Regulation effect in river Nea

The aim of the project was to assess the effect of regulation and weirs on diversity of river benthic macroinvertebrates. Macroinvertebrates were sampled by four-minute kick-net sampling, using a 500-µm net. Samples were collected in spring and autumn 2019 from 19 stations along a 29-km reach of a the river Nea, between the lakes Heggsetsjøen and Selbusjøen. Samples were collected incloste to the weirs, one sample upstream a weir in a stationary part and one sample downstream a weir in a rapid. The samples were taken by holding the net downstream and kicking up the substrate while backing upstream. In stationary parts, the net was moved from side to side in front of the kicking feet to catch the material that was swirling up. All benthic groups were determined at the lowest possible taxonomic level and number of specimens was counted. Two different biological quality indices were calculated for the study reach to assess the ecological status of the river.