3.2 Holding your broodstock in temperate zones

In the tropics, where berried females are readily available, special broodstock holding facilities within hatcheries are not necessary, although the advantages of maintaining special broodstock ponds have already been mentioned. However, in temperate zones where freshwater prawns are reared in the summer, indoor broodstock facilities are essential.

In temperate zones it is necessary to provide holding facilities for over-wintering.
Broodstock need to be maintained for up to six months and the temperature needs to be above 25°C to prevent loss of eggs. To conserve water and maintain good water quality, a recirculation system is suggested, similar to that used in recirculation hatcheries, as described later in this manual. Nylon mesh netting should be hung vertically or horizontally in the water column (buoyed with PVC piping and floats) and placed on the bottom of he tanks. This minimizes the total tank volume needed, reduces cannibalism, and increases fecundity. The use of large mesh sizes reduces the amount of fouling.

The egg-carrying capacity of the females is reduced at higher broodstock densities.
A maximum stocking rate of one adult prawn per 40 L of water is recommended. For every twenty females, you should hold one or two BC males and two or three OC males (each >35 g), if eggs are required 3-4 months after the adults are stocked. If newly hatched larvae are not required until six months after the adults are stocked into broodstock facilities, the number of OC males should be adjusted to three or four per 20 females (to allow for male mortalities).
The total quantity of broodstock to be maintained in temperate facilities obviously depends on the final demand for PL. Only about 5% of the females will spawn together and an adult mortality of 50% should be anticipated during the holding period. Assuming an average of 45 000 larvae/45 g female, obtaining a single batch of 100 000 larvae at the end of the holding season would therefore require you to over-winter about 90 females, each about 45 g in weight (plus, using the proportions and timing indicated in the previous paragraph, 5-9 BC males and 9-18 OC males). This would provide a batch of 100 000 larvae at least once a week, thus allowing your hatchery to supply enough PL to stock 1 ha of ponds (assuming a stocking rate of 5 PL/L and a 50% hatchery survival rate to the PL stage) per week. These numbers can be adjusted according to your needs. It would be foolish to base the whole cycle of operations on a single tank, however; many accidents and other unforeseen circumstances can arise. It is therefore suggested that you split whatever broodstock animals you hold into a minimum of three holding systems.