Giant freshwater prawns live in freshwater environments but their larvae require brackishwater to survive. These  crustaceans are common in the tropical and sub-tropical waters of the Indo-Pacific region and are reported to grow to a length of 255 mm. Based on breeding trials, they take more than a year and a half to mature.

Why culture freshwater prawn?

• Can be a good alternative to tilapia and tiger shrimp
• Can be polycultured with carp, tilapia, catfish, etc.
• Established market niche and high export potential
• Native to the Philippines and other Asian countries

Broodstock

• Broodstock are stocked in a 4:1 female-male ratio. Blue- and orange-clawed males are preferred.
• Orange eggs of berried females will take about 3 weeks to hatch while grayish or brownish eggs will hatch in 2 to 3 days, usually at midnight to early morning.

Larval rearing

• Larval rearing tanks may be made of fiberglass, polyethylene, or concrete. Water with a salinity of 12 ppt is used and stocking density is 100-300 larvae/L.
• Larvae are fed brine shrimp nauplii, egg custard (solidified egg emulsion), and Moina sp.
• Water quality is maintained at pH=7.2-8.5, dissolved oxygen (DO)>3 ppm, temp=28-31°C, ammonia<0.1 ppm.
• The larvae undergo several stages of development before they metamorphose to post larvae (PL) in 28-35 days depending on temperature, nutrition, and other factors.

Nursery

• The larvae metamorphose to PL and are acclimated to freshwater.
• PL are reared in nursery tanks, ponds, or lake-based hapa net cages and fed commercial feeds at 10-20% of body weight.
• Fifteen-day old PL (PL15) and older are ready for grow-out.

Stocking density for nursery
a. Ponds

• 1,000 PL/m2 no aeration and substrates
• 2,000 PL/m2 with aeration and substrates

b. Tanks

• 1,000 PL/m2 without substrates
• 2,000 PL/m2 with substrates

c. Cages

• 1,000 PL/m2

Technical assumptions for seed production

• Project duration : 5 yrs
• No. of broodstock (F=2,500 M=500) : 3,000
• Survival rate : 0.20 %
• No. of days/run : 45
• Survival rate of PL : 0.70 %
• Production/60 days : 700,000 pcs
• Number of runs/year : 4
• Farm gate price (PL 15) : P 1.00

Production of Grow-Out

Stocking density for grow-out – Culture system : Density

• Extensive system : 1-4 PL/m2
• Semi-intensive : 5-20 PL/m2
• Intensive : more than 20 PL/m2

Feeding rate (semi-intensive)

Average prawn weight (g)  /  Amount of feed (% of total prawn weight)
<5                                                       10
5 – 15                                                  7
15 – 25                                               5
>25                                                      3

• Procure quality prawn postlarvae (PL) from a reputable hatchery or supplier. Ensure minimal transport stress to PLs.
• Stock 15-day-old PLs depending on the culture system to be used. Higher stocking densities could result in smaller prawns at harvest. Cage size varies from 25-200 m2 submerged at 1m depth.
• Provide submerged feeding trays for prawns cultured in cages. Formulated diets for shrimp or fish may be used.
• In both pond and cage culture, stock management could be a batch system (waiting until prawns reach average marketable sizes), or cull-harvest system where marketable size are periodically culled out before one final harvest of the stocks.
• In ponds, use shelters/substrates to increase pond surface area, improve survival of molting prawns, and allow for higher stocking densities.
• Prawns reach marketable size in 4 to 5 months. Mean size at harvest is 25-35 grams. Longer culture period may be required for higher stocking densities.

Technical assumptions for grow-out:

• Project duration : 5 yrs
• Stocking density : 15 pcs/sq.m.
• Cost of post-larvae : P 1.00
• Crops per year :  2
• Ave. weight at harvest : 30 g
• Recovery at harvest : 75 %
• Total number of stock/crop : 120,000
• Total recovery at harvest/crop :  90,000
• Total weight at harvest/crop : 2,700 kg

For more information, contact:

Southeast Asian Fisheries Development Center (SEAFDEC) – Aquaculture Department
Contact: (02) 9275501, (033) 511-9174
Email: aqdchief@seafdec.org.ph
Web: www.seafdec.org.ph

Source: seafdec.org.ph; Photo: kingfisher.co.nz