A preliminary snapshot of the trophic model and ecosystem attributes of Kaptai reservoir ecosystem, Bangladesh

Abstract

A mass-balanced Ecopath model presents a quantitative description of the trophic structure, flow of energy and trophic interaction among ecological groups of an ecosystem. The Ecopath with Ecosim (EwE) modeling program (Version 6.5) was used to develop a preliminary trophic model for a tropical freshwater reservoir. The total fish biomass was 6.245 t/km2 and the highest trophic level of the reservoir was 3.362 (for snakehead). The ecosystem is phytoplankton based because primary producers originated 68% and detritus originated 32% of the total flow from lower trophic level. The gross efficiency of the fishery was 0.004, suggesting the inefficiency of the system. The positive effect of phytoplankton and detritus on most of the other groups were evident from mixed trophic analysis while moderately higher ecotrophic efficiency (EE) of phytoplankton shows the ecosystem’s potential bottom-up control. The competition for the same resources among different groups was also obvious. The ratio of primary production/respiration (1.969) suggests that the ecosystem is at the developing stage and utmost contemplation should be given to concerned human activities. The low value of relative ascendancy (30.13) and overhead (69.87) reveals the stability of the ecosystem and some degrees of maturity. It also predicts the presence of significant strength in reserve of the system to withstand or overcome any perturbation. However, ecologically sustainable resource management plans should be implemented to ensure the sustainability of this reservoir resources.