Changes in soil and water quality at sediment–water interface of Penaeus vannamei culture pond at varying salinities

The health of the pond environment in shrimp farming is important for sustainable and profitable aquaculture, in which sediment–water interface is the most important influencing area. With this objective, the key parameters of water and sediment at the interface was studied in shrimp ponds with varying salinities and compared with the surface water and soil to understand the variations and the underlying causes. Total ammonia nitrogen and total alkalinity were higher in water at the interface as compared to surface water, whereas pH, nitrite, oxide forms of nitrogen (NO₃), phosphorus (PO₄) and oxidizing bacteria were observed to be lower. There was no significant difference with respect to macrominerals such as sodium, potassium, calcium and magnesium between water at the interface and surface. These changes are profoundly influenced by the uppermost 1.0‐cm thick sediment layer, where the maximum transition of nutrients takes place with the water column. The outcome of the study highlights the effectiveness of water sampling for metabolites at the interface, which reflects at an early stage any potential deterioration of pond environment, which will help the farmer to initiate timely mitigation measures.     

Fecundity and egg dimension of freshwater prawn Macrobrachium assamense peninsulare (Tiwari, 1958) from Rawasan stream of Garhwal,Central Himalaya,India

The population of the freshwater animal was declined day by day due to the degradation of habitat and use of illegal fishing methods, which cause a great threat to these aquatic animals. The main purpose of this study was to scrutinize the wild population and fecundity of freshwater prawn Macrobrachium assamense peninsulare in Rawasan stream to assess the health status of prawn. Fecundity was estimated by a random sampling of prawn from five selected sites of Rawasan stream. A wild collection of a total of 35 ovigerous females was collected for an interval of 2 years (August 2013–July 2015) from May to September month, that is breeding session. The maximum number of eggs was 102 eggs in an individual having 52 mm total length and 2.66 g body weight. It was concluded that fecundity of Macrobrachium assamense peninsulare was low, and egg dimension was larger than other closely related species of freshwater prawn. Fecundity of Macrobrachium assamense peninsulare showed a positive relationship with a total weight (R² = .71) and moderate with the total length (R² = .38). A strong correlation exists between egg mass and total weight, and between egg mass and total length of female (R² = .849 and R² = .77 at p < .05) respectively. The numbers of eggs, that is fecundity, in a female were increased with the body growth of an individual, which results in a linear graph.     

Response of strawberry to organic versus inorganic fertilizers

The aim of this research was designed in order to optimize integrated plant nutrient supply (IPNS) through balanced fertilization of organic, inorganic and microbial inoculants in strawberry cv. Chandler. The potential efficiency of bio-organics used along with chemical fertilizers on cropping behaviour, physical-chemical and biological properties of rhizosphere soil, fruit yield, quality attributes and leaf nutrient content was investigated. The significant improvement in physico-chemical properties of the soil and nutrient uptake was recorded. The uninoculated control received farmyard manure (FYM) and inorganic nitrogen (N) recorded the highest cation exchange capacity (CEC) and soil organic carbon (OC) content. Highest available N and phosphorus (P) of soil were recorded in vermicompost and inorganic N applied in two and one split, respectively. The concentration of micronutrients cations viz., iron (Fe), zinc (Zn), manganese (Mn) in soil was higher in treatment received vermicompost and inorganic N in two splits. The integration of bio-organic nutrient supplements also significantly enriched the microbial status of the rhizosphere soil, leaf nutrient concentration and maintained soil health and productivity on long term basis for sustainable fruit production.     

Heat shock protein 70 expression in different tissues of Cirrhinus mrigala (Ham.) following heat stress

Members of heat shock protein 70 (HSP70) are highly conserved proteins of about 70 kDa and play important roles in protein folding. Levels of these proteins increase when cells are under stress. Environmental temperature influences both the basal and induced levels of HSPs. However, studies on HSPs in fishes from a tropical country such as India are lacking. In the present study, Indian major carp (IMC) Cirrhinus mrigala (Ham.) acclimatized at 25±2°C had high levels of HSP70, viz., 1.2–1.3 ng μg^?1 total protein in kidney and gill and 4.2–5.3 ng μg^?1 total protein in liver and brain tissues, indicating the presence of biochemically significant levels of stress. However, maintenance of acclimatized fish at 17°C for up to 48 h did not lead to a significant decrease in stress protein levels. A heat shock at 37°C for up to 48 h resulted in only two to threefold increase in HSP70 levels in these organs. Although the increase in HSP70 levels was apparent from the first hour of heat stress in all these tissues, the increase was significant from the second hour in the brain, the sixth hour in liver and kidney and the 20th hour in the gills.     

Estimation of gut contents of freshwater mussel, Lamellidens marginalis L.

This study examined the food organisms found in the gut of freshwater mussels, Lamellidens marginalis L. A total of 34 taxa of food organisms were recorded, out of which 30 taxa belonged to phytoplankton and four taxa to zooplankton. Both the groups comprised three families each: Cyanophyceae (blue‐green algae), Chlorophycea (green algae) and Bacillariophyceae (diatoms) constituted phytoplankton, whereas Euglenaceae, Chlamydodontidae and Brachionidae belonged to zooplankton. The total number of frequencies of phytoplankton (n=537) were almost nine times more than that of zooplankton (n=60). When blue‐green algae, green algae, diatoms and zooplankton (all the three families together) were tested for significant difference (P<0.05) following Duncan's multiple range test, the result showed only two groups. Blue‐green algae, green algae and zooplankton were not significantly different (P<0.05), forming group A, whereas diatoms were significantly different from others, forming group B. The present study showed that the maximum number of organisms that mussels feed upon belong to green algae, followed by diatoms, blue‐green algae and few taxa of zooplankton.     

Immunogene expression in head kidney and spleen of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) following thermal stress and challenge with Gram-negative bacterium, <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

To evaluate the effect of thermal and microbial stress on the immune response of common carp (Cyprinus carpio L.), relative mRNA expression level of pro-inflammatory cytokines [tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β] and other genes related to immune or stress response [inducible nitric oxide synthase (iNOS), heat shock protein 70 (Hsp70), superoxide dismutase one (SOD1), and glucocorticoid receptor (GR)] was measured by quantitative PCR (qPCR). In addition, total protein and total immunoglobulin level in blood plasma of experimental common carp was also assayed. All the above parameters were estimated 24 h post-challenge with Gram-negative bacterium, Aeromonas hydrophila. Common carp (54.89?±?6.90 g) were initially exposed to 20 °C (control group) and 30 °C (thermal stress group) water temperature for 30 days, followed by experimental challenge with 2.29?×?10⁸ colony forming unit/mL (CFU/mL; LD₅₀ dose) of A. hydrophila. Exposure of fish to thermal stress and subsequently challenge with A. hydrophila significantly (P?<?0.05) increases the IL-1β mRNA expression in head kidney and spleen of common carp by ~?39.94 and ~?4.11-fold, respectively. However, TNF-α mRNA expression in spleen decreased ~?5.63-fold in control fish challenged with A. hydrophila. Thermal stress and challenge with bacterium suppresses the iNOS and GR mRNA expression in spleen of common carp. Moreover, significant (P?<?0.05) increase in total protein content of blood plasma (~?43 mg/g) was evident in fish exposed to thermal stress and challenged with A. hydrophila. In conclusion, our study highlights the importance of elevated temperature stress and microbial infection in differential regulation of expression of several immunogenes in common carp.     

Haematological modulation and growth of Labeo rohita fingerlings: effect of dietary mannan oligosaccharide,yeast extract,protein hydrolysate and chlorella

The present study was conducted for 60 days to delineate the efficacy of various dietary immunomodulators like mannan oligosaccharide (MOS), yeast extract (YE), protein hydrolysate (PH) and chlorella (CL) in Labeo rohita fingerlings. Five hundred and eighty‐five L. rohita fingerlings (average weight: 4.15 ± 0.07 g) were randomly distributed in 13 treatment groups with each of three replicates. Thirteen semi‐purified isonitrogenous (crude protein 324.7–332.5 g kg^?1) and isocaloric (17.66–17.80 MJ kg^?1) diets were prepared with three graded levels (1%, 2% or 4%) of immunostimulants, except the control. At the end of the feeding trial, weight gain%, specific growth rate, feed conversion ratio, leucocyte count, erythrocyte count, haemoglobin content, serum protein, globulin, albumin–globulin ratio, nitroblue tetrazolium (NBT) value and survival percentage were evaluated. Growth was significantly higher in the MOS‐fed group. All the immune parameters studied were also recorded higher in the MOS 1%‐supplemented group. The survival percentage after challenging with Aeromonas hydrophila was higher (P<0.05) in the MOS‐, YE‐ and PH‐fed groups and the lowest in the CL‐treated group. It can be concluded that dietary supplementation of MOS at a 1% dietary level promotes growth and survival in L. rohita fingerlings. In contrast, higher inclusion levels of immunostimulants led to an immunosuppressive effect in L. rohita fingerlings.     

The Effect of Hybrid Catfish Fingerling Prices on the Relative Profitability of Hybrid Channel Catfish

Previous studies have indicated that the price premium charged for hybrid catfish fingerlings may be a significant factor in the adoption and profitability of hybrid catfish production. An enterprise budgeting simulation analysis was developed to compare costs, risk, and effect of hybrid fingerling costs. Feed, fingerling, and total costs ($/ha and $/kg) were highest for hybrid catfish production, intermediate for NWAC‐103, and lowest for normal channel catfish production. Net returns were highest for hybrid catfish production, but breakeven prices were also highest. Risk analysis showed that downside risk (risk of losing money) was higher for hybrid production for all farm sizes. Risk‐averse farmers would not select hybrid catfish at the mean fingerling values used in the analysis. However, at hybrid fingerling prices less than $0.0081/cm, hybrid catfish production was superior in profitability and breakeven cost of production. Thus, for hybrid catfish production to be preferred economically to normal channel catfish, the price premium for hybrid catfish fingerlings can be no more than 84% ($0.0037/cm) above that of normal channel catfish fingerlings and 57% ($0.0025/cm) above that of NWAC‐103 fingerling prices.     

Impact of Aeration on the Growth Performance of Silver Barb,Puntius gonionotus,during Fingerling Rearing

Impact of aeration on growth of silver barb, Puntius gonionotus during fingerling rearing was studied through a 100‐d rearing experiment conducted in 18 concrete tanks of 50 m² (10 × 5 × 1.2 m) size. Fry (0.74 ± 0.27 g, 35 ± 6 mm) were stocked in the experimental tanks at three stocking densities (25, 50, and 75 fry/m²) and were evaluated with and without provision of 6 h (2400–0600 h) of night time aeration. Aeration resulted in higher pH and dissolved oxygen regime and increased fingerling length and weight. The results suggest a rearing density of 75/m² to be ideal for rearing fry to fingerling of this species when aeration is provided, whereas, under non‐aerated condition, rearing the fry to fingerling stage at 50/m² was found advantageous over those at 25 and 75/m².     

Effect of biofilm on water quality and growth of <Emphasis Type="Italic">Etroplus suratensis</Emphasis> (Bloch, 1790)

An experiment was conducted to compare the efficiency of biofilm production in natural and artificial substrates and to study their effect on water quality and growth of Etroplus suratensis. Four different substrates were used for biofilm formation: paddy straw (T1), sugarcane bagasse (T2), polyvinylchloride (PVC) pipe (T3) and plastic sheet (T4). The experiment was carried out in mud-bottomed fibre-reinforced plastic tanks (300 L) in triplicates. About 3000 cm² surface area (600 g) of each substrate was suspended in water supplemented with fertilizers. Only cow dung and urea were applied in control tanks. The tanks were stocked with 25 fishes with average weight of 9.1 ± 0.22 g. The overall mean value of heterotrophic bacteria in substrate was found higher in straw followed by bagasse, plastic and PVC. The dominant genera of bacteria in the substrate were Bacillus, Pseudomonas and Micrococcus in that order of preponderance. The mean phytoplankton and zooplankton density on the substrates were higher in bagasse followed by straw, plastic and PVC. The biofilm developed on the substrate significantly reduced the ammonia nitrogen and nitrite-nitrogen content of water. The growth of fishes was significantly (P < 0.05) higher in substrate-based treatments than that in the control with better results in bagasse followed by straw, plastic and PVC. The conclusions of the present study are that biofilm produced on natural substrates, especially on bagasse, enhanced growth of E. suratensis and reduced the necessity of water exchange during the culture, which certainly decreases the cost of Etroplus production.