Frontiers in Marine Science (Nov 2015)
Typology of Danubian fish assemblages
Abstract
Environmental management needs well definable management units for the establishment of which typological approaches are often applied. However, inconsistent sampling strategies among countries can hinder large scale evaluation of aquatic assemblages for bioassessment purposes in very large transboundary rivers. We examined spatial changes in fish assemblages along the longitudinal profile of the Danube River, the second largest river in Europe, using a standardized sampling protocol, to define management units and thereby aid water management at the international level. The conventionally applied inshore electrofishing protocol was combined with sampling of offshore benthic habitats with an electrified trawl to provide a more accurate picture on fish assemblages, for the first time in any transboundary large river survey. We found that well definable assemblage classes can be set up at large spatial scales, although fish assemblages of relatively natural and impounded stretches show some separation. Contrary to the zonation concept many characteristic species could be found along the profile of the whole river, although indicator species analysis defined many character species for the typology classes. Results of the two sampling protocols complemented each other and revealed that multi gear evaluations are necessary for a better assessment of fish assemblages in very large rivers.
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