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Ref:649/03 |
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New zealand
- Mar 29, 2003 |
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Farming paua in
recirculation systems – fad or future? |
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New Zealand paua farmers are increasingly
interested in recirculation technology, but is
this a likely future direction for the industry or
just a current fad? This article answers some
questions about paua production in recirculation
systems, and leads into one in the next Update
that will report results from a
NIWA trial. |
What are the advantages of
recirculation?
Environmental concerns are of increasing
importance to the aquaculture industry, which
relies on precious water resources. Recirculation
systems use a fraction of the water used by
flow-through systems, and continuous internal
treatment of the water within the system makes
treatment of the wastewater feasible, both
technically and financially.
Growth rates of
organisms within recirculation systems are often
higher than those cultured in open systems.
Recirculation systems can maintain constant high
water quality by controlling a host of
environmental variables. The stock, therefore, use
energy on growth rather than on adapting to a
changing environment and do not experience periods
of low growth when seasonal conditions are
unfavourable. Well-designed systems provide
protection from disease, pollution, and toxic
algae and the risk of stock loss is reduced.
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Click
images for more information
Six-month-old
juvenile paua.
Growth of two groups
each of European and Japanese abalone reared in a
recirculation system.
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Recirculation systems
are more expensive to set up than flow-through
systems, but the running costs are lower, due to
reduced pumping costs. However, the greatest
financial gains are to be made from improved
growth rates and reduced risks.
Is it proven for paua?
Plenty of work has been done on growing abalone in
recirculation systems and it is generally believed
that it is achievable on a commercial scale.
Trials in Ireland, the U.K., and Israel, at less
than commercially viable scale, have shown
promising results. A trial in the U.K. indicated
that growth to market size of European abalone
could be reduced from over 4 years to 2.5 years in
a recirculation system. New Zealand already has
recirculation or semi-recirculation systems in use
for paua production, but little information is
coming from these systems on performance or
productivity.
What are we doing to
prove it?
At NIWA’s Mahanga Bay facility we are endeavouring
to test the suitability of recirculation for paua
production. Our research aims to quantify
parameters, such as growth rate and ammonia
production rates, which are critical to designing
reliable systems and to modelling the cost of paua
cultivation in closed systems. These trials will
enable us to specify design criteria, predict the
scale of system required for profitable operation,
and allow us to confidently say whether
recirculation systems can play a positive role in
the development of paua farming.
Meanwhile, we are
keen to work with producers who already operate
recirculation systems so that the findings from
our trials can be tested on a commercial scale.
Philip Heath
[ p.heath@niwa.co.nz ] |
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