Dietary biofloc supplementation in black tiger shrimp,Penaeus monodon: effects on immunity,antioxidant and metabolic enzyme activities

A 60‐day indoor experiment was conducted to study the effect of dietary supplementation of biofloc on metabolic enzyme activities and immune responses in Penaeus monodon juveniles. Biofloc developed in indoor fibreglass‐reinforced plastic (FRP) tanks (1000 L) was used as dietary supplement in P. monodon (2.90 ± 0.10 g) reared in 1000‐L FRP tanks. Graded level of dried biofloc was included in shrimp basal diets, 0% (control, B0), 4% (B4), 8% (B8) and 12% (B12). The level of metabolic enzymes like malate dehydrogenase (MDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was not significantly different with control up to 8% dietary supplementation. A higher level of total haemocyte count (THC) was noticed in B8 (22.16 ± 2.17 × 10⁶ cells mL^?1) and B4 (21.11 ± 0.56 × 10⁶ cells mL^?1) compared with control, C (14.61 ± 2.74 × 10⁶ cells mL^?1). Biofloc‐supplemented groups recorded significantly higher (P < 0.05) serum SOD and catalase activity (P < 0.01) in comparison with control. The groups fed with 4% dietary biofloc supplement recorded highest relative percentage survival (RPS), 45% after challenge with Vibrio harveyi followed by 36% and 27% RPS in B8 and B12 groups. Based on these results, it can be concluded that supplementation of biofloc even at 4% level in the feed improves immune responses and metabolic activities in black tiger shrimp juveniles.     

Apparent digestibility coefficient of poultry by‐product meal (PBM) in diets of Penaeus monodon (Fabricius) and Litopenaeus vannamei (Boone), and replacement of fishmeal with PBM in diets of P. monodon

Nutrient apparent digestibility coefficients (ADCs) of pet food grade poultry by‐product meal (PBM) were determined for black tiger prawn, Penaeus monodon and Pacific white shrimp, Litopenaeus vannamei by the indirect method (reference diet and test diet at 7:3 ratio). Subsequently, an 8‐week growth trial was conducted to evaluate the effects of substitution of fishmeal (FM) with PBM in diets of P. monodon (initial weight = 0.21 ± 0.01 g). In the growth trial, six isonitrogenous and isoenergetic diets PBM0, PBM25, PBM50, PBM75, PBM100 and PBMA100, containing a gradient of PBM 0, 88.7, 177.4, 266, 354.7 and 354 g kg^?1 to replace 0, 92.5, 185, 277.5, 370 and 370 g kg^?1 FM were fed to four replicate groups respectively. The diet PBMA100 was supplemented with DL‐Met to be similar to PBM0. The results showed that both P. monodon and L. vannamei had relatively high ADC of crude protein (77.6% and 84.2% respectively) and gross energy (72.8% and 84.0% respectively) for PBM. Litopenaeus vannamei showed significantly higher digestion ability for PBM than P. monodon (P < 0.05). In growth trial, no significant difference in growth performance was observed among shrimp fed the experimental diets. DL‐Met supplementation did not improve the growth of P. monodon. PBM is a suitable protein ingredient for P. monodon feeds and can be used up to 354.7 g kg^?1 to totally replaced FM.     

Effects of biofloc under different carbon sources and protein levels on water quality,growth performance and immune responses in black tiger shrimp Penaeus monodon (Fabricius, 1978)

A 75‐day 2 × 3 factorial experiment was conducted to evaluate the effect of two levels of dietary protein (32 and 40%) and two different carbon sources (rice flour–R and molasses‐M), and without carbohydrate (control–C) in black tiger shrimp Penaeus monodon juveniles (3.37 ± 0.04 g) at 100 nos. m^?3 in 100 L fibre reinforced plastic tanks. Biofloc volume and total suspended solid were higher in molasses added groups (32 + M and 40 + M) followed by rice flour (32 + R and 40 + R) and controls (32C and 40C). Molasses and rice flour addition significantly reduced (P < 0.01) the total ammonia–N compared to controls. The highest Vibrio, Bacillus and Lactobacillus counts were recorded in 40 + M, 32 + M and 32 + R respectively. Among the treatments, significantly higher (P < 0.01) final body weight was recorded in 40 + R (8.5 ± 0.3 g), 40 + M (7.8 ± 0.3 g) and 32 + R (7.5 ± 0.4 g) compared to control groups, 32C (6.1 ± 0.3 g), 40C (6.4 ± 0.3 g) and molasses added group, 32 + M (5.7 ± 0.4 g). Rice flour supplementation significantly increased (P < 0.01) the total haemocyte count (×10⁶ cells mL^?1) in 32 + R (45.7 ± 3.7) and 40 + R (44.3 ± 3.1) compared to controls, 32C (27.3 ± 3.4) and 40C (25.8 ± 0.9). Similarly, higher superoxide dismutase, catalase, serum protein and glucose were recorded in the rice flour added groups, 40 + R followed by 32 + R. Among the treatments, the highest level of prophenoloxidase (OD 490 nm, 0.3 ± 0.0) and survival after challenge with Vibrio harveyi (55.6%) was observed in 32 + R. The study elucidates that rice flour addition produces optimum level of biofloc with better growth and immune responses compared to molasses and control. Furthermore, rice flour addition at 32% protein level could replace 40% protein feed.     

Retracted: Effect of concentration of the microalga Dunaliella tertiolecta on survival and growth of fairy shrimp,Phallocryptus spinosa Milne Edwards, 1840 (Crustacea: Anostraca)

We investigated the effects of concentration of the microalga Dunaliella tertiolecta on the growth and survival of fairy shrimp, Phallocryptus spinosa. Newly hatched nauplii were stocked into containers, maintained at different concentrations of D. tertiolecta (at 18, 36, 54, 72 and 90 × 10⁶ cells mL^?1). All treatments were in quadruplicate and each replicate was stocked with 100 larvae in a 2‐L cylindrical bowl. We studied the survival and growth of the fairy shrimp after 3, 6, 9, 12 and 15 days of culture. The results indicated significant differences, in terms of growth and survival, of fairy shrimps fed at different algal densities. The highest and lowest growth and survival among the treatments were observed on Day 15, the highest in animals fed at a concentration of 90 × 10⁶ cells mL^?1 and the lowest in animals fed at a concentration of 18 × 10⁶ cells mL^?1. We conclude that the growth and survival of the P. spinosa increased with increasing density of algae, to a threshold level. Within certain concentration limits, the addition of D. tertiolecta substantially improved the performance of larval culture of P. spinosa, suggesting that this fairy shrimp has potential in terms of aquaculture development.     

White spot syndrome virus (WSSV) prevalence associated with disease resistance among wild populations of black tiger shrimp,Penaeus monodon (Fabricius)

White spot disease caused by white spot syndrome virus (WSSV) is the major issue of huge economic destruction globally in the shrimp aquaculture industry. In the present investigation, WSSV prevalence associated with disease resistance was studied among wild black tiger shrimp, Penaeus monodon (Fabricius) from four distant geographic locations along the East coast of India during 2009–2010. Results suggested that the WSSV prevalence in wild P. monodon was the highest (56.2%) in Chennai, Tamil Nadu followed by Digha, West Bengal (10.9%), Visakhapatnam, Andhra Pradesh (0.6%) and Chilika, Orissa (0%). Quantitative data suggested that the mean copy number of WSSV among these four places was 1.4 × 10⁶, 4.6 × 10⁴, 1.6 × 10² and 2.3 × 10² copies μg^?1 shrimp genomic DNA respectively. The disease resistant prevalence using the 71 bp microsatellite DNA marker was the highest among Chilika, Orissa (63.6%) and Visakhapatnam, Andhra Pradesh (63.5%). Higher WSSV prevalence in Chennai, Tamil Nadu and Digha, West Bengal corresponded to lower disease resistant prevalence (24% and 40.2%). Conclusively, probably collection of broodstock of P. monodon from places like Chilika and Visakhapatnam would be a much safer approach for the development of specific pathogen‐resistant shrimp aquaculture.     

Enhancement of innate immune system,survival and yield in Penaeus monodon reared in ponds using Streptococcus phocae PI80

The objective of this study was to evaluate the effect of dietary and water supplementation of probiotic Streptococcus phocae PI80 on growth, immune response and feed utilization of tiger shrimp Penaeus monodon in earthen ponds. The probiotic bacterium S. phocae PI80 was cultured in large fermenter (50 L) by adding additional carbon source in the form of molasses and glucose along with yeast extract as nitrogen source to enrich S. phocae PI80 biomass. This enriched S. phocae PI80 was administered to shrimp in feed (6.5 × 10¹³ bacterial cells mL^?1) as well as in pond water (5 L/pond). Shrimp growth performance was significantly improved (P < 0.05) in 120 days culture when the average body weight of treated molasses + yeast extract (MY) (28.41 ± 0.874 g), glucose + yeast extract (GY) (27.013 ± 0.698 g) was significantly higher than control (23.63 ± 0.684 g). Food conversion ratio FCR was also found to be reduced significantly in ponds treated with probiotics when compared with control pond (1.89 ± 0.09). Vibrio and luminescent bacteria were found to be lower in the treatment receiving MY group, and we hypothesize that this may lead to greater shrimp survival. Furthermore, fermentation product of S. phocae PI80 added to pond water and feed additives enhanced the shrimp immune system. The results indicated that total haemocytes count (THC), phenoloxidase (PO) activity, NBT reductase assay and phagocytic activity significantly increased in shrimps treated with S. phocae PI80. Our study demonstrates that administration of S. phocae PI80 in the water and feed at 6.5 × 10¹³ colony‐forming units (CFU) mL^?1 bacterial cells induce immune modulation and enhances the immune ability of P. monodon in pond‐reared shrimp and increased the shrimp production.     

Hybridization between Haliotis rufescens and Haliotis discus hannai: evaluation of fertilization,larval development,growth and thermal tolerance

Two introduced abalone species are currently produced in Chile, red abalone Haliotis rufescens and Japanese abalone Haliotis discus hannai. However, red abalone accounts for 99% of total production, while the Japanese abalone has not adapted well to Chilean coastal waters. This study reports the hatching, growth and thermal tolerance performance in interspecific hybrids produced between red (R) and Japanese (J) abalone. Our results show that egg age and sperm concentration were critical factors to produce hybrids. The cross R♀ × J♂ showed a fertilization rate of 55.3 ± 3.5% using 20‐min‐old eggs and sperm concentrations of 14 × 10⁶ cells mL^?1, while the reciprocal cross (J♀ × R♂) was not successful. Further, larval development stages were similar in RR, JJ and RJ hybrid abalones. Among the experimental trials, settlement rate varied from 12.3% to 18.6% and final survival from 20.1% to 31.7%, being the RJ hybrid rates intermediate between parental species. The final shell lengths were similar between RR and RJ hybrids, but significantly higher in JJ abalones. In addition, thermal tolerance was ascertained due its pivotal role for the abalone physiology. Thus, RJ hybrids showed the highest HSP70 gene expression and offers new possibilities to expand Chilean abalone production in warm waters zones.     

Comparison of the physiological energetics between Mytilus chilensis,Mytilus galloprovincialis and their hybrids,under laboratory conditions

Laboratory‐produced juvenile individuals of the species Mytilus chilensis, M. galloprovincialis and their hybrids were subjected to physiological measurements under an experimental diet of Isochrysis galbana (30 × 10⁶ cells L^?1), 13°C temperature and a salinity of 30 psu. Pure species individuals showed a higher clearance rate (CR). Mytilus chilensis had a CR of 1.13 L h^?1, while M. galloprovincialis registered only 0.78 L h^?1. Also, pure taxa registered higher values (above 70%) of absorption efficiency when compared with hybrid individuals. Ammonia excretion in M. chilensis and M. galloprovincialis was 1.5% and 0.4%, respectively, while hybrids registered significantly lower values. Under these experimental conditions, M. chilensis registered the highest scope for growth (P < 0.05), compared with M. galloprovincialis and their hybrids. However, the net growth efficiency index (K ₂) in hybridization type I (♀Mg × ♂Mc) was higher (P < 0.05) than other experimental groups. The invasive mytilid M. galloprovincialis showed values that are very similar to those obtained with the hybridization I group (♀Mg × ♂Mc). Finally, we discuss that water temperature is an important factor in the biogeographic separation of both species and the potential effects that the settlement of the invasive species may have for Chilean mussel production.     

Influence of feeding regime and temperature on development and settlement of oyster Ostrea edulis (Linnaeus, 1758) larvae

Under controlled conditions of food density and temperature, larval performances (ingestion, growth, survival and settlement success) of the flat oyster, Ostrea edulis, were investigated using a flow‐through rearing system. In the first experiment, oyster larvae were reared at five different phytoplankton densities (70, 500, 1500, 2500 and 3500 μm³ μL^?1: ≈1, 8, 25, 42 and 58 cells μL^?1 equivalent TCg), and in the second, larvae were grown at four different temperatures (15, 20, 25 and 30°C). Overall, larvae survived a wide range of food density and temperature, with high survival recorded at the end of the experiments. Microalgae concentration and temperature both impacted significantly larval development and settlement success. A mixed diet of Chaetoceros neogracile and Tisochrysis lutea (1:1 cell volume) maintained throughout the whole larval life at a concentration of 1500 μm³ μL^?1 allowed the best larval development of O. edulis at 25°C with high survival (98%), good growth (16 μm day^?1) and high settlement success (68%). In addition, optimum larval development (survival ≥97%; growth ≥17 μm day^?1) and settlement (≥78%) were achieved at 25 and 30°C, at microalgae concentrations of 1500 μm³ μL^?1. In contrast, temperature of 20°C led to lower development (≤10 μm day^?1) and weaker settlement (≤27%), whereas at 15°C, no settlement occurred. The design experiments allowed the estimation of the maximum surface‐area‐specific ingestion rate  = 120 ± 4 μm³ day^?1 μm^?2, the half saturation coefficient {X_K} = 537 ± 142 μm³ μL^?1 and the Arrhenius temperature T_A = 8355 K. This contribution put a tangible basis for a future O. edulis Dynamic Energy Budget (DEB) larval growth model.     

Efficacy of garlic (Allium sativum) extract applied as a therapeutic immersion treatment for Neobenedenia sp. management in aquaculture

Garlic, Allium sativum L., extract administered as a therapeutic bath was shown to have antiparasitic properties towards Neobenedenia sp. (MacCallum) (Platyhelminthes: Monogenea) infecting farmed barramundi, Lates calcarifer (Bloch). The effect of garlic extract (active component allicin) immersion on Neobenedenia sp. egg development, hatching success, oncomiracidia (larvae) longevity, infection success and juvenile Neobenedenia survival was examined and compared with freshwater and formalin immersion. Garlic extract was found to significantly impede hatching success (5% ± 5%) and oncomiracidia longevity (<2 h) at allicin concentrations of 15.2 μL L^?1, while eggs in the seawater control had >95% hatching success and mean oncomiracidia longevity of 37 ± 3 h. At much lower allicin concentrations (0.76 and 1.52 μL L^?1), garlic extract also significantly reduced Neobenedenia infection success of L. calcarifer to 25% ± 4% and 11% ± 4%, respectively, compared with 55% ± 7% in the seawater control. Juvenile Neobenedenia attached to host fish proved to be highly resistant to allicin with 96% surviving 1‐h immersion in 10 mL L^?1 (15.2 μL L^?1 allicin) of garlic extract. Allicin‐containing garlic extracts show potential for development as a therapy to manage monogenean infections in intensive aquaculture with the greatest impact at the egg and larval stages.     

Utilization of diets with different fish oil content in common octopus (Octopus vulgaris Cuvier, 1797) and resulting changes in its biochemical composition

The aim of the present work was to obtain the lipid utilization of Octopus vulgaris supplying formulated semi‐moist diets with different contents in cod oil (reduced from water content): 0 g kg^?1 (A0, 138 g kg^?1 lipids DW; N = 4), 100 g kg^?1 (A100, 286 g kg^?1 lipids DW; N = 6) and 200 g kg^?1 (A200, 388 g kg^?1 lipids DW; N = 6). The rest of the ingredients were constant in the three diets: 200 g kg^?1 gelatin, 100 g kg^?1 egg yolk powder, 150 g kg^?1 freeze‐dried Todarodes sagittatus and 50 g kg^?1 freeze‐dried Sardinella aurita). Survival was 100% with the three diets. The highest absolute feeding (15.8 ± 1.2 g day^?1), growth (9.6 ± 1.4 g day^?1; 0.91% BW day^?1) and feed efficiency rates (60.3%) were obtained with diet A0. This diet also showed greater retention of lipid and protein than A100 and A200. Protein digestibility was above 95% in all of the diets. Only diet A0 led to a high lipid digestibility coefficient (81.25%), which fell drastically to 12.3% in A200. It was notable the high polar lipid digestibility rates (83–89%) respect to neutral lipids (2–87%) in all diets. The best results were obtained with lipid feeding rates of around 1 g day^?1 and a suitable lipid content on 130–140 g kg^?1 DW in formulated diets for O. vulgaris.     

Enhanced growth and retarded gonadal development of farmed rainbow trout,Oncorhynchus mykiss (Walbaum) following a long‐day photoperiod

Long‐day photoperiods are considered as an effective managerial tool in manipulating of reproduction and somatic growth in a number of fish species. In this study, the effects of three different artificial photoperiods on the gonadal development and somatic growth of rainbow trout (Oncorhynchus mykiss L.) were investigated. Two years‐old immature female rainbow trout (279.94 ±2.25 g) were exposed to three artificial photoperiod regimes of 24L:0D, 18L:6D and 6L:18D and natural light (NL) regime for 5 months. The highest gonadosomatic indices were recorded in NL and 6L:18D groups while the rates were significantly lower in fish maintained under 18L:6D and 24L:0D photoperiods (P < 0.05). Mean oocyte diameters in fish exposed to 24L:0D and also to 18L:6D were significantly lower than the 6L:18D and NL groups. Photoperiods with 24L:0D and 18L:6D regimes resulted in significantly higher mean final weights and specific growth rates (SGR) than NL regime. The highest mean final weight (635.45 ± 16.19 g) and SGR (1.03 ± 0.04% day^?1) were obtained under 24L:0D photoperiod. Fish exposed to 24L:0D and 18L:6D showed the highest condition factor as 1.44 ± 0.01 and 1.44 ± 0.02 respectively, when compared with the NL (1.27 ± 0.01) and 6L:18D (1.34 ± 0.02) groups. Basically, the results suggested that continuous artificial lightning can be used as an influential factor in delaying gonadal development and enhancing somatic growth in rainbow trout during gonadal growth phase.     

Constructed wetlands for treatment of harvest effluents from grow‐out ponds of the Amazon river prawn

Effluent discharges from aquaculture can reduce water quality in receiving water bodies and that strategies or practices to reduce this are necessary. One possibility is to reduce, or eliminate, water renewal in grow‐out ponds. In this study, we eliminated water renewal in grow‐out ponds associated with the culture of 40 individuals m^?2 of Amazon river prawn (Macrobrachium amazonicum). At the end of the culture period it was, however, necessary to drain the pond to harvest the prawns. An experiment was performed in triplicate, in which the water supply characteristics and harvest water characteristics of ponds were evaluated. To reduce these concentrations of total N and P, an aquatic macrophyte (Eichhornia crassipes, water hyacinth) treatment system (CWs) was adopted. The water characteristics in the CWs were evaluated after 1, 3, 7, 14 and 21 days. The water supply of ponds presented the average concentrations of 0.67 ± 0.32 mg L^?1 and 17.4 ± 14.7 μg L^?1 of total‐N and total‐P respectively. The harvest effluent of ponds had elevated concentrations of different forms of nitrogen (4.44 mg L^?1 of total‐N) and phosphorous (100.9 μg L^?1 of total‐P). After 1 day of the experiment we found the following reductions in key nutrients in treatment system containing E. crassipes: 90%, 78% and 45% reductions in the concentrations of particulate matter, orthophosphates and nitrates respectively. We noted that after 3 days the nitrates had been reduced by 53%. We concluded that 3 days of this treatment was sufficient for the removal of the additional nutrients that had accumulated in the Amazon river prawn ponds.     

Effects of dietary mannan oligosaccharide on growth,survival, physiological,immunological and gut morphological conditions of black tiger prawn (Penaeus monodon Fabricius 1798)

The aim of this experiment was to determine the effects of dietary inclusion with mannan oligosaccharide (Bio‐Mos, Alltech, Nicholasville, KY, USA) on growth, survival, physiological and immunological conditions and gut morphology of the black tiger prawn (Penaeus monodon). Five diets supplemented with MOS at 0 g kg^?1 (control diet), 1, 2, 4 and 8 g kg^?1 were fed to the prawn juveniles (0.4 ± 0.06 g, total weight) for the duration of 63 days. Growth was the highest (P < 0.05) when the prawns were fed the 1 g kg^?1 MOS included diet. Wet tail muscle index (Tw/B), dry tail muscle index (Td/B) and tail muscle protein (Tmp) were higher (P < 0.05) in the prawns fed MOS included diets MOS compared with the prawns fed the control diet. Total haemocyte counts (THCs) of the prawns fed MOS included diets were higher (P < 0.05) than THCs of the prawns fed the control diet. Epithelium layer and epidermal cell density of the gut of the prawns fed 1 g kg^?1 and 2 g kg^?1 MOS diets were better than the prawns fed the control and other MOS diets. The results imply a positive effect of dietary supplementation of 1–2 g kg^?1 MOS in the culture of black tiger prawns.     

Effects of dietary inactivated Pediococcus pentosaceus on growth performance,feed utilization and blood characteristics of red sea bream,Pagrus major juvenile

A feeding trial was carried out to determine effects of dietary supplements of inactivated Pediococcus pentosaceus (PP) on growth, feed utilization and blood characteristics of red sea bream. Five diets containing different concentrations [0 (PP0), 1.6 × 10¹⁰ (PPI), 1.6 × 10¹¹ (PPII), 1.6 × 10¹² (PPIII) and 3.2 × 10¹² (PPIV) cells g^?1] of PP were fed to fish for 56 days. At the end of the feeding trial, the obtained results revealed a significant increase (P < 0.05) in weight gain, specific growth rate and skin mucus secretion in all PP‐supplemented groups when compared with control group. Moreover, fish fed PPIII and PPIV diets resulted in significantly higher final body weight, feed efficiency ratio and bactericidal activity than those of fish fed PP0 diet (P < 0.05). Further, fish fed the PPIII diet also had a higher feed intake, protein efficiency retention, haematocrit, mucus lysozyme activity (LA), plasma and serum proteins than those of PP0 fed group (P < 0.05). Similarly, fish fed PPIV diet resulted in a significant increase in serum LA, peroxidase activity and tolerance against low‐salinity stress test (P < 0.05). Considering these promising results, we suggest that the supplementation of PP Prep improves growth and health conditions of Pagrus major.     

Effects of supplementary fennel (Foeniculum vulgare) essential oil in diet on growth and reproductive performance of the ornamental fish,Convict cichlid (Cichlasoma nigrofasciatum)

This study evaluated the effects of diet containing 0 (C: control), 75 (D₁), 100 (D₂), 125 (D₃) and 150 (D₄) mg kg^?1 F. vulgare essential oil on growth and reproductive performance of C. nigrofasciatum. A total of 225 Convict cichlids female with mean weight (1.65 ± 0.02 g) were distributed into 15 glass aquaria (15 fish tank^?1) in triplicate treatments. During 40 days of experimental period, fish fed at 3% of their body weight daily. At the end of experiment, growth indices, gonadosomatic index and reproductive indices were determined. The best feed conversion ratio was obtained in D₄ (1.19 ± 0.03, P < 0.05). The addition of F. vulgare essential oil did not have any statistical effects on other growth indices (specific growth rate, weight gain and condition factor). Total survival rates in all treatments and control were uniformly high, ranging from 93% to 97% (P > 0.05). F. vulgare essential oil has no negative effect on survival rate of C. nigrofasciatum. There were no significant differences among protein content of fish body (P > 0.05). The lowest value of fat content (26.5 ± 0.5%) was observed in D_2, and it had significant difference with control and other groups (P < 0.05). The ash percentage in treatments fed with F. vulgare essential oil were higher than control fish (P < 0.05). The highest moisture content was detected in D₄ (72.68 ± 0.19%) and D₂ (71.23 ± 2%) groups. Among the used dosage, D₄ was the most effective dosage that could significantly increase GSI (11.06 ± 1.55%), fecundity (340 ± 21) and hatching ratio (92.33 ± 1.63%). There were no significant differences in diameter of eggs among various treatments (P > 0.05).     

Resistance to vibriosis,production performance and tolerance to stress of the selected giant freshwater prawn (Macrobrachium rosenbergii)

The purpose of this study was to evaluate the resistance to vibriosis, growth, survival and tolerance to stress of the selected prawn, second generation, compared to a non‐selected control. The first generation of selected giant freshwater prawn, which has 10.4% higher of resistance, was used to attain disease resistant freshwater prawn (Macrobrachium rosenbergii) generation through challenge test‐based selection. Resistance test was conducted by infecting the prawn (mean body weight of 10.29 ± 1.40 g) with pathogenic Vibrio harveyi (5 × 10⁵ cfu prawn^?1). The growth and survival of the prawn were evaluated by rearing the two populations of prawn in both nursery and grow‐out phases. Stress tolerance test was done by evaluating the viability of postlarvae exposed to environmental stressors, i.e. temperature, salinity, NH₃ and formaldehide. Post‐challenge survival of the selected prawn (55.0 ± 5.0%) was about 46% higher than that of the control (37.5 ± 7.5%). The survival of the selected prawn in nursery culture (77.16 ± 0.841%) was significantly higher (p < .05) than that of the control (51.31 ± 2.938%), while the survival in grow‐out culture was similar (p > .05). The growth of selected prawn (4.99 ± 0.03% day^?1) was significantly higher than that of the control (4.81 ± 0.05% day^?1). There was no difference between treatments on the tolerance level against the tested environmental stressor. Overall data suggested that the selected prawn showed better performance in growth and resistance against vibriosis.     

Effects of feeding rate and frequency on growth performance,digestion and nutrients balances of Atlantic salmon (Salmo salar) in recirculating aquaculture systems (RAS)

A 10‐week study was conducted to investigate the effects of feeding rate and frequency on growth performance, digestion and nutrients balances of Atlantic salmon (Salmo salar) in replicated recirculating aquaculture systems (RAS). Replicated groups of juvenile salmon weighing 90 ± 2.5 g (mean ± SD) were fed a commercial feed (21.63 MJ kg^?1 gross energy) to designed feeding rate (1.4%, 1.6% and 1.8% body weight day^?1, BW day^?1) and feeding frequency (2 and 4 meals day^?1) combinations. Specific growth ratio varied between 1.15 ± 0.02 and 1.37 ± 0.16% day^?1, and feed conversion ratio ranged from 0.96 ± 0.03 to 1.16 ± 0.02. The nitrogen and phosphorus retention rates were from 36.50 ± 1.94 to 47.08 ± 5.23% and from 20.42 ± 1.05 to 38.59 ± 2.80%. Apparent digestibility coefficients (ADC) in dry matter, protein, lipid and energy showed no significant differences for all groups. However, fish fed at 1.6% BW day^?1 and 4 meal day^?1 groups had relatively better growth and nutrient retention efficiency compared to other groups. In addition, concentrations of nitrogenous and phosphorous compounds were also detected in this study. These results suggested that salmon of 100–200 g in RAS could in practice be fed at 1.6% BW day^?1 and 4 meals day^?1, taking environmental impacts into account.     

Evaluation of selected metal nanoparticles on hatching and survival of larvae and fry of Indian major carp,rohu (Labeo rohita)

Different laboratory synthesized metal nanoparticles viz. Copper oxide (CuO), Zinc oxide (ZnO) and silver doped titanium dioxide (Ag‐TiO₂) were studied for their effect on hatching and survival of larvae and fry of Indian major carp, rohu, Labeo rohita both in direct application in tank water & coated onto tanks. Among these nanoparticles, CuO and ZnO nanoparticles exhibited highest percentage of hatching in both direct addition (78.0 ± 3.1% and 78.05 ± 4.2%, respectively) and coating onto tanks (58.6 ± 2.1% and 61.2 ± 2.7%, respectively) at 1 mg mL^?1 while least percentage of hatching was recorded in Ag‐TiO₂ nanoparticles irrespective of its concentration & mode of supplementation. Highest survival of L. rohita fry (50.13 ± 2.2%) was observed after 15 days post hatching in CuO coated tanks followed by ZnO coated tanks (38.6 ± 2.8%) while least was recorded in Ag‐TiO₂ coated tanks (22.53 ± 3.0%). However in control tanks coated with Poly‐Urethane base with hardener and uncoated control tanks, the survival was 42.4 ± 1.2% and 41.36 ± 1.8% respectively. Further, significantly lower microbial load of water was recorded in CuO nanoparticles coated tanks (1.5 × 10¹⁰ CFU L^?1) as compared to uncoated control tanks (1.1 × 10¹⁶ CFU L^?1) without affecting water quality parameters. On the other hand, in Ag‐TiO₂ coated tanks, significantly lower microbial load (1.0 × 10⁶ CFU L^?1) as compared to uncoated control tanks at 15 days post hatching was recorded. However, Ag‐TiO₂ was toxic to L. rohita larvae & fry both in direct application and coating onto tanks. Considering the beneficial effects of CuO nanoparticle application, it has the scope of being used in a more eco‐friendly way in hatchery operations.