Functional diversity in European estuaries: Relating the composition of fish assemblages to the abiotic environment

Based on a large standardised data set, the present study proposed a meta-analysis to describe general patterns in the functional diversity of estuarine fish assemblage in terms of both number of species and density along the European Atlantic coast. Fish species collected from 31 European estuaries from Portugal to Scotland were allocated to functional groups according to their ecological utilization of estuaries. A clustering analysis was performed to compare the overall functional structure of estuaries based on fish composition. Generalised linear models were computed to identify relationships between large-scale abiotic and intra-estuarine descriptors and functional attributes of estuarine fish assemblages. The total number of species, and more especially of marine species, was higher in larger estuaries with a wide entrance and, locally, in polyhaline waters. The total density was mainly related to the proportion of intertidal mudflats and, locally, was greater in mesohaline waters. In terms of relative density, northern systems were dominated by marine and catadromous species, while estuarine species were prevalent in the southern ones.