Low-cost diet for monoculture of giant freshwater prawn (Macrobrachium rosenbergii de Man) in Bangladesh

An experiment was conducted for 3 months in 12 experimental ponds, each of 30 m², with a view to develop a low‐cost diet for monoculture of Macrobrachium rosenbergii in ponds. Three experimental diets (30% protein) were formulated using fish meal, meat and bone meal, mustard oilcake, sesame meal and rice bran in different combinations partially replacing fish meal by meat and bone meal and sesame meal and assigned to treatments T₁, T₂ and T₃ respectively. A commercial golda feed (Starter‐III) was assigned to T₄ (reference diet). Each treatment had three replicates. Juveniles of M. rosenbergii (2.90±0.21 g) were stocked at the rate of 40 000 ha⁻¹. Prawns were fed three times daily at the rate of 10% and 5% of their body weight at the beginning and for the last 2 months respectively. The ponds were provided with aeration during the night using air pumps. The ranges of water quality parameters recorded in different ponds were: temperature 28.9–32.5°C, dissolved oxygen 5.1–8.1 mg L⁻¹ and pH 6.4–7.7. The results showed that the weight gain of prawns fed diet 1 was significantly higher (P<0.05) than those fed diets 2 and 3, but was not significantly different from those fed diet 4 (reference diet). The feed conversion ratio (FCR) values of diets ranged between 2.21 and 2.96 with diets 1 and 4 showing significantly lower (P<0.05) FCR values. The survivals (%) ranged between 68% and 78% with prawns fed diets 1 and 4 showing significantly higher survival. The production of prawn ranged between 921 and 1428 kg ha⁻¹ and diet 1 resulted in a significantly high (P<0.05) production. A simple economic analysis showed that diet 1 generated the maximum net profit of Tk 159 178 ha⁻¹. The results of the study showed that a diet containing 20% fish meal, 10% meat and bone meal, 15% mustard oilcake, 15% sesame meal, 35% rice bran, 4% molasses and 1% vitamin–mineral premixes may be recommended to the farmers for monoculture of M. rosenbergii in ponds.     

Osmoregulation,growth and moulting cycles of the giant freshwater prawn (Macrobrachium rosenbergii) at different salinities

The giant freshwater prawn, Macrobrachium rosenbergii, is a species with a high commercial value in aquaculture. Two experiments were performed to determine the effects of salinities on the osmoregulation, growth and molting cycles of M. rosenbergii during growout. The first experiment was designed to determine whether these animals are capable of adapting to the changes in salinity seen in salinity intrusions in tropical deltas, with an incremental increase in salinity of 3‰ per day from 0‰ to 30‰ Haemolymph osmolality was rapidly regulated up to salinities of 15‰ , whereas animals conformed at higher salinities. The second experiment determined the growth, moulting cycle, osmolality, muscle water content and mortality during a 4‐month experiment at 0‰, 15‰ or 25‰ salinity. The weight gains in 0‰ and 15‰ were not significantly different and were comparable to the growth rates achieved in production farms with body mass increases of 2.6 and 2.3‐fold their initial body mass, respectively, after 4 months. The 25‰ group suffered from low growth, high mortality and a significantly lower moulting frequency. These data show that this species can be reared in brackish water up to 15‰, allowing for farming in the large areas impacted by salt water intrusions in tropical deltas.     

Economic analysis of monosex culture of giant freshwater prawn (Macrobrachium rosenbergii De Man): a case study

All‐male monosex culture of Macrobrachium rosenbergii (De Man) has emerged as a popular practice in India, especially in the state of Andhra Pradesh. A study was conducted to compare the economics of all‐male, mixed and all‐female culture in 15 adjacent, rectangular ponds of 4000 m² each by stocking juveniles previously reared in a nursery for 60 days. The experiment was conducted using a completely randomized design with three treatments; T₁ (all male), T₂ (mixed) and T₃ (all female), and five replicates for a period of 5 months after the nursery phase. Statistical analysis showed highly significant (P<0.01) differences among the three types of culture. The cost of production was estimated and the economic feasibility of the culture methods was evaluated by cost‐return and partial budgeting analysis. The average weight, productivity and specific growth rate were the highest for all male culture, being 80.92±2.41 g, 1532 kg ha^?1 and 1.97±0.02 respectively. All‐female culture registered significantly higher survival (89.16±0.77%) and the best apparent feed conversion ratio of 1.26±0.02. The economic analysis revealed that all‐male monosex culture of M. rosenbergii was 63.13% and 60.20% more profitable than mixed and all‐female cultures respectively.     

Genetic diversity of cultured and wild populations of the giant freshwater prawn Macrobrachium rosenbergii (de Man, 1879) based on microsatellite analysis

Freshwater prawn (Macrobrachium rosenbergii) culture in the Western Hemisphere is primarily, if not entirely, derived from 36 individual prawns originally introduced to Hawaii from Malaysia in 1965 and 1966. Little information is available regarding genetic variation within and among cultured prawn stocks worldwide. The goal of the current study was to characterize genetic diversity in various prawn populations with emphasis on those cultured in North America. Five microsatellite loci were screened to estimate genetic diversity in two wild (Myanmar and India‐wild) and seven cultured (Hawaii‐1, Hawaii‐2, India‐cultured, Israel, Kentucky, Mississippi and Texas) populations. Average allelic richness ranged from 3.96 (Israel) to 20.45 (Myanmar). Average expected heterozygosity ranged from 0.580 (Israel) to 0.935 (Myanmar). Many of the cultured populations exhibited reduced genetic diversity when compared with the Myanmar and the India‐cultured populations. Significant deficiency in heterozygotes was detected in the India‐cultured, Mississippi and Kentucky populations (overall F_is estimated of 0.053, 0.067 and 0.108 respectively) reflecting moderate levels of inbreeding. Overall estimate of fixation index (F_st = 0.1569) revealed moderately high levels of differentiation among the populations. Outcome of this study provide a baseline assessment of genetic diversity in some available strains that will be useful for the development of breeding programmes.     

Liver oil of pharaoh cuttlefish Sepia pharaonis Ehrenberg, 1831 as a lipid source in the feed of giant freshwater prawn, Macrobrachium rosenbergii (De Man 1879)

The efficacy of pharaoh cuttlefish ( Sepia pharaonis Ehrenberg, 1831) liver lipid in the feed for juveniles of giant freshwater prawn Macrobrachium rosenbergii (De Man 1879) was tested by feeding five experimental diets prepared using clam meat, groundnut oil cake, wheat bran, tapioca powder, vitamin–mineral mixture and cellulose powder as the major ingredients. The test diets T₁, T₂, T₃, T₄ and T₅, containing five levels (1, 2, 3, 4 and 5%, respectively) of lipid, extracted from the liver of pharaoh cuttlefish, were fed to 30-day-old prawn juveniles for 60 days, in triplicates and compared against a control. Analysis of variance of the growth parameters showed that the juveniles fed with T₂, containing 2% cuttlefish liver lipid with a total lipid content of 9.85% and lipid–carbohydrate ratio of 1 : 3.8, showed significantly better growth ( P  < 0.05) with the highest weight gain of 118%, greatest food conversion and protein utilization efficiency, and the highest body protein content, although the survival rates remained unaffected among treatments. Growth of the juveniles, however, declined at lipid levels >2%. Addition of cuttlefish liver lipid led to an increase of ω-3 and ω-6 fatty acids in T₂, the proportion of ω-6 being higher than the former. The crude lipid content of the body of test animals also increased with the increase in dietary lipid from 1.51% in T₁ to 3.27% in T₅. The present study indicates that cuttlefish liver lipid can be successfully used as a substitute for conventional lipid sources in rearing juveniles of giant freshwater prawn, an eco-friendly practice in recycling cuttlefish waste – a discarded fishery by-product.     

Experimental susceptibility of different life-stages of the giant freshwater prawn, Macrobrachium rosenbergii (de Man), to white spot syndrome virus (WSSV)

Studies were conducted by injecting/feeding white spot syndrome virus (WSSV) derived from infected shrimp, Penaeus monodon (Fabricius), to different life-stages, namely post-larvae, juveniles, sub-adults and adults of Macrobrachium rosenbergii (de Man). The disease was also induced in brood stock, and the eggs and larvae derived from these animals were subsequently tested for WSSV infection. All the stages except egg used for the experiment were found WSSV positive in histopathology, cross infection bioassay and polymerase chain reaction (PCR) analysis. Experimentally infected post-larvae and juveniles showed a high percentage of mortality and an increased rate of cannibalism. The cumulative mortality in post-larvae was up to 28%; with 28–40% cannibalism resulting in a maximum loss of up to 68%. In juveniles, observed mortality and cannibalism were 10–20% and 6.7–30.0%, respectively, and the maximum loss recorded was 50%. In sub-adults, mortality ranged from 2.8 to 6.7%, cannibalism was up to 20% and the total loss was up to 26.7%. Sub-adults and adults were found to be more tolerant to the infection as evidenced by the mortality pattern. A nested (two-step) PCR resulted in a 570-bp product specific to WSSV in all stages, except the eggs.     

Long-term cryopreservation of spermatophore of the giant freshwater prawn, Macrobrachium rosenbergii (de Man)

Long‐term cryopreservation of the giant freshwater prawn, Macrobrachium rosenbergii, spermatophores using glycerol (Gly) and ethylene glycol (EG) as cryoprotective agents (CPAs) was studied. The tolerance of sperm to cryopreservation was evaluated on the basis of sperm survival and fertilizing ability. The survival of the sperm was determined by trypan blue staining, while the fertilizing ability was assessed from artificial insemination of the cryopreserved spermatophores. The rates of embryo survival on day 5 after spawning and of spermatophores capable of producing embryos survived to hatching were determined. Storage of spermatophores at ?20°C without CPA for a short period of up of 1–5 days decreased the sperm survival significantly and did not preserve fertilizing ability. Preservation at ?20°C in the presence of 10% or 20% Gly or of 10% or 20% EG offered a simple and efficient short‐term storage up to 10 days. For a long‐term storage, cryopreservation in the presence of 20% EG at ?196°C was more efficient than at ?20°C. High sperm survival rates and high fertilizing ability were recorded from those cryopreserved at ?196°C for up to 150 days. High sperm survival rates with moderate levels of fertilizing ability were obtained from those cryopreserved at ?20°C for not more than 30 days. The results indicate that preservation at ?196°C with 20% EG is a suitable procedure for long‐term storage of the giant freshwater prawn spermatophores.     

River pen culture of giant freshwater prawn Macrobrachium rosenbergii (De Man) in southern Vietnam

A technical and socio‐economic survey conducted in the Dong Thap province of Vietnam to assess the current status of river pen culture of giant freshwater prawn Macrobrachium rosenbergii (De Man) showed that pen culture, which has been developed and operated by farmers' indigenous knowledge, requires more study in order to optimize stocking density and to assess its environmental impacts. In this study, the prawn pens were of rectangular shape, with an average size of 209 m². Prawns were stocked in June at an average density of 62 pieces m^?2 and fed on farm‐made feed and were harvested 2–4 times starting from 4 months after stocking until late December or the following January. The average prawn yield was 0.52 kg m^?2 year^?1, ranging from 0.14 to 1.6 kg m^?2 year^?1. The average net return was US$0.71 m^?2 year^?1, ranging from US$1.24 to 4.37 m^?2 year^?1. About 73% of the farmers achieved positive net returns. The top five constraints for prawn pen culture were lack of knowledge of culture technologies, poor water quality, disease problems, poor quality of wild seed and lack of capital. Almost all farmers have no environmental awareness, and environmental regulations for prawn pen culture have not been established. Field measurements showed that all measured water quality parameters were within the range for good growth of giant freshwater prawns, and indicated that there was no significant accumulation of nutrients and organic matter at the bottoms of rivers or canals.     

Comparison of larval performance between Thai and Vietnamese freshwater giant prawn, Macrobrachium rosenbergii (de Man): a preliminary study

This study compared the performance of larvae of giant freshwater prawn (Macrobrachium rosenbergii) from Thailand and Vietnam. Thai broods were collected from a farm and Vietnamese broods were collected from a river. Larvae from these two sources were raised in identical environments, and their rates of development and survival as well as their ability to withstand environmental stresses were assessed. The first postlarval stage was observed in both strains on day 22. All larvae (100%) from Thai broods completed metamorphosis by day 36, but only 89% of the Vietnam strain completed metamorphosis by day 45. The stages of development were more uniform in larvae from the Thai stock than the Vietnamese stock. Survival differences were observed within the first week (92% in the Thai group vs. 55% in the Vietnamese group). These differences were most pronounced beginning in week 5 (52% and 16% respectively) and week 7 (33% and 2% respectively). No clear difference was found in brood size and fecundity between the two groups. No difference in survival was observed between the two groups of larvae challenged with salinity, oxygen or formalin. Differential development rates of larvae in the same batch would naturally create conditions favourable for cannibalism and impaired ability to capture food. The earlier and more uniform rate of development, and subsequent higher rate of survival of Thai stock compared with the Vietnamese wild stock is suggested to be due to inadvertent selection in the domesticated stock.     

Bacterial microflora associated with farmed freshwater prawn Macrobrachium rosenbergii (de Man) and the aquaculture environment

The initial counts of bacteria associated with farmed giant freshwater prawn (Macrobrachium rosenbergii de Man) as well as with the water and sediment from two farms located at Kottayam district in Kerala (India) were determined. A total of 367 randomly selected isolates were characterized and identified. Prawn samples yielded mean microbiological counts of 4.92 log CFU g^?1 of shell with muscle and 7.78 log CFU g^?1 of intestine at 30°C. Bacterial numbers in the intestine of prawn were much higher than those in the pond water. Motile and non‐motile aerobic Gram‐negative bacteria together with Enterobacteriaceae accounted for 60–70% of the mesophiles isolated from water and prawn. However, the microorganisms isolated in significant numbers from shell with muscle and intestine of prawn were not recovered from the growing waters. Among Gram‐positive bacteria, Micrococcus, Bacillus, coryneforms, and Arthrobacter were found. Faecal coliforms and enterococci were found in significant numbers in M. rosenbergii. The rearing practices such as feeding and pond fertilization could have influenced the microflora in prawn. The commensal microflora of freshwater prawn included opportunistic pathogens such as Aeromonas spp. and Streptococcus spp. Storage of prawn at elevated temperatures can permit their survival and growth leading to quality loss. Care should be exercised during handling and processing to prevent contamination of edible meat.     

Overview of recent research and development in temperate culture of the freshwater prawn (Macrobrachium rosenbergii De Man) in the South Central United States

Research and development efforts concerning freshwater prawn farming have in the past been principally conducted in tropical regions. However, activities in temperate regions also date back several decades. Culture of Macrobrachium in temperate zones offers positive opportunities, despite the inability to culture year‐round. Unique problems imposed by a restricted growing season must be addressed, and opportunities capitalized on, to attain commercially viable production in these regions. Much recent research in the South and Central USA has been directed towards intensifying production (kg ha^?1) without decreasing average harvest sizes or deteriorating water quality. Particular areas of research include evaluating and maximizing the relative contributions of natural foods, effects of artificial substrates on growth and prawn population structure and grading of animals before pond stocking to reduce heterogeneous individual growth and aggressive interactions. Recent studies have concentrated on combining these factors into a ‘best management practices’ (BMPs) production model. With these factors combined, production has increased from an average of 1000 kg ha^?1 of 30 g animals to almost 3000 kg ha^?1 of 40 g animals produced in research ponds in 110 days of culture. In commercial ponds, 1500–2000 kg ha^?1 has been achieved in a similar period using BMPs.     

Effects of salinity on standard metabolic rate and critical oxygen tension in the giant freshwater prawn (Macrobrachium rosenbergii)

The extensively farmed giant freshwater shrimp, Macrobrachium rosenbergii, can survive salinities up to 26 g L^?1, but the commercially important grow‐out occurs exclusively in freshwater areas. Recent studies suggest the shrimp equally capable of growing in brackish as fresh water and a better understanding of how this species responds to changing salinity could significantly impact freshwater prawn farming in deltas and coastal areas. Here, the effect of salinity (0 and 15 g L^?1) on standard metabolic rate (SMR) and critical oxygen tension (P_crit) was measured in adult M. rosenbergii using intermittent closed respirometry. SMR was 79.8 ± 3.1 and 72.7 ± 2.9 μmol kg^?1 min^?1 in fresh and brackish water, respectively, with no significant difference between the two salinities (P = 0.122). During hypoxia M. rosenbergii maintained oxygen uptake down to a P_crit of 26.3 ± 1.4 mmHg in fresh and 27.2 ± 2.0 mmHg in brackish water (P = 0.682), showing that salinity had no overall effect on oxygen conductance in the animals. These findings are in agreement with recent growth studies and provide further evidence that grow‐out phase could be accomplished in brackish water areas. Thus, the predicted intrusions of brackish water in tropical deltas as a consequence of future global warming may not impact this important production.     

Effects of different dosages of astaxanthin on giant freshwater prawn Macrobrachium rosenbergii (De Man) challenged with Lactococcus garvieae

The effects of astaxanthin (AX) injected at 0.67 and 1.34 nmol g^?1 BW^?1 on the survival, antioxidant capacity, total haemocyte count (THC) and hepatopancreas astaxanthin content of giant freshwater prawn, Macrobrachium rosenbergii, challenged with Lactococcus garvieae were evaluated. AX‐injected M. rosenbergii at 1.34 nmol g^?1 BW^?1 had significantly (P≤0.05) higher survival rates. However, AX showed no significant effects on the capacity of certain antioxidant indicators (superoxide dismutase, glutathione peroxidase and glutathione reductase). This implies that L. garvieae infection suppressed the activity of the haemolymph antioxidant system of infected M. rosenbergii. This result suggests that the two different dosages used in this study could not exert significant effects on the tested antioxidant capacity of L. garvieae‐infected M. rosenbergii. On the other hand, AX‐injected M. rosenbergii at either dose showed a significant increase in the THC and hepatopancreas AX content when compared with the challenged control group. Overall, the results of this study indicate that the injected AX led to an improvement in M. rosenbergii's resistance against L. garvieae infection.     

Growth and immune response of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae fed diets containing Chlorella vulgaris (Beijerinck)

A 50‐day growth trial was conducted to evaluate the efficacy of Chlorella vulgaris (Beijerinck) as an ingredient in the diets of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae (PL30). Immune response (total haemocyte count and prophenoloxidase activity) was also assessed by subjecting postlarvae to a challenge test against Aeromonas hydrophila (Chester) for 14 days. Iso‐nitrogenous and iso‐lipidic test diets were prepared using a fishmeal‐based‐positive control diet (D0) and four basal diets with inclusion levels of 2% (D2), 4% (D4), 6% (D6) and 8% (D8) C. vulgaris. Postlarvae of M. rosenbergii were randomly stocked (mean initial body weight of 0.19 ± 0.02 g) in 30‐L tanks in three replicates per dietary treatment for evaluation of growth performance. Another set of postlarvae (mean initial body weight of 1.25 ± 0.02 g) was randomly distributed in 95‐L tanks in three replicates per dietary treatment for the assessment of immune response. Results showed that specific growth rate was significantly higher (P < 0.05) in postlarvae fed D4 and D6. Variations in values for carcass protein, lipid, moisture and ash were also evident. Postlarvae fed diets with Chlorella showed increased prophenol oxidase activity and total haemocyte counts. Moreover, survival rate after challenge with A. hydrophila was significantly increased (P < 0.05). Inclusion of C. vulgaris in diets enhanced immune response and resistance of M. rosenbergii postlarvae against A. hydrophila infection.     

Culture of Macrobrachium rosenbergii (De Man 1879) in experimental cages in a freshwater eutrophic lake at different stocking densities

Macrobrachium rosenbergii (de Man 1879) juveniles (0.4 g) were cultured in experimental cages (L × W × H: 2.5 × 1 × 1 m) in Laguna de Bay, the largest lake in the Philippines. The following stocking densities at four replicates each were used: 15, 30, 60 and 90 prawns m⁻² of cage bottom. The mean sizes at harvest after 5 months of culture ranged from 14.3 g for the highest stocking density to 26.3 g for the lowest. The mean size at harvest, daily growth rate and size class distribution were significantly influenced by stocking density, with those at the lowest stocking density showing significantly better growth and overall proportion of larger prawns. Heterogeneous individual growth (HIG) was fairly evident in all treatments. The percentage of blue‐clawed males was not influenced by treatment but the mean weight was significantly higher in the lower stocking densities. Both the percentage and mean weight of berried females were significantly higher in the lowest stocking density. Survival was the highest in the lower stocking densities (55.3%, 54.0%, 52.7% and 36.9% for 15, 30, 60 and 90 prawns m⁻² respectively). Feed conversion ratio (FCR) improved with decreasing stocking density, ranging from 2.1 to 3. As expected, yield per cropping increased with stocking density and ranged from 450 to 1089 g m⁻² yr⁻¹ of actual cage area. Production values obtained in the cage cultured M. rosenbergii were comparable to or even higher than those reported from pond culture, given that the stocking densities used in this study were generally higher than in ponds. The results show that the farming of M. rosenbergii in cages in lakes is a viable alternative to pond culture and has the potential of improve aquaculture production in lakeshore fish farming communities.     

Immunomodulatory effect of Cynodon dactylon against white tail disease of giant freshwater prawn,Macrobrachium rosenbergii (de Man, 1879)

The giant freshwater prawn, Macrobrachium rosenbergii, is an economically important and extensively cultured crustacean worldwide. The viral pathogens, Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV) are responsible for causing severe mortalities in the hatchery and nursery phases. This study investigates the protection of postlarvae of freshwater against white tail disease (WTD) using plant extract derived from Cyanodon dactylon and the modulation of the prawn non‐specific immunity. To determine the immunomodulatory effect of C. dactylon extract, the prawn was injected with plant extract and various immunological parameters were estimated. The immunological parameters such as proPO, SOD, THC and clotting time were found to be significantly higher in the plant extract‐injected prawn when compared with control groups. The results of real time PCR analysis revealed up regulation on the expression proPO, SOD and lysozyme genes in MrNV and XSV challenged prawn postlarvae treated with C. dactylon extract. Infectivity experiment showed high relative per cent survival in MrNV and XSV‐challenged prawn postlarvae treated with C. dactylon extract. These results strongly indicate that the administration of C. dactylon plant extract enhances immunity of the prawn. Based on the results, this study recommends that the immersion of postlarvae in C. dactylon plant extract is a potential prophylactic agent against WTD.