Modelling coral reefs to support their local Management : A case study in the Spermonde Archipelago, Indonesia

The potential of simulation models to provide insights on ecological questions that are crucial for the management of marine resources has become more relevant in light of the apparent demise of coral reefs. Multiple coral reef stressors can interact in nonlinear ways, confounding ecological interpretation through field studies alone. Theoretical computer modelling offers a platform to test ecological hypotheses about multiple stressors and their systemic impacts. The main purpose of this thesis was to use coral reef ecological theory to create a model as a basis for a scientifically sound, user-friendly decision support tool for the local management of coral reefs. Four major objectives were established: (1) develop a local coral reef model representing the impacts of simultaneous stressors on key ecological groups, (2) turn it into a user-friendly decision-support tool to explore different management options, (3) collect qualitative and quantitative information on the artisanal fishery of Spermonde (Indonesia) to help understand its social drivers, and (4) apply the model to real case scenarios to project the trajectory of selected coral reef response variables. Chapter two contains the description of SEAMANCORE (Spatially Explicit simulation model for Assisting the local MANagement of COral REefs) and its development. The model has two distinct compartments, benthos and fish, which run at different spatiotemporal scales and are affected by each other and by the three modelled stressors: fishing, bleaching and nutrients. Chapter three outlines an assessment of the coral reef fishery in Spermonde, focusing on the role of the patron-client system in the fishing behaviour of individual fishermen. This study contributes to the body of scientific literature on social drivers influencing fishing behaviour by empirically showing catch and behavioural differences between fishermen within the patron-client system and independent fishermen. Quantitative data on catches obtained in this study were used to parameterize fishing scenarios in Spermonde for a real case application of the model. Chapter four stems from the previous studies and adds ecological field collected data to parameterize SEAMANCORE. First, basic scenarios of nutrients and fishery were run under standardized conditions to appraise the stressorsa effects on the modelled response variables. Fishery scenarios included a fishery ban, subsistence fishery, commercial fishery, and commercial combined with destructive fishing practices. In the second part, ten-year simulations were run for four sites in Spermonde (Indonesia) exposed to varying degrees of human impacts and different initial conditions to project their local coral reefa s trajectories. Chapter 5 summarizes the contributions of this dissertation, highlighting the limitations of the modelling approach, and provides recommendations on research directions for modelling local coral reefs and management of their associated artisanal fisheries