Multi-metric indices are widely used in water quality assessments since they often provide integrative and more holistic perspectives. Fish-based indices have been proposed worldwide, especially in Europe due to the implementation of Water Framework Directive (WFD). It is expected that these indices and their respective metrics reflect human pressures and may be useful recognising specific measures for management and rehabilitation. However, in the paste few years a wide diversity of indices have been proposed, which have considerable differences in what concerns their ability to evaluate cause-effects relationships between the state of fish assemblages and human pressures. In the present study we evaluate the strength of cause-effect relationships based on ecological census and published literature of the fish-based indices that have been proposed in the context of WFD. For each index, their metrics were evaluated and scored in what regards their sensitiveness to several human pressures and the expected time-lag in their respective response. Most of the metrics are influenced by several human pressures, being difficult to identify cause-effect relationships. For the majority of the indices the metrics used to evaluate certain pressures are expected to give indications in a medium or long-term basis, which clearly collides with the assessment and management schedule commitments in the scope of WFD.