A sampling strategy and methodology for assessment and monitoring of Mediterranean small-scale fisheries

In order to reach a quantitative assessment of the Mediterranean small-scale fisheries one of the main problems is to evaluate in space and time the elementary fishing efforts and yields of every component and their corresponding variations. These elements are essential for the evaluation of global production and fishing effort, the monitoring of which is of paramount interest for the study of the fisheries and exploited resource dynamics. This paper presents a methodology based on the statistical principles of so-called "stratified random sampling" which we have developed in an attempt to solve this problem. The collection of data is achieved in the field by a team of investigators which operates within a space-time stratification of the study area. The sampling strategy is based on two types of questions aimed to provide independent data series on effort and landings for each space-time stratum. The processing of the samples allows us to evaluate average yields and effort and their variance per stratum. Total catches and effort values are finally extrapolated after an appropriate weighting of these results.