Sea Bass,
Sea Bream and Meagre
Commercial-scale
closed cycle aquaculture operations in Malta started with the production of
gilthead seabream Sparus aurata and
European seabass Dicentrarchus labrax
in 1990. The production processes employed for both species are virtually
identical, although the performance indicators for these species differ
somewhat. Both species’ production is based on the supply of hatchery-reared
juveniles, with no reliance on wild stocks – closed cycle.
Juvenile
seabass and seabream are purchased from overseas hatcheries at a size of
between 1g and 3g, and are delivered by truck to Malta, with a typical delivery
time of 2-4 days. Specialized live fish transportation trucks are used for
shipment, and transport-related mortalities are generally very low, amounting to
a few percent. Upon arrival in Malta, the juveniles are discharged into small
transport cages and then towed out to the nursery cage site.
Because
of the small size of the juveniles the production of seabass and seabream
requires that the initial growth stages be carried out at sheltered inshore
locations. At a size of 30-50g the seabass or seabream can then be transferred
to semi-exposed offshore sites for on-growing to the usual market size of
300-500g.
Seabass
and seabream are fed on proprietary pelleted and extruded feeds, formulated
specifically for these species. Typical feed formulations include a protein
content of 40-50% and an oil content of 15-20%. A lot of research work is being
carried out by feed companies to replace fish meal and fish oil components with
vegetable-based products such as soya meal and soyabean oil to reduce costs and
to reduce reliance on marine-based products.
Some
producers routinely grade their fish stocks, primarily to assist in marketing a
uniform-sized product. Whereas seabream is relatively resistant to handling
operations, seabass is very sensitive and are not normally handled beyond an
average weight of 50-100g.
The
bulk of seabream and seabass produced in Malta is exported by truck fresh, on
ice, to Italy. Seabream are sold as whole portion-sized fish, of 300-400g
average weight, packed in 6kg polystyrene boxes. Because of higher mortality
rates and a vulnerability to the viral disease VNN, the cost of production of
seabass is higher than that of seabream. Consequently, seabass production has
dropped significantly in recent years.
Seabream producers have shown some interest
in the production of meagre, Argyrosomus
regius, over recent years, following the availability of juveniles of this
species from commercial hatcheries. Production methods and systems are
identical to those used for seabass and seabream, and so bass and bream
producers can grow this species without the need for dedicated production
systems. Growth rates are impressive, with fish reaching an average weight of
1.2kg within 12 months at a food conversion ratio of only 1.25, and survival
rates are good. The main constraint to the expansion in the production of this
species is poor market demand, however, and so production volumes can be
expected to remain low unless some market development is carried out to
increase demand.