Energy transfer and trophic organization in an Integrated Fish-Livestock-Horticulture System (IFLH) from Bicholim (Goa), the western coast of India

Abstract

An integrated farming system (IFS) is a farming approach that helps to conserve agrobiodiversity, provides food security, enhances ecosystem services, maintains environmental quality, and also achieves sustainability. In this study, we analyzed the energy transfer and trophic organization in an IFS comprising of fish (seabass, catfish, tilapia), livestock (piggery and poultry), and horticulture components situated in Goa, western coast of India. The ‘IFS’ is designated as ‘Integrated Fish Livestock Horticulture system (IFLH)’. An Ecopath model was constructed for the IFLH to delineate the trophic organization and generate ecological indicators on energy transfer, resource use and recycling, ecosystem maturity and stability. In the IFLH model, thirteen ecological groups were defined ranging from trophic level 1.00 (detritus and benthic nitrogen fixers (BNF)) to 4.00 (catfish), seabass (0.99) and piggery (0.98) demonstrated the highest ecotrophic efficiencies and the lowest value was recorded for detritus (0.20). The energy transfer from detritus (90%) was much higher than the transfer from primary producers (10%). The transfer efficiency at the second trophic level was as high as 0.6 for the IFLH. The fish and livestock components (tilapia-31%, weedfish-21%, piggery-20%, and seabass-8%) showed the highest consumption rates in the IFLH. A high total system throughput (22,417.9 kg N ha−1 year−1) and gross efficiency (0.34) for the IFLH indicated greater levels of ecosystem activity and growth rate at low maintenance energy costs. The system yielded moderate values for Finn's cycling index (8.51), system omnivory index (0.32), and connectance index (0.18). Thus, these ecological indices showed that the IFLH system is moderately mature, stable, and resilient. The ecological indices; ascendency (44%), system overhead (56%), mean path length (3.4) and Finn's cycling index suggested that the ecosystem is comparatively stable, developing, resource-efficient, and sustainable system based on the ecosystem properties. The eco-exergy index (4434.25 g detritus equivalent m−2), specific eco-exergy (55.86), and robustness index (0.13) also classified the IFLH as moderately mature, relatively stable, and reasonably organized. To date, this model serves as the first IFLH model from India's western coast and would supplement the evaluation of other IFS using the modeling approach. However, the ecosystem indices also indicated further scope for improvement in the IFLH system to improve energy utilization, resource recycling and stability.