How to Farm Penaeus Vannamei: A Comprehensive Guide to White Shrimp Farming – Biology, Culture, and Practices

Introduction:

Penaeus vannamei, also known as the South American White Shrimp, whiteleg shrimp, or Pacific white shrimp, is a globally dominant species in shrimp aquaculture. Originating from the Pacific coast of South America, particularly concentrated around Ecuador, it’s one of the top three shrimp species in terms of production volume. This article provides a comprehensive overview of P. vannamei, covering its biology, life cycle, farming requirements, feeding strategies, and disease prevention, with a focus on optimizing production for a successful aquaculture operation.

Advantages of P. vannamei Farming:

Compared to other farmed shrimp species, P. vannamei offers several key advantages:

• Long Breeding Cycle: Allows for year-round seedstock production.
• High Resilience: Strong tolerance to changes in water parameters, making it suitable for both saltwater and brackish water pond farming. They have very high adaptability to a wide range of salinities from 0.5 ppt up to 45 ppt.
• Extended Shelf Life Out of Water: Enables live shrimp sales, commanding higher prices.
• Rapid Growth: Adaptable and disease-resistant, allowing for high-density farming with survival rates typically exceeding 70%.
• Lower Protein Feed Requirements: Can thrive on feed with 25-30% protein content, reducing feed costs. Some studies say even as low as 18-35%.
• High Meat Yield: Thin shell and small head, resulting in a meat yield of over 65%.

Biological Characteristics:

P. vannamei belongs to the Arthropoda phylum, Crustacea class, Decapoda order, Penaeidae family, and Penaeus genus. It closely resembles the Chinese shrimp (Penaeus chinensis) and can reach a maximum length of 23 cm. Key morphological features include:

• Thin Exoskeleton: A light bluish-grey (or white) body.
• Rostrum: Slightly curved downwards, with the tip not extending beyond the second segment of the first antennae. The teeth formula of rostrum is 2-9/2-4.
• Short Cephalothorax: Results in a higher meat yield. The cephalothorax has a short lateral groove that disappears below the epigastric tooth.
• Distinct Appendages: The first antennae have two flagella of roughly equal length. The first three pairs of walking legs have well-developed exopods (outer branches), while the fourth and fifth pairs lack them.
• Open Thelycum: Females lack a spermatheca (sperm storage organ), making it an “open” type. This can make obtaining fertilized eggs more challenging.
• Petasma: Males have a modified endopod on the first abdominal appendage, forming a copulatory organ with distinct grooves and protrusions.

I. Morphological Characteristics:

P. vannamei shares similarities with Penaeus chinensis and Penaeus merguiensis. Key features:

• Coloration: Typically a bluish-grey, with no patterns, and chalky white walking legs (hence the name “whiteleg shrimp”).
• Rostrum: The tip does not extend beyond the second segment of the first antennae.
• Cephalothorax to Abdomen Ratio: Approximately 1:3, contributing to a high meat yield.
• Spines: Possesses hepatic and antennal spines on the cephalothorax, but lacks adrostral and branchiostegal spines. A clear hepatic ridge is present.
• First Antennae: Double flagella, with the inner flagellum thinner and about 1/3 the length of the first antennal segment.
• Walking Legs: Well-developed exopods on the first three pairs, none on the fourth and fifth, with a rudimentary exopod on the fifth.
• Abdomen: Dorsal ridges on the fourth to sixth segments. The telson has a central groove but no marginal spines.
• Open Thelycum: The mature individuals have an inverted “Q” shaped external structure where the thelycum normally is.

II. Life Cycle:

In their natural marine habitat, P. vannamei follows a distinct life cycle:

1. Adult Stage: Adults move to deeper waters (around 70 meters) with temperatures of 26-28°C and salinity of 34‰. They mature, mate, and spawn here.
2. Larval Stages: Eggs hatch into planktonic larvae, progressing through nauplius, zoea, and mysis stages in the stable offshore environment.
3. Post-larvae: Post-larvae migrate towards shallower coastal areas, including estuaries and bays, rich in nutrients.
4. Juvenile Stage: Juveniles thrive in these nearshore environments, benefiting from the fluctuating salinity and temperature.
5. Return to Deep Water: As they mature into adults, they return to the deeper ocean to complete the reproductive cycle.
   The whole life cycle takes around 1.5 years.

III. Environmental Requirements:

For successful aquaculture, P. vannamei requires specific water conditions:

• Temperature: Optimal range is 25-32°C. They can tolerate up to 43.5°C with gradual warming but are sensitive to cold. Feeding stops below 18°C, and mortality begins at 9°C.
• Salinity: Highly adaptable, tolerating 5-45‰, with an optimal range of 10-25‰. They can even grow in freshwater (0-2‰) with gradual acclimation.
• pH: Optimal range is 8.0 ± 0.3, with a tolerance range of 7.3-8.6. Activity decreases below pH 7 or above 9.5.
• Dissolved Oxygen (DO): Can tolerate low DO levels (minimum 1.2 mg/L), but aquaculture requires levels above 4.0 mg/L, and never below 2.0 mg/L. This is where aeration becomes crucial.
• Water Color: Oil-green or reddish-brown water is preferred.

IV. Molting and Growth:

Shrimp growth is directly linked to molting:

• Molting Frequency: Larvae at 28°C molt every 30-40 hours. Molting is also influenced by the lunar cycle, with increased molting around the new and full moon. Shrimp over 15g molt most frequently (45-73% of the population) within 5 days before or after the new or full moon.
• Environmental and Nutritional Factors: Lower salinity and higher temperatures increase molting frequency. Stress from environmental changes or chemical treatments can also trigger molting. Balanced nutrition is essential for successful molting.
• Growth Rate: P. vannamei grows rapidly. In salinities of 20-40‰ and temperatures of 30-32°C without feeding, they can reach 40g in 180 days, growing from 1 cm to over 14 cm.
• Ovarian Maturation: Ovarian maturation is difficult in pond conditions. In the wild, females with a cephalothorax length of around 40 mm show signs of egg development.
• Lifespan: Females typically mature after 12 weeks and have an average lifespan of at least 32 months.

V. Feeding Habits:

While traditionally considered omnivorous scavengers, recent research indicates a preference for a more carnivorous diet in the wild, primarily consuming small crustaceans and copepods. Key points:

• Growth in Different Environments: Studies show that P. vannamei grow about 50% slower in clear laboratory conditions with only artificial feed compared to outdoor ponds with soil bottoms and rich algae/microbial communities.
• Protein Requirements: P. vannamei has a relatively low protein requirement. 25-30% protein in artificial feed is sufficient. Higher protein levels may not improve growth and can even be detrimental.
• Soybean Meal: Soybean meal is a palatable and effective feed ingredient, potentially comprising 53-75% of the diet.
• Feeding Behavior: While wild shrimp don’t actively hunt, they will feed during the day if stimulated by nearby food. Growth is faster with more frequent feeding. A feeding schedule of 25-35% during the day and 65-75% at night is considered optimal.
• Feed Conversion: P. vannamei has efficient feed conversion. Under normal growth, they consume about 5% of their body weight. During reproduction, especially during ovarian development, consumption increases significantly (3-5 times).

VI. Reproductive Habits:

• Breeding Period: P. vannamei has a long breeding season, with spawning occurring year-round in their main distribution areas. However, peak seasons vary (e.g., April-September in northern Ecuador, December-April in Peru).
• Open vs. Closed Thelycum: P. vannamei has an open thelycum, differing significantly from species with closed thelyca.
  • Open Thelycum (e.g., P. vannamei): Molting (female) → Maturation → Mating (fertilization) → Spawning → Hatching
  • Closed Thelycum (e.g., Penaeus chinensis): Molting (female) → Mating → Maturation → Spawning (fertilization) → Hatching
  The open thelycum makes artificial breeding more difficult due to the easy detachment of the spermatophore.
• Mating: Mating typically occurs at sunset, a few hours before or after spawning. Mature females don’t need to molt before mating. The male approaches the female, engaging in courtship behavior, then positions himself below the female, transferring the spermatophore to the area between the 3rd-5th pairs of walking legs.
• Spawning and Fecundity: Mature eggs are red, but spawned eggs are bean-green. A shrimp around 14 cm long typically produces 100,000-150,000 eggs. P. vannamei can spawn multiple times, with intervals of 2-3 days.
• Male Maturation: Male spermatophores can also be repeatedly formed, but maturation takes longer (about 20 days between spermatophore expulsions). Unilateral eyestalk ablation can accelerate spermatophore development.
• Darkness and lower temperature will inhibit the development of ovaries.
• Unmated females can spawn but the eggs will not be fertilized.

VII. Freshwater Acclimation and Farming Techniques:

P. vannamei‘s adaptability makes it suitable for freshwater farming:

1. Basic Requirements:

• Location: Access to ample, clean water, convenient transportation, reliable power, and no pollution sources within 3-5 km.
• Pond Design: 3000-7000 m² ponds are ideal, with a rectangular shape (east-west orientation), water depth of 2.0 meters, a flat bottom, a dike width of at least 2 meters, and separate inlet and outlet canals.
• Equipment: Each pond needs a power supply and aeration equipment. Approximately 1 kW of aeration power per 1000 m² is recommended, combining methods like paddle wheel aerators, impeller aerators, or Blower with bottom aeration tubes. For optimal oxygenation, especially in high-density farming, Paddle wheel aerators are highly effective. Products like those from Synergy Spray Systems offer robust and efficient aeration, with models like the 2 HP 4 Paddle Wheel Aerator being suitable for many shrimp ponds. These aerators help maintain dissolved oxygen levels, reduce ammonia and nitrite concentrations, and improve overall water quality.

2. Pre-Stocking Preparation:

• Pond Clearing: Remove weeds and excess silt during winter. Repair and sun-dry the pond bottom until cracked.
• Disinfection: About a month before stocking, use lime (100-150 kg/1000 m²), bleach (15-20 kg/1000 m²), or tea seed cake (50 kg/1000 m²) to eliminate pathogens and fish eggs. Lime is generally preferred.
• Water Intake: After the disinfectant’s effect dissipates (about 10 days before stocking), add water. If filamentous algae are present, add water to 10 cm, apply a moss killer, and then fill to 40-50 cm for fertilization. Use a 60-mesh filter at the inlet to prevent unwanted organisms.
• Fertilization: Cultivating a base food supply is crucial for shrimp survival and growth. Methods include:
  • Organic Fertilizer: Use fully fermented organic fertilizer (around 25 kg/mu, adjusted based on pond conditions). Mix with lime for disinfection.
  • Ammonium Carbonate and Phosphate Fertilizer: Use about 20 kg/mu, with a 3:1 ratio of ammonium carbonate to phosphate.
  • Commercial Organic Fertilizers: Products like specialized P. vannamei organic fertilizers can be used (20-40 kg/mu), often combined with compound fertilizers.
  • Other Options: Bio-fertilizers and active water conditioners are also available. The best result will be an organic fertilizer, chemical fertilizer and bio-fertilizer combination.

3. Shrimp Seed Stocking:

• Seed Selection:
  • Choose first or second-generation (F1 or F2) seedlings, especially SPF (Specific Pathogen Free) stock.
  • Select healthy seedlings: Active, strong, with complete appendages, clean body surface, normal body shape, uniform size, and full, clear intestines.
• Size: Around 1 cm.
• Salinity: Below 3‰, matching the pond’s salinity.
• Trial Stocking: Before full stocking, test a small batch of seedlings in a container with pond water. If no mortality occurs after 12 hours, proceed with stocking.
• Stocking Time: Ideal water temperature is above 23°C (typically May-June in many regions).
• Stocking Density: 40,000-60,000 shrimp per mu is typical. Stock in the morning or evening on a clear day, avoiding midday sun or rainy weather.
• Water Quality:
  • Water Color: Yellow-green or tea-brown.
  • Transparency: 30-40 cm.
  • pH: 7.8-9.0.
  • Salinity: Close to the nursery pond’s salinity.
  • Temperature: Difference should not exceed 2°C. Acclimate seedlings by placing the transport bags in the pond for 10-15 minutes before release.

4. Feeding Techniques:

• Feed Selection: Choose high-quality, pollution-free P. vannamei feed.
• Feed Requirements: Vary with growth stage:
  • <6 cm (Juvenile): High protein and unsaturated fatty acid needs (protein >38%).
  • 6-10 cm (Medium): Protein can be slightly reduced (36-38%).
  • >10 cm (Adult): Protein content of 32-36% is sufficient.
• Feeding Amount: Adjust based on weather, survival rate, estimated biomass, and leftover feed.
  • Early Stage (first 2 weeks): Small amounts of starter feed or crushed feed.
  • Juvenile Stage: Feed #1 (protein >38%), feeding time 2-3 hours.
  • Medium Stage: Feed #2 (protein 36-38%), feeding time 1-2 hours.
  • Adult Stage: Feed #3 (protein 32-36%), feeding time around 1 hour.
• Feeding times: When feeding twice daily, use an early morning feeding time, and an evening feeding time.
• Feeding Strategies:
  • Feed frequently in small amounts.
  • Reduce or stop feeding when water temperature is below 15°C or above 32°C.
  • Increase feeding on warm, sunny days; reduce or stop during storms, cold snaps (temperature drops >5°C).
  • Reduce feeding on the day of mass molting; increase after molting.
  • Increase feeding when water quality is good; reduce or stop when it deteriorates.

5. Water Quality Management:

• Water Color Control: Maintain a yellow-green or tea-brown color. Transparency should be 30-40 cm in the early stages and around 30 cm in later stages. Add fresh water every 7-10 days, and consider using microbial preparations every 10-15 days to improve water quality.
• pH Adjustment: Keep pH within 7.8-8.6. Use lime to raise pH if it’s too low, but avoid exceeding 9.0.
• Bottom Improvement: Use bottom-improving agents, especially in the later stages of farming when organic matter accumulates.
• Oxygen Monitoring: Oxygen demand increases as shrimp grow. Use Paddle wheel aerators intermittently in the early stages, gradually increasing the operating time as shrimp grow. This ensures dissolved oxygen levels remain above 5 mg/L, with bottom oxygen above 3 mg/L. Bottom aeration agents can also be used. Synergy Spray Systems’ aerators, for instance, are designed to reduce ammonia, nitrite, and carbon dioxide levels while increasing pH and overall pond productivity.
• Aerator Operation: For the first month, operate aerators for 2-3 hours during rainy weather or when adding water. After a month, run aerators daily at noon and night for 2-4 hours, gradually increasing the duration. Extend operation or run continuously during cloudy/rainy days or when water quality is poor.
• Water Quality Testing: Regularly measure pH, dissolved oxygen, ammonia, nitrite, and transparency. Address any issues promptly.

6. Disease Prevention:

• Strengthen Resistance: Use products like “Stress King” in the water and add multivitamins and immune-boosting supplements to the feed to enhance disease resistance.
• Oxygen Management: Prevent oxygen deficiency (floating or “dark floating”) by using aerators and oxygen-increasing agents.
• Environmental Improvement: Use microbial preparations and bottom improvers to maintain water quality and balance the algal and bacterial communities.
• Regular Monitoring: Test water quality regularly to maintain optimal conditions.
• Drug Prevention: Use disinfectants like bromine, chlorine dioxide, or povidone-iodine. Administer internal medications with anti-stress properties (e.g., multivitamins, vitamin C, immune polysaccharides).
• Sick and dead shrimp: Sick/dead shrimp must be removed immediately, and the cause of disease/death must be found.

7. Harvesting:

• Preparation: After about 90 days, when shrimp reach a size of around 120 individuals per kilogram, prepare for harvest. Conduct market research, contact buyers, and understand weather forecasts.
• Harvesting Methods: Use ground cages, seine nets, or drain the pond.
• Phased Harvesting: Catch larger shrimp first, leaving smaller ones to grow.
• Pre-Typhoon Harvesting: If a typhoon is approaching, harvest based on shrimp size to reduce pond load.
• Avoid Cold Snaps: Do not harvest during sudden temperature drops (over 8°C).
• Early Harvesting: Harvest early if water quality deteriorates or shrimp show abnormal behavior.

By following these guidelines, farmers can optimize P. vannamei production, achieving high yields and profitability while maintaining sustainable practices. The use of appropriate technology, such as high-quality paddle wheel aerators, is essential for maintaining optimal water quality and ensuring the success of the shrimp farming operation.