Optimal Stocking Density Research Articles

The implementation of rice-crab co-culture system to ensure cleaner rice and farm production

The traditional co-culture systems have attained the attention for better production, still have gaps to identify key factors influencing the safe grain production, yield enhancement, and economic viability. Here, a field survey and a field experiment was conducted in Panjin city, including two production systems: rice-monoculture (RM) and RC system. The treatments of field experiments were: rice-monoculture (RM), 3000 crabs ha−1 without feed (RC3000), 6000 crabs ha−1 with feed (RC6000), and 12000 crabs ha−1 with 2 × feed (RC12000). During field survey, higher number of crabs reduced the number of productive tillers while, the productive traits were improved significantly except 1000-grain weight was insignificant. Field experiment indicated that suitable stocking density and feed management has no negative effect on agronomic or productive trait. Grain yield was improved (19.9%) in RC3000, (22.0%) in RC6000, and (14.7%) in RC12000 as compared to RM. The reduction in shrivelled grains spike−1, and the increase in filled grains spike−1, seed setting percentage, and 1000-grain weight in RC system improved the rice production. Grain nitrogen, phosphorus, and potassium contents were also improved by RC6000. Farm income and benefit-cost ratio were higher in RC system, meanwhile, the maximum farm production (16231-yuan ha−1) and benefit-cost ratio (0.51) were in RC6000. The RC system can control drained out water nutrients concentrations, which helps in water pollution control. The results suggested that RC system improves the clean grain and farm production, resource utilization, and the economic status with managed optimum stocking density and feed.

Stocking density alters growth performance, serum biochemistry, digestive enzymes, immune response, and muscle quality of largemouth bass (Micropterus salmoides) in in-pond raceway system.

The effects of stocking density on growth performance, serum biochemistry, digestive enzymes, immune response, and muscle quality of largemouth bass (Micropterus salmoides) reared in nine in-pond raceway systems (IPRS, 22.0 m × 5.0 m × 2.0 m) were studied. M. salmoides with initial an body weight of 8.25 ± 0.51 g and body length of 6.99 ± 0.44 cm were reared at an initial stocking density of 90.91 ind./m3 (low stocking density, LSD), 113.63 ind./m3 (middle stocking density, MSD), and 136.36 ind./m3 (high stocking density, HSD) with triplication. After 300 days of culture, MSD recorded the highest final body weight, weight gain, specific growth rate, and yield, but the food conversion ratio in MSD was the lowest. The viscerosomatic index in LSD was significantly higher than other groups. The fish serum reared at HSD showed significantly lower total protein, higher total cholesterol, triglyceride, total bilirubin, glucose content, alanine transaminase, and aspartate transaminase activity. Significantly lower intestinal amylase, lipase, trypsin activities, hepatic superoxide dismutase (SOD) and catalase (CAT) activities, and higher malondialdehyde content were detected in HSD compared to others. The content of crude lipid, saturated fatty acid decreased, and total essential amino acid, delicious amino acid, and polyunsaturated fatty acid increased in muscle with stocking density increase. No significant difference was observed in muscle texture. Profitability analysis indicated the benefit-to-cost ratio varied between 1.10 and 1.68, of which MSD was significantly higher than others. The optimal stocking density for M. salmoides should be 113.63 ind./m3 in an IPRS farm.

Quantitative analysis of density dependent resource utilization, cannibalism, and competition of the red swamp crayfish (Procambarus clarkii) in rice-crayfish cocultures without supplementary food

A 90-day, integrated rice-crayfish coculture experiment using net enclosures (8 m × 10 m each) was performed to determine resource utilization, cannibalism, and inter-sexual competition in the red swamp crayfish (Procambarus clarkii) at four stocking densities (4 ind/m2, 6 ind/m2, 9 ind/m2, and 12 ind/m2). The results were as follows: (1) With increasing stocking density of crayfish, the relative contribution of animal feed sources to male and female crayfish diets initially decreased and then increased, whereas the contributions of plant feed sources and detritus as a feed source initially increased and then decreased. There was no significant difference in the diets of female and male crayfish between 4 ind/m2 and 12 ind/m2; plants (> 50%) were predominant, followed by animal feed (> 20%), cannibalism (~ 18%), and detritus (> 6%). At 6 ind/m2 and 9 ind/m2, the contributions of feed sources for both male and female diets were as follows: plants (> 60%), animal feed (> 15%), detritus (> 10%), and cannibalism (< 8%). The trophic and spatial niche area per individual unit (SEA/density, SEA·m2/ind) of female and male crayfish decreased as stocking density increased. (2) With increasing stocking density, the contribution of cannibalized feed sources to crayfish initially decreased (from 4 ind/m2 to 6 ind/m2) and then increased (from 6 ind/m2 to 12 ind/m2). The SEA f,m (representing the similarity of diets between female and male crayfish and, therefore, the potential for inter-sexual competition) initially increased with stocking density (from 4 ind/m2 to 9 ind/m2) and then decreased (from 9 ind/m2 to 12 ind/m2). This indicated that cannibalism might reduce the competition between sexes for natural resources. (3) Based on the high trophic and spatial niche area per individual unit (SEA·m2/ind; female = 0.37 and male = 0.88), low contributions of cannibalized feed sources (female = 5.88 ± 2.62% and male = 7.97 ± 3.44%), and low degree of inter-sexual competition (SEA f,m = 0.25), 6 ind/m2 (crayfish tail weight 9.60 g) was identified as the optimal stocking density for P. clarkii in rice fields without supplementary artificial feed.

Comparative analysis of profitability and resource use efficiency between Penaeus monodon and Litopenaeus vannamei in India.

The study aimed to highlight the profitability and production function analysis of Penaeus monodon and Litopenaeus vannamei in intensified shrimp farms in Gujarat (India). Two hundred and twenty (220) shrimp farm households were used to identify (principal component and cluster analyses) 8 clusters of management practices that reflected various scales of production intensity ranging from 0-2999 kg/ha/crop to 9000kg/ha/crop and above for both the species. The Cobb-Douglas production function, which relates production output to several independent input variables, was used to determine productivity. The budgeting analysis for both the species showed that more intensively managed farms performed more than the less intensive farm. Empirical results show feed as most significant input for Penaeus monodon and Litopenaeus vannamei seed and labor that affected production. Average net returns/ha/year for Penaeus monodon was $16313.13 and for Litopenaeus vannamei $41640.99. Aquaculture exhibited decreasing returns to scale for both the species and estimates on resource use efficiency revealed that in Penaeus monodon the resources were economically utilized and in case of Litopenaeus vannamei the output was likely to increase if more of seed and less of labor would have been used. The major constraint for the shrimp farmers was diseases which can be mitigated by optimum stocking densities and proper feed management.

Cultivation and biomass production of the diatom Thalassiosira weissflogii as a live feed for white-leg shrimp in hatcheries and commercial farms in Vietnam

This study investigated the biomass production process from the laboratory to the pilot scale in order to use the nutrient-rich biomass of the diatom Thalassiosira weissflogii as live feed for white-leg shrimp (Litopenaeus vannamei) at larval stages (zoeal, mysis, and postlarval) and in commercial production in hatcheries in Vietnam. Our results showed that T. weissflogii was successfully cultured in 1–2 L Erlenmeyer flasks, 0.2–3.5 m3 composite tanks, and 6.5 m3 tubular photobioreactors, with the highest cell density of 1.6 × 106 cells mL−1 reached after 6 days of culture. Under optimal culture conditions, the protein, lipid, and carbohydrate contents in this algal biomass were 13.2%, 20.0%, and 10.0% of dry cell weight, respectively. The fatty acid composition contains high amount of palmitic acid (C16:0, 43.11% of total fatty acid), and polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA, C20:5ω-3), approximated 16.5% of total fatty acid. In a 50 L larval rearing tank, at the optimal stocking density of 125 nauplii L−1, the survival percentage (75.55%), the total body length (from 5.376 ± 0.007 to 10.860 ± 0.030 mm), and weight (at from PL1 to PL12 stages) (from 0.145 ± 0.002 to 1.158 ± 0.005 g) of the white-leg shrimp larvae reached the highest values but the metamorphosis time (234 h) was shortest compared with the other stocking densities. Further, adding living T. weissflogii biomass to the diet of white-leg shrimp larvae at the nauplii 6 stage led to an increase in the body length, weight, and survival percentage of white-leg shrimp larvae of 21.17%, 35.7%, and 33% higher compared with those of larvae fed the control diet (without the addition of T. weissflogii), respectively. At the same time, the metamorphosis time of larvae (from Z1 to PL1) decreased by 4 h compared to the control group. In intensive ponds (area of 6400 m2 pond−1), using seed stocks at the postlarvae 12 stage that had been fed T. weissflogii, the final weight, yield, and survival percentage of the shrimp were increased by 7.3%, 14.2%, and 16.3%, respectively, compared with those of the control group. There were no statistically significant differences in the protein and carbohydrate contents in the shrimp flesh among the experimental and control group (p > 0.05). The lipid, omega-3, omega-6, and omega-9 fatty acid contents of shrimp flesh in experiment formula (per 100 g shrimp) were 1.21 g, 72.9 mg, 114 mg, and 86.1 mg, 11%, 29%, 21.6%, and 17.7% higher than that those in control, respectively. The obtained results show the great potential of using T. weissflogii as live feed on white-leg shrimp farms in Vietnam.

ОБОСНОВАНИЕ МАСШТАБОВ ПОДОБИЯ ОПТИЧЕСКИХ ВЕЛИЧИН В УСТАНОВКАХ ДЛЯ ВЫРАЩИВАНИЯ ГИДРОБИОНТОВ

The article highlights the problems of physical modeling the elements of recirculating aquaculture systems (RAS) and open aquaculture cages (OAC) for hydrobionts growing, in particular, the question of substantiating the rules of optical quantities similarity has been raised. Formulation of the problem is based on the assumption that using the computer vision which controls the behavioral reactions of hydrobionts to the growing conditions (e.g. light effect) will make the biotechnological process controllable in RAS and OAC and, as a result, more efficient. Evaluating the light effect on biological objects as to the depth of its penetration into the basins, the degree of its dispersion among the aquatic organisms and other characteristics can become an important element of computer vision. This fact will help to choose the optimal algorithm for the biotechnical process, for example, to calculate the daily feed portion and feeding periods, to define the optimal place for feeding, to determine the appropriate sorting time, the optimal stocking density, etc. There have been proposed the additional similarity scales for optical quantities, methods for their calculation and graphs of their dependences on the geometric scale Cl. However, one should know that achieving the complete similarity is absolutely impossible, no matter how large the list of similarity criteria is.

Influence of Stocking Density on Growth Performance of Labeo bata in Cage at River Padma, Rajshahi, Bangladesh

As a result of climate change, aquaculturists are seeking adaptive culture techniques for sustainable aquaculture. In this case, cage culture is a suitable technique that can mitigate the challenge of climate change, but due to the lack of knowledge of proper stocking density, often productions are not satisfactory. Therefore, the experiment was conducted to evaluate the influence of stocking density on growth and production of an endangered minor carp bata (Labeo bata) in cages for a period of 120 days in Padma River, Rajshahi, Bangladesh. On an average initial weight of bata fingerling of 5 g was stoked in cages under three treatments each with containing three replications using three different stocking densities (106, 71 and 35 fingerling/m3 for T1, T2 and T3, respectively). Supplementary feed (3% per body weight) was given to the cultured species twice in a day. The mean values of water temperature, transparency, pH and dissolved oxygen were in suitable range throughout the experimental period. Significantly (p&lt;0.05) highest mean gross weight (85.82±0.70 g), specific growth rate (2.37± 0.02%), survival rate (83± 3.00%) and food conversion ratio (2.27± 0.03) was found in T3 rather than T2 and T1. The net production in terms of biomass (18.23±2.43 kg/cage) was significantly (p&lt;0.05) higher in T2.The study suggests that, treatment T2 (71 fingerling /m3) as the optimum stocking density to produce maximum production by cage culture of Labeo bata.

Optimization of stocking density and feeding ration for rearing of stunted Labeo rohita fingerlings in cages

Aim: To rear stunted Labeo rohita fingerlings in cages and determine the optimum stocking density and feeding ration for better growth performance of fishes. Methodology: Eight-month-old stunted fingerlings of Labeo rohita (14.65cm/38.23g) were stocked in floating net square cages at different stocking densities (10, 15, 20 and 25 fishm-2) and fed with different feeding ration (3%, 4%, 5% and 6% of body weight), further reared for 330 days and fed twice a day with commercial floating pellets with 25% crude protein. The study followed 4*4 factorial design and were triplicated for each treatment and level. Results: The study found a decrease in the final body weight, average body weight gain, and specific growth rate with increasing stocking density. The highest final body weight (732.64 g), body weight gain (694.30 g) and specific growth rate (0.89 % day-1) were recorded in 10/m2 stocking density with feed ration of 6% body weight. In contrast to this, fish reared in higher stocking density (25/m2) exhibited poor feed conversion ratio. Fish reared in lower stocking density (10/m2) and fed with 6% feeding ration displayed an enhanced feed conversion ratio, feed efficiency ratio and protein efficiency ratio which indicated that rearing of stunted rohu in intensive cage culture at lower stocking density (10/m2) with higher feeding ration (6%) increase their feed utilization capacity. Interpretation: Rearing of stunted rohu in intensive cage culture is possible, however, the stocking density and feeding ration should be 10/m2 and 6%, respectively, compared to traditional cage practices, in order to reduce stress and to get optimum production. Key words: Cage culture, Feeding ration, Fingerling, Labeo rohita, Stocking density

Effect of stocking density of the growth performance, survival rate and feed utilization of the eels Anguilla bicolor (pisces: anguillidae) Larvae

The objective of this study was to determine the optimum stocking density of Anguilla bicolor larva on the growth performance, feed utilization, and survival rate. The study was conducted in the Laboratory of Ichthyology, Faculty of Marine and Fisheries, Syiah Kuala University. A Completely Randomized Design (CRD) was used in this study. The treatment included six different levels of stocking density (3 eels L-1, 4 eels L-1, 5 eels L-1, 6 eels L-1, 7 eels L-1 and 8 eels L-1). The fish samples ranged between 7-9 cm in total length and 2-3 g in body weight. The fishes fed on a commercial diet twice a day at a feeding ration of 10% body weight a day for 60 days. The data was analyzed using One-way Analysis of Variance (One-way ANOVA) and followed by Duncan’s multiple range test. The results showed that the stocking density had a significant effect on the weight gain, specific growth rate and survival rate (P <0.05). However, it did not have a significant effect on feed conversion ratio and feed efficiency (P> 0.05). It is concluded that the best stocking density was found at 3 fish L-1, it resulted in a weight gain of 1.43 g, specific growth rate of 1.62% day-1, survival rate of 79.00%, a feed conversion ratio of 5.17 and a feed efficiency of 19.52%.

THE EFFECTS OF STOCKING DENSITY ON THE PERFORMANCE OF BROILER CHICKENS

THREE trials were conducted to determine the optimum stocking density for broiler chickens raised in a tropical environment In Trial 1, 100,67, 50,40, 34 and 29 birds were placed in duplicates in each pen with an area of 3.72 M2 to give stocking densities of 0.037, 0.056, 0.074, 0.093, 0.10 and 0 128 M2 per bird respectively. In Trial 2, stocking densities of 0.046, 0056, 0.064, 0.074, 0.083 and 0.093 M2 per bird were compared. Trial 3 involved studying the effects of providing equal feeder space (5cm/bird) or equal number of similar sized feeders (2 feeders per pen) when birds were stocked at floor spaces of 0.056, 0.064, 0.74, 0.083 and 0.093 sq meter per bird. Results showed that weight gain and feed consumption decreased, while total meat yield and net income per unit area increased, with increase in stocking rates. Feed efficiency, mortality and carcass dressing percentages were not significantly affected by the stocking rates. The effects of stocking densities on the performance of the birds were not altered by equalizing the feeder space per bird or by providing equal number of feeders per unit space. Management problems in terms of wetness of litter, feeding and watering were encountered with stocking densities of 0.037, 0.046 and 0.056 M2/ bird. Stocking rates of 0.083, 0.093, 0.10 and 0.128 M2 were uneconomic and did not produce superior performances to stocking densities of 0.064 or 0.074 M2/bird. On the basis of the results, floor spaces of 0.064 or 0.074 M2 per bird may be recommended as the optimum for broiler chickens raised in the tropics. The feeder space at these optimum stocking rates need not be more than 5cm per bird.

Effect of stocking density on the growth and survival of the critically endangered peninsular carpHypselobarbus pulchellus(Day, 1870) in fingerling rearing

The present study was undertaken to generate first time information on the optimal stocking density for fry to fingerling rearing of Hypselobarbus pulchellus. Rearing was carried out for 90 days at stocking densities of 15, 30, 45, 60, 75, 90, 105 and 120 fish/m2 in 24 m2 cement tanks. While the length of fish at harvest ranged from 3.42 cm in 120/m2 to 6.11 cm in 15/m2 densities, the weight ranged from 0.41 g in 120/m2 to 2.62 g in 15/m2. The final length and weight were inversely related to the stocking density. However, no significant variation (p > 0.05) in length was observed among the stocking densities of 15, 30, 45 and 60/m2. Similarly, the final weight of the fingerlings also did not differ (p > 0.05) between the stocking densities 15, 30 and 45/m2. Further, increase in stocking densities resulted in significant reduction in final length and weight, with the highest stocking density of 120/m2 recording the lowest values. The condition factor varied between 0.95 and 1.17 with no difference (p > 0.05) among the stocking densities. The survival of fingerlings at harvest ranged between 81 and 90%, but was not statistically different. The growth in terms of length and weight of H. pulchellus was superior under stocking densities 15, 30 and 45 fish/m2 compared to higher densities. Hence, the stocking density of 45 fish /m2 is recommended as the optimum for fry to fingerling rearing of H. pulchellus.

Efecto de la densidad sobre el crecimiento en fase de engorde del mejillón, &lt;i&gt;Mytilus edulis platensis&lt;/i&gt;, en el golfo San Jorge, Patagonia argentina

The aim of this study was to determine the stock density effect on size and biomass on mussel Mytilus edulis platensis, at growth up phase ropes. These ropes were made using three initial stocking densities: 200, 300 and 400 mussels m-1 and hung on in a longline at Belvedere site on San Jorge gulf, Argentina. Stock density showed no influence on individual mussel biomass. Higher growth length was obtained at higher densities. According to these results, when the mussels are in the fattening or thinning out phase, the optimum stocking density would be 300 to 400 mussels m-1.

Effects of Caulerpa lentillifera added into culture media on the growth and nutritional values of Phronima pacifica, a natural fish-feed crustacean

Abstract. Herawati VE, Pinandoyo, Ariyati RW, Rismaningsih N, Windarto S, Prayitno SB, Darmanto YS, Radjasa OK. 2021. Effects of Caulerpa lentillifera added into culture media on the growth and nutritional values of Phronima pacifica, a natural fish-feed crustacean Biodiversitas 22: 424-431. Phronima pacifica is a microcrustacean commonly used as natural feed in fish farming as it has high nutrient contents and is suitable based on larval fish mouth gap size and mass cultivation capacity. However, P. pacifica is not produced optimally and its supply is inadequate, so that P. pacifica culturing techniques need to be improved. The culture of P. pacifica is mostly done using sea grape seaweed (Caulerpa lentillifera). The aim of this study was to investigate the optimal stocking density of C. lentillifera added into media culture on the growth and nutritional values of P. pacifica. We applied a complete random design experiment with four treatments of stocking density of C. lentillifera (i.e., 0 g/m2 (Control), 20 g/m2, 40 g/m2, and 60 g/m2) with 3 replicates for each treatment. The following parameters were analyzed, namely specific growth rate (SGR) of C. lentillifera, and the growth, biomass, growth rate, proximate analysis, and amino and fatty acid concentrations of P. pacifica. This study found that the addition of C. lentillifera into culture media significantly enhanced the growth of P. pacifica. The highest effect on the growth was observed in the treatment of 60 g/m2 with C. lentillifera SGR value of 4.76 ± 0.12%/day, and P. pacifica growth rate, population density and biomass of 4.41 ± 0.12 ind/day, 53.81 ± 8.79 ind/L, and 1.14 ± 0.14 g, respectively. Similarly, the highest protein and fat contained in P. pacifica was obtained in the treatment of 60 g/m2 with 60.23% protein and 10.24% fat. Furthermore, the highest fatty acid profile was C20: 5n-3 of 13.23% ± 0.08% and amino acid profile of 45.23% ± 0.01%. The application of the optimal stocking density of C. lentillifera in culture media could increase the growth and nutritional quality of P. pacifica which in turn could enhance aquaculture productivity.

Effect of stocking density on growth and yield of Labeo bata fingerlings reared in cages

An experiment was carried out to evaluate the growth performance and yield of Labeo bata reared in cages at different stocking densities in a floodplain wetland of Assam, India. Fifteen cages (effective water volume 40 m3 each) installed in the wetland were stocked with fingerlings of L. bata (mean length 8.20 ± 0.08 cm; mean weight 4.82 ± 0.13 g) at five different stocking densities, i.e., 25 (D25), 50 (D50), 75 (D75), 100 (D100) and 150 fingerlings m−3 (D150) in triplicates. Fish were fed with pelleted feed containing 30 % CP at 3–5 % body weight twice-a-day for six months. Specific growth rate of the reared fish recorded at different stocking densities were 1.08 ± 0.03, 0.89 ± 0.01, 0.90 ± 0.05, 0.77 ± 0.02 and 0.57 ± 0.02 % day-1, respectively, in D25, D50, D75, D100 and D150. The corresponding weight gain percent were 604.77 ± 35.63, 395.37 ± 11.32, 407.88 ± 44.91, 296.61 ± 13.07 and 180.70 ± 11.02. In general, growth performance of the reared fish was inversely proportional to stocking density. However, yield (biomass) increased with increase in stocking density of up to 75 fingerlings m-3 after which no significant increase was observed. Economics of the cage aquaculture system also showed highest net revenue and benefit-cost ratio at 75 fingerlings m-3. Rearing of fish at this stocking density yielded 50 % higher fish production and generated 92.5 % higher net revenue than rearing at the lowest stocking density. The results suggest 75 fingerlings m-3 as the optimum stocking density for rearing L. bata in net cages.

Optimization of stocking density of koi carp (Cyprinus carpio var. koi) with gotukola (Centella asiatica) in an aquaponic system using phytoremediated aquaculture wastewater

The stocking density of koi carp (Cyprinus carpio var. koi) was optimized with gotukola (Centella asiatica) in an aquaponic system using phytoremediated aquaculture wastewater. Fingerlings of koi carp were stocked in different stocking densities as 1.4 (T1), 2.1 (T2), 2.8 kg m−3 (T3), and the control (1) 1.4 kg m−3(C1) without hydroponic component. The control 2 (C2); plant grown in field condition was assigned to compare the efficiency with aquaponics. The highest length (10.79 ± 0.24 cm) and weight gain (12.53 ± 0.19 g) in fish were observed in T1 and the highest nitroblue tetrazolium (NBT) activity of the fish was found in T1. However, the highest catalase activity, glucose, and cortisol level were obtained in (T3), which concluded that the fish growth was significantly affected by the highest stocking density. However; the medium stocking density (T2) didn't show a significant difference with the lowest stocking density (T1). In contrast to the biomass of koi carp, the yield of C. asiatica increased significantly with fish stocking density. The highest yield (203.76 ± 11.03 g) was obtained by the maximum stocking density (T3) but it was not significantly different from T2. Considering the water quality parameters, nutrient dynamics, plant growth as well as fish health monitoring parameters, the stocking density of 2.1 kg m−3 (T2) could be suggested as the optimum stocking density for this system.

A study to understand the reasons for the low productivity of shrimp farms in Kerala

Kerala is an important state contributing to farmed shrimp production in India. However, the productivity of shrimp farms in the state is the lowest among all Indian states. The present study was undertaken to understand the reasons for the low productivity of shrimp farms in the state of Kerala. For the collection of data, a survey was conducted among 220 shrimp farms with a total water spread area of 1,113.77 ha (traditional farms: 162 farms with 845.32 ha. area and scientific farms: 58 farms with 268.45 ha. area). Data were collected for two consecutive crops during the period from November 2016 to May, 2018. Analysis of information collected in the present study revealed that over-reliance on traditional mode of farming, lack of species diversity, improper site selection, insufficient attention paid on construction of ponds, inadequate pond preparation, poor pond management, use of poor quality of seed, non-acclimatisation of seed, use of sub optimal stocking density, poor dissolved oxygen management, insufficient water exchange, inadequate feeding, inadequate management of plankton growth, recurrence of diseases, poaching, shortage of labourers, discontinuance of paddy farming, failure in year- round utilisation of ponds etc. were found to be the principal reasons for the reported low productivity of shrimp farms in Kerala.

Effects of different stocking densities on Nile tilapia performance and profitability of a biofloc system with a minimum water exchange

The determination of an optimum stocking density should be obtained according to a complex assessment, in which growth performance, water quality, animal welfare, and production costs need to be considered. In this context, the objective of this work was to evaluate different stocking densities of Nile tilapias in biofloc technology (BFT) with minimal water renewal. Six hundred masculinized Nile tilapia juveniles with an initial average weight of 133.91 g were evaluated at four different stocking densities (18.75, 37.50, 56.25, and 75.00 fish‧m−3) and four replications, during 260 days of trial. The increase in stocking density resulted in a reduction of DO and pH. The minimum water renewal at a rate of 5%‧day−1 promoted an average reduction of settleable solids in the system of 23.75% at each discharge. The final biomass followed a quadratic regression on the stocking density, with a maximum at 72.27 fish‧m−3 or 36.86 kg‧m−3. However, the greatest daily weight gain (2.84 g‧day−1) that resulted in the highest average final body weight (842.26 g) was obtained at the lowest stocking density. We did not obtain any significant differences in body composition. The biofloc, on the other hand, had lower ash content and higher gross energy in the high stocking densities. Regarding gill morphometry, we found a greater number of branchial lesions in the highest and lowest stocking density evaluated. By an economical assessment, if the sales price is influenced by the final body weight, the reduced average harvest weight in higher stocking densities could lead to low profitability or even financial loss. Therefore, it is concluded that the use of intermediate stocking density, around 33 fish‧m−3, has higher profitability since it produces a large proportion of harvested fish that reach high body weights, and possible high selling prices, combined with desirable biomass.

Effect of Stocking Density on Survival Rate and Growth of Tilapia (Oreochromis niloticus Linnaeus, 1758) in Round Container with Water Current Combined with Venturi Aeration System

The aim of this research is determine of the optimal stocking density for survival rate and growth of tilapia in round container with water current combined with venturi aeration system. Place of research in the Aquaculture Laboratory, Building 4 Faculty of Fisheries and Marine Sciences, Universitas Padjadjaran. The research method used is experimentally with using the Completely Randomized Design (CRD) method which consists of three treatments, there are 15 fish, 22 fish, 30 fish, with five replications. Using water of 15 L per container. The fish used are 3-5 cm tilapia fingerlings. Fish were maintained for 40 days. The feed given is 5% from biomass which is adjusted every 10 days. The parameters observed were survival rate (SR) and observed everyday, daily grow rate (DGR), feed conversion ratio (FCR) and feed efficiency were observed every 10 days. The result was significantly different from the analysis of variance (ANOVA) with the F test at 95% confidence intervals and then using Duncan test to compare the rates between treatments. The results showed that the best treatment was stocking density of 15 fish / 15 L in round container with current combined with venturi aeration system with survival rate of 78.67 ±10.95%, daily grow rate of 3.68 ± 0.12%, feed conversion ratio of 1.19 ± 0.13 and feed efficiency of 85.01 ± 8.97%.

EXPERIENCE OF TILAPIA INTRODUCTION AT GEOTHERMAL SOURCES OF KAZAKHSTAN

Over recent years much attention has been paid to the fishery use of geothermal sources. The prospects for this area are enormous, as it opens up possibilities for managing fish-breeding processes, regardless of climatic conditions. The main objective of the research was a comprehensive study of the technological processes of growing. One of the promising reserves for increasing fish production is the rational fishery use of waste warm water and geothermal sources. Research work was carried out in 2019 based on the farm of “Tengri Fish” LLP, which is located 270 kilometers from Almaty. The collection and processing of materials were carried out according to generally accepted methods in ichthyology and fish farming, followed by their analysis on a PC. Based on the results of the research, technological primaries of growing tilapia in a RAS (Recirculating Aquaculture System) using geothermal waters were determined. During the research, work was carried out to optimize the hydrochemical regime. The main fish breeding and biological indicators for the growth and development of tilapia were established. The optimal stocking density of tilapias in recirculating aquaculture systems using geothermal waters and the temperature when tilapias have a higher average daily weight gain were found. The novelty of the research: a complex study of biology and adaptation of a new object of industrial fish farming of tilapia and clarium catfish has been carried out outside the range and determined the adaptation possibilities of tilapia and clarium catfish to extreme factors of the aquatic environment.

Estimating the biomass density of macroalgae in land-based cultivation systems using spectral reflectance imagery

Sub-sampling large-scale, land-based macroalgal cultures to estimate stocking densities is time-consuming, labour-intensive, and inaccurate. Therefore, the development of innovative methods to monitor stocking densities are required to maximise macroalgal productivity. In this study the spectral reflectance of a range of biomass densities (0.5–12.0 g L−1) of Ulva ohnoi was measured using a spectroradiometer (ASD) and a multispectral camera (REMX). A two-band normalised difference vegetation index (NDVI), which was standardised by depth of the culture system, was quantified from both sets of data, and used to establish biomass density sensing models. The models developed using the ASD and REMX data had strong piecewise linear relationships between the standardised NDVI and biomass density (R2 > 0.85, residual mean standard error < 1.31, and mean standard error < 0.99), but differed in breakpoint and slope of the regression lines. Subsequently, both models were validated using data collected in 4000 L high-rate algal ponds, representing practical conditions of the commercial land-based production of macroalgae. Notably, the REMX model had a better fit with the validation data, and the mean difference in the actual versus predicted densities was ≤0.76 g L−1, with a maximum difference of 1.73 g L−1. Therefore, the REMX biomass density model is a useful management tool for differentiating between low (<2 g L−1), medium (2–4 g L−1), and high densities (>4 g L−1) using the standardised NDVI. This study has demonstrated that there is a predictive relationship between spectral reflectance and the biomass density of U. ohnoi. Notably, the REMX model will inform decision making around the frequency of harvest, as well as the quantity of biomass to be harvested, to maintain an optimal stocking density and, therefore, high productivities at a commercial scale.