Page 33 - World Aquaculture Magazine - March 2011

World Aquaculture 31
Fig. 6. Semi-intensive aquaculture – Materaqua (Photo: A.
Ramalho)
under development with new licences requested every year.
In Algarve a specific zone to install new units is now pre-
viewed with potential to further develop this practice. This
method is almost exclusively used for mussels production,
the exception being one farm in Algarve (Sagres) producing
oysters mainly for export.
The advantages of these systems are mainly reflected in
the low energetic costs, inexistence of pumping systems,
and reduced manpower. However, long-lines show some
disadvantages like exposure to predators (e.g. crabs and
seabirds), a lower control on animals’ growth rates, and the
complete dependence on uncontrolled environmental condi-
tions. Present research in Portugal is dedicated to selecting
mollusc strains, to the study of native species life cycle and
the major diseases affecting commercial species.
Extensive fish production systems
Extensive aquaculture is an environmental friendly farm-
ing method. However, its optimal management is depend-
ent on the availability of natural resources, either biotic or
abiotic. Extensive production of fish in earthen ponds is a
polyculture activity and farms are usually ancient salt ponds
restored for fish culture, when difficulties in the salt market
began. Extensive fish farming are also facing difficulties and
is gradually disappearing, nowadays production is limited to
2% of Portuguese aquaculture.
Fish are produced in very low densities and many of
the species reared have, like mullets, low market price,
making this activity less and less profitable. Some of the
still existing exploitations are based on an added value to
salt production and are not a primary activity, while other
farmers maintain the extensive systems as a complement
to the family income. Considering difficulties on passing
the knowledge of this family-based activity to the next
generation combined with poor economic attractiveness,
it is expected that many of these wetlands will soon be
abandoned. Nonetheless, extensive production is an ac-
tivity which might provide an amount of goods and serv-
ices beyond the seafood products. These products include
socially popular goods such as appreciated landscapes,
protection and preservation of wild fauna and biodiversi-
ty, prevention against flooding (buffer zone), preservation
of cultural heritage, rural communities’ viability, food
safety (see Publishable Summary Report of the SEACASE
project,www.seacase.org).
Semi-intensive fish production systems
Semi-intensive fish rearing is found in all coastal re-
gions, except in the North. In the Centre, where condi-
tions are harder and temperatures are colder during the
winter, production cycles are longer and portion size
seabass and seabream are usually harvested after a 24
to 26 months cycle. In Southern regions, with favour-
able ecological conditions and higher temperatures, the
production cycle is smaller and harvest occurs after 14 to
20 months. Equilibrium with the environment is crucial
to maintain healthy animals. The risks are related with
the water quality, nutrient control, juveniles quality, and
harvesting. The control of water key parameters must be
accurate and solutions must be fast, since higher densities
mean higher losses. Birds like egrets or cormorants and
mammals like otters are the fish main predators in these
systems. Losses up to 30% of production due to predators
often occur.
Intensive fish production systems
Freshwater intensive farming is exclusively devoted to
trout (Oncorhynchus mykiss and Salmo trutta fario) in con-
crete tanks in the North and Central regions. Production is
only to the national market and has reached a plateau of
around 1000 tons for the last 10 years.
The adverse conditions on the West Atlantic coast have
been conditioning the implementation of cages units. There-
fore Portuguese intensive marine farming has grown slowly
over the past years reaching, 1200 tons in 2008. Marine in-
tensive systems are mainly used for fish farming, both land-
based usually in concrete tanks to produce turbot, seabass,
seabream and sole, and in off-shore cages for rearing sea-
bream and, very recently, meagre. Cages units, which are
beginning to have more expression, are now implemented in
Sines and Madeira Island, several are planned to lead off in
Algarve using offshore technology.
Final Remarks
Traditionally Portugal is one of the leading fish consum-
ers per capita in the world, however Portuguese aquaculture
and fisheries is far from satisfying the market needs and im-
ports are inevitable. The difficulties faced by the aquacul-
ture industry are mostly due to bureaucratic impediments,
incomplete use of EU structural funds, insufficient coastal
management plans and decreasing market prices, leading to
poor investment and delaying the progress of Portuguese
aquaculture.
But how this might be inverted?
Currently, research is more directed to zootechnical de-
velopment; feeding and nutrition; reproduction, water qual-
ity and product safety. It is however necessary to ally the
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