# Freshwater Prawn Hatchery Management ## Key Takeaways - **Water quality is paramount for larval survival:** Maintaining specific parameters within defined ranges is critical, with target ranges including salinity (12-16 ppt), temperature (28-31°C), dissolved oxygen (>5 mg/L), pH (7.5-8.5), total ammonia-nitrogen (<0.5 mg/L), and nitrite-nitrogen (<1.0 mg/L). Deviations necessitate immediate corrective actions such as water exchange, aeration adjustments, or buffering. - **Broodstock health and genetic history directly impact hatchery output:** Sourcing broodstock from reputable suppliers and implementing routine health screening for pathogens like IHHNV is essential. Furthermore, understanding that genetic selection for growth can influence reproductive traits necessitates careful consideration of breeding programs. - **Larval rearing requires precise environmental control and nutrition:** Brackish water (12-16 ppt) is mandatory, prepared at least 24 hours in advance. Larvae are filter feeders requiring live food (*Artemia*) from stage II, supplemented with micro-diets (50-200 microns) from stage III, with feeding protocols adjusted based on larval stage and gut fullness assessments. - **Biosecurity and pathogen monitoring are crucial for disease prevention:** Strict facility access, hygiene protocols, and dedicated equipment are vital. Awareness of viral pathogens such as Macrobrachium rosenbergii nodavirus (MrNV) and Macrobrachium rosenbergii Golda Virus (MrGV), which cause significant mortality, underscores the importance of quarantine procedures and ongoing health surveillance. - **Accurate larval stage identification is fundamental for feeding management and survival:** Differentiating between the 11-12 larval stages based on morphological features allows for precise adjustments in feed type, particle size, and feeding frequency, preventing underfeeding, overfeeding, and subsequent water quality degradation or starvation. - **Technological integration and robust record-keeping enhance operational efficiency and disease management:** Implementing automated monitoring systems (IoT) for water quality and maintaining detailed records of broodstock, larval rearing, water parameters, feeding, and mortality are essential for identifying trends, troubleshooting issues, and optimizing production metrics. --- Freshwater prawn hatchery management involves the controlled production of post-larvae (PL) from broodstock through larval rearing, water quality maintenance, and biosecurity protocols. This guide covers the operational decisions, record-keeping requirements, and common failure patterns for hatchery technicians working with *Macrobrachium rosenbergii* and related species. The content draws on published research and official sources to support practical hatchery decisions. ## At a Glance | Parameter | Target Range | Monitoring Frequency | Critical Action if Outside Range | |-----------|--------------|----------------------|----------------------------------| | Salinity (larval rearing) | 12-16 ppt | Twice daily | Adjust with freshwater or brine, check mixing equipment | | Temperature (larval tanks) | 28-31°C | Every 4 hours | Adjust heaters or cooling, check for stratification | | Dissolved oxygen | >5 mg/L | Continuous or every 2 hours | Increase aeration, reduce feeding, check for biofilter failure | | pH | 7.5-8.5 | Daily | Adjust with buffer, check alkalinity, inspect for organic load | | Total ammonia-nitrogen | <0.5 mg/L | Daily | Reduce feeding, increase water exchange, check biofilter | | Nitrite-nitrogen | <1.0 mg/L | Every 2 days | Increase water exchange, check biofilter maturity | | Broodstock holding temperature | 26-28°C | Daily | Adjust heaters, check for disease signs | | Larval stocking density | 50-100 larvae/L | At stocking | Adjust based on tank size and aeration capacity | ## Broodstock Selection and Management ### Source and Health Screening Broodstock quality directly affects larval survival and hatchery output. Source animals from reputable suppliers with documented health records. Wild-caught berried females may carry pathogens. A study on *Macrobrachium rosenbergii* in hatchery production detected infectious hypodermal and haematopoietic necrosis virus (IHHNV) infections in wild berried females collected for hatchery use (Detection and genetic profiling of infectious hypodermal and haematopoietic necrosis virus (IHHNV) infections in wild berried freshwater prawn, Macrobrachium rosenbergii collected for hatchery production, Molecular biology reports, 2012, https://pubmed.ncbi.nlm.nih.gov/21755294). This finding supports routine screening of incoming broodstock. Select females with intact appendages, firm carapace, and active swimming behavior. Males should have large claws and show no signs of injury or disease. Maintain a male-to-female ratio of 1:3 to 1:4 in maturation tanks. ### Reproductive Performance and Selection History Genetic selection for growth rate can influence reproductive traits. A study examining quantitative genetic changes in reproductive performance after 10 years of selection for increased growth rate in giant freshwater prawn found that selection for growth affected reproductive parameters (Quantitative genetic changes in reproductive performance of giant freshwater prawn after 10 years of selection for increased growth rate, Reproduction in domestic animals = Zuchthygiene, 2019, https://pubmed.ncbi.nlm.nih.gov/30180292). Hatchery managers should track reproductive output across generations and consider maintaining separate lines for growth and reproduction if both traits are important. ### Broodstock Holding Systems Use flow-through or recirculating systems with adequate filtration. Provide substrate such as PVC pipes or netting to reduce cannibalism and stress. Feed broodstock a high-protein diet (35-40% crude protein) supplemented with fresh or frozen foods such as squid, mussel, or polychaete worms. Maintain photoperiod at 12-14 hours light per day. Record for each broodstock batch: - Source and date of arrival - Weight and carapace length of females - Mating dates and observed spawning - Egg color and development stage - Health observations and any treatments ## Larval Rearing Systems ### Tank Design and Configuration Larval rearing tanks should have conical or V-shaped bottoms to facilitate water exchange and waste removal. Round or square tanks with rounded corners work well. Tank volume typically ranges from 1 to 10 metric tons depending on production scale. Use dark-colored tanks to reduce light reflection and stress. Provide gentle aeration through air stones or perforated pipes. Aeration should maintain dissolved oxygen above 5 mg/L without creating excessive turbulence that damages larvae. Install heaters with thermostats and backup systems. ### Water Preparation and Salinity Freshwater prawn larvae require brackish water for development. Prepare artificial seawater or use natural seawater diluted to 12-16 ppt. A study on recirculating freshwater prawn hatcheries using artificial seawater evaluated rotating biological contactors for water treatment (Design and performance evaluation of rotating biological contactors for recirculating freshwater prawn (Macrobrachium rosenbergii) hatchery using artificial seawater, Aquaculture International, 2023, https://doi.org/10.1007/s10499-023-01060-4). This technology can reduce water exchange requirements. Mix artificial seawater at least 24 hours before use and aerate vigorously. Check salinity with a refractometer or conductivity meter calibrated daily. Filter water through 1-5 micron cartridges or bag filters before entering larval tanks. ### Larval Stocking Stock larvae at 50-100 per liter depending on tank size, aeration capacity, and management intensity. Lower densities improve survival but reduce total output per tank. Acclimate larvae to tank conditions over 30-60 minutes by gradually mixing tank water with transport water. Record for each larval batch: - Source of larvae (hatchery batch number) - Age at stocking (hours post-hatch) - Stocking density - Initial water quality parameters - Any observed abnormalities ## Water Quality Management ### Critical Parameters and Monitoring Water quality is the most frequently cited cause of larval mortality in freshwater prawn hatcheries. Monitor temperature, salinity, dissolved oxygen, pH, total ammonia-nitrogen, and nitrite-nitrogen at the frequencies listed in the At a Glance table. Keep a logbook with time-stamped entries. Temperature fluctuations above 1°C per hour stress larvae. Maintain stable temperature with heaters and insulation. Salinity changes should not exceed 1 ppt per day during larval development. ### Filtration and Water Exchange Use mechanical filtration to remove solids. Biological filtration through biofilters or rotating biological contactors converts ammonia to nitrate. The study on rotating biological contactors for recirculating freshwater prawn hatcheries using artificial seawater demonstrated that this technology can maintain water quality for larval rearing (Design and performance evaluation of rotating biological contactors for recirculating freshwater prawn (Macrobrachium rosenbergii) hatchery using artificial seawater, Aquaculture International, 2023, https://doi.org/10.1007/s10499-023-01060-4). Water exchange rates depend on system design. Flow-through systems may exchange 100-300% of tank volume daily. Recirculating systems exchange 5-20% daily with continuous treatment. Adjust exchange rates based on ammonia and nitrite levels. ### Algae and Green Water Technique Some hatcheries use green water techniques with microalgae such as *Chlorella* or *Nannochloropsis* to stabilize water quality and provide nutrition. Add algae at 0.5-1.0 x 10^6 cells/mL. Monitor algae density with a hemocytometer or spectrophotometer. Algae can also shade larvae and reduce stress. ## Feeding and Nutrition ### Larval Feeding Protocol Freshwater prawn larvae are filter feeders that require live food during early stages. Feed newly hatched *Artemia* nauplii starting at stage II or III (2-3 days post-hatch). Provide *Artemia* at 1-5 nauplii/mL per day, increasing as larvae grow. Supplement with artificial diets formulated for crustacean larvae. Particle size should match larval mouth size, typically 50-200 microns for early stages and 200-500 microns for later stages. Feed artificial diets 4-6 times daily at 0.5-2.0 g per 1000 larvae per day. ### Feeding Management Observe larval gut fullness and feeding activity. Larvae with full guts appear orange or brown from *Artemia* consumption. Empty guts indicate underfeeding or stress. Adjust feeding rates based on observation. Record for each feeding: - Feed type and batch number - Amount fed - Time of feeding - Larval stage and estimated number - Observations on feeding activity ### Weaning to Post-Larval Diet As larvae metamorphose to post-larvae (PL), gradually reduce *Artemia* and increase artificial diet. PL can accept crumbled or pelleted feeds with 35-40% crude protein. Weaning typically takes 5-7 days. Monitor for size variation and cannibalism during this period. ## Biosecurity Protocols ### Facility Access and Hygiene Restrict access to hatchery buildings. Install footbaths with disinfectant at all entrances. Require dedicated clothing and footwear for each production area. Use separate equipment for broodstock, larval, and post-larval areas. Disinfect tanks, pipes, and equipment between production cycles. Use chlorine at 200 ppm for 30 minutes followed by thorough rinsing and drying. Test for residual chlorine before restocking. ### Pathogen Monitoring Several viruses affect freshwater prawn hatcheries. Macrobrachium rosenbergii nodavirus (MrNV) causes white tail disease and can cause significant losses. A study on a DNA vaccine for MrNV showed protective immunity in giant freshwater prawn (Macrobrachium rosenbergii nodavirus (MrNV)-CP-RNA-2 DNA vaccine confers protective immunity in giant freshwater prawn Macrobrachium rosenbergii against MrNV infection, Fish & shellfish immunology, 2019, https://pubmed.ncbi.nlm.nih.gov/30471336). While vaccines are not yet commercially available, this research indicates potential future tools. A novel RNA virus, Macrobrachium rosenbergii Golda Virus (MrGV), has been linked to mass mortalities of larval giant freshwater prawn in Bangladesh (A Novel RNA Virus, Macrobrachium rosenbergii Golda Virus (MrGV), Linked to Mass Mortalities of the Larval Giant Freshwater Prawn in Bangladesh, Viruses, 2020, https://pubmed.ncbi.nlm.nih.gov/33023199). The complete genome sequence of MrGV from China has also been reported (Complete Genome Sequence of Macrobrachium rosenbergii Golda Virus (MrGV) from China, Animals, 2021, https://pubmed.ncbi.nlm.nih.gov/35011135). Hatchery managers should be aware of these pathogens and include them in health monitoring programs. ### Quarantine Procedures Quarantine all incoming broodstock for at least 14 days in a separate facility or isolated system. Observe for signs of disease including lethargy, anorexia, discoloration, or abnormal swimming. Test a sample of animals for common pathogens before introducing to the main hatchery. ### Waste and Effluent Management Treat all hatchery effluent before discharge. Use sedimentation, filtration, and disinfection. Follow local regulations for aquaculture effluent. The FAO provides guidance on sustainable aquaculture practices including waste management (FAO Animal Production and Health, Food and Agriculture Organization of the United Nations, https://www.fao.org/animal-production/en). ## Disease Recognition and Response ### Common Disease Signs Monitor larvae and post-larvae daily for: - Reduced feeding activity - Lethargy or weak swimming - Discoloration (white, red, or opaque areas) - Body deformities - Attachment of parasites or fouling organisms - Sudden increase in mortality ### Diagnostic Procedures When disease is suspected, collect moribund or freshly dead animals for examination. Preserve samples in 95% ethanol or 10% formalin for laboratory analysis. Contact a veterinary diagnostic laboratory with experience in crustacean diseases. The USDA Agricultural Research Service conducts research on aquaculture health and disease management (USDA Agricultural Research Service, https://www.ars.usda.gov/animal-production-and-protection/aquaculture). The USDA National Agricultural Library provides resources on animal health and welfare including aquatic species (Animal Health and Welfare, USDA National Agricultural Library, https://www.nal.usda.gov/animal-health-and-welfare). ### Escalation Criteria Contact a veterinarian or aquatic animal health specialist when: - Mortality exceeds 5% per day for two consecutive days - Unusual clinical signs appear in multiple tanks - Known notifiable disease is suspected - Treatment attempts fail to improve condition ## Records and Measurements ### Essential Records Maintain the following records for each production cycle: - Broodstock source, weight, and spawning dates - Larval stocking date, density, and source - Daily water quality parameters - Daily feeding amounts and feed types - Mortality counts and estimated survival - Disease observations and treatments - Post-larval harvest date, count, and size ### Survival and Production Metrics Calculate survival at key stages: - Hatching rate: number of larvae hatched / number of eggs - Larval survival to PL: number of PL harvested / number of larvae stocked - Overall hatchery survival: number of PL harvested / number of eggs Track production per tank and per cycle. Compare performance across cycles to identify trends. The FAO provides species-specific culture information including production metrics for *Macrobrachium rosenbergii* (FAO Fisheries and Aquaculture, https://www.fao.org/fishery/en/culturedspecies). ## Common Failure Patterns ### Water Quality Crashes Sudden drops in dissolved oxygen or spikes in ammonia often result from overfeeding, biofilter failure, or power outages. Install backup aeration systems and alarms. Train staff to recognize early warning signs such as reduced feeding activity or larvae gathering at the water surface. ### Disease Outbreaks Viral diseases such as MrNV and MrGV can cause catastrophic losses. The study linking MrGV to mass mortalities in Bangladesh highlights the risk (A Novel RNA Virus, Macrobrachium rosenbergii Golda Virus (MrGV), Linked to Mass Mortalities of the Larval Giant Freshwater Prawn in Bangladesh, Viruses, 2020, https://pubmed.ncbi.nlm.nih.gov/33023199). Prevention through biosecurity is more effective than treatment. ### Cannibalism and Size Variation Cannibalism increases when larvae are underfed, overcrowded, or have size variation. Grade larvae by size at regular intervals. Provide adequate food and shelter. Maintain stocking densities within recommended ranges. ### Equipment Failure Heater failure, pump breakdown, or aeration loss can cause rapid mortality. Maintain spare equipment and conduct regular inspections. Install alarms for temperature, dissolved oxygen, and power failure. ## Technology Integration ### Monitoring and Control Systems Internet of Things (IoT) and machine learning technologies are being applied to freshwater prawn farming for enhanced efficiency and disease management (Applying IoT and Machine Learning for Enhanced Efficiency and Disease Management, Advancing Sustainability in Freshwater Prawn Farming, 2024 3rd International Conference on Artificial Intelligence for Internet of Things Aiiot 2024, 2024, https://doi.org/10.1109/AIIoT58432.2024.10574631). These systems can monitor water quality continuously and alert staff to deviations. Consider implementing automated monitoring for temperature, dissolved oxygen, pH, and salinity. Data logging systems can track trends and support decision-making. Start with simple sensors and expand as experience grows. ### Recirculating Aquaculture Systems Recirculating systems reduce water use and improve biosecurity. The study on rotating biological contactors for recirculating freshwater prawn hatcheries using artificial seawater provides a design option for water treatment (Design and performance evaluation of rotating biological contactors for recirculating freshwater prawn (Macrobrachium rosenbergii) hatchery using artificial seawater, Aquaculture International, 2023, https://doi.org/10.1007/s10499-023-01060-4). Evaluate system costs, maintenance requirements, and reliability before adoption. ## Seed Production and Distribution ### Post-Larval Harvest and Grading Harvest PL when they reach stage XI or XII, typically 25-35 days post-hatch. Drain tanks and collect PL in mesh nets. Grade by size using mesh screens or manual sorting. Count PL by weight or volume using established conversion factors. ### Transportation and Acclimation Transport PL in oxygenated bags or tanks at 20-25°C. Acclimate to freshwater over 2-4 hours before stocking in nursery ponds or tanks. Monitor survival during transport and after stocking. ### Technology Transfer The development and transfer of seed production technology has supported freshwater prawn culture expansion in countries such as Vietnam (Current status of freshwater prawn culture in Vietnam and the development and transfer of seed production technology, Fisheries Science, 2006, https://doi.org/10.1111/j.1444-2906.2006.01109.x). Hatchery managers should stay informed about advances in seed production methods and consider participating in technology transfer programs. ## Welfare and Safety Considerations ### Larval Welfare Minimize handling stress during stocking, grading, and harvest. Maintain stable water quality and appropriate stocking densities. Provide adequate nutrition and shelter. Remove dead and moribund animals promptly. ### Worker Safety Hatchery work involves electrical equipment, water, and chemicals. Follow electrical safety practices including ground fault circuit interrupters. Use personal protective equipment when handling disinfectants and cleaning agents. Train staff on emergency procedures including first aid for chemical exposure. ### Food Safety Post-larvae destined for grow-out should be free from notifiable diseases. Maintain records of treatments and withdrawals. Follow local regulations for aquaculture health certification. ## Larval Stage Identification and Feeding Transition Protocol Accurate larval stage identification is the foundation of feeding management and survival optimization in freshwater prawn hatcheries. Without reliable staging, feeding schedules become guesswork and mortality patterns remain unexplained. This section provides a practical framework for staging larvae, adjusting feed types and particle sizes at each transition point, and recording observations that support timely management decisions. ### Larval Stage Characteristics and Identification *Macrobrachium rosenbergii* larvae pass through 11 to 12 distinct stages before metamorphosis to post-larvae. Each stage has recognizable morphological features that determine feeding capability and nutritional requirements. Use a dissecting microscope or strong hand lens at 10-40x magnification to examine larvae daily. Collect 10-20 larvae from each tank using a wide-bore pipette to avoid damage. Place them in a shallow dish with tank water and observe under good lighting. Stage I larvae are newly hatched, measuring 1.5-2.0 mm total length. They have a large yolk sac and do not feed externally. The body is transparent with three pairs of appendages. No feeding is required during this stage, which lasts 24-36 hours at 28-30°C. Stage II larvae show yolk sac absorption and begin active swimming. The rostrum becomes visible and the eyes are pigmented. This is the first feeding stage. Offer newly hatched *Artemia* nauplii at 1-2 nauplii/mL. Do not offer artificial feed at this stage as larvae cannot capture particles effectively. Stage III to V larvae develop functional maxillipeds and begin filter feeding. The body becomes more elongated and the tail fan appears. Increase *Artemia* density to 3-5 nauplii/mL. Begin offering artificial microdiets with particle sizes of 50-100 microns at 0.5 g per 1000 larvae per day. Observe gut fullness to confirm feeding. Stage VI to VIII larvae show distinct segmentation and developing pleopods. The rostrum has dorsal teeth. Feeding activity increases substantially. Maintain *Artemia* at 5-8 nauplii/mL. Increase artificial feed particle size to 100-200 microns and feed rate to 1.0-1.5 g per 1000 larvae per day. Stage IX to XI larvae have fully developed pleopods and begin swimming with the abdomen curved. The uropods are well formed. Reduce *Artemia* gradually to 3-5 nauplii/mL. Increase artificial feed particle size to 200-400 microns and feed rate to 1.5-2.0 g per 1000 larvae per day. Stage XII or post-larvae (PL) have the adult body form with a curved abdomen and functional walking legs. They swim forward instead of backward. Discontinue *Artemia* and offer crumbled or pelleted feed with 35-40% crude protein at 2.0-3.0 g per 1000 PL per day. ### Feeding Transition Decision Framework Use the following decision framework to adjust feeding based on stage progression and observed feeding behavior. This framework replaces guesswork with structured observation and response. Step 1: Stage confirmation. Examine larvae from each tank every morning before the first feeding. Record the dominant stage and the range of stages present. If more than 20% of larvae are at a different stage than the majority, note this as size variation. Step 2: Gut fullness assessment. Two hours after feeding, examine 10-20 larvae from each tank. Score gut fullness on a 0-3 scale where 0 is empty, 1 is partially full, 2 is mostly full, and 3 is completely full. A score below 1.5 indicates underfeeding or poor feed acceptance. Step 3: Feed adjustment. If gut fullness score is below 1.5, increase feed amount by 20% or adjust particle size to match the dominant stage. If score is above 2.5 and water quality is deteriorating, reduce feed amount by 10-15%. Step 4: Stage transition timing. When 50% or more of larvae reach a new stage, adjust feed type and particle size within 12 hours. Delaying this adjustment by more than 24 hours reduces growth and increases mortality. Step 5: Size grading trigger. When the range of stages spans three or more stages (for example, stages IV through VII), grade larvae by size using mesh screens. Grade immediately to reduce cannibalism and competition. ### Records and Measurements for Feeding Management Maintain a daily larval stage and feeding record for each tank. Include the following fields: - Tank identification number - Date and time of observation - Dominant larval stage (I through XII or PL) - Range of stages present - Gut fullness score (0-3 average) - *Artemia* density (nauplii/mL) before feeding - Artificial feed type and batch number - Artificial feed particle size range (microns) - Amount of artificial feed offered (g per 1000 larvae) - Amount of *Artemia* offered (nauplii per larva) - Estimated feed consumption (percentage of offered feed consumed within 2 hours) - Water quality parameters at time of feeding (temperature, salinity, dissolved oxygen) - Staff initials Calculate feed conversion ratio for each larval batch by dividing total dry feed offered by total larval biomass gain. Track this metric across cycles to identify trends and improve feeding efficiency. ### Common Failure Patterns in Feeding Transitions Delayed stage transition is the most common feeding-related failure. When larvae remain at the same stage for more than three days, check temperature, salinity, and feed quality. Low temperature below 27°C slows development. Salinity below 10 ppt reduces feeding activity. Poor quality *Artemia* with low hatch rate or nutrient content also delays development. Overfeeding artificial diets before larvae can capture particles causes water quality deterioration and increased ammonia levels. Do not offer artificial feed before stage III. When starting artificial feed, offer small amounts and confirm consumption by checking gut fullness and observing feed particles in the water column after 30 minutes. Underfeeding *Artemia* during stages II through V causes starvation and size variation. Larvae at these stages rely almost entirely on live feed. If *Artemia* supply is limited, prioritize early stages and reduce stocking density instead of reducing feed per larva. Cannibalism increases when larvae at different stages are mixed without grading. The larger larvae prey on smaller ones, especially during molting. Grade immediately when stage range exceeds three stages. Provide shelter such as fine mesh netting or artificial substrate to reduce contact between larvae. ### Welfare and Safety Context Proper feeding management directly supports larval welfare. Starved larvae show reduced swimming activity, increased susceptibility to disease, and higher mortality. Overfed larvae experience poor water quality and increased stress. The gut fullness scoring system provides a simple welfare indicator that staff can assess without specialized equipment. Worker safety during feeding includes handling live *Artemia* cysts and artificial feeds. *Artemia* cysts may contain allergens. Wear gloves and a dust mask when handling dry cysts. Store artificial feeds in sealed containers in a cool, dry location to prevent mold growth and pest infestation. The USDA National Agricultural Library provides resources on animal health and welfare including guidance on aquaculture species (Animal Health and Welfare, USDA National Agricultural Library, https://www.nal.usda.gov/animal-health-and-welfare). The FAO offers species-specific culture information for *Macrobrachium rosenbergii* including feeding recommendations (FAO Fisheries and Aquaculture, https://www.fao.org/fishery/en/culturedspecies). ## Frequently Asked Questions ### What salinity is required for freshwater prawn larval rearing? Freshwater prawn larvae require brackish water at 12-16 ppt for normal development. Lower salinity reduces survival and growth. Higher salinity increases osmotic stress. Maintain salinity within this range throughout the larval period. ### How long does it take for freshwater prawn larvae to reach post-larvae? Under optimal conditions at 28-31°C, larvae reach post-larval stage XI or XII in 25-35 days. Lower temperatures slow development. Higher temperatures accelerate development but may reduce survival. Monitor larval stage progression daily. ### What causes white tail disease in freshwater prawn larvae? White tail disease is caused by Macrobrachium rosenbergii nodavirus (MrNV). Clinical signs include white or opaque tail muscle, lethargy, and mortality. Prevention through biosecurity is essential. Research on DNA vaccines shows promise for future control (Macrobrachium rosenbergii nodavirus (MrNV)-CP-RNA-2 DNA vaccine confers protective immunity in giant freshwater prawn Macrobrachium rosenbergii against MrNV infection, Fish & shellfish immunology, 2019, https://pubmed.ncbi.nlm.nih.gov/30471336). ### How can I prevent cannibalism in larval rearing tanks? Prevent cannibalism by maintaining adequate feeding rates, grading larvae by size, providing shelter such as netting or substrate, and avoiding overcrowding. Monitor for size variation and separate larger individuals if needed. ### What water quality parameters are most critical for larval survival? Temperature, salinity, dissolved oxygen, and ammonia are the most critical parameters. Maintain temperature at 28-31°C, salinity at 12-16 ppt, dissolved oxygen above 5 mg/L, and total ammonia-nitrogen below 0.5 mg/L. Monitor these parameters at least daily. ### Can I use artificial seawater for freshwater prawn hatcheries? Yes, artificial seawater can be used for larval rearing. The study on rotating biological contactors for recirculating freshwater prawn hatcheries using artificial seawater demonstrates that this approach is feasible (Design and performance evaluation of rotating biological contactors for recirculating freshwater prawn (Macrobrachium rosenbergii) hatchery using artificial seawater, Aquaculture International, 2023, https://doi.org/10.1007/s10499-023-01060-4). Mix artificial seawater at least 24 hours before use and verify salinity. ### What should I do if I suspect a viral disease outbreak in my hatchery? Isolate affected tanks immediately. Reduce feeding and water exchange to minimize stress. Collect samples of moribund animals for laboratory diagnosis. Contact a veterinary diagnostic laboratory or aquatic animal health specialist. Report notifiable diseases to local authorities. ### How do I select broodstock for optimal hatchery performance? Select broodstock from reputable sources with documented health records. Choose females with intact appendages and firm carapace. Maintain a male-to-female ratio of 1:3 to 1:4. Consider genetic background and selection history, as selection for growth can affect reproductive performance (Quantitative genetic changes in reproductive performance of giant freshwater prawn after 10 years of selection for increased growth rate, Reproduction in domestic animals = Zuchthygiene, 2019, https://pubmed.ncbi.nlm.nih.gov/30180292). ## Related Farming Guides - [Aquaculture Water Quality Monitoring](/knowledge/animal-farming/aquaculture/aquaculture-water-quality-monitoring) - [Shrimp Farming Biosecurity Water Management And Crop Observation](/knowledge/animal-farming/aquaculture/shrimp-farming-biosecurity-water-management-and-crop-observation) - [Freshwater Prawn Farming Stocking Shelter Feeding And Harvest Management](/knowledge/animal-farming/aquaculture/freshwater-prawn-farming-stocking-shelter-feeding-and-harvest-management) - [Pullet Rearing Management For Laying Hens](/knowledge/animal-farming/poultry/pullet-rearing-management-for-laying-hens) - [Fish Farming Water Feed Stocking Biosecurity Welfare And Harvest Decisions](/knowledge/animal-farming/aquaculture/fish-farming-water-feed-stocking-biosecurity-welfare-and-harvest-decisions) ## Related Clinical & Scientific Guides * [Pond Sediment Management and Dredging Options](/knowledge/animal-farming/aquaculture/pond-sediment-management-dredging-options) * [Indoor Aquaculture Facilities: Lighting and Insulation](/knowledge/animal-farming/aquaculture/indoor-aquaculture-facilities-lighting-insulation) * [Greenhouse Aquaculture: Extending Growing Seasons](/knowledge/animal-farming/aquaculture/greenhouse-aquaculture-extending-growing-seasons) ## References and Further Reading - [www.fao.org](https://www.fao.org/fishery/en/culturedspecies) - [www.ars.usda.gov](https://www.ars.usda.gov/animal-production-and-protection/aquaculture) - [FAO Animal Production and Health](https://www.fao.org/animal-production/en). Food and Agriculture Organization of the United Nations. - [Animal Health and Welfare](https://www.nal.usda.gov/animal-health-and-welfare). USDA National Agricultural Library. - [Macrobrachium rosenbergii nodavirus (MrNV)-CP-RNA-2 DNA vaccine confers protective immunity in giant freshwater prawn Macrobrachium rosenbergii against MrNV infection.](https://pubmed.ncbi.nlm.nih.gov/30471336). Fish & shellfish immunology, 2019. - [Detection and genetic profiling of infectious hypodermal and haematopoietic necrosis virus (IHHNV) infections in wild berried freshwater prawn, Macrobrachium rosenbergii collected for hatchery production.](https://pubmed.ncbi.nlm.nih.gov/21755294). Molecular biology reports, 2012. - [A Novel RNA Virus, Macrobrachium rosenbergii Golda Virus (MrGV), Linked to Mass Mortalities of the Larval Giant Freshwater Prawn in Bangladesh.](https://pubmed.ncbi.nlm.nih.gov/33023199). Viruses, 2020. - [Quantitative genetic changes in reproductive performance of giant freshwater prawn after 10 years of selection for increased growth rate.](https://pubmed.ncbi.nlm.nih.gov/30180292). Reproduction in domestic animals = Zuchthygiene, 2019. - [Predation and control of laboratory populations of the snail Biomphalaria glabrata by the freshwater prawn Macrobrachium rosenbergii.](https://pubmed.ncbi.nlm.nih.gov/2260905). Annals of tropical medicine and parasitology, 1990. - [Complete Genome Sequence of Macrobrachium rosenbergii Golda Virus (MrGV) from China.](https://pubmed.ncbi.nlm.nih.gov/35011135). Animals : an open access journal from MDPI, 2021. - [Applying IoT and Machine Learning for Enhanced Efficiency and Disease Management, Advancing Sustainability in Freshwater Prawn Farming](https://doi.org/10.1109/AIIoT58432.2024.10574631). 2024 3rd International Conference on Artificial Intelligence for Internet of Things Aiiot 2024, 2024. - [Design and performance evaluation of rotating biological contactors for recirculating freshwater prawn (Macrobrachium rosenbergii) hatchery using artificial seawater](https://doi.org/10.1007/s10499-023-01060-4). Aquaculture International, 2023. - [Current status of freshwater prawn culture in Vietnam and the development and transfer of seed production technology](https://doi.org/10.1111/j.1444-2906.2006.01109.x). Fisheries Science, 2006. > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.