State of the Art in Simulating Future Changes in Ecosystem Services

Abstract

The goal of fisheries assessment is to predict the consequences of fishing and other environmental interventions and, on that basis, evaluate how different management schemes fare at achieving various management goals. Forecasting the state and harvest of exploited populations and communities is thus central to fishery science.There are two broad approaches that can be used to forecast fisheries population and harvest. On the one hand, there are short-term forecasts aimed at predicting the size of the exploitable stock for the upcoming fishing season in order to implement a predetermined feedback harvest rule. In this case, the forecast is part of the tactic used to define regulatory measures for the fishing season, such as the total allowable catch or the number of allowable effort units. This type of forecast is critical for fisheries based on shortlived or semelparous species (species that reproduce once and then die), where the bulk or all of the annual catch is made up of new recruits.Mid- and long-term forecasts of populations, on the other hand, are used in policy design to examine likely consequences of different management options and thus guide strategic decision-making. In contrast to short-term tactical forecasts, mid- and long-term forecasts are not meant to actually predict the future of the system under exploitation; rather, they attempt to represent a full range of scenarios that are deemed possible based on historical experience. Because our ability to actually predict the responses of natural systems to harvest is admittedly limited, the emphasis in policy design is on feedback and robustness of performance across scenarios. Mid- and long-term forecasts aimed at guiding general management approaches are difficult because they require more information than the most recent harvest rates and data on catch per unit of effort, but it is not clear which of many possible auxiliary data will be most useful or how much history to consider.