Ecological intensification
of tropical aquaculture
Integrated multi-trophic systems
E
cological intensification of aquaculture involves
Integrated Multi-Trophic Aquaculture (IMTA), which
has been spreading since the 1990s. The strategy
consists in using effluent from intensive aquaculture for
associated production operations. CIRAD and IFREMER,
through the Joint Research Unit on Integrated and Ecological
Intensification for Sustainable Fish Farming (UMR Intrepid),
are working to apply these principles and adapt them to tropical
aquaculture, notably by coupling them with the domestication of
suitable, complementary local species.
Combined rice/fish farming system in Cameroon.
© APDRA pisciculture paysanne (www.apdra.org)
Contacts
Jean-François Baroiller
I
Milkfish (Chanos chanos) are reared in the Philippines in
extensive multi-trophic polyculture systems, with crabs
and shrimps, in large brackish coastal ponds.
© P. Morissens/CIRAD
ntensive
monoculture
aquaculture
systems are characterized by the use of
large quantities of feed and, as a result,
generate significant amounts of effluent:
organic matter (faeces and uneaten feed),
inorganic substances (mainly nitrates and
phosphates). The question of nitrates – and
ammoniac – is crucial, since no less than
70% of the nitrogen provided by the proteins
in fish feed is excreted by carnivorous fish
(salmonids, bass) and shellfish. This effluent
causes pollution that may result in mass
development of algae (micro- or macro-),
eutrophication or silting up of sheltered
coastal zones.
A new type of aquaculture, Integrated Multi-Trophic Aquaculture (IMTA), has been spreading
since the 1990s. It consists in using effluent from intensive aquaculture for associated
production operations. For instance, intensive fish farming in cages may be associated with
mussel and seaweed production; the mussels filter the organic matter and the seaweed
recovers the inorganic matter. This type of system is also under study for land-based
production systems, and indeed, this is where it appears to be most effective, as the effluent
is concentrated and easier to manage than offshore.
CIRAD, UMR Intrepid
Integrated and Ecological
Intensification for
Sustainable Fish Farming
Campus international de
Baillarguet
34398 Montpellier Cedex 5
jean-francois.baroiller@
cirad.fr
Béatrice Chatain
IFREMER, UMR Intrepid
Integrated and Ecological
Intensification for
Sustainable Fish Farming
Station expérimentale
d’aquaculture
Chemin de Maguelone
34250 Palavas-les-Flots
France
[email protected]
Offshore IMTA installation. © François Dolambi
Seaweed for fish
UMR Intrepid’s operations centre
more particularly on the use of
seaweed produced in IMTA to feed
fish. It is used for mainly vegetarian
omnivorous fish. Some of the species
chosen have proved to be of interest as
“new species” for aquaculture, in addition
to their specific use for IMTA. The team is
concentrating on seaweeds that are considered
easy to produce but difficult to use, such as sea lettuce types or filamentous seaweeds, as
their purification capacity is remarkable and they sometimes have high protein contents (30%
of dry matter). This is a novel option compared to the IMTA systems studied to date, which
mainly involved seaweed for use in agro-industry, such as brown and red seaweeds, from
which polysaccharides can be extracted. However, these types are not the most suitable for
recycling aquacultural effluent, particularly in coastal pools.
The research covers three topics, more or less in sequence:
• identifying the best seaweed-fish combinations taking account of the food preferences of
the fish concerned (some ten types of seaweed may be suitable for tropical IMTA systems);
• defining how best to use seaweed: fresh with a single species or mixed; dried, powdered
and mixed into a complete feed formula in line with a set proximal composition; or fresh, in
addition to a standard complete feed;
• determining how to integrate the different compartments of the system under production
conditions: to come up with systems that are both effective in terms of recycling nutrients
and economically viable, technical solutions are being sought to optimize seaweed and
herbivorous fish production; modelling tools are being used assess nutrient fluxes through the
various compartments of the systems being tested.
Partners
• France:
AquaMay, Mayotte; ARDA,
Association réunionnaise
de développement de
l’aquaculture; LEGTA, Lycée
d’enseignement général et
technologique agricole, La
Canourgue
• Philippines:
BFAR, Bureau of Fisheries
and Aquatic Resources; WFC,
World Fish Center; University
of the Philippines; Mindanao
State University
• Thailand:
AIT, Asian Institute of
Technology
From freshwater systems to systems suited to varying degrees of
salinity
Coastal ponds are the main target, but other marine production systems, including fish cages
and raised systems (hatching in tanks with a water recycling system), are also under study,
based on practices commonly used in continental aquaculture, particularly in polyculture
ponds.
This IMTA operation is closely linked to UMR Intrepid’s other operations, notably: selection
of worthwhile species, control of the biological cycle, capacity for
using plant-based feeds and adaptation to salinity. In these last two
cases, more particularly, the work involves studying feed efficacy
and optimizing farming systems to make use of seaweed as fish
feed, and rearing euryhaline species in coastal ponds characterized
by variable salinity.
Tilapia alevin rearing in hapa
cages. © P. Cacot/CIRAD
Paste feed comprising
50%, 80% and 100% sea
lettuce. © P. Cacot/CIRAD
© CIRAD, February 2012
www.cirad.fr