Session E2: Benefits of New Management of the Haringvliet Sluices and the Effects on Fish Migration

Abstract: The Rhine West Water Council is responsible for the regional implementation of the Water Framework Directive (WFD) and contributes to the River Basin Management Plan of the Rhine. The Rhine-West river basin is situated in the most western part of the Netherlands. It is highly industrialized and urbanized. Yet it is of major ecological importance with several ecologically important areas and main open connections from the sea to the rivers of the Dutch Delta. Thus, the Rhine-West region is a gateway to Europe, both economically and ecologically. In this duo-presentation, we would like to focus on: The Rhine-West Roadmap for Fish Migration, which complements the (inter)national Masterplan for fish migration (ICPR) which focuses on national waters. The roadmap highlights the importance of connecting the highways (national waters) to the regional roads (waters) in regards to fish migration. Its planning method makes good use of regional fish expert knowledge. The Roadmap easily identifies obstacles to fish migration and enables the selection and prioritizing of successful measures. The method is relevant to the restoration of all migratory fish, particularly in regard to the EU Eel Directive. The re-opening of the Haringvliet sluices (the Kier), one of the main hotspots for fish migration in The Netherlands. The presentation will highlights how ‘the Kier’ will give a strong impulse to the recovery of estuarine fish such as salmon, eel and sea trout in the Rhine and Meuse river basins. The presentation will also focus on the difficult decision making process which was necessary to re-open the estuary partly, with respect to all water users in the delta (including agriculture, fisheries, industry and drinking water)

Session E2: Downstream Migration of 2+ Salmon Smolts (Salmo Salar) in the River Meuse in the Netherlands

Abstract: Downstream migration of 2+ salmon smolts (Salmo salar) was studied in the Meuse in the Netherlands, in the period 2009-2013. Smolts (n =897) with implanted NEDAP transponders, were released at different locations in the lower part of the Meuse in Belgium (Berwijn, Moelingen) and the upper part of the Meuse in the Netherlands (Stevensweert, Linne), and tracked by NEDAP trail stations at 41 fixed locations distributed along the Meuse and the Berwijn to the North sea (distance more than 300 km). Over the period 2009-2013 70% (n =628) of the smolts were detected. Numbers of smolts reaching the North sea varied per year, with a minimum of 0% and a maximum of 15% of the detected fish. The route prevailingly used to migrated to sea by way of the Haringvliet. Duration of smolt migration was mostly less than one month, with average migration speeds always below 1.2 m/s. The influence of the hydro power station (HPS) Linne on the migration was examined. Yearly mortality per km of smolts, over the river stretch Linne – Lith (130 km) turned out to be higher especially in a short distance downstream of the HPS, indicating a vulnerability of the species which is higher for passing the hydropower station than for passing the weir. Also attention was paid on losses by predation of Cormorants

Session C5: Downstream Migration of Silver Eel (Anguilla Anguilla) in the River Meuse in the Netherlands 2008 – 2012

Abstract: Downstream migration of European silver eel (Anguilla anguilla) was studied in the Meuse in the Netherlands, in the period 2008-2012. Silver eel (n = 840), with implanted NEDAP transponders, were released at different locations, in the lower part of the Meuse in Belgium (Berwijn at Moelingen) and in the upper part of the Meuse in the Netherlands (Ohé en Laak). Fish were tracked by telemetry at 41 fixed NEDAP Trail detection stations distributed along the Meuse from the confluence with the Berwijn to the North sea, a distance of more than 330 km. Over the period 2008- 2013 75% (n = 630) of the eels were detected. Eel numbers reaching the North sea varied between 6-10% yearly. Most eels migrated to sea by way of the Haringvliet. Silver eel migration showed much individual variation, with fish reaching the sea within several days after being released and fish postponing their downstream migration for more than one year. The onset of migration was stimulated by increasing river discharge. Fish from different maturation classes showed no significant differences in migration speeds. Average individual migrations speed ranged from 0,3 to 1,6 m/s, indicative for at least a partly active migration (average river flow being 1 m/s). Generally migration speed slowed when fish approached sluices and weirs in the Meuse. The influence of the hydro power station (HPS) Linne on the migration was examined. Mortality of silver eel per kilometre, over the river stretch Linne – Lith (130 km) turned out to be twice as high after fish had passed the HPS (0,43% versus 0,22% passing the weir at the same location)

Outmigration Pathways of Stocked Juvenile European Sturgeon (Acipenser Sturio L., 1758) in the Lower Rhine River, as Revealed by Telemetry

International audienceWorking towards a future Rhine Sturgeon Action Plan the outmigration pathways of stocked juvenile European sturgeon (Acipenser sturio L., 1758) were studied in the River Rhine in 2012 and 2015 using the NEDAP Trail system. A total of 87 sturgeonof 3 to 5 years old (n = 43 in 2012, n = 44 in 2015) were implanted with transponders and released in May and June in the river Rhine at the Dutch‐German border, approximately 160 km from the sea. In total three sturgeons (3%) were found dead on river banks within seven days after the release. Based upon their wounds these sturgeons were likely hit by ship‐propellers. Tracking results were obtained from 57 (66%) of the sturgeons, of which 39 (45%) indicated movement into the Port of Rotterdam. Here the sturgeons remained for an average of two weeks, which suggests they spent time to acclimatize to higher salinities before entering the North Sea. Of the 45 (52%) sturgeons that were confirmed to have entered the North Sea, ten (22%) were recaptured (mainly by shrimpers and gill‐nets) close to the Dutch coastline; nine were alive and were released. From the results we obtained the preferred outmigration pathways, movement speeds and an indication of impacting factors (i.e. ship propellers and bycatch). Bycatches provided also localisations information in the coastal area. A next step to complete this work would be to assess habitat selection in freshwater and downstream migration of young of the year (YOY sturgeons) in the Lower Rhine

Terug naar de oertijd : herintroductie van de Atlantische steur in de Rijn

De Atlantische steur (Acipenser sturio) behoort tot een ruim 200 miljoen jaar oude diergroep. Deze kraakbeenvissen overleefden de dinosauriërs. Echter, tussen 1920 en 1990 verdween de steur door toedoen van de mens uit vrijwel alle grote rivieren van West-Europa. Het is een geweldige uitdaging om deze oervis met beenplaten en vier snorharen voor uitsterven te behoede