicators of Largemouth Bass (Micropterus salmoides) under Recirculating Water Conditions in Land-Based Round Ponds

To identify the optimal stocking rate of Micropterus salmoides culture in a land-based round pond recirculating aquaculture system, five stocking densities were tested, i.e., D1–D5 with 60, 70, 80, 90, and 100 fish/m2, respectively. The water temperature of the experimental pond was 20.0–26.5°C. The effects of stocking density on culture productivity and physiological indexes of M. salmoides (initial body weight 50.83 ± 7.28 g) were examined. The D1 and D5 treatments exhibited significantly improved growth performance. The population weight gain in the D5 treatment was the highest, which increased by 63.73%, 52.82%, 60.93%, and 45.08%, compared with groups D1–D4 ( P < 0.05 , each), and the feed conversion ratio was the lowest, which was decreased by 5.65%, 12.03%, 26.42%, and 21.48% compared with groups D1–D4. The levels of crude protein, essential amino acids, and total free amino acids in muscle tissue of group D3 were higher than those in the other groups. Stocking density did not differ significantly on muscle fatty acid composition P > 0.05 , each). The activities of serum AKP and LZM and liver SOD, AKP, and LZM in group D5 were significantly higher than those in the other groups. Thus, 100 fish/m2 was the optimal stocking density of M. salmoides at a size stage of 50.83∼130.13 g in the circulating water of land-based round ponds.

EFFECTS OF STOCKING DENSITY ON GROWTH AND DEVELOPMENT OF REPLACEMENT YOUNG DUCKS IN SEPARATE GROWING BY GENDER

An excessively high stocking density can affect the growth and development of ducks. The optimal stocking density should change with the age of ducks. The article presented the results of the experiment on the effect of stocking density on the growth, development and viability of replacement young ducks of the local population during separate growing at the Bishkul Poultry Farm LLP in Northern Kazakhstan in 2022. The study was carried out in ages the day of birth to 49 days in 3 stages with a transfer on day 22 and day 35, respectively. The stocking density of ducks before transfer in the first growing period, in the control group was 20 birds/m2, in the first experimental group - 18 birds/m2; in the second experimental group - 16 birds/m2; and in the third experimental group - 14 birds/m2, respectively. After transfer in the second growing period, the stocking density of the ducks in the control group was 10 birds/m2, in the first experimental group - 9 birds/m2; in the second experimental group - 8 birds/m2; and in the third experimental group - 7 birds/m2. In the third period, the stocking density in the control group was 7 birds/m2, in the first experimental group - 6 birds/m2; in the second experimental group - 5 birds/m2; and in the third experimental group - 4 birds/m2. In the study, increasing stocking density had a negative effect on the growth and development of ducks. It is noted that with an increase in stocking density in experimental groups bodyweight, absolute gain and average daily gain decreased, thus negatively affected these indicators.

Sustainable intensification of small-scale mariculture systems: Farm-level insights from the coastal regions of India

This study undertakes a comprehensive assessment of selected mariculture enterprises in the coastal regions of India, centered on long-term sustainability as the key focus. This is juxtaposed against India's ambitious blue economy targets and policy thrust that pin on the expansion of mariculture as a promising avenue for enhancing marine fish production. Farm-level, region-specific, techno-economic, and socio-cultural factors associated with, and conditional on, sustainable intensification of mariculture-based production systems are examined in detail. The Principles-Criteria-Indicators (PCI) approach is used to establish the linkage between identified farm-level indicators and various dimensions of sustainability. While the selected enterprises were assessed to be technically and economically viable in general, glaring gaps were evident on key indicators of sustainability such as the legitimacy of access over water bodies, use of quality seed and feed, institutional credit access, market access, and fair marketing practices, optimal stocking density, mechanization, use of renewable energy, adoption of environmental-friendly culture practices, farm surveillance, crew safety, and social protection. This indicates the need for taking proactive measures to ensure the long-term sustainability of mariculture, particularly in the initial stages of establishment when such interventions are easy to adopt. Based on the insights obtained from the analysis, a broad set of strategies, policy options, and institutional interventions critical to scaling-up coastal mariculture enterprises along the east and west coasts of India are presented.

The green seaweed, Enteromorpha intestinalis: An efficient inorganic extractive species for environmental remediation and improved performances of fed species in brackishwater integrated multi-trophic aquaculture (BIMTA) system

Seaweed has vast utilization benefits, in terms of food, cosmetics, fertilizers, and extraction of industrial gums and chemicals. Moreover, in integrated multi-trophic aquaculture (IMTA), seaweed can be utilized as an inorganic extractive species, but a very few studies were conducted so far involving the green seaweed, Enteromorpha sp. An experimental trial of 60 days was executed to ascertain the effect of varied stocking densities of Enteromorpha intestinalis on growth parameters, survival and physiological status of milkfish, Chanos chanos and the Pacific white-leg shrimp, Penaeus vannamei, and bioremediation effect in brackishwater IMTA (BIMTA) systems. There were three BIMTA systems with different biomass densities of seaweed, 0.5 (T1), 1.0 (T2), and 1.5 (T3) kg m−3 placed in 1000 L FRP tanks stocked with C. chanos (3.50 ± 0.01 g) at 25 number m−3 and P. vannamei (4.25 ± 0.04 g) at 50 number m−3 as fed species. The control (polyculture) had same number of milkfish and shrimp with no seaweed. Three treatments and control were maintained in triplicate. The fed species were provided with a polyculture feed containing 30% crude protein at 5% of the biomass daily. The results displayed that nitrogenous and phosphorus compounds were significantly lower (P < 0.05) in all three BIMTA treatments compared to the control. A better growth (P < 0.05) of C. chanos (12.52 ± 0.24 g) and P. vannamei (14.77 ± 0.35 g) was obtained in T3 and T2 BIMTA systems, respectively when compared with the control (milkfish: 11.01 ± 0.08 g, shrimp: 11.79 ± 0.58 g). Survival in shrimp was the highest in T3 treatment, but in milkfish, survival did not vary between different systems (P > 0.05). The blood (red blood cells, white blood cells and haemoglobin) and haemolymph (haemocyanin and total haemocyte count) parameters were better in fish and shrimp, respectively under BIMTA at harvest. Presence of seaweed provided a significant positive effect on the welfare parameter (glucose), whereas stress parameters (catalase, superoxide dismutase and cortisol) were comparatively low in fed species of BIMTA treatments than that of polyculture system. This trial suggested that T2 and T3 performed better among all and E. intestinalis can be an efficient inorganic extractive species for BIMTA at the optimum stocking density of 1.0–1.5 kg m−3.

Appraisal of culture‐based fisheries of giant freshwater prawn (Macrobrachium rosenbergii, De Man, 1879) in reservoirs of Sri Lanka

AbstractThe introduction of high economic value species like giant freshwater prawn (GFWP) makes culture‐based fisheries (CBF) a substantial source of income and simultaneously supports the livelihood development of rural fishers in Sri Lanka. However, this CBF strategy has been implemented without any scientific basis, and therefore, this paper evaluated the stocking and production data of GFWP in Sri Lankan reservoirs from 2011 to 2017 to identify interventions for achieving future sustainability. We used two distinct approaches to appraise the CBF strategies practised so far and decrypt the identified shortcomings in the initiatives. The first approach was a straight‐head univariate generalized additive model (GAM) analysis of stocking density (SD), production (PRD), recapture efficiency (RCE) and reservoir surface area (A). The latter approach was a hybrid PCoA‐GAM for detained data mining for a better management perspective. The relationships among SD, PRD RCE and A were significant and, stochastic PRD and RCE were reasoned by the biased stocking practices identified in the GAM analysis. The hybrid PCoA‐GAM is seemingly robust in predicting and explaining the deviances of PRD and RCE of GFWP CBF. Results indicated that the present practices of CBF of GFWP in Sri Lankan reservoirs suffer several weaknesses, overstocking in minor and understocking in both medium and major reservoirs are primarily under consideration, which includes inter alia, the need for effective tools for identification of suitable reservoirs, the inefficient harvesting practices, non‐optimal SDs coupled with the possible vulnerability of stocked postlarvae to high mortalities. According to the study, we prefer to set the optimum SD as 1500 PLs ha−1 to all reservoirs. A comprehensive study has been launched for the enhancement of CBF of GFWP in Sri Lankan reservoirs.

Exploration of the optimal stocking density of red swamp crayfish (Procambarus clarkii) larvae by using the biofloc technology

Exploration of the optimal stocking density of red swamp crayfish (Procambarus clarkii) larvae by using the biofloc technology

Evaluation of gardi bangana dero and sahar tor putitora with rohu labeo rohita and Naini cirrhinus mrigala in poly culture at different stocking combinations

Conventional multispecies poly culture with compatible native species intercrop augments optimum utilization of the ecological niches in the pond ecosystem, diversity conservation, food value, and poverty alleviation potential through the direct involvement of rural people. Given the conservational value and the aquaculture potential of several indigenous species, Gardi Bangana dero and Sahar Tor putitora have been identified as important food fish. Rohu Labeo rohita and Naini Cirrhinus mrigala are two other native fishes that fetch a very high market price and are of high cultural value. A polyculture experiment was carried out on the Rohu, Naini, Gardi, and Sahar with the objectives to evaluate the optimum stocking density in terms of average body weight, specific growth rate, and total fish production of these fishes for nine months. Results showed that the final body weight of Rohu, Naini, Gardi were high in respective major poly culture systems, but Sahar was high in Naini major system. In case of survival, all fish species had high survival rate in Naini major system. Also, net fish yield of Rohu was observed significantly higher in Rohu major pol yculture system than in Naini major and Gardi major poly culture systems but not with control poly culture systems. Whereas, parameters of Naini, Gardi and Sahar observed similar in all poly culture systems. Apparent Feed Conversion Ratio was found higher in Gardi major poly culture system than others. Thus, for getting optimal stocking density, Naini polyculture system with supplementary feed is recommended.

ВЛИЯНИЕ ПЛОТНОСТИ ПОСАДКИ ГУСЕЙ РОДИТЕЛЬСКОГО СТАДА С УЧЕТОМ ПОКАЗАТЕЛЕЙ ЖИВОЙ МАССЫ НА ПОКАЗАТЕЛИ ВОСПРОИЗВОДСТВА

Of great practical importance in the maintenance and breeding of poultry is the identification of the optimal stocking density of various breeds of geese of the parent flock, depending on the live weight. Factors such as climate, house type, bird species, age, body weight, etc. should be taken into account to correctly estimate stocking density. Incorrectly calculated stocking density can lead to leg disease, increased mortality, increased feed consumption, and a decrease in the productive and reproductive qualities of the bird. The optimal planting density in the Kuban, large gray and white Hungarian breeds of geese was revealed, at which positive results were obtained for the main values of reproductive qualities and live weight.

Egg‐laying capacity of parent flock geese at different stocking densities

This article presents the results of studies aimed at establishing the optimal stocking density of purebred and hybrid geese of the parent flock, taking into account the indicators of their live weight and egg production. When conducting research, the stocking density of geese was established depending on the breed and shape. Different stocking densities of geese in groups were achieved due to their different numbers in groups: Kuban 1.2; 1.5; 1.8 birds/m2 , large gray 0.9; 1.2; 1.5 birds/m2 , hybrid bird 1.0; 1.3; 1.5 birds/m2 . It was revealed on the basis of the analysis of the productive qualities of adult geese that the optimal planting density of the Kuban geese is 1.8 heads/m2 , large sulfur = 0.9, hybrid = 1.3. The safety of geese at a given stocking density ensured an increase in the safety of geese of the Kuban breed by 95.3%, large gray = 94.0%, hybrid = 97.0%. The live weight of Kuban geese increased by 0.9%, large gray geese = 0.10, hybrids = 1.2, egg production by 0.6%, 2.2% and 0.5%, respectively.

MATERIALS FOR THE RECOMMENDATIONS ON PRE-SPHERING MAINTENANCE, NATURAL SPRINGING OF THE BAIKAL OMUL IN THE SELENGA RIVER FOR THE PURPOSE OF ARTIFICIAL REPRODUCTION IN 2020

This paper presents data on the collection, analysis, processing of materials for keeping spawners of the Baikal omul, determining the optimal stocking density of fish in cages, determining the efficiency of using spawners in 2020.

Effect of stocking density on the growth, body composition, and blood parameters of cage-reared Gangetic mystus catfish (Mystus cavasius)

Suitable stocking density of Gulsa tengra (Mystus cavasius) was observed by measuring growth performance, production, and survival in nylon net cages for 120 days in Chalan Beel floodplain ecosystem. Fry of Gulsha tengra (5.55 ± 0.49 g in weight) were stocked into 6 × 3 × 2-m (36 m3) floating net cages with treatments: T1-50, T2-100, T3-150, and T4-200 fry/m3 (in triplicates). The stocked fry was fed twice daily with commercial floating pellet containing 32 % protein at the rate of 5 % /fish body weight during the first 2 months and then reduced to 3 % for the next 2 months. The highest weight gain was observed in the lowest density treatment, T1 (18.70 ± 1.37 g) and the lowest (8.66 ± 0.99 g) in highest density treatment, T4 (all tests for significance were performed at a 5 % level). The rate of survival varied from 86.6 % and 95.8 %, with T1 resulting in the significantly highest survival. A better feed conversion ratio was also observed in T1 (1.75 ± 0.26). Significantly higher protein (16.86 ± 0.36) and fat (2.78 ± 0.02) contents were recorded in the fish body composition in T1. Water quality parameters (temperature: 26.0 ± 1.0 °C, pH: 7.2 ± 0.2, DO: 6.4 ± 0.1 mg/l, NH3-N: 0.002 ± 0.001) recorded throughout the study period were within the suitable range for fish culture. The highest red (119.0 ± 4.85 ×106 µl) and white blood cell (233.2 ± 16.02 ×103 µl), hemoglobin (5.65 ± 0.30 g/dl), total protein (5.50 ± 0.03 g/dl), albumin (1.82 ± 0.06 g/dl), and globulin (3.65 ± 0.15 g/dl) were also observed in T1 indicating optimum condition. Total and net production per cage were the highest in T1 with approximately 50 % increase (88.31 ± 6.72 and 59.27 ± 5.79 kg, respectively) compared to T4. The net income and benefit–cost ratio was increased by approximately 42 % and 30 %, respectively, in T1. Thus, this study recommended an optimal stocking density of 50 fish/m3 for Gulsha tengra to achieve a profitable and robust yield in cage culture.

Effects of Stocking Density on Production Performance of nile Tilapia (Oreochromis niloticus) in grow-out Culture Cages

A 120-day cage grow-out production performance of Nile Tilapia, Oreochromis niloticus was conducted in the Dakatia river, Echoli, Chandpur to identify an optimal stocking density. The three stocking densities were used at 30, 50, and 70 tilapia m-3 under three treatments with triplicate. The initial average weight of tilapia fingerlings at 32.31±9.59 g was stocked. Final weight, specific growth rate, and survival were significantly (p &lt; 0.05) higher in the 30 tilapia m-3 stocking density than those in the 50 and 70 tilapia m-3 stocking densities. The best food conversion ratio of 1.47 was found in the 30 tilapia m-3 stocking density and followed by 2.0 and 2.90 in the 50 and 70 tilapia m-3 stocking densities, respectively. The production was comparable (p &gt; 0.05) between the 50 and 70 tilapia m-3 stocking densities; however, the net profit was higher (p &lt; 0.05) in the 50 tilapia m-3 stocking density group compared to the two other stocking density groups. This study suggests a stocking of density at 50 tilapia m-3 to increase Nile Tilapia O. niloticus productivity in the riverine cage culture system. Bangladesh J. Zool. 50 (2): 239-250, 2022

Stocking density-induced changes in growth performance, blood parameters, meat quality traits, and welfare of broiler chickens reared under semi-arid subtropical conditions.

Broiler production in semi-arid tropics must contend with high levels of heat stress, which have implications on stocking density, bird welfare, and profitability. Under these conditions, optimal stocking densities are likely to be lower than expected, thus must be experimentally determined. Therefore, this study investigated growth performance, haematology, serum biochemistry, carcass and meat quality, sizes of internal organs, and stress biomarkers in response to different stocking densities in broilers reared under semi-arid subtropical conditions. Five hundred, day-old Ross 308 broilers (44.0 ± 5.24 g live-weights) were randomly distributed to 25 replicate pens (1.32 m2 floor space each) to create five stocking densities: 1) 10 birds/pen (SD10); 2) 15 birds/pen (SD15); 3) 20 birds/pen (SD20); 4) 25 birds/pen (SD25); and 5) 30 birds/pen (SD30). There was a linear decrease (P < 0.05) in overall feed intake and weight gain in weeks 2 and 3 as stocking density increased. However, weight gain showed positive and negative quadratic responses (P < 0.05) in weeks 5 and 6, respectively, as stocking density increased. No linear or quadratic effects (P ˃ 0.05) were observed for overall feed conversion ratio, haematological parameters, and meat quality traits in response to stocking density. Symmetric dimethylarginine, alanine transaminase, and albumin levels quadratically increased (P < 0.05) in response to increasing stocking densities. Serum glucose and thigh weight were not affected (P < 0.05) while final body, drumstick, breast, and wing weights linearly declined with stocking density. Increasing stocking density linearly reduced (P < 0.05) the weights of gizzard, proventriculus, caecum, and colon. Stocking density had no effect (P ˃ 0.05) on latency-to-lie. It was concluded that higher stocking densities compromised feed intake, resulting in poor weight gains. Based on weight gain trends observed in week 5, it was determined that Ross 308 broilers should be reared at no more than 20 birds/pen (~15 birds/m2 or 27.27 kg/m2) under the experimental ambient conditions compared to the much higher globally accepted industry standard of 20 birds/m2.

Finding the “golden stocking density”: A balance between fish welfare and farmers' perspectives

The effects of stocking density on fish welfare are complex and involve many interacting parameters. This complex relationship between fish welfare, stocking density and influencing factors make it challenging to define a specific optimal (“golden”) stocking density. Indeed, previously published recommendations on stocking density for different species of aquaculture interest are incredibly variable even at the same life stage, and can also vary widely within a rearing unit. Production density can be estimated quite accurately if the farmer has good biomass control and a known water volume, but it is difficult to set minimum and maximum stocking density levels that will protect welfare. However, there is little doubt that stocking densities that are too low or too high can have negative impacts on welfare and/or production. Here, we propose how to select density on captive fish and monitor its potential effects integrating 1) solid welfare assessment based on operational welfare indicators and 2) good management practices. Regulation directly limiting stocking density is likely to be unworkable and ineffective, and a more rational option might be to prescribe acceptable levels of different welfare indicators (e.g., water quality, health, nutritional condition and behavioral indicators), which together with a positive economic balance of the company, allow to estimate the most suitable range of fish density for each particular species, life-stage and production systems.

A review on recirculating aquaculture system: influence of stocking density on fish and crustacean behavior, growth performance, and immunity

Abstract The human population is expected to reach 9.7 billion by 2050. This in turn will put more pressure on the limited available resources such as land and freshwater. Combined with the high food demand, highly virulent pathogens, and worsening effects of climate change, cases of chronic hunger and malnutrition are expected to escalate in the future. Therefore, the implementation of sustainable food production systems is crucial in safeguarding food security. Recirculating aquaculture systems (RAS) have gained much attention today for the intensive production of certain aquatic species in controlled conditions. In these systems, wastewater is purified via several water purification steps and recycled back into the system. As such, water quality parameters such as water temperature, dissolved oxygen, dissolved carbon dioxide, pH, total ammonia-nitrogen, nitrites, nitrates, and total soluble solutes are maintained within the desirable range required for proper growth and survival of the reared species. However, maintenance of good water quality largely depends on certain factors, most noticeably, the stocking density. Stocking densities below and above the recommended optimal levels negatively impact the behavior, growth performance, and immunity of reared animals. As a consequence, huge production losses are incurred. This review, therefore, aims to discuss the effect of stocking density on behavior, growth performance, feed utilization, and immunity of reared species in RAS. Moreover, optimum stocking densities of several aquatic species reared in RAS under certain culturing conditions are highlighted for sustainable production of food.

The effect of different stocking densities on ammonia (NH3) and nitrate (NO3) concentration on striped snakehead (Channa striata) culture in the bucket

Fish farming in the bucket is a fishery technology that is being developed using an aquaponic system. Striped snakehead fish (Channa striata) is one of the economically important types of fish but the cultivation of striped snakehead fish using an aquaponic system has never been carried out, so it is necessary to know the optimal stocking density of striped snakehead fish to minimize the risk of stress for fish. This study aims to determine the effect of different stocking densities on ammonia (NH3) and nitrate (NO3) concentration on striped snakehead (Channa striata) culture in the bucket. This research using 5 treatments and 4 replications, namely P0 1 fish/Liters; P1 2 fish/Liters; P2 3 fish/Liters; P3 4 fish/Liters; and P4 5 fish/Liters. The observed parameters are ammonia (NH3) and nitrate (NO3) concentration. The results of this study showed that the value of the ammonia concentration was between 0,089-0,609 mg/L and the nitrate concentration was between 0,931-1,539 mg/L. Based on the results of this study, it can be cocluded that treatment of different stocking density affect the concentration of ammonia (NH3) and nitrate (NO3) in the cultivation of Snakehead fish (Channa striata) in the bucket.

Aquaculture practices among the fish farmers of Bhaluka upazila, Mymensingh - Scenario from a decade and half ago

Mymensingh is the top inland aquaculture producer in Bangladesh. This study was undertaken to identify the barriers to develop earthen pond fish farming entrepreneurship in Bhaluka Upazila, Mymensingh about a decade and half ago when the fish culture revolution has been started. In this study, fish farmers were selected randomly from three villages that followed mono or composite-fish culture in earthen pond environment. More than 14 species being cultured of which half of them were exotic. The feasibility of pond fish culture was found viable due to proper communication with Dhaka wholesale fish market along with other destinations. In addition, hatchery sources of fish fry and fingerling, access to fish feed and financial support were further encouraged farming these perishable items. Education level of farmers, lack of technical knowledge of fish culture, poor extension service and lack of information about the pond management were identified as the potential barriers for the improvement of fish farming entrepreneurship. The higher stocking density as well as poor water quality conditions were facilitated to lead lower fish production and profit. The small-scale farmers (47.79%) with higher stocking density had lower profit (Tk 1.44 /fish) and large-scale farmers (19.85%) with lower stocking density showed higher profit margin of Tk 3.53 /fish. Therefore, this study suggests the optimal fish stocking density in earthen pond fish farming system which could be augment the fish production and enhanced profitability. Dhaka Univ. J. Biol. Sci. 30(3 CSI): 499-509, 2022 (June)