The physico-chemical characteristics, biota and fisheries of estuaries

The characteristics of the biota and fisheries of estuaries are considered in the context of a contemporary definition that recognizes the physico-chemical features of the different estuary types found worldwide, i.e. macrotidal v. microtidal and permanently open v. seasonally open v. normally closed. The ways in which fishes use estuaries as a habitat and for feeding and reproduction are categorized and exemplified by fishery-important species from their constituent guilds. Marine species, and particularly their juveniles, dominate the fish faunas of permanently open estuaries. The prevalence and abundance of species either confined to estuaries or represented by estuarine populations that are discrete from their marine counterparts are far greater in systems that are periodically closed to the sea by sandbars at their mouths. Anthropogenic activities are continuing to have marked effects on estuarine environments and, in extreme circumstances, have had highly deleterious impacts on the fish faunas and fisheries of these systems.