Growth enhancement and protective potential of feed-based outer membrane proteins against vibriosis in <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

The use of antibiotics to curtail vibriosis, which is a major infectious disease, plaguing shrimp and prawn is rather becoming less effective and the need for a better alternative is expedient. The outer membrane proteins (OMPs) of V. alginolyticus were extracted, mixed with powdered commercial feed and fed to the prawns to evaluate its effect on growth performance and protective potential. Sixty prawns were divided into groups A, B and C of 10 prawns each, with two replicates in six (150 L) glass aquaria. Groups A, B and C were fed with OMPs mixed diet, with OMPs-Freund’s incomplete adjuvant mixed diet and OMPs or adjuvant free diet (control diet) respectively. All the prawns were weighed weekly, and haemolymph was collected to determine the total haemocyte count (THC) and phenoloxidase (PO) activity. At the end of the feeding trial, prawns were intramuscularly challenged with 50 μL of 10⁷ CFU V. alginolyticus. The treated groups were significantly higher in growth performance and THC than the control group, but no significant difference between the groups in terms of PO activity and mortality rate. The study, however, submitted that oral administration of OMPs with or without adjuvant is a good growth promoter and has the potential for protection against vibriosis in giant freshwater prawn (Macrobrachium rosenbergii).     

Effects of all‐male,mixed‐sex and all‐female freshwater prawn in polyculture with major carps and molas in the fallow rice fields

This study was conducted to evaluate the effects of all‐male, mixed‐sex and all‐female freshwater prawn (Macrobrachium rosenbergii) in a polyculture with major carps (Catla catla and Labeo rohita) and self‐recruiting small fish molas (Amblypharyngodon mola) in the fallow rice fields of Bangladesh. There were three treatments with three replicates. All ponds were stocked with carps and molas plus either all‐male prawns (treatment MP), mixed‐sex prawns (MFP) or all‐female prawns (FP). Prawn, mola, catla and rohu were stocked 20 000, 20 000, 1750 and 750 ha^?1, respectively, in all treatments. The prawns were fed twice daily, starting at 8% body weight and gradually reduced to 3% body weight. The fish were fed in the morning with mustard oil cake and rice bran (1:2 ratios) at 3% body weight. Significantly higher production of prawns (697 kg ha^?1) was obtained in treatment MP, which yielded 34.7% and 56.2% more production than MFP and FP respectively. Significantly higher total production of 1620 kg ha^?1 and a higher benefit–cost ratio of 2.10:1 were also obtained in treatment MP. It can be concluded that an all‐male prawn culture is economically more viable than all‐female and mixed‐sex prawn cultures, along with other fish like major carps and the nutrient‐dense molas in the polyculture.     

Effects of selective harvesting and claw ablation of all‐male freshwater prawn (Macrobrachium rosenbergii ) on water quality,production and economics in polyculture ponds

The effects of selective harvesting (SH) and claw ablation (CA) of blue‐clawed (BC) prawns on an all‐male freshwater prawn–finfish polyculture system were compared with control (Co) in quadruplicate. Ponds were stocked with all‐male freshwater prawn Macrobrachium rosenbergii, silver carp Hypophthalmichthys molitrix, catla Catla catla and mola Amblypharyngodon mola at 12 000, 2000, 500 and 20 000 ha^?1 respectively. Prawns were fed with pelleted feed. Ponds were fertilized regularly with urea, triple super phosphate and cow‐dung. SH of BC prawns in treatment SH and CA in treatment CA started on the 60th day during a 137‐day culture and continued at 15‐day intervals until the final harvest. Water quality parameters and plankton abundance did not vary significantly (P>0.05) among the treatments. Treatment SH resulted in a higher (P<0.05) net production of freshwater prawn (437 kg ha^?1), with better survival and mean weight, followed by CA (354 kg ha^?1) and Co (322 kg ha^?1). The combined net production of prawn plus finfish was also higher in SH (1244 kg ha^?1) as compared with CA (1161 kg ha^?1) and Co (1137 kg ha^?1), although the finfish production did not differ significantly. The periodic SH of BC prawns showed a better economic return with a BCR of 1.71.     

Effects of Two Densities of Caged Monosex Nile Tilapia, Oreochromis niloticus, on Water Quality, Phytoplankton Populations, and Production When Polycultured with Macrobrachium rosenbergii in Temperate Ponds

The effects of different densities of caged Nile tilapia, Oreochromis niloticus, on water quality, phytoplankton populations, prawn, and total pond production were evaluated in freshwater prawn, Macrobrachium rosenbergii, production ponds. The experiment consisted of three treatments with three 0.04‐ha replicates each. All ponds were stocked with graded, nursed juvenile prawn (0.9 ± 0.6 g) at 69,000/ha. Control (CTL) ponds contained only prawns. Low‐density polyculture (LDP) ponds also contained two cages (1 m³; 100 fish/cage) of monosex male tilapia (115.6 ± 22 g), and high‐density polyculture (HDP) ponds had four cages. Total culture period was 106 d for tilapia and 114 d for prawn. Overall mean afternoon pH level was significantly lower (P ≤ 0.05) in polyculture ponds than in CTL ponds but did not differ (P > 0.05) between LDP and HDP. Phytoplankton biovolume was reduced in polyculture treatments. Tilapia in the LDP treatment had significantly higher (P ≤ 0.05) harvest weights than in the HDP treatment. Prawn weights were higher (P ≤ 0.05) in polyculture than prawn monoculture. These data indicate that a caged tilapia/freshwater prawn polyculture system may provide pH control while maximizing pond resources in temperate areas.     

Potential of mixed culture of freshwater prawn (Macrobrachium rosenbergii) and self-recruiting small species mola (Amblypharyngodon mola) in rotational rice–fish/prawn culture systems in Bangladesh

The effects of different stocking densities of freshwater prawn (Macrobrachium rosenbergii) on its growth and production in relation to the presence of small self‐recruiting species mola (Amblypharyngodon mola) were investigated in modified rice fields after rice harvest at Mymensingh, Bangladesh. Keeping the stocking density of mola fixed at 20 000 ha^?1 in each treatment, four densities of freshwater prawn (treatments) were maintained: 10 000, 15 000, 20 000 and 25 000 ha^?1 respectively. The rice plots were limed (CaCO₃) and fertilized with urea, triple super phosphate and cowdung regularly. The prawns were fed daily with commercial pellets. Water quality parameters such as temperature, dissolved oxygen, transparency, pH, total alkalinity, inorganic nitrogen (nitrate, nitrite and total ammonia), chlorophyll a and orthophosphate were determined fortnightly. Numerical analysis of plankton communities was performed monthly. All water quality parameters were found to be within the suitable range for freshwater prawn culture, except high temperature, in the peak summer months. There was a homogenous abundance of plankton communities in all treatments throughout the experimental period. Mola started to breed in the second month of the original stocking with partial harvesting after the second month and continued until the final harvest. The total production of mola ranged between 124 and 152 kg ha^?1 during the 4‐month culture period. The average prawn survival ranged from 49% to 57% without any significant difference among treatments. Freshwater prawn production ranged from 294 to 596 kg ha^?1 with significantly higher production in the treatment where 20 000 ha^?1 freshwater prawn were stocked. This treatment also resulted in a higher net profit margin (74%), indicating that stocking at a combination of 20 000 ha^?1 freshwater prawn and 20 000 ha^?1 mola could be the optimum proposition for prawn–mola culture in modified rain‐fed rice fields after rice cultivation.     

A review on the diseases of freshwater prawns with special focus on white tail disease of Macrobrachium rosenbergii

Freshwater prawns, particularly, the Giant Freshwater prawn Macrobrachium rosenbergii, are one of the most economically important farmed species in the world. Faced with increasing disease problems in penaeid shrimp culture, farmers turned to freshwater prawn farming. Freshwater prawns were considered relatively less susceptible to diseases. However, with intensification of culture and increased world trade of the farmed species, emerging diseases are beginning to constitute an increasingly serious health problem in freshwater prawn culture. This article is a review of the important diseases reported in freshwater prawns, with particular emphasis on the white tail disease of M. rosenbergii as it is the most important disease recorded to date and also the most well studied among the diseases of freshwater prawns. Steps to be taken for proper health management in the farming of this species is also touched upon.     

Prawn (Macrobrachium rosenbergii)–plant (Hydrilla verticillata) co‐culture system improves water quality,prawn production and economic benefit through stocking density and feeding regime manage

The effects and commercial implications of aquatic plant addition, and variable prawn stocking density and supply of commercial aquafeed on water quality, prawn production and economic benefit, are investigated in a prawn (Macrobrachium rosenbergii) + plant (Hydrilla verticillata) co‐culture system. Our experimental design includes a control (PM, prawn monoculture without H. verticillata, with 30 prawns/m²) and four treatments with 15% plant cover of total pond area in each replicate. Dissolved oxygen, pH, N, P, total ammoniacal nitrogen, nitrite and nitrate in this co‐culture system were significantly lower than those of PM. Prawn survival (96.2 ± 14.9%), average final weight (68.5 ± 4.9 g) and yield (879.1 ± 102.4 kg/ha) in treatment 20W80%A (20 prawns/m², 80% of control aquafeed) were obviously greater than in PM and other treatments. Despite small males (SM) and immature females (IF) being predominant in prawn + plant cultures, more than 77.2% of prawns reached or exceeded 40 g on completion of trials, and by six months were of appropriate size for market. We report culture of M. rosenbergii with H. verticillata to be both feasible and profitable. The optimal treatment, a stocking density of 20 prawns/m² with these plants, enabled reduction of commercial aquafeed to 20% conventional culture levels. For this optimal treatment, we estimate total gross revenue, profit and internal rate of return to be US$ 6,593.3 ± 103.3 ha^?1, US$ 3,095.5 ± 42.6 ha^?1 and 127.5 ± 20.7% for 20W80%A respectively; we estimate U.S. Dollar (US$) invested generates 3.87 times conventional culture revenue. Co‐culture of M. rosenbergii and plants renders prawn production ecologically and economically feasible on larger farms.     

Effects of different fertilization and feeding regimes on the production of integrated farming of rice and prawn Macrobrachium rosenbergii (De Man)

An experiment was conducted in rice field plots each of 30 m² to determine the appropriate combination of feeding and fertilization regimes for the giant freshwater prawn Macrobrachium rosenbergii (De Man, 1879) cultured along with rice in rice fields. There were four treatments: rice culture only with regular fertilization (A, control); rice–prawn integrated culture with regular fertilization (B); rice–prawn integrated culture with basal fertilization and commercial feed (C) and rice–prawn integrated culture with regular fertilization and commercial feed (D). Juvenile prawns of 1.5‐g size were stocked on the third day after rice transplantation at a density of 2 prawns m^?2 and fed twice daily at 5% reducing to 2% of body weight during the experiment. The rice yield in treatment D (0.42 kg m^?2) was significantly higher than that in other treatments (0.34, 0.36, 0.34 kg m^?2 in treatments A, B, C respectively). Prawns grew significantly faster (P<0.05) in treatments C and D (23.8±0.9 and 22.0±1.7 g prawn^?1 respectively) than in treatment B (14.7±1.6 g prawn^?1). Prawn production in treatment C (347±13 kg ha^?1 crop^?1) was significantly (P<0.05) higher than that (234±30 kg ha^?1 crop^?1) in treatment B, while in treatment D (296±53 kg ha^?1 crop^?1) it was not significantly different from that in treatments B and C (P>0.05). Treatment C gave the highest economic returns among all treatments, followed by treatments D and B, indicating that the combination of basal fertilization and commercial feed is the most appropriate nutrient input regime for the rice–prawn integrated culture system.     

Productive performance of juvenile freshwater prawns Macrobrachium rosenbergii in biofloc system

The aim of this study was to compare two rearing systems for freshwater prawn Macrobrachium rosenbergii: one with use of a recirculating aquaculture system with biofilters (RAS) and another with use of microbial flocs (F). Thirty postlarvae of freshwater prawn with an initial average weight of 0.13 ± 0.05 g were randomly stocked in six experimental units with 0.20 m² and volume of 50 L. The experiment lasted thirty days. Dissolved oxygen, temperature and pH were monitored daily; ammonia concentration was determined three times per week; nitrite concentration, alkalinity and hardness were measured weekly. For the formation of microbial floc, molasses was used to keep the ammonia concentrations within safe levels for prawn farming. The variables of water quality remained within the suitable range for the production of the species, except for ammonia concentrations at the F treatment, which exceeded the safe levels. At the end of the experiment, the following parameters were evaluated: survival, specific growth rate, weight gain and feed conversion rate. Differences were found only in feed conversion rate with better values on RAS treatment. The microorganisms present in the RAS and F treatment were also evaluated. The densities of rotifers, amoebas and total bacteria were higher at the F treatment although the same organisms were found at the RAS treatment. The results of this study showed the possibility of rearing M. rosenbergii in biofloc system technology.     

Global scale of freshwater prawn farming

In welcoming participants to Giant Prawn 2011, the authors briefly review the current scale of this component of global aquaculture. The expansion of freshwater prawn farming over the 30 years since the first global conference on this topic [Giant Prawn 1980 (GP1980)] is examined. At the time of GP1980, the output of farmed giant river prawns (Macrobrachium rosenbergii) was <3000 t. Almost three decades later (2009) the total annual aquaculture production of all species of freshwater prawns had risen to almost 444 000 t, with a value of US$2.2 billion. The farmed production of M. rosenbergii constituted 51.7% of the global total, while the oriental river prawn M. nipponense (reared totally in China) contributed 47.2%. The contribution of the monsoon river prawn M. malcolmsonii remains quite small so far, and does not show in the above percentages because no recent FAO data are available for this species. In 2007, however, the latter species contributed 1.0% of the total global production of freshwater prawns. The major freshwater prawn producing countries are in Asia (e.g. Bangladesh, China, India, Myanmar, Taiwan, Thailand and Vietnam) but Macrobrachium spp. are also farmed in other continents.     

Current status of the giant freshwater prawn ( Macrobrachium rosenbergii) industry in China,with special reference to live transportation

The giant freshwater prawn Macrobrachium rosenbergii was first introduced into mainland China by the Chinese Academy of Agricultural Sciences from Japan in 1976. It was cultured at the Guangdong Province Fishery Institute (now as Pearl River Fishery Institute, Chinese Academy of Fishery Sciences). Following these early efforts, giant freshwater prawn culture has gradually spread to northern and inland areas. At this time (2011), China has become the largest producer of giant freshwater prawn in the world. Due to a preference of cooking with fresh aquatic products, Chinese retail markets have developed which have special live‐holding counters. From small rural shops to urban supermarkets and specialty restaurants, live seafoods are commonly available whereby customers pick out the products they wish to purchase and consume. Giant freshwater prawns are produced in over 35 countries throughout the world. They are usually sold either fresh, on‐ice, or frozen. What makes the Chinese prawn industry unique is its focus on a live transportation and marketing model. As a result, numerous innovative live‐transport technologies have been developed which have been key to the success of this expanding domestic industry. In this article, we would like to give a general overview of the giant freshwater prawn industry, its status in China, and the special role live‐transportation has for expanding production of giant freshwater prawns.     

Yield characteristics of prawns, Macrobrachium rosenbergii (de Man), with fish polycultures at low feeding rates

Abstract. As currently practiced, freshwater prawn, Macrobrachium rosenbergii (de Man), aquaculture in Hawaii requires large inputs of supplementary feed, water and labour. The high cost of these inputs greatly restricts profit potential. An experiment was conducted to compare an alternative prawn production system which used lower feeding rates and fish polycultures to reduce inputs. Three treatments were run in quadruplicate: (1) control—prawns stocked at standard densities (11.5 per n2) in monoculture and fed standard prawn pellets at the commercial ration recommendations by New & Singholka (1982); (2) low feed—prawns at standard densities and fish [silver carp, Hypophthalmichthys molitrix (Valenciennes), grass carp, Ctenopharyngodon idella (Valenciennes), and grey mullet, Mugil cephalus (L.)] fed one-half commercial ration; and (3) maintenance feed—prawns at standard densities and fish fed one-tenth commercial ration. Although prawn yield characteristics (mean weights, harvestable sizes, survival, net yields) were not significantly different (P > 0.05) based on an analysis of variance in the three treatments over the approximately 9.5-month culture period, this lack of significance most likely resulted from interpond variability and the lack of a large number of replicates. The relatively poor survival (60–63%) of gray mullet and an almost twofold difference in prawn yields in the control and maintenance feed treatments suggest that there was in fact competition for resources in the nominally polyculture systems. Nevertheless, the wet weight yield of biomass from all species was twice as high in the low feed ponds as in the control ponds.     

Fish meal replacement with squilla (<Emphasis Type="Italic">Oratosquilla nepa</Emphasis>, Latreille) silage in a practical diet for the juvenile giant freshwater prawn, <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> de man, 1879

Replacement of fish meal with squilla silage in practical diet for the juvenile giant freshwater prawn, Macrobrachium rosenbergii, was evaluated. Five iso-nitrogenous and iso-caloric diets were prepared in which protein requirements were met with 100% fish meal (control, diet 1) and squilla silage replacing fish meal at 25, 50, 75 and 100% (diets 2, 3, 4 and 5, respectively). Water stability and water absorption of five feeds revealed significant differences (P?<?0.05). The weight gain varied between a maximum of 248.50?±?34.07% in diet 4 to lowest 132.45?±?14.34% in diet 1. The average daily gain in weight in grams varied from 0.091?±?0.01 (diet 5) to 0.154?±?0.04 (diet 3), whilst the specific growth rate and gross growth coefficient values were recorded highest in diet 4. Highest survival rates (86.66?±?5.77%) were recorded in both experimental diets 4 and 5. Low feed conversion ratio of 1.19?±?0.21 was recorded from diet 4, whilst the highest value of 2.16?±?0.09% was estimated from the diet 5. Proximate carcass composition showed highest crude protein content in post-larvae fed with diet 5 (47.24%) in contrast to lowest diet 1 (36.12%). Lipid values fluctuated significantly between 2.45 and 7.18% (P?<?0.05) between treatments. The ash content significantly increased from diet 1 (16.34%) to diet 5 (20.69%) (P?<?0.05). Highest feed efficiency (gain/feed) value was recorded in diet 4 (1.52?±?0.22), whilst the diet 5 showed lowest value (0.99?±?0.06). The results suggested that squilla silage can be utilised up to 75% of the protein in prawn diets for fish meal replacement.     

The effect of density of Macrobrachium rosenbergii raised in earthen ponds on their population structure and weight distribution

The population structure and weight distribution of Macrobrachium rosenbergii raised in earthen ponds in polyculture with fish were studied. Over 10 000 prawns were grown in 12 ponds stocked with 1, 2, 3 or 4 prawns per m². Females were more abundant than males in all of the treatments. The proportions of three different male morphotypes, blue claw, orange claw and small males, changed with density but those of the female morphotypes did not. A detailed analysis of prawn weight distribution (mean, coefficient of variation and skewness) was carried out separately for each sex and for the morphotypes within each sex. Prawn survival was approximately 85%, independent of prawn density. Yield increased and mean prawn size decreased with prawn density. The most profitable density was 2 prawns per m². The biological mechanisms controlling variation in sex ratio and morphotype frequency and the social control of growth are discussed.     

Density effects of silver carp Hypophthalmichthys molitrix and catla Catla catla on the production system in all‐male freshwater prawn–finfish polyculture ponds

The effects of three different combinations of silver carp Hypophthalmichthys molitrix and catla Catla catla density on the production system in all‐male freshwater prawn–finfish polyculture ponds were evaluated in triplicate. The stocking density of silver carp and catla, respectively, were maintained at 2000 and 500 ha^?1 in treatment SC₂₀₀₀C₅₀₀, 1500 and 1000 ha^?1 in treatment SC₁₅₀₀C₁₀₀₀ and 1000 and 1500 ha^?1 in treatment SC₁₀₀₀C₁₅₀₀. Male freshwater prawn Macrobrachium rosenbergii and small fish mola Amblypharyngodon mola densities were fixed in all treatments at 12 000 and 20 000 ha^?1 respectively. Management practices were same for all treatments. Blue‐clawed male prawns were harvested twice during the 122‐day culture at 15‐day intervals before the final harvest. Plankton and macro‐benthos abundance and water quality parameters (except transparency and chlorophyll a) did not vary significantly (P>0.05) among treatments. Mean final weights of both silver carp and catla were decreased with the increasing of their own stocking density. The treatment SC₁₅₀₀C₁₀₀₀ resulted in 25–32% increased net production of silver carp plus catla (461 kg ha^?1) and 20–21% increased net production of all species combined (874 kg ha^?1) as compared with the other treatments, although the differences in production of prawn and mola among treatments were not significant.     

Combined diet of yeast,fermented soybean meal,and microparticulate as larval feed in extensive rearing systems for seed production of the oriental river prawn <Emphasis Type="Italic">Macrobrachium nipponense</Emphasis>

The present study aims to evaluate the effects of several types of larval feed on seed production of the oriental river prawn Macrobrachium nipponense and water quality in extensive rearing systems. Healthy M. nipponense were distributed into fifteen 15-m² pond outdoors, and each pond was stocked with 90 prawns including 41 egg-bearing (berried) female prawns, 37 not bearing female prawns, and 12 male prawns for larval production. The experimental design was completely randomized, with four diet groups (diet A: soybean homogenate, diet B: yeast, diet C: yeast?+?fermented soybean meal, and diet D: yeast?+?fermented soybean meal?+?microparticulate diet) and one no feeding control and three replications. There are equal levels of the total protein content in diets A–D. Higher larvae and postlarvae number was obtained for diet C and diet D. Furthermore, the increase of M. nipponense larvae and postlarvae in diets B–D can result in the decrease of zooplankton and increase of phytoplankton in the pond during some periods, simultaneously improving the water quality. The Spearman correlation coefficient (r_M,N) between the amounts of larvae and postlarvae of M. nipponense per pond and zooplankton per pond during the entire experiment period was ??0.56. The highest juvenile M. nipponense production was obtained in the diet D group (3140.00?±?461.63), which was slightly higher than that in the diet C group (2940.33?±?382.60). The juvenile M. nipponense production in diet B (2303.00?±?449.23) was also significantly higher compared to diet A (1106.33?±?176.64) and the control group (1039.67?±?212.85). There were no significant differences in the amounts of juvenile M. nipponense between the control and diet A groups, which indicated that the soybean homogenate could not increase the amount of M. nipponense juveniles. Our results clearly showed that diet D significantly raised per unit yield of prawn seed comparing with no feeding and other diet group in extensive rearing systems and that the cost of producing prawn seed with diet D is low, which provide an important foundation for the expansion of oriental river prawn culture.     

Growth and carcass composition of giant freshwater prawn, Macrobrachium rosenbergii (De Man), fed different isonitrogenous and isocaloric diets

A feeding experiment was conducted for 135 days to observe the effect of different isonitrogenous (35% crude protein) and isocaloric (385 kcal) diets on the growth and carcass composition of giant freshwater prawn, Macrobrachium rosenbergii ( De Man 1879 ). Three experimental diets (ED1, ED2 and ED3) were prepared using locally available ingredients. These diets differed mainly in terms of percent contribution of major protein sources such as fish meal, soybean meal, groundnut oil cake and mustard oil cake. Experimental diets were evaluated against a commercial diet, which served as the control (CD). Juveniles 1.87–2.44 g in size were stocked at a population density of 40 000 ha⁻¹ and fed thrice daily at 10% in the beginning and reducing gradually to 7% and 5% of the body weight during the experimental period. No significant differences (P>0.05) in the growth performance were observed; however, a significantly (P<0.05) higher yield (721.9 kg ha⁻¹ 135 days⁻¹) was recorded for prawn fed with control diet, followed by experimental diet 2 (676.5 kg ha⁻¹ 135 days⁻¹, having soybean meal as a major protein source). The survival ranged between 63.8% and 77.7%, with different diets showing significantly higher survival. The apparent feed conversion ratio values of diets ranged between 3.15 and 3.49, with experimental and control diets showing non‐significantly lower AFCR values. At the end of the experiment, representative specimens from each treatment were collected and their carcass composition was measured. Analysis of variance showed that carcass protein and total carbohydrate contents were significantly (P<0.05) higher in prawns fed on a fish–soybean meal‐based diet (ED3) and a control diet. The total lipid contents of prawns, however, did not differ significantly among the various dietary treatments. The results of our study suggest that the experimental diets could be used effectively for M. rosenbergii without compromising growth and flesh quality.     

Effects of replacing dietary fish oil and squid liver oil with vegetable oils on the growth,tissue fatty acid profile and total carotenoids of the giant freshwater prawn, Macrobrachium rosenbergii

A feeding trial was conducted to investigate the complete substitution of either fish oil (FO) or squid liver oil (SLO) with crude palm oil (CPO), canola oil (CO) sunflower oil (SFO) or linseed oil (LO), as the sole added lipid source in diets fed to triplicate groups of giant freshwater prawn, Macrobrachium rosenbergii (initial weight = 0.42 ± 0.01 g) for 6 weeks. Prawns fed the CO or SLO diets showed significantly higher (P < 0.05) specific growth rate than those fed the FO or CPO diets. The feed conversion ratio of the prawns was significantly better when fed the CO diet, compared with the FO, CPO, SFO and LO diets. The muscle eicosapentaenoic acid content of prawns fed the vegetable oil (VO) diets were not significantly different (P > 0.05) from those fed the FO diet, although all VO‐based diets led to a significantly lower docosahexaenoic acid content compared with prawns fed the FO or SLO diet. The whole‐body total carotenoid content was significantly lower for prawns fed the SLO diet compared with prawns on the CO or CPO diets. The successful use of VO instead of marine‐based oils in prawn diets will likely reduce feeding costs associated with M. rosenbergii aquaculture.     

The effects of dietary lipid sources and lecithin on the production of giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> larvae in the Mekong Delta region of Vietnam

The giant freshwater prawn, Macrobrachium rosenbergii, is cultured widely in the Mekong Delta region of Vietnam but it is often difficult or expensive for hatchery operators to purchase commercial diets used as a feeding supplement to Artemia nauplii. Therefore, in the present study, the effects of lipid sources and lecithin on the growth and survival rate of M. rosenbergii larvae were examined in order to develop suitable hand-prepared larval diets for seed production of M. rosenbergii in this area. Six egg custard diets consisting of various ratios of lipid (originating from soybean oil and squid oil) and lecithin were used for rearing Macrobrachium rosenbergii larvae. Treatments in which larvae were fed diets containing squid oil exhibited the highest body length and survival rates (7.14–7.43 mm and 51.1–68.1%, respectively), and differed significantly from other treatments (P<0.05). Use of dietary soybean oil yielded the lowest body length and survival rates (6.29–6.75 mm and 22.0–48.7%), respectively). The supplementation of dietary lecithin did not increase final body weight but did improve larval survival rates. The n-3 HUFA content of prawns fed dietary squid oil was higher than those of animals provided with other diets. These results indicated that the most appropriate diet for rearing M. rosenbergii larvae is the diet containing 3% squid oil and 1.5% lecithin.     

Fatty acid and amino acid composition of eggs, muscle and midgut glands of freshwater prawns, Macrobrachium rosenbergii (de Man), raised in fertilized ponds, unfertilized ponds or fed prepared diets

Fatty acid and amino acid profiles were determined in three tissues (eggs, muscle and midgut glands) from freshwater prawns, Macrobrachium rosenbergii (De Man), raised unfed in ponds with no organic fertilization, unfed in ponds with organic fertilization or fed a formulated, pelleted diet. Amino acid profiles of tail muscle and eggs were not treatment-dependent. Comparison of amino acid profiles of the diet with those of tissues of animals fed that diet suggest that dietary levels of arginine, histidine, methionine, and especially lysine may be suboptimal. Fatty acid profiles of the midgut gland, tail muscle, and to a lesser extent, eggs reflected the fatty acid composition of the diet in the fed treatment, the organic fertilizer material in the fertilized treatment and natural food organisms in the unfed treatment. Direct consumption of organic fertilizer particles by the prawns is supported by these data. Selective retention of essential fatty acids appears likely in all three treatments. Comparison of the fatty acid composition of prawn eggs and muscle tissue with that of the pelleted diet indicates that 18: 3(n-3), 20: 5(n-3), and especially 20: 4(n-6) are probably below optimal levels. However, under practical culture conditions, prawn growth may not be significantly reduced because of relatively low dietary requirements and contributions from natural foods in the ponds.