Benthivorous fishes interaction with submerged vegetation – A simple exclosure experiment (original) (raw)

This study tested the setup of an exclosure experiment to exclude or at least diminish direct impacts of medium-to large size benthivorous fishes on submerged macrophytes in three EU habitat type 3140 lakes in NE-Germany. In lakes Großer Glietzen and Peetsch no effect on stimulation of regrowth of macrophytes could be observed, the exclosures remained free of macrophyte vegetation like the reference plots. This is likely caused by water level fluctuations resulting in lake bottom conditions unsuitable for macrophyte development. Only in Lake Stechlin significant differences of macrophyte development between inside and outside the exclosure have been observed in 2014 and 2015. The ratio of covered vs. uncovered sediment was significantly influenced by presence or absence of benthivorous fishes. Also the ratio of charophytes vs. angiosperms and other groups was significantly influenced. In 2014 and 2015 Charophytes dominated the macrophyte vegetation inside the exclosure, while at the reference plot in 2014 angiosperms dominated and in 2015 significantly increased. The experiment results support the hypothesis, that benthivorous fishes are key species and strongly influencing macrophyte communities. Additionally species-specific direct impacts of certain benthivorous fishes on macrophytes are documented from direct observations.