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In
the 1980s, NIWA’s Mahanga Bay aquaculture facility
pioneered hatchery techniques to produce paua seed,
and we supplied the first two paua farms with small
quantities of ready-to-settle larvae and juveniles.
Many of the techniques developed then are still used
by paua farmers today, but seed remains in short
supply.
Rearing trays
at a commercial paua farm.
Tub tanks with
juvenile paua. |
Forty-four licences
have been issued for land-based paua farming, and
there are two sea-based paua farms. Some have been
operating for many years; others are in the
planning or early development stage. Interest in
paua farming is growing, both for large
open-circuit farms and for the new recirculation
technology. Other marine farms may consider
diversifying into paua farming in the future. The
paua fishing industry has shown interest in
enhancing wild stocks by larval or juvenile
out-planting. If all these developments come to
fruition, they will exacerbate the current seed
supply problem.How many
seed?
So, how big is the
seed supply problem? A paua farm producing 25 t a
year (or 500 000 animals 75 mm long a year) needs
750 000 juveniles (10 mm long) a year. Not all the
44 farms will reach this target; some will exceed
it, but our best estimate is that the industry’s
annual production will reach 400 t by 2010, at
which point the industry will require 12 million
seed each year. Assuming an optimistic settlement
success of 5%, the industry needs to rear 240
million larvae per year. Adding the potential seed
requirements of other marine farmers and the quota
holders in the paua fishery could increase this
figure by up to 50 times. |
Paua farmers have three
ways of obtaining seed. They can build a hatchery to
supply their needs, they can buy excess seed from
other farmers, or they can contract another farm to
supply their seed. The excess and contract options,
although often attractive on a cost-per-seed basis,
make it difficult for ongrowers to plan their
production, and the hatchery option tends to divert
attention from the primary business of growing paua.
The unit price and the availability of excess or
contract seed will vary depending on the success of
the few farms that have seed production capability.
Is there another option?
Shellfish and fish
farming industries overseas have long supported
dedicated hatcheries and juvenile production systems
to supply seed stock. But why have separate
hatchery/nursery systems for paua? Essentially,
because the requirements for larval and juvenile
rearing and for ongrowing are different, and the time
frame for the two operations is markedly different.
Larval and juvenile rearing requires more stringent
control over water quality parameters, such as
filtration and temperature, but the water flow
required for even large numbers of seed is far less
than that required during growout to market size.
Also, the technology of micro-algae production to
supply diatoms is required only for larval settlement.
The hatchery/nursery phase to produce seed for sale to
ongrowers can be completed within 6 months.
So how many hatcheries
do we need? This is difficult to estimate, but at
least three would be needed to supply the potential
seed requirement of the farming and fishery industries
of about 400 million 10 mm juveniles per year, and to
ensure a consistent supply with some competitive
control on price. To achieve this, the hatcheries will
also need to solve the major problem of how to
maintain and condition paua broodstock, so that
controlled spawning and settlement can take place
several times each year.
If some of those in the
industry with the necessary hatchery skills are to
focus on seed production, they will need a commitment
from others in the industry to buy the seed produced.
Peter
Redfearn
[ p.redfearn@niwa.co.nz ] |
