Sandfish hatchery techniques - English version - ACIAR

Possible problems: Heavy rain can lead to stratification of water in the pond. Stratification can be detected by
the presence of a thin layer of low-salinity water at the surface. The consequences of stratification can include an
increase in temperature, fall in dissolved oxygen especially in the bottom layers, and development of anaerobic
areas in the sediment. The combination of these extreme conditions can be dangerous for sandfish, which are
benthic and slow moving. It can lead to total loss of broodstock in a few days.
High temperatures and
low dissolved oxygen
How to overcome tHese problems
Regularly check water temperature and dissolved oxygen (especially in the early
morning).
Increase water flow, preferably continuously 24 hours per day.
Set up paddle wheels or other pond aeration equipment; installation should provide
aeration on the bottom where the animals are located.
Heavy rain Remove the surface layer of freshwater by adjusting the height of the outlet pipe.
If a cyclone is predicted, transfer the animals from ponds to indoor tanks (where
possible).
Figure 10. Feeding broodstock.
Ways to increase spawning success
Animals held in ponds or tanks for several months
to 2 years are easier to spawn than broodstock
maintained in sea pens or animals taken directly from
the wild. Another advantage of holding broodstock
in ponds is that they generally spawn earlier in the
season than wild individuals, presumably because of
the higher temperatures in ponds. Note, however,
that holding broodstock in ponds or tanks for several
months before spawning is not essential. In Solomon
Islands, for example, newly collected sandfish were
often induced to spawn.
The advantages and disadvantages of keeping
broodstock in captivity, or collecting individuals from
the wild, should be evaluated for each location.
Summary
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Batches of 30–45 individuals (average weight
500 g) are needed to induce spawning.
When relying on wild broodstock, ripe and
healthy broodstock must be collected during
the spawning season.
Transport wild broodstock individually in
oxygen-filled bags with seawater, using
insulated containers at 27–30°C. Avoid
changes in temperature and other shocks
during transport.
Broodstock can be conditioned by keeping
them in: (a) tanks (15–30 animals/1000 L)
with a sand or mud substratum, with flowthrough
seawater and a supply of food; (b) sea
pens of 800 m 2 at densities of