Survey sampling for fisheries monitoring in Brazil: implementation and analysis

Abstract

Census of fishing data about the landings carried out along the Sao Paulo coast during 2011 was used to evaluate and compare the survey sampling for fisheries monitoring, expecting reliable results along with an important cost reduction. Estimates of total catch for the Sao Paulo State as a whole and by municipality were relatively accurate (high precision and low bias). Estimated catch by month, by fish categories and both (factors not considered in the sampling design) demonstrated that, as the level of required detail increased, the catch estimates became more biased and less precise. However, when comparing to the 2011 true catches, the order of importance of fish categories based on estimated catches changed slightly in some positions after the fifth place. There was a minor cost reduction due to the sampling in comparison with the census methodology currently in use (15.4% at most). The results demonstrated that fisheries monitoring costs are directly proportional to the required level of details and data quality.