Concordance between expert judgment and fish-based multimetric indices in the assessment of estuarine waters ecological quality

Abstract

Many fish multimetric indices have been proposed worldwide during the last two decades to assess ecological quality of estuaries. Methods and monitoring plans consist often in the application of a sampling protocol and calculation of these indices, and are usually performed without a marked intervention of experts. Also, these surveys are resource demanding and its cost-effectiveness is generally not discussed. In this study, we analyzed the assessments made by experts of the ecological quality of estuaries based on fish data and we compared these evaluations with those given by the Estuarine Fish Assessment Index (EFAI) developed to estimate the quality of Portuguese estuaries. Twenty-four virtual data sets, simulated based on real fish data collected in Portuguese estuaries, were used in the analyses. Seventeen Portuguese experts were requested to determine their ecological quality and the EFAI was also calculated for each data set. For most of the systems, the assessments made by the experts were relatively close between them, and the levels of agreement between the experts and ecological quality status (EQS) obtained from the EFAI were high. The number and type of criteria used by experts differed, although some communalities were found. A positive relationship between the number of criteria used and the level of agreement was also noticed. The utilization of fish-based indices presents several advantages, namely the standardization of criteria used and critical boundaries assigning EQS of the systems, but expert judgments can indeed be of major relevance in assessments.