Reaching the spawning site - Insights into migration efficiency of river lamprey in the Grift In this study, the impact of a weir on the passage by adult river lamprey (Lampetra fluviatilis) was evaluated in the Apeldoorns Kanaal and Grift catchment over migration season 1 (MS1, winter 2019-2020) and MS2 (winter 2020-2021). The effectiveness of facilitating passage by a ramp instrumented with studded tiles (‘lamprey tiles’) on the weir was monitored with a Passive Integrated Transponder (PIT) setup. The same PIT setup was used at stream junctions (n = 3) located upstream of the weir to monitor the degree to which individually tagged river lamprey entered the stream during the spawning migration. Furthermore, presence of river lamprey was manually surveyed by using a mobile PIT scanning device in MS2. Adult river lamprey were caught (n=95 and n=101 in MS and MS2, respectively) using electrofishing in the Oude Grift and displaced over a hydropower turbine into the Apeldoorns Kanaal (MS1) or into the Grift, downstream and upstream of the weir (MS2). In MS1, 27 (28,4%) of river lamprey tagged arrived at the weir 8.8 km upstream, showing willingness to migrate up in the Grift-system. None of these passed the weir, at the time not yet instrumented with the studded tiles ramp. In MS2, 19 river lamprey released downstream of the weir successfully passed, making use of the lamprey-tiles and passed over the weir. Particularly the Horsthoekerbeek was entered by river lamprey (21 out of 28 individuals detected at upstream stations). With the mobile scanning device, 13 river lamprey were found, all of which in the Horsthoekerbeek. Based on the findings of this multi-year study, we hope to advise on adequate restoration measures for enhanced conservation of the threatened river lamprey. De rivierprik is een van onze zeldzaamste trekvissen, waarvan minder dan een handvol paaiplekken bekend is binnen ons land. Sinds kort weten we dat ze in de winter ook het Griftsysteem op willen trekken. Een sluis en waterkrachtcentrale beletten zijn doorgang, maar ook verderop in het systeem zijn barrières aanwezig. We zijn een onderzoek gestart naar de kansen en knelpunten en zoeken samen met Waterschap Vallei en Veluwe en Provincie Gelderland naar oplossingen. In dit artikel beschrijven we de aanpak en eerste resultaten.

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RAVON

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RAVON

J. Tummers. (2021). De paaitrek van rivierprik in de Grift. Een telemetrisch onderzoek naar vismigratie. RAVON, 23(2), 34–37.
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