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

10 Broodstock
& population genetics
Fig. 10.1 Collecton
and management
of broodstock.
Top left: Checking
sex and condition
of silver perch
broodstock.
Top right: A syringe is
used to insert the tag
just forward of the
preoperculum flap.
Right: Using a tag
reader to check tag
number.
Far right: Capturing
Murray cod broodstock
using a gill net.
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NSW Department of Primary Industries | Broodstock & population genetics
10.1 - SUMMARY
Broodstock are the most important component
of a fish hatchery and significant resources and
effort must be committed to their collection and
management. The quality and quantity of broodstock
directly influence the production and
success of breeding programs, as well as the
suitability of fingerlings for conservation stocking,
harvest stocking and commercial aquaculture.
Murray cod, golden perch and silver perch
each consists of separate populations (or strains)
within the Murray-Darling River System. These
populations are genetically distinct, but the
number of populations of each species, and the
distribution of each population are not known.
Genetic variation is the raw material for
evolution, and so the maintenance of both
genetic identity and genetic variation is essential
for the reproductive fitness of wild populations
and the conservation of threatened species.
To satisfy the requirements of breeding programs
(see Chapter 11), a minimum of 10 pairs
(%:$ = 1:1) of Murray cod and golden perch,
and 20 pairs of silver perch should be collected
from each river (i.e. each population or strain)
that is to be stocked. Individual broodstock must
be tagged and fish of each strain held in separate
ponds, cages or tanks. The reproductive
performance (fecundity, hatch rate) of native fish
decreases within 5 years in captivity, and so to
maximise performance and production, and to
facilitate the maintenance of genetic variation,
broodstock should be replaced with mature fish
from the wild after 5 years.
Silver perch broodstock can be bred and reared
in captivity (i.e. domesticated), and the reproductive
performance of these fish remains high,
at least until 10 years of age. Domesticated
broodstock of each species can be used in
hatcheries to produce fingerlings for commercial
grow-out. However, they must not be used in
conservation and harvest stocking programs
because domestication results in a loss of genetic
variation through selection for traits that are
favourable under culture conditions, but may
be detrimental in the wild.
Methods for the capture and transportation
of broodstock are described.
10.2 - POPULATION GENETICS OF
NATIVE FISH
Species are groups of populations that are reproductively
isolated from other such groups; there
is no gene flow between species. In the wild,
species usually consist of distinct, isolated
populations that can potentially interbreed
but have characteristics (appearance, aspects
of biology and genetics) that distinguish them