Holistic modelling of a subtidal benthic ecosystem of northern Chile (Tongoy Bay), to improve the knowledge and understanding of its structure and function: assessing the effects of intensive fisheries upon different invertebrates and algae speciesHolistic modelling of natural complex systems

Abstract

Along the Chilean coast an intensive harvest of intertidal and subtidal benthic resources has been developed historically. As a consequence, many invertebrate and macroalgae species are over-exploited with negative impacts on their biological fitness, ecological interactions, recruitment success, etc, as well as on the community function as whole. Management strategies are required to avoid these negative impacts and to arrive at a sustainable fishery. Based on the holistic modelling the following questions were explored and answered: (1) What are the principal benthic predators, their consumption rates and prey item?; (2) What is the carrying capacity of the systems in terms of food availability for target species and predators?; (3) Is it possible to recognise and quantify Redundancy in the systems?; (4) How sustainable are different management policies?. Four different holistic modelling approaches were applied (1) ECOPATH II; (2) ECOSIM; (3) ECOPACE; (4) LOOP ANALYSIS. ECOPATH II models revealed all habitat systems appear immature and highly resistant to external perturbations. The seagrass and sand-gravel habitats have a potential for a three fold increase of the present standing stock of the scallop A. purpuratus and the red algae Ch. chamissoi. The ECOSIM models show that the maximum sustainable yield (FMSY) for the scallop A. purpuratus were relatively lower than those estimated by single species approaches previously applied in this system. ECOSPACE models revealed that a habitat rotation fishery is recommended. LOOP ANALYSIS models were found sustainable only if the fishermen were self-damped , which means when the fishing effort and fish quota are restricted.