Cage culture of sutchi catfish, Pangasius sutchi (Fowler 1937): effects of stocking density on growth, survival, yield and farm profitability

The sutchi catfish, Pangasius sutchi (Fowler 1937) was grown at 10 stocking densities in cages suspended in a river‐fed channel during the summer of 2000. Catfish fingerlings (mean length 9.1–9.7 cm and mean weight 5.9–6.7 g) were stocked at densities of 60, 70, 80, 90, 100, 110, 120, 130, 140 and 150 fish m^?3. After 150 days, growth and yield parameters were studied and a simple economic analysis was carried out to calculate profitability. The mean gross yield ranged from 15.6±0.27 to 34.5±0.44 kg m^?3 and the net yield ranged from 15.2±0.22 to 33.5±0.36 kg m^?3 and showed significant variations (P<0.05). The mean weights of fish at harvest were inversely related to stocking density. Both gross and net yields were significantly different and were directly influenced by stocking density but the specific growth rate, survival rate and feed conversion rate were unaffected. Higher stocking density resulted in higher yield per unit of production cost and lower cost per unit of yield. The net revenue increased positively with increasing stocking density. A density of 150 fish m^?3 produced the best production and farm economics among the densities tested in this experiment.     

Growout production of camouflage grouper, Epinephelus polyphekadion (Bleeker), in a tank culture system

Growout production of the camouflage grouper, Epinephelus polyphekadion (Bleeker), in a 10-m³-capacity fibreglass tank culture system was evaluated, using hatchery-produced fingerlings (56-59 g initial weight) at stocking densities of five, 15 and 45 fish m^?3. During the first 9 months of a 12-month growout period, the fish were fed twice a day with a moist pellet feed containing 40.9% protein. From month 10 onwards until harvest, the fish were fed moist pellets in the morning and trash fish in the evening at a 1:1 ratio. The final weight of fish at harvest was up to 900 g, with mean weights of 544.6 ± 170.72 g at five fish m^?3, 540.2 ± 150.82 g at 15 fish m-^?3 and 513.3 ± 134.52 g at 45 fish m^?3. The results showed no significant differences (P > 0.05) in growth rate and fish size between the different stocking densities tested. The average daily growth rate ranged from 0.62 to 3.38 g fish^?1 day^?1, with mean weights of 1.49 ± 0.74 g fish^?1 day^?1 at five fish m^?3 through 0.53 to 2.38 g fish^?1 day^?1, 1.32 ± 0.57 g fish^?1 day^?1 at 15 fish m^?3 to 0.48-3.32 g fish^?1 day^?1 and 1.31 g fish^?1 day^?1 at 45 fish m^?3 stocking density. Although up to 100% survival was observed at the lowest stocking density, the survival rate significantly decreased (P < 0.05) with increasing stocking density. The food conversion ratio (FCR) significantly decreased (P <0.05) with increasing stocking densities, showing efficient feed utilization with increasing stocking densities of E. polyphekadion. The FCR averaged 2.1 at a stocking density of 45 fish m^?3. The yield in terms of kg fish produced m^?3 of water used in the culture system significantly increased (P < 0.001) from five to 45 fish m^?3. The yield averaged 17.3 ±0.53 kg m^?3 at a stocking density of 45 fish m^?3. The present results show that the present tank culture system could sustain more biomass in terms of increasing fish stocking densities. The growth performance of E. polyphekadion observed during this investigation has been reviewed with other grouper species.     

Effect of stocking density on the growth performance and yield of Nile tilapia [Oreochromis niloticus (L., 1758)] in a cage culture system in Lake Kuriftu,Ethiopia

This research was conducted to investigate the effect of stocking density on the growth performance and yield of Oreochromis niloticus in cage culture in Lake Kuriftu. The treatments had stocking densities of 50 (50F), 100 (100F), 150 (150F), and 200 (200F) fish per m^?3. All treatments were in duplicate. Juveniles with an average weight of 45. 76±0.25 g were stocked in the treatments. The fish were fed a composite mixture of mill sweeping, cotton seed, and Bora food complex at 2% of their body weight twice per day using feeding trays for 150 days in powdered form. The growth performance of O. niloticus was density dependent. The final mean weight of O. niloticus ranged 147.76±0.28–219.71±1.42 g and the mean daily weight gain was 0.69±0.01–1.15±0.02 g day^?1. Fish held in cages with lower density were heavier than the ones held at higher densities, and showed higher weight gain and daily weight gain. The most effective stocking density, in terms of growth parameters, was 50 fish m^?3. The gross yield (4.5–20.55 kg cage^?1) showed a significant difference with increasing stocking density (P<0.05). Moreover, the apparent food conversion ratio (2.48–7.22) was significantly affected by stocking density (P<0.05). However, survival rate was not affected by stocking density (P>0.05). It can be concluded that the most effective stocking densities were at 50 fish m^?3 cage for larger size fish demand in a short period and 200 fish m^?3 for higher gross production with supplementary feed.     

Effect of stocking density on growth performance of juvenile sea cucumber Holothuria tubulosa (Gmelin, 1788)

Stock density is one among the most important factors in aquaculture that directly influences the growth of organisms; however, there is limited information about the effects of stocking density on growth performance of sea cucumber Holothuria tubulosa (Gmelin, 1788) that has a commercial potential and represents a new species for aquaculture. In this study, we investigated the effect of stocking densities on the growth performance of juvenile H. tubulosa (40.3 ± 3.34 g) in laboratory conditions. Stocking densities were selected as 6, 15 and 30 ind m^?2 with total biomass 253.3 ± 0.18, 601.2 ± 0.11 and 1201.4 ± 0.15 g m^?2 respectively. We monitored the growth by wet weights and calculated the growth performance through weight gain, growth rate, specific growth rate, relative weight gain, coefficients of variation and survival rate during 8 weeks of research period. We found that individual mean weight gain in 6 ind m^?2 group was approximately 29.53 g while it was 3.03 g and ?4.36 g for 15 ind and 30 ind m^?2 groups respectively. Results have shown that the specific growth rate tends to decrease as the number of individuals in unit area increases. The final mean weight, growth rate, specific growth rate, relative weight gain and coefficients of variation were significantly different among treatment groups. In conclusion, a density of 6 ind m^?2 is recommended for stocking juvenile H. tubulosa under rearing conditions. Stocking density of 15 ind m^?2 is not favourable for long term as the growth rate is negligible where 30 ind m^?2 should be avoided in tank‐based rearing units.     

Survival rates of tilapia, Oreochromis spilurus (Günther), fingerlings reared at high densities during winter using warm underground sea water

The study was conducted to determine the optimum stocking density for rearing tilapia. Oreochromis spilurus (Günther), fingerlings in tanks during winter using warm (21-26°C) underground sea water (37%o). Seawater-acclimated fingerlings with mean weight of 2 g were stocked in eighteen 400-1 fibreglass tanks at 750 and 1000 fish m^?3. Fish were fed at the rates of 2.5, 3.0 and 3.5% day^?1 of the fish biomass. After 83 days, the mean individual daily weight gain was significantly higher (P < 0.028) at stocking of 750 fish m^?3 than at 1000 fish m^?3. Feed conversion ratio was significantly higher at stocking of 1000 fish m^?3 than at 750 fish m^?3 and at feeding rate of 3.5% day¹ than at 2.5% day^?1. However, because no significant differences were observed on survival rates between the two stocking densities and among feeding rates, it is recommended that the stocking density of 1000 fish m^?3 and a feeding rate of 2.5% day^?1 be used for optimum production of tilapia fingerlings in tanks during winter using warm underground sea water.     

Enhanced growth and immuno‐physiological response of Genetically Improved Farmed Tilapia in indoor biofloc units at different stocking densities

An experimental trial was conducted for 90 days to evaluate the growth performance, immunophysiological response of GIFT strain of Tilapia in biofloc‐based rearing system and to assess the relative percentage survival in 3 days after challenging with the virulent strain of Aeromonas hydrophila. Fingerlings with an average body weight 0.98 ± 0.06 g were stocked in triplicate at different stocking densities of 200 (SD1), 250 (SD2), 300 (SD3) and 350 (SD4) m^?3 in biofloc‐based treatments and 150 (C) m^?3 in control (clear water). Biofloc‐based units (SD1 and SD2) obtained significantly better (P < 0.05) growth performances at the end of the experimental period. Mean body weight of fish in biofloc‐based units showed a decreasing trend with increase in stocking density with 100% survival in all units including control. The stress parameters were significantly lower in biofloc‐based rearing units especially in treatments SD1 and SD2 as compared to the control. The fish from the biofloc‐based units (SD1 and SD2) possessed significantly (P < 0.05) higher immune status as compared to control and other biofloc treatments in terms of respiratory burst, serum lysozyme and myeloperoxidase activity. Relative survival percentages were significantly better in biofloc treatments with highest in SD1 and SD2 (83.33%) after challenge study. GIFT strain of Tilapia at higher stocking densities 200–250 nos m^?3 can be taken as optimum stocking density whereas higher stocking densities up to 350 nos m^?3 can be reared in the biofloc systems without compromising the growth and immunity.     

Influence of Stocking Density on Growth and Physiological Responses of Beluga,Huso huso (Brandt, 1869), and Ship Sturgeon,Acipenser nudiventris (Lovetsky, 1828), Juveniles in a Flow‐through System

The influence of three different initial stocking densities (low stocking density [LSD] = 1.5 kg/m²; medium stocking density [MSD] = 3 kg/m²; and high stocking density [HSD] = 6 kg/m²) in flow‐through systems was evaluated on growth and welfare in beluga, Huso huso, and ship sturgeon, Acipenser nudiventris, juveniles for 2 mo. Fish were kept in 18 concrete square tanks (2.0 × 1.0 × 1.2 m³) at 22.3 ± 0.4 C and under a natural photoperiod. In both species, the growth performance in terms of final body weight, weight gain, specific growth rate, and feed intake significantly decreased with increasing stocking density (P < 0.05). In both species, the percent of neutrophils increased after 60 d of trial (P < 0.05). Moreover, hematocrit and white blood cell counts increased after 60 d of trial in ship sturgeon (P < 0.05). Plasma immunoglobulin significantly decreased with increasing stocking density in both species. Plasma insulin‐like growth factor I decreased with increasing stocking density in beluga; however, it was not affected in ship sturgeon. Overall, these results showed that the LSD group in both species demonstrated more homogeneous and higher growth rate than the MSD and HSD groups.     

Growth and production of endangered Indian butter catfish,Ompok bimaculatus (Bloch) at different stocking densities in earthen ponds

Growth, survival and production of endangered Indian butter catfish (Ompok bimaculatus) fingerlings were examined at different stocking densities. The experiment was conducted for 8 months in nine earthen ponds having an area of 0.03 ha each. 30‐day‐old fingerling, stocked at 40 000 ha^?1 was designated as treatment‐1 (T1), 50 000 ha^?1 as treatment‐2 (T2) and 60 000 ha^?1 as treatment‐3 (T3). At stocking, all fingerlings were of same age group with a mean length and weight of 3.36 ± 0.08 cm and weight of 0.83 ± 0.02 g respectively. Fish in all the treatments were fed with a mixture of rice bran (50%), mustard oil cake (30%), fish meal (19%) and vitamin‐mineral premix (1%). Physicochemical parameters, plankton populations and soil parameters were at the optimum level for fish culture. Highest weight gain was observed in T1 and lowest in T3. Final length, weight and survival of fish also followed the same trend as weight gain. Highest specific growth rate was observed in T1 followed by T2 and T3. Feed conversion ratio was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher amount of fish was produced in T1 than T2 and T3 respectively. Higher net benefit was obtained from T1 than from T2 and T3. Overall, the highest growth, survival and benefit of fish were obtained at a density of 40 000 fingerlings ha^?1. Hence, of the three stocking densities, 40 000 fingerlings ha^?1 appears to be the most suitable stocking density for culturing of Indian butter catfish in grow‐out system.     

Enhancing productivity of Labeo victorianus ponds using maize flour as a carbohydrate source

This study investigated the effects of manipulating carbon–nitrogen (C/N) ratio and fish stocking density on pond productivity: total heterotrophic bacteria counts, plankton biovolume and benthic macro‐invertebrates. Labeo victorianus juveniles were reared for 72 days in 18 hapas suspended in six ponds measuring 150 m² at densities of 10, 15 and 25 fish m^?2. Fish in hapas received a locally formulated and prepared feed containing 295 g kg^?1 crude protein, and ponds were treated with a C/N ratio of either 10 or 20. All treatments were carried out in triplicate. Increasing C/N ratio from 10 to 20 increased phytoplankton by 13% and zooplankton biovolume by 25% in the water column (P < 0.001). Total benthic macro‐invertebrates biovolumes were also 30% higher (P < 0.05) with a C/N ratio of 20 compared to 10. Total heterotrophic bacteria counts increased both in water and sediment by 29% while net yield increased by 15% from 1534 (C/N 10) to 1821 (C/N 20) kg ha^?1 72 day^?1. C/N ratio of 20 and a stocking density of 25 fish m^?2 led to the highest yield, survival, production and net benefits. It is suggested that polyculture may lead to better utilization of pond communities to further improve pond productivity.     

Growth and survival of the grouper Epinephelus coioides (Hamilton) at different loading rates in tanks

The effect of increasing fish loading (decreasing water exchange rate, while holding fish stocking density constant) on growth, survival and feed conversion ratio was determined for two size groups of the orange‐spotted grouper Epinephelus coioides (Hamilton). Fingerlings (124.3–145.8 g initial body weight) and subadults (990.6–1147.1 g initial body weight) were reared in 1‐m³ circular tanks for 14 weeks. For the fingerlings experiment, three loading rates of 0.5, 2 and 6 kg L^?1 min^?1 were used, while in the experiment with subadults, the loading rates were 1, 3 and 6 kg L^?1 min^?1. The mean growth rate of fingerlings ranged from 1.60 to 2.14 g fish^?1 day^?1, and survival was high (95–100%); however, there were no significant differences (P > 0.05) as a result of the different loading rates. Similar results were obtained in the subadults experiment, in which the growth rate (3.10–4.90 g fish^?1 day^?1) and survival (86.7–100%) were not significantly (P > 0.05) affected by the different loading rates. In both experiments, the feed conversion ratios were also not affected significantly by the loading rates. These results show that water exchange in aerated, flowthrough tanks can be reduced to as low as 6 kg L^?1 min^?1 without adversely affecting growth, survival and feed conversion of fingerling and subadult groupers.     

Effects of stocking density of Labeo rohita on survival, growth and production in cages

Labeo rohita (139.92 ± 0.76 mm/24.33 ± 0.45 g) was reared for 92 days in floating square cages (10 m² area, 1.5 m height) in a pond (2 ha) at six stocking densities (5, 7.5, 10, 15, 20 and 25 fish m^?2) each with 3 replicates. Fish were fed daily once in the morning with rice polish and groundnut oil cake (1:1) in dough form at 3 % of the total body weight. Survival ranged from 96 to 100 % in different stocking densities. Final average body weight, average body weight gain, mean daily body weight gain and SGR decreased (P < 0.05) with increasing stocking density. Conversely, final biomass, biomass gain and FCR increased (P < 0.05) with increasing stocking density. The highest growth rate of fish could be achieved up to 60 days at 5 fish m^?2 and 92 days at other densities. The reduced growth rate at 10–25 fish m^?2 for 60 days of culture indicated that stress is related to size and density of the fish, suggesting that utmost care is required to reduce the stress at high densities. Maximum production and profit was observed at the highest stocking density. Non-lethal levels of water and soil qualities at different sites (cage premises, and 20 and 200 m away from cage area) suggested that cage aquaculture could be done safely covering 0.9 % of pond area. Production of advanced fingerlings in cages was found a viable alternative to their culture in pond.     

Maximum yield approximation and size distribution patterns of stocker size largemouth bass,Micropterus salmoides reared in a semi‐closed indoor system

The main objectives of this study were to approximate the maximum yield and evaluate size dispersion of stocker size largemouth bass, Micropterus salmoides reared in a semi‐closed recirculating system for 60 days. Fingerlings with an average body weight of 36.7 g were utilized for the study. An experimental system consisting of 18 square plastic tanks (165 L) equipped with a radial flow settler, a sump, a moving bed filter, a centrifugal pump, a rapid sand filter, a down‐flow oxygen saturator and a UV sterilizer was utilized for the trial. The system was operated semi‐closed, accounting for a daily exchange rate of 30–50% of total system water volume. Experimental stocking densities were 4.5, 9.1, 18.8, 36.5, 54.6 and 73 kg m^?3 with three replicates per treatment. At the end of the experimental trial, largemouth bass showed acceptable feed conversion (1.00–1.48), specific growth rate (1.16–1.45% day^?1) and survival rate (81.8–96.6%) in all treatments, displaying the highest performance at an initial stocking density range of 18–36 kg m^?3. Based on a piecewise regression model with breakpoint analysis, maximum yield of largemouth bass fingerlings should not exceed 70 kg m^?3. As stocking density increased, relatively more underweight fingerlings were produced with a higher uniformity of fatness.     

Stocking density effects on growth and production of the threatened silurid catfish,Mystus cavasius (Hamilton) fingerlings in nursery ponds

The fingerling‐rearing experiment of the threatened catfish, Mystus cavasius was carried out at different stocking densities in earthen nursery ponds. Twelve‐day‐old fry were stocked at 200 000 ha^?1 in treatment‐1 (T₁), 250 000 ha^?1 in treatment‐2 (T₂) and 300 000 ha^?1 in treatment‐3 (T₃) respectively. The mean length and weight of fry at stocking was 1.24 ± 0.25 cm and 0.11 ± 0.04 g respectively. Fry in all the experimental ponds were supplemented with SABINCO nursery feed for the first 14 days and starter‐I feed for days 15–56. The physico‐chemical parameters and plankton population of pond water were within the suitable level for fish culture. Growth in terms of final weight, final length, weight gain, length gain and specific growth rate and survival of fingerlings were significantly higher in T₁ than those in T₂ and T₃. Feed conversion rate was significantly lower in T₁ followed by T₂ and T₃ in that order. Significantly higher number of fingerlings was produced in T₃ than that in T₂ and T₁. Even then, consistently higher net benefits were obtained from T₁ than those from T₃ and T₂. Among the treatments evaluated, 200 000 fry ha^?1 was the best stocking density considering the highest growth, production and net benefits of fingerlings of M. cavasius in nursery ponds.     

Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

Two consecutive experiments were conducted to study the effects of stocking density on growth, food utilization, production and farming profitability of Nile tilapia (Oreochromis niloticus) fingerlings (initial mean weight: 16.2 ± 0.2 g) fed Azolla, as a main component in diet. In experiment 1, fish were hand‐fed twice daily with three isonitrogenous (28.5% crude protein) and isocaloric (14.5 kJ g⁻¹) diets A30, A35 and A40 containing 30%, 35% and 40%Azolla, respectively, for 90 days. Diets were formulated by mixing Azolla with locally available by‐products. No significant differences were found in growth parameters and production (P>0.05). Total investment cost was significantly higher with A30 (P<0.05), but same profitability values were obtained with all diets (P>0.05). In experiment 2, three stocking densities, 1, 3 and 5 m⁻², were assigned to three treatments T₁, T₂ and T₃ respectively. Fish were hand‐fed twice daily with diet A40. The final mean weight (89.53–115.12 g), the mean weight gain (0.81–1.10 g day⁻¹), the specific growth rate (1.90–2.20% day⁻¹) and the apparent food conversion ratio (1.29–1.58) were affected by stocking density, with significant difference (P<0.05) at 5 m⁻², compared with the other densities. Stocking density did not affect survival rate (P>0.05). Yield and annual production increased with increasing stocking density, ranging from 7.10 ± 0.90 to 25.01 ± 1.84 kg are⁻¹ and 28.79 ± 3.66 to 101.42 ± 7.48 kg are⁻¹ year⁻¹, respectively, with significant differences between all densities (P<0.05). Higher stocking density resulted in higher gross return and lower cost of fish production, with significant variations (P<0.05). The net return increased with increasing stocking density (P<0.05). However, both densities of 3 and 5 m⁻² produced the same profitability values. On the basis of growth values and economic return, it was concluded that Nile tilapia could be raised at a density of 3 fish m⁻² with A40 to improve production and generate profit for nutritional security and poverty alleviation in rural areas.     

Effects of stocking density on mortality,growth and physiology of juvenile Amur sturgeon (Acipenser schrenckii)

To evaluate effects of stocking density on welfare of Amur sturgeon (Acipenser schrenckii), an experiment was designed using three initial stocking densities in flow‐through tanks (LSD = 3.7 kg m^?3, MSD = 6.9 kg m^?3, and HSD = 9.3 kg m^?3, respectively) for 60 days. Growth, body composition, and haematological and biochemical parameters were monitored. The mortality and feed conversion rate (FCR) were not affected by stocking density. However, the specific growth rate (SGR), final weight and weight gain in the HSD group were significantly lower than in the LSD and MSD groups. The hepatosomatic (HSI) and viscerosomatic indices (VSI) varied inversely with regard to stocking density. Stocking density did not affect crude protein levels in fish. In contrast, the total lipid level was significantly higher in the LSD group compared to the MSD and HSD groups. The levels of erythrocytes and haemoglobin were positively correlated with stocking density. Serum total bilirubin and urea in HSD group were significantly higher than in the LSD group while serum triglycerides showed opposite tendencies. Differences between treatments were not registered for glucose, total protein and albumin. In conclusion, higher stocking density resulted in increased immunosuppression and enhanced energy mobilization. The latter was necessary to enable Amur sturgeon to cope with crowding.     

The effects of water temperature and stocking density on survival,feeding and growth of the juveniles of the hybrid yellow catfish from Pelteobagrus fulvidraco (♀) × Pelteobagrus vachelli (♂)

In this study, we aimed to investigate the effects of water temperature and stocking density on the survival, feeding and growth of the juveniles of the hybrid yellow catfish from Pelteobagrus fulvidraco (♀) × Pelteobagrus vachelli (♂) using the parameters as follows: survival rate (%), feeding rate (% day^?1), feed conversion ratio, specific growth rate (% day^?1), coefficient of variation (%), productivity (P, g m^?3 day^?1) and condition factor. We reared the juvenile fish (3.25 ± 0.21 g) at 12 water temperature levels and six stocking density levels (each level included three aquaria in two batches of experiments). The results showed that all groups survived at a temperature range of ≤35°C during a 46‐day experimental period, and they could achieve a high growth at a water temperature range of 26–32°C. The optimal temperature for growth was 29.8°C. Productivity peaked at a stocking density of 1.9 kg m^?3. Our results indicated that the hybrid is very suitable for commercial aquaculture.     

Growth Performance and Body Composition of Aspikutum: A New Hybrid of Asp,Leuciscus aspius ♀, × Caspian Kutum,Rutilus frisii ♂, Cultured under Different Stocking Densities in Circular Concrete Tanks

The first step for rearing the newly produced hybrid of Asp, Leuciscus aspius ♀, × Caspian Kutum, Rutilus frisii ♂ (so‐called “Aspikutum”) is to understand essential production requirements such as stocking density. For this purpose, fish (60.4 g) were held at five stocking densities of 2, 4, 6, 8, and 10 kg/m³ in circular concrete tanks (603 L) for a period of 56 d. The culture system was maintained at natural temperature and photoperiod. Fish were fed thrice a day using a commercial diet. At the end of the trial, growth indices, including final mean weight, weight gain, and specific growth rate, were significantly higher at the density of 10 kg/m³ compared with 2 kg/m³ (P< 0.05). Feed intake was significantly greater at 10 kg/m³ compared with 2 kg/m³ (P< 0.05); however, feed efficiency, protein efficiency ratio, protein productive value, and hepatosomatic index remained unchanged among the stocking densities (P> 0.05). Increased stocking density caused significant increase in body protein and fat contents (P< 0.05). Condition factor in higher densities (8 and 10 kg/m³) was significantly higher compared with 2 kg/m³ (P< 0.05). The results indicated that rearing this hybrid in the studied weight range at high density of 10 kg/m³ or more is possible without negative impacts on growth performance and body composition.     

High density rearing of rohu,Labeo rohita (Hamilton) from spawn to fry in concrete tanks: effect of daily feed ration and soil base on fry growth and survival

Rearing of rohu spawn to fry size was carried out at high density (2000 spawn m^?2) in large concrete nursery tanks (10 m × 5 m × 1.2 m) to standardize the daily ration of supplementary feed and to assess the impact of soil base on the fry performance. In Set‐1, supplementary feed was provided at 100% (control), 75% and 50% of the daily ration that is commonly used in earthen carp nursery ponds and named as the three treatments T‐1, T‐2 and T‐3 respectively. Although in Set‐II, performance of fry were evaluated in tanks provided with and without soil base. The fry survival was to the tune of 45–59% at this high density of 2000 spawn m^?2, indicating the efficacy of the concrete nursery system for high density seed rearing. In Set‐I, T‐2 receiving 75% of the control ration exhibited similar fry growth as that of T‐1, but its fry survival (58.8%) was 10% higher than the latter. This indicated that supplementary feed in a concrete nursery can be reduced up to 25% of that provided in earthen nursery system while ensuring a higher fry yield. However, further reduction up to 50% of the control ration in T‐3 yielded lower fry survival and growth (P < 0.05) revealing inadequacy of the available feed. In Set‐II, treatment without soil base (T‐ns) yielded similar fry growth but 10% higher survival compared to that with the soil base (T‐s) revealing non‐essentiality of soil base in concrete tanks for such short‐term nursery rearing of rohu.     

Polyculture of milkfish Chanos chanos (Forsskal) and the red seaweed Gracilariopsis bailinae (Zhang et Xia) in brackish water earthen ponds

Growth, net production, and survival rates of milkfish cultured with Gracilariopsis bailinae at two stocking density combinations (T₁– 30 fingerlings 100‐m^?2 pond+1‐kg G. bailinae 4‐m^?2 net cage, T₂– 30 fingerlings 100‐m^?2 pond+2‐kg G. bailinae 4‐m^?2 net cage) in brackish water earthen ponds over four culture periods were determined. The control (T₃) was stocked at 30 fingerlings 100‐m^?2 pond. Specific growth and production rates of G. bailinae were also calculated. There were no significant differences in mean growth, survival, and net production rates of milkfish between the three treatments. Irrespective of stocking singly or in combination with G. bailinae, significantly higher mean growth and mean production rates for milkfish were obtained during the third culture period of year 1 than those obtained from the other culture periods. Survival rates were not significantly different among the four culture periods. There were no significant differences in mean specific growth and mean net production rates between the two stocking densities of G. bailinae. Significantly higher mean specific growth and mean net production rates of red seaweed were also obtained during the third culture period of year 1 than those obtained from other culture periods. The production of milkfish and red seaweed was higher during the dry season. Growth rates of milkfish was positively correlated with temperature and salinity, while net production rates were positively correlated with temperature and total rainfall, but was inversely correlated with dissolved oxygen. G. bailinae growth and net production rates were positively correlated with water temperature and salinity. Results show that milkfish can be polycultured with G. bailinae grown in net cages in brackish water ponds at stocking density combination of 30 fingerlings 100‐m^?2 pond+1‐kg G. bailinae 4‐m^?2 net cage.     

Dietary administration of natural immunostimulants on growth performance,haematological, biochemical parameters and disease resistance of Asian Sea bass Lates calcarifer (Bloch, 1790)

This study was aimed to address the promising evaluation of Cissus quadrangularis plant (stem) and lipopolysaccharide (LPS from bacteria) supplemented diets on innate immune response in Lates calcarifer fingerlings against Aeromonas hydrophila infection. Fingerlings were fed supplemented diets containing four different concentrations of C. quadrangularis (0.5, 1.0, 1.5 and 2.0 g kg^?1 feed), LPS (25, 50, 75 and 100 mg kg^?1 feed) and control (normal formulated diet) for 60 days. The fish fingerlings fed supplemented diet displayed significant differences (P < 0.05) in specific growth rate (SGR) and relative percentage survival compared to the control group fed without C. quadrangularis and LPS‐supplemented diet. Fingerlings were injected intraperitoneally with 100 μL lethal dose of A. hydrophila containing 1 × 10⁶ CFU g^?1. Supplementation of C. quadrangularis and LPS diet significantly increased biochemical profile such as protein, lipid and carbohydrate content, haematological parameters of L. calcarifer fingerlings in different experimental periods when compared with the control group. Dietary doses of C. quadrangularis and LPS‐supplemented diet significantly influenced growth performance and increased survival rate in L. calcarifer fingerlings against A. hydrophila infection.