Ecological importance of snappers in the stability of modeled coastal ecosystems

Based on mass-balanced Ecopath models from tropical shelves and lagoons, the importance of snappers (Family: Lutjanidae) on the ecosystem stability was analyzed. Using ECOSIM software, extra mortality of snappers was simulated and the effects of this mortality on the stability of the whole ecosystem was measured as persistence (time without changes), resilience (recovery capability), and resistance (absorption of disturbance). Simulation of extra mortality lasted 3, 6, and 9 years, and results were analyzed through the next 90 years. Stability showed different patterns for persistence, resilience, and resistance. Resistance decreased when mortality level and disturbance time was increased, persistence only decreased when mortality level was increased, and resilience sometimes decreased when mortality level was increased and other times increased. Reasons of this behavior are discussed. In general, rates of change were larger when the disturbance factor was lower. Lagoons were more resistant and persistent than shelves, however shelves were more resilient. Importance of trophic level, biomass, and consumption rate of snappers as responsible for these results are also discussed.