Trophic interactions and energy flows in ponds used for culture-based fisheries, with emphasis on giant freshwater prawn

Abstract

A culture-based fishery (CBF) is a simple technology with a low capital cost to enhance fisheries production by stocking fish in small water bodies. A mass-balance Ecopath model was constructed in two CBF ponds in Nonghai and Nongtubkwai, Northeastern Thailand. A steady-state trophic model was constructed and used to examine the roles in ecological processes of each component in the CBF ponds with an emphasis on the stocked giant freshwater prawn Macrobrachium rosenbergii De Man, 1879. There were 12 and 7 fish components in the Nonghai and Nongtubkwai models, respectively. The trophic levels (TL) of the components ranged from 1 (for plant, phytoplankton and detritus) to over 3 for carnivorous fish. The TLs of the stocked components were between 2 and 3. The ecotrophic efficiency (EE) values of all components were less than 1 ranging from 0.13 to 0.89. The EE value of M. rosenbergii was about 0.8 and higher than for the other stocked fish species. The results also revealed that the grazing food chain was prominent in the CBF ecosystem. However, it was the detrital food chain that M. rosenbergii depended on, which made the prawn less competitive with other fish components in the ecosystem. The mixed trophic impact showed that the TL = 1 components had positive impacts on all the higher TL components, indicating bottom-up control.