Table 54 Characteristics of a typical 10 million PLyr hatchery operating with two rearing phases

Larval rearing tank type

#1 (initial stocking)

#2 (final stocking)

Number of larval rearing tanks 8 16

Effective volume of each tank (L) 900 1800

Stocking density (larvae/L) 400 75

Total larvae stocked per tank 360 000 135 000

Approximate period of culture (days) 12 25

Estimated survival rate (%) 75 (range 70-80) 50 (range 40-60)

Number of larvae to be transferred from #1 to #2 tanks 270 000

Yield of postlarvae (PL/tank) - 67 500

Total yield of postlarvae/cycle - 1 080 000

Annual production capacity (10 months operation) 10.8 million

2007, Valenti & Moraes-Riodades 2004, Valenti & Tidwell

2006). Parseval et al. 1989 presented a simulated comparison among different commercial-scale hatchery systems. Estimated average productivity values for greenwater, flow-through and recirculating clearwater systems were 40, 50 and 60 to 80PL/L, respectively. Ang (1996) reported the production of 17 to 50 PL/L in a recirculation system. Production for commercial recirculation hatcheries of 60 and 70 PL/L were reported by Aquacop (1983) and Carvalho & Mathias (1998), respectively. A hatchery with eight 900 L pre-stocking larval rearing tanks and sixteen 1800 L final larval rearing tanks allows a production of 10 million PL/yr (Table 5.4).

In 1995, 600 to 800 million freshwater prawn larvae were being produced annually from 50 backyard hatcheries in Thailand, sufficient to supply 6400 ha of grow-out ponds (Suwannatous 1996). Government hatcheries in Thailand, which stimulated the development of commercial hatcheries through a joint FAO-Royal Thai Government project nearly 30 years ago (New et al. 1982), continue to produce PL for stocking in open waters (Chapter 17). At the end of the millennium, prices for 20- to 30-day-old PL were US$ 1.25/1000 in Thailand, the same as in 1993 (New 1995), indicating some over-supply there at that time. Since then, the freshwater prawn sector in Thailand has expanded considerably and shortages of PL were reported as a major constraint for freshwater prawn culture development there by Schwantes et al. (2007). Similar shortages have been reported in Brazil (Valenti & Moraes-Riodades 2004, Valenti

2007) and India (Balamurugan etal. 2004).

How To Have A Perfect Boating Experience

How To Have A Perfect Boating Experience

Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.

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