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

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.

KEYWORDS:

• Macrophytes
• sustainability
• IMTA
• small scale aquaculture
• alternative feed

Acknowledgments

This paper forms part of the COFASP ERA-NET project “IMTA-EFFECT” funded by the European Union and French National Research Agency. The authors thank Bang Macho and the local fish farmers in the village of Babakan for sharing their experiences and for their help throughout the study. The authors acknowledge Gusnia Sundari from IRD for her help with laboratory analyses. This is publication ISEM 2021- 109.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by COFA - ERA-Net COFASP through ANR (Agence Nationale de la Recherche). The project number was ANR-15-COFA-0001.