Effect of Bacillus subtilis on growth development and survival of larvae Macrobrachium rosenbergii (de Man)

A feeding experiment was conducted to investigate the effect of Bacillus subtilis bacterium, on larval growth and development rate of Macrobrachium rosenbergii (de Man) during February 28 to April 8, 2005 in University Putra Malaysia hatchery. Newly hatched larvae of M. rosenbergii were reared with two dietary treatments consisting of newly hatched Artemia salina nauplii with B. subtilis (10⁸ cells ml⁻¹), and newly hatched A. salina nauplii without B. subtilis carried out in triplicate in 60‐L aquarium (50 L⁻¹). After trial, the larvae that fed B. subtilis‐treated Artemia naupli were found to have higher survival and a faster rate of metamorphosis than larvae that were fed with nontreated Artemia naupli. There were significant differences between B. subtilis‐treated Artemia naupli and nontreated Artemia diet in larval growth and development rate of metamorphosis (P < 0.05). Larval survival after 40 days was significantly greater (P < 0.05) in the B. subtilis‐treated groups (55.3 ± 1.02) compared with the nontreated groups (36.2 ± 5.02%).     

Effect of ammonia-N on growth and feeding of juvenile Macrobrachium rosenbergii (De-Man)

Survival rate, growth and feed intake were determined for late juveniles (4.31 ± 0.18 g) of river prawn Macrobrachium rosenbergii in freshwater with total ammonia‐N (NH₃‐N+NH₄‐N) concentrations of 0.015 (control), 0.5, 1.0 and 1.5 mg L⁻¹ for 60 days at pH 7.53 ± 0.04 and temperature 24.0 ± 2.5°C. Survival rate was significantly (P<0.05) lower (54 ± 4.2–70 ± 5.4%) for total ammonia concentrations from 0.5 to 1.5 mg L⁻¹ [0.0139–0.0419 mg L⁻¹ of unionized ammonia (NH₃)]. Growth (0.026–0.030 g day⁻¹ range) of the prawns did not differ for the different NH₃ levels but were significantly (P<0.05) lower compared with control (0.056 g day⁻¹). Feed intake rates also diminished significantly (P<0.05) from 77.60 ± 2.45% at control (0.015 mg L⁻¹ NH₃‐N) to 48.69 ± 2.13% at 1.5 mg L⁻¹ NH₃‐N (0.0419 mg L⁻¹ of unionized NH₃).     

Management strategies associating batch-graded and size-graded postlarvae can reduce heterogeneous individual growth in Macrobrachium rosenbergii (de Man)

Two sets of adaptive trials were performed to determine the effects of size grading and batch grading on size heterogeneity in cultured Macrobrachium rosenbergii raised in the Coconut Garden channels of Kuttanad, Southern India. In the first set of trials, postlarvae were batch graded on the basis of their hatching order, segregated and grown separately as first‐hatched and second‐hatched groups. In the second set of trials, postlarvae were size graded as jumpers and laggards and were grown in separate channels. The average weight attained by prawns after 10 months of culture was highest for jumpers (83.11 g) and lowest for the prawns from the first‐hatched group (43.76 g). The percentage of males was highest in the population of jumpers (58.23%). Highest production was recorded in the channel stocked with postlarvae from the second‐hatched group (103.4 kg ha^?1) and lowest production was obtained from the first‐hatched group (63.74 kg ha^?1). The proportions of undesirable small males were highest among laggards and the first‐hatched group: 24.8% and 15.1% respectively. The level of heterozygosity within morphotypes was also high in these groups. Jumpers attained good growth by the end of culture but, because of their low survival rate, this approach was not economically feasible. However, higher production and survival in the second‐hatched group improved economic viability. Thus, for better results, stocking with later‐hatched groups would be more appropriate than stocking with the first‐hatched group.     

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.     

Effects of temperature on food consumption, growth and oxygen consumption of freshwater prawn Macrobrachium rosenbergii (de Man 1879) postlarvae

Effects of temperature on food consumption, growth and oxygen consumption were estimated for the freshwater prawn Macrobrachium rosenbergii postlarvae at 23 °C, 28 °C and 33 °C in the laboratory. The results showed that the animal's initial body weight had a close linear relationship with food consumption and growth. Food consumption increased directly with temperature. Consumption rates (C; mg day^?1 ind^?1 ) of the 28 °C and 33 °C groups were much higher than that of the 23 °C group (P < 0.001), and the 33 °C group's consumption rate was higher than that of the 28 °C group (P < 0.05). The relationship of food consumption with temperature and initial body weight (W; mg) could be described as: C = 0.0679W + 0.185t? 3.17. Growth increased significantly with increased temperature. The relationship among specific growth rate, temperature and initial body weight was as follows: SGR = ?0.110W + 0.213t + 0.176. However, temperature showed no effect on growth efficiency. Oxygen consumption increased significantly with temperature (P < 0.01). The weight‐specific oxygen consumption rates (mg O₂ g^?1 h^?1) at 23 °C, 28 °C and 33 °C were 0.83, 1.16 and 1.49 mg O₂ g^?1 h^?1 for 61.92 mg M. rosenbergii.     

A test of two methods for marking larvae and postlarvae of the giant freshwater prawn, Macrobrachium rosenbergii

This paper describes the successful use of two tagging systems, both produced by Northwest Marine Technology Inc., on larval and postlarval giant freshwater prawns, Macrobrachium rosenbergii. Visible implant (VI) elastomer tags (a coloured liquid that solidifies under the epidermis) were used on stage XI larval prawns (mean weight 0.01 g) and postlarval prawns (mean weight 0.07 g). VI alphanumeric tags (small biocompatible plastic labels also inserted under the epidermis) were tested on postlarval prawns (from a weight of 0.5 g). Tags were inserted using clove oil as anaesthetic, and survival, mortality and growth rates of tagged animals were compared with those of controls that were handled but not anaesthetized or marked. Twenty per cent of the larval prawns (the smallest of the group) died just after tagging, but thereafter the remaining prawns survived well, as did all the tagged postlarval prawns. Visibility of the VI elastomer tags in larval prawns deteriorated with time, though 79% of marks were still visible to the naked eye 70 days after tagging. VI elastomer tags in the postlarval group remained clearly visible for up to 100 days. Visibility of the VI alphanumeric tags fell shortly after tagging, but remained adequate thereafter. Moult rates in control and tagged animals were the same in larvae with VI elastomer tags and postlarvae with VI alphanumeric tags, but the moult rate in the postlarval prawns given elastomer tags was slower than in controls. Rates of growth were similar in tagged (elastomer and alphanumeric) and control postlarval prawns, once the size‐dependent mortality of tagged larval prawns was taken into account. We conclude that VI elastomer tags could be used to mark small numbers of individual larval and immediately postlarval prawns for periods of several months, and that VI alphanumeric tags could be used to mark an unlimited number of individuals from a size of approximately 0.5 g.     

Probiotic effect of Bacillus NL110 and Vibrio NE17 on the survival,growth performance and immune response of Macrobrachium rosenbergii (de Man)

Eight hundred and eighty‐five strains of bacterial isolates from various samples associated with the natural habitat of Macrobrachium rosenbergii were screened for their probiotic potential. Two putative probionts namely Bacillus NL110 and Vibrio NE17 isolated from the larvae and egg samples, respectively, were selected for experimental studies and were introduced to the juveniles of M. rosenbergii (0.080±0.001 g) through different modes such as through feed, water and both. The probiotic potential of the above bacteria in terms of improvements in water quality, growth, survival, specific growth rate (SGR), feed conversion ratio and immune parameters was evaluated. The treatment groups showed a significant improvement in SGR and weight gain (P<0.001). Survival among different treatment groups was better than that in the control group. There were also significant improvements in the water quality parameters such as the concentration of nitrate and ammonia in the treatment groups (P<0.05). Improvements in immune parameters such as the total haemocyte count (P<0.05), phenoloxidase activity and respiratory burst were also significant (P<0.001). It is concluded that screening of the natural microflora of cultured fish and shellfish for putative probionts might yield probiotic strains of bacteria that could be utilized for an environment‐friendly and organic mode of aquaculture.     

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.     

Effect of cold shock and hormone on growth and male morphotypes of freshwater prawn,Macrobrachium rosenbergii (de Man)

A study was carried out to determine the effects of cold shock and 17α‐methyl testosterone hormone on growth in male morphotypes of giant freshwater prawn Macrobrachium rosenbergii. Juvenile males were exposed at 18 ± 0.25°C for 24 h with normal feed and cultured at 27 ± 0.7°C for 70 days as well as administrated feed with hormone separately at 400 mg kg^?1 feed for the first 30 days of culture period (70 days). The growth (Mean ± SD) of male juveniles at harvest was closely homogenous in the cold shock (CLS) treated group; while it was heterogeneous in hormone‐treated (MH) and control (CO) groups. Although total body weight of blue claw (BC) males was not significantly different in the controls and the treatments, the 2nd pereiopods (claw) weight and length of the BC was significantly lower in CLS (0.52 ± 0.05 g, 10.02 ± 0.65 cm) than that in the CO (0.71 ± 0.16 g, 12.53 ± 0.57 cm) and MH (0.75 ± 0.08 g, 12.85 ± 1.18 cm) treatments. Survival of prawns was similar in treatments. The morphotypes of male prawn were significantly different with 59% of BC males with small‐sized claws in CLS and, 45% and 30% of BC males with large‐sized claws in MH and CO respectively. Cold shock adversely affected male morphotypes of the prawn so that numbers of BC males with small‐sized claw was the highest in CLS tank. However, the CLS treatment resulted in more uniform marketable prawns and suggested a high production of BC males in an all‐male culture system.     

Social control of growth in Macrobrachium rosenbergii (De Man): a review and prospects for future research

The wide range of sizes of sexually mature prawn populations and particularly of the males is very typical of Macrobrachium rosenbergii (De Man) and a major obstacle to increased profitability of prawn culture. Prawn size variation reflects a complex population structure composed of three major male morphotypes – the small males, the orange‐claw males and the blue‐claw males – which differ in their morphology, physiology and behaviour. Social interactions among juveniles and among sexually mature males affect their growth. Four different social mechanisms have been suggested to control growth in crustaceans: direct competition for food, appetite suppression, altered food‐conversion efficiency and increased energy expenditure on motor activity. Since all growth‐controlling mechanisms involve an aggressive behavioural component, our knowledge of prawn agonistic behaviour and prawn social organization has been reviewed. Present knowledge of the social mechanisms regulating growth among juveniles and among sexually mature male morphotypes as well as the sensory modalities involved was evaluated. The possible evolution of social growth‐controlling mechanisms is discussed. Various ways for implementing our knowledge on social control of growth into prawn culture to increase profitability are suggested.     

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.     

On the breeding behaviour and reproduction of the freshwater prawn,Macrobrachium rosenbergii (de Man 1879) (Decapoda‐Crustacea) under laboratory conditions

The giant freshwater prawn, Macrobrachium rosenbergii is one of the most common decapod species, and now getting more attention from the aquaculturists world wide due to its high market demand. It is commercially important because of its size as well as its eating flesh qualities. The breeding behaviour, reproduction and hatching of this species were observed for about 8 months during 2009. Juveniles (0.55 ± 0.177 g total weight and 2.7 ± 0.12 cm, total length) were reared in rounded fibre glass tanks (1.3 m, diameter). Pre‐mating moult occurs in prawns once the ovaries ripen in their carapace cavity so as to transform the prawn into berried stage. Recorded incubation period ranged from 18 to 24 days. The number of eggs ranged from 2050 to 150 500 and the fecundity ranged from 435.2 to 3849.1 eggs. Number of hatched larvae ranged from 1825 to 123 410 larvae for females of 4.71 to 39.1 g respectively. The number of eggs carried by female prawn was directly proportional to its body weight (no. of eggs = 3441.3 wt. of female – 32 292, r² = 0.819). (fecundity = 82.066 wt. of female ? 235.04, r² = 0.7779; fecundity = 317.86 length of female ? 2651, r² = 0.833). Hatching rate ranged from 65% to 91%, and there was a correlation between number of hatched larvae and size of female parent (no. of larvae = 10 369 length of female – 102 965, r² = 0.8159; no. of larvae = 2792.9 wt. of female – 26 268, r² = 0.829). This study can greatly help in the management strategies of prawn hatcheries and improve its hatching technology.     

Characterization and pathogenicity studies of Vibrio parahaemolyticus isolated from diseased freshwater prawn, Macrobrachium rosenbergii (de Man)

Vibrio parahaemolyticus, an important pathogen of freshwater prawn, Macrobrachium rosenbergii causes high mortality. Four strains of V. parahaemolyticus were isolated from the gill, haepatopancreas, hemolymph and carapace of diseased prawn. The species were characterized based on biochemical and serological tests. On performing an antibiotic assay, these strains were found to be highly susceptible to cephalaxin, tetracycline and erythomycin. During the in vitro pathogenicity test, all the strains were found to be positive to the Congo red binding assay and to be haemolytic in nature, whereas an in vivo pathogenicity test revealed that 2 × 10⁹ CFUs mL^?1of bacteria induced disease symptoms such as black colouration on the carapace, red discolouration of the exoskeleton and loss of appendages within 6 days and 80% mortality. In histopathological studies, a prominent necrosis was seen in gill lamellae, and branchial arches were thickened at places due to hyperplasia and haemocytic infiltration. Hepatopancreatic tissue showed dilation of tubules, vacuolation of hepatocytes and marked necrosis in acinar cells. Development of an immunological technique for the detection and screening of V. parahaemolyticus infection and its treatment is highly important in freshwater prawn aquaculture.     

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.     

Optimization of stocking density of freshwater prawn Macrobrachium rosenbergii (de Man) in carp polyculture in Bangladesh

A study was conducted to optimize stocking density of freshwater prawn, Macrobrachium rosenbergii, in carp polyculture for 3 months in 10 experimental ponds of 80 m². Five stocking densities of prawn, 2500, 5000, 7500, 10 000 and 12 500 ha^?1, were assigned to treatments T₁, T₂, T₃, T₄ and T₅ respectively. The densities of catla, Catla catla, rohu, Labeo rohita and silver carp, Hypophthalmicthys molitrix, were 2500, 5000, and 2500 ha^?1, respectively, in each treatment. Each treatment had two replicate ponds. The mean initial weights of prawn, catla, rohu and silver carp were 1.1±0.02, 8.28±0.1, 25.2±1.1 and 36.32±1.2 g respectively. A pelleted diet containing 30% protein was prepared using fish meal, meat and bone meal, mustard oilcake, rice bran, wheat bran and molasses, and was fed twice daily at a rate of 5% of fish biomass. Water quality parameters were measured fortnightly and the ranges of temperature, pH and dissolved oxygen were 27.5–1.3°C, 6.9–8.6 and 4.5–8.6 mg L^?1 respectively. Feed conversion ratios ranged from 2.05 to 2.20 among the treatments. Per cent survival (%) of prawns ranged from 72% to 78%, while it varied from 80% to 93%, 90% to 95% and 90% to 92% for catla, rohu and silver carp respectively. The results showed that there were no significant differences among the weight gains of prawn and carp in different treatments. However, the overall total production of prawn and fish together was significantly (P<0.05) higher in T₃ and T₄ compared with other treatments. The total production for 3 months ranged between 2618 and 2916 kg ha^?1. The production of prawn was significantly higher (361.3 kg ha^?1) in T₅ with a highest stocking density of 12 500 prawn ha^?1. Although there was no significant difference (P>0.05) between the total production of prawn and fish together in T₃ and T₄, the highest net profit (Tk. 69 006 ha^?1) was obtained in T₄. Therefore, from the result of the study it may be concluded that a stocking ratio of 4:1:2:1 of prawn:catla:rohu:silver carp at a total density of 20 000 ha^?1 may be recommended for prawn–carp polyculture in ponds.     

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.     

Comparative evaluation of dietary protein levels and plant–animal protein ratios in Macrobrachium rosenbergii (de Man)

The effects of varying dietary protein level (200, 250, 300 and 350 g protein kg^?1 diet) and plant : animal protein ratio (1 : 2, 1 : 1, 1 : 1.5 and 2 : 1) on growth of juvenile Macrobrachium rosenbergii (de Man) with approximately 0.27 g initial body weight were evaluated in two separate 30‐days study using practical diets. Significantly lower survival rate was recorded in prawns fed a diet containing 200 g kg^?1 dietary protein (66.67%) whilst 300 and 350 g kg^?1 protein gave the highest survival (96.67%). Significant differences (P < 0.05) in feed conversion ratio and protein efficiency ratio were recorded among different dietary protein levels. The results of the study showed that highest growth rate and maximum utilization of protein were recorded in prawns fed 300 g kg^?1 dietary protein and further increase in the dietary protein does not have any added advantage. There existed no statistically significant difference (P > 0.05) in the specific growth rate, protein efficiency ratio, weight gain and survival rate among the juveniles of M. rosenbergii fed varying plant–animal protein ratios at 300 g kg^?1 protein. Better‐feed conversion ratio was recorded in diets having a plant to animal protein ratio of 1 : 1 (2.62) followed by 1 : 1.5 (2.66), however there was no significant difference between them (P > 0.05). Based on the present study, it would be possible to replace animal protein by low‐cost plant protein in prawn feed. Better growth performance in juveniles of M. rosenbergii can be achieved by the incorporation of equal proportions of plant and animal protein (A : P = 1) in the diet.