Biogeographical region and environmental conditions drive functional traits of estuarine fish assemblages worldwide

Abstract

Assessing trait–environment relationships is crucial for predicting effects of natural andhuman-inducedenvironmentalchangeonbiota.Wecompiledaglobaldatabaseof fishassemblagesinestuaries,functionaltraitsoffishesandecosystemfeaturesofes-tuaries.Andwequantifiedtherelativeimportanceofecosystemfeaturesasdriversof patternsoffishfunctionaltraitsamongestuariesworldwide(i.e.driversofthepropor-tions of fish traits). In addition to biogeographical context, two main environmental gradientsregulatetraitspatterns:firstlytemperature,andsecondlyestuarysizeand hydrologicalconnectivityoftheestuarywiththemarineecosystem.Overall,estuaries incolderregions,withlargerareasandwithhigherhydrologicalconnectivitywiththe marineecosystem,havehigherproportionsofmarinefish(versusfreshwater),macro-carnivoresandplanktivores(versusomnivores,herbivoresanddetritivores)andlarger fish, with greater maximum depth of distribution andlongerlifespan. The observed trait patterns and trait–environment relationships are likely generated by multiple causalprocesseslinkedtophysiologicalconstraintsduetotemperatureandsalinity, size-dependent biotic interactions, as well as habitat availability and connectivity. Biogeographical context and environmental conditions drive species richness and composition,andpresentresultsshowthattheyalsodriveassemblagetraits.Theob-served trait patterns and trait–environment relationships suggest that assemblage composition is determined by the functional role of species within ecosystems. Conservationstrategiesshouldbecoordinatedgloballyandensureprotectionofan arrayofestuariesthatdifferinecosystemfeatures,evenifsomeofthoseestuariesdo notsupporthighspeciesrichness.

Publication
Fish and Fisheries
Date