1This is the great paradox of aquaculture: it offers a solution to overfishing while at the same time being one of its drivers, when it uses fishmeal to feed fish in farms. Its effluents can also be a source of water pollution.

Fish farm combining panga with duckweed and gourami, Indonesia.

2These findings prompted researchers to conceive alternative strategies to counteract the adverse effects on the environment. In Indonesia, studies made it possible to replace fishmeal with an insect powder resulting from a bioconversion process. To make this powder, researchers used and recovered organic, household or agro-industrial waste that the larvae of diptera, nicknamed “black soldier” (Hermetia illucens), feed on. Once ground into a powder, these larvae form a cheap protein-rich meal which can replace fishmeal, at least in part.

Floating fish farms, Vietnam.

3To reduce pollution, researchers designed fish farms involving several fish, plant and/or mollusc species, whereby waste from one species becomes inputs for another. This “integrated multi-trophic aquaculture” (IMTA) principle was developed in panga farms in Indonesia, by adding a floating plant to production ponds. This duckweed (genus Lemna) grows by purifying the water of breeding ponds. It is also eaten by a herbivorous fish species, the giant gourami, whose production complements that of panga, improving the farm’s economic benefits. A similar approach was used in Senegal with an artificial, closed-circuit ecosystem which combines euryhaline tilapia with zooplankton and single-celled Chlorella algae.

4To limit the use of antibiotics, an inventory was conducted of plants traditionally used by fish farmers in northern Vietnam and on the island of Java to care for fish. Fifteen of these plants are currently being examined.