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

4 Overview
of hatchery techniques
4.1 - GENERAL
Hatchery techniques for Murray cod, golden
perch and silver perch are well established and
have been described in detail in a number of
scientific and technical publications (Rowland,
1983a, b, c, d, 1984, 1988, 1992, 1996;
Rowland et al., 1983; Cadwallader and Gooley,
1985; Thurstan and Rowland, 1995; Ingram,
2000, 2001).
MAJOR STEPS (CHRONOLOGICALLY)
Collection and maintenance of broodstock
(late summer, autumn)
Broodstock are collected from a number of
sources – the wild (rivers, creeks, lagoons, canals,
impoundments), farm dams or other hatcheries.
Each species and each population (or strain) is
held in separate earthen ponds, cages or tanks
throughout the year. Murray cod and golden
perch are fed live food (yabbies, fish, shrimp)
and silver perch artificial diets, supplemented
with live food at some hatcheries. Water quality
and disease monitoring programs are required to
ensure healthy broodstock.
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NSW Department of Primary Industries | Overview of hatchery techniques
Preparation of larval rearing ponds
(winter, early spring)
The larvae of the three species are reared
extensively in earthen ponds (0.1 – 0.5 ha
surface area). To provide optimum conditions
for larval rearing, the ponds are left dry during
winter and early spring, and filled 1-2 weeks
before stocking. They are fertilised with inorganic
and organic fertilisers to promote blooms of
phytoplankton and zooplankton.
Fig. 4.2
Below left: Injecting a golden perch with the hormone HCG.
Below middle: Golden perch eggs being extracted for inspection.
Below right: Eggs are then examined for quality.
Fig. 4.1 Silver perch broodstock are housed in cages for effective
management and control. Inset: Broodstock cages are numbered
to identify separate strains.
Hormone-induced spawning and/or
collection of cod eggs (spring, summer)
Hatchery production takes place within the
normal breeding season of each species, and
usually commences with Murray cod in spring
when water temperatures are around 20ºC,
i.e. late September-early October in northern
NSW, and early October-November in southern
NSW. Production of golden perch and silver
perch is based on the induction of final oocyte
maturation, ovulation and spawning using the
hormone, human chorionic gonadotrophin
(HCG). Injected broodstock are placed into
spawning tanks (1,000 – 2,000 L) where
spawning takes place within 48 hours.
Although Murray cod can be induced to ovulate
using HCG and eggs stripped for fertilisation, cod
spawn naturally in ponds, and production of this
species at most hatcheries is based on the
collection of fertilised eggs from artificial sites,
e.g. cylindrical drums lined with nylon gauze,
see Fig. 4.3.