Hatchery Quality Assurance Program - NSW Department of Primary ...

• Internal sump:
e.g. 50 cm deep, 50 cm wide, 20 m long for 0.1 – 0.2
ha ponds (Fig. 6.4); for collection of broodfish and
fingerlings after the pond is drained.
• External sump:
for collection of fish outside the pond.
• Aeration (3-phase power):
to maintain optimum water quality. These should
be fitted with automatic timers and manual
overides.
• Overhead netting of larval rearing ponds:
to prevent bird predation.
Fig. 6.5 Broodstock pond (0.1–ha surface area) with aerator.
• Broodstock ponds to be drained and dried
annually or at least each 2-3 years:
for the following reasons;
(i) to remove all fish, especially trash fish;
(ii) to desiccate pathogens;
(iii) to treat with lime if necessary;
(iv) to enable silt to be removed and/or the substrate
to be tilled or scraped;
(iv) to enable repairs and general maintenance;
(v) to provide conditions for good water quality;
(vi) to reduce or prevent growth of macrophytes;
(vii) to facilitate the rotation of Murray cod
broodstock (see Chapters 10 and 11).
20
NSW Department of Primary Industries | Design and operation of facilities
EARTHEN PONDS
RECOMMENDED CRITERIA
• Shape:
square (0.1 ha surface area) or rectangular
(0.2 – 0.5 ha).
• Size:
broodstock 0.05 – 0.1 ha; larval rearing
0.1 – 0.5 ha.
• Outlet tower - concrete:
also called a monk or penstock; contains boards
to control water level and screens to prevent escape
of fish; vertical PVC pipes are acceptable as outlets,
but are not recommended.
• Inlet pipe:
150 mm (6”) diameter, with valve.
• Outlet pipe:
at least 150 – 200 mm (6” – 8”) diameter;
a diameter of 500 mm (20”) enables rapid water
exchange and facilitates external drain harvest
of fish.
• Larval rearing ponds dry over winter
and early spring:
to facilitate plankton blooms and good water
quality.
• Plant a crop (wheat, oats, rye grass) every
2 years in larval rearing ponds during late
autumn and winter:
to use phosphorus bound-up in the soil and to
promote rotifer blooms.
• Lime bottom of larval rearing ponds:
especially if alkalinity is low (< 20 mg/L); may
promote rotifer blooms and reduce problems with
fairy shrimp; 500 – 1,000 kg/ha agricultural
limestone (CaCO 3 ).
• Vehicular access to all banks.