Prawn farming, also known as freshwater or marine shrimp aquaculture, is a lucrative sector in the global aquaculture industry. Understanding the growth rate of prawns is crucial for optimizing production, feed management, and profitability in commercial farming. The growth rate of prawns depends on various factors, including species, water quality, feed, stocking density, and environmental conditions.
The monthly growth rate of prawns in commercial farming, focusing on key species such as Macrobrachium rosenbergii (Giant Freshwater Prawn) and Penaeus vannamei (Whiteleg Shrimp). We will examine growth patterns, influencing factors, and best practices to maximize growth rates in aquaculture systems.
Table of Contents
1. Prawn Species and Their Growth Rates
Different prawn species exhibit varying growth rates. The two most commonly farmed species are:
1.1 Giant Freshwater Prawn (Macrobrachium rosenbergii)
- Average Growth Rate: 1–3 grams per week (4–12 grams per month)
- Harvest Size: 50–100 grams in 6–8 months
- Key Features:
- Grows well in freshwater and low-salinity conditions.
- Males grow faster than females.
- Growth slows down after reaching 30–40 grams.
1.2 Whiteleg Shrimp (Penaeus vannamei)
- Average Growth Rate: 1–1.5 grams per week (4–6 grams per month in extensive systems; up to 10–15 grams per month in intensive systems)
- Harvest Size: 15–25 grams in 3–5 months
- Key Features:
- Faster growth in high-density, controlled environments.
- Highly adaptable to varying salinity levels.
- Preferred for commercial farming due to rapid growth.
2. Monthly Growth Rate Breakdown
The growth rate of prawns is not linear and varies depending on farming conditions. Below is a general monthly growth estimation for commercial farming:
2.1 Giant Freshwater Prawn (Macrobrachium rosenbergii)
| Month | Average Weight (grams) | Growth Rate (grams/month) |
|---|---|---|
| 1 | 1–2 | 1–2 |
| 2 | 5–8 | 3–6 |
| 3 | 10–15 | 5–7 |
| 4 | 20–30 | 10–15 |
| 5 | 35–50 | 15–20 |
| 6 | 50–70 | 15–20 |
| 7 | 70–90 | 10–20 |
| 8 | 80–100+ | 10–15 |
2.2 Whiteleg Shrimp (Penaeus vannamei)
| Month | Average Weight (grams) | Growth Rate (grams/month) |
|---|---|---|
| 1 | 1–3 | 1–3 |
| 2 | 5–8 | 4–5 |
| 3 | 10–15 | 5–7 |
| 4 | 15–20 | 5–10 |
| 5 | 20–25 | 5–10 |
Note: Growth rates can vary based on farming intensity (extensive, semi-intensive, or intensive).
3. Factors Affecting Prawn Growth Rate
Several factors influence the growth rate of prawns in commercial farming:
3.1 Water Quality Parameters
- Temperature: Optimal range is 26–32°C for most species. Growth slows below 20°C.
- Dissolved Oxygen (DO): Should be >5 mg/L for optimal growth.
- pH Levels: Ideal range is 7.0–8.5.
- Salinity: P. vannamei tolerates 5–35 ppt, while M. rosenbergii prefers 0–10 ppt.
- Ammonia & Nitrite: High levels (>0.5 mg/L) stunt growth and increase mortality.
3.2 Feed and Nutrition
- Protein Requirements: Prawns need 25–35% protein in their diet.
- Feeding Frequency: 3–5 times daily for juveniles, 2–3 times for adults.
- Feed Conversion Ratio (FCR): Ideal FCR is 1.2–1.8 (lower is better).
3.3 Stocking Density
- Low Density (5–10 prawns/m²): Better growth but lower total yield.
- High Density (20–30 prawns/m²): Faster biomass accumulation but may reduce individual growth.
3.4 Genetics and Seed Quality
- High-quality post-larvae (PL) from reputable hatcheries grow faster.
- Selective breeding programs improve growth rates.
3.5 Disease and Stress Management
- Bacterial infections (e.g., Vibrio), parasites, and poor handling reduce growth.
- Probiotics and biosecurity measures improve survival and growth.
4. Best Practices to Enhance Prawn Growth Rate
To maximize growth in commercial prawn farming, farmers should adopt the following practices:
4.1 Optimal Pond Management
- Regular water exchange (10–20% weekly).
- Aeration to maintain DO levels.
- Liming to stabilize pH.
4.2 High-Quality Feed Management
- Use commercially formulated prawn feed.
- Adjust feeding based on growth stage (higher protein for juveniles).
- Avoid overfeeding to prevent water pollution.
4.3 Stocking Density Optimization
- Semi-intensive: 10–15 prawns/m²
- Intensive: 20–30 prawns/m² (with strong aeration)
4.4 Regular Monitoring
- Weekly weight sampling to track growth.
- Water quality testing (pH, DO, ammonia, temperature).
4.5 Disease Prevention
- Quarantine new stock before introduction.
- Use probiotics and immunostimulants.
- Avoid sudden environmental changes.
5. Economic Implications of Growth Rate in Prawn Farming
Faster growth rates lead to:
- Shorter production cycles (more harvests per year).
- Higher biomass yield (increased profits).
- Lower FCR (reduced feed costs).
Farmers must balance growth rate with operational costs (feed, electricity, labor) to maximize profitability.
Here are ten frequently asked questions (FAQs) about prawns:
1. What is the difference between prawns and shrimp?
Prawns and shrimp are different crustaceans. Prawns have three pairs of claw-like legs, while shrimp have two. Prawns also have branching gills and a straighter body compared to shrimp.
2. Are prawns healthy to eat?
Yes, prawns are a good source of protein, low in fat, and rich in omega-3 fatty acids, vitamins (B12, E), and minerals (selenium, zinc). However, they contain cholesterol, so moderation is advised for some diets.
3. How can I tell if prawns are fresh?
Fresh prawns should have a firm texture, a mild ocean-like smell (not fishy), and a translucent appearance. Avoid prawns with black spots, a slimy texture, or a strong ammonia odor.
4. How should I store fresh prawns?
Keep fresh prawns in the coldest part of the fridge (0–4°C) and use them within 1–2 days. For longer storage, freeze them in an airtight container for up to 3 months.
5. Can you eat prawns raw?
Raw prawns can carry parasites or bacteria, so it’s safer to cook them thoroughly. If consuming raw (e.g., in sushi), ensure they are sashimi-grade and properly frozen to kill pathogens.
6. How do you peel and devein prawns?
- Remove the head (if attached).
- Peel off the shell, leaving the tail if desired.
- Make a shallow cut along the back and remove the dark digestive tract (vein) with a knife or toothpick.
7. What’s the best way to cook prawns?
Prawns cook quickly (2–3 minutes per side) and can be grilled, boiled, fried, or sautéed. Overcooking makes them rubbery—they’re done when they turn opaque and pink.
8. Why do prawns turn pink when cooked?
The color change is due to a protein called astaxanthin, which is naturally present in prawns but bound to other molecules. Heat releases astaxanthin, turning the prawns pink.
9. Are prawns safe for people with shellfish allergies?
No. Prawns are shellfish, and people with shellfish allergies should avoid them as they can trigger severe allergic reactions.
10. Are farmed or wild-caught prawns better?
- Wild prawns are often considered tastier but may have sustainability concerns.
- Farmed prawns can be more eco-friendly if responsibly sourced (look for certifications like ASC or MSC), but some farms use antibiotics or harm mangroves.