Toward ecological intensification through the co-production of the floating macrophyte Azolla filiculoides and the giant gourami Osphronemus goramy Lacepède (1801) in Indonesian ponds

Abstract

ABSTRACT The feasibility of the co-culture production of giant gourami Osphronemus goramy, an omnivorous with a herbivorous tendency fish, with high economic and patrimonial value in Indonesia, and floating macrophyte Azolla filiculoides was tested. A three months trial was carried out in an Indonesian small-scale fish farm from November 2017 to February 2018. Four earthen ponds (from 353 to 482 m2) were used. Two ponds were managed as conventional monoculture aquaculture; in the two others, 20% of the pond’s surface was dedicated to the production of A. filiculoides. The objective of this co-production was to replace partially the commercial pellets with fresh, unprocessed Azolla. All ponds were fertilized with chicken manure and stocked with juveniles of giant gourami (24–34 g) bought in the local live fish market at a density of 6 individuals per m2 under both management schemes. Production of Azolla was discontinuous, covering only 40 days over 90 days of the production cycle of Giant gourami. Azollawas harvested every three days producing 571 ± 359 g m−2 (mean ± SD) of biomass. This discontinuity might be attributed to insufficient phosphorous (P) fertilization and predation by other fish, aquatic snails, and insect larvae. In the co-cultured ponds, a total of 15% of commercial pellets were spared by their replacement with fresh Azolla. The specific growth rate (SGR) and the fish biomass gain were similar for both systems. Azolla did not influence water quality. Both production systems were negative economic net-benefice (−17% for conventional ponds and −4% for co-cultured ponds), mainly because of high costs for seeds and sub-optimal feed performance. We demonstrated that the co-production of A. filiculoides did not generate any significant extra cost. We discussed the benefits of ecological intensification with macrophytes in semi-intensive production systems in the tropics.