Session A2: From Banging Your Head into a Tidal Barrier to Migration Further Upstream. Migration Doesn\u27t Stop at the Coastline

Abstract: For many decades the abundance of small diadromous fish has been monitored in the Waddensea region by IMARES on a small selection of locations. In 2001 Rijkswaterstaat Noord Nederland initiated a 3 year study at 23 locations to get a better spatial understanding of the abundance of diadromous fish at the different tidal barriers. This study was carried out by RIKZ and Wintermans Ecologenbureau in close cooperation with several Regional Water Authorities, professional fishermen, sport fishermen and many other volunteers. As part of the “Ruim Baan voor Vissen” project this study was repeated from 2012-2014 in order to determine if there were any long term developments notable in the numbers of diadromous fish. During the presentation the results of this study will be shown. Showing up at a tidal barrier and getting past it is one thing…but how do the fish succeed migrating further inland to their spawning grounds? The last few years several studies have been carried out (or are still running) to answer this question. Examples like the migration of River Lamprey to the River Drentsche Aa (VEMCO) or smaller diadromous species (PIT) in River Westerwoldsche Aa will be presented. These results will be combined with more technical information about barriers on the route and the chosen technical fish pass solutions

Session C3- From Sea to Source

The last decade the problems concerning the well being of migratory fish has become one of the basic themes in Dutch water management. Some water managers are experienced on tackling fish migration and others are now starting up. Fish migration visions have been developed and different types of measures are implemented, monitored and evaluated. The Netherlands is especially famous for its huge amount of pumping stations. The damaging effect these pumping stations. The damaging effect these pumping stations have on fish has come under the attention of politicians just recently and is high on the agenda of policy makers. Especially the implementation of the European Water Framework Directive has given an enormous boost to restoring fish migration routes and the development of new (fish friendly) techniques. In 2009 the goals for this directive were set. Almost 2500 obstacles will be removed until 2027 following a from sea to source principle. It\u27s an ambitious goal and it asks for a strong coordination, cooperation on a regional basis and sufficient financial means. The oral presentation will give an overview on the Dutch experiences and learning points on tackling fish migration problems. It will headline the following topics: Experiences on tackling fish migration in the region of the Huze & Aa\u27s Regional Water Authority Setting the priorities for fish migration in the Netherlands (European Water Framework Directive and Eel Management plan) Examples of fish migration measures at pumping stations; The Living North Sea project; tackling river connectivity problems in the North Sea region; Introducing the worldwide Guidance on fish migration From sea to source ; www.vismigratie.nl ; a new dutch web page on fish migration. A map of fish migration measures and obstacles is presented. International network on fish migration on LINKEDin (http://www.linkedin.com/groups?gid=1215847&trk=hb_side_g

Concurrent Sessions D: Fish Passage at Tidal Barriers: Herman Wanningen and Greg Apke - Fish Friendly Tide Gate Management in the Netherlands, a Regional Perspective

Regional Water Authority Hunze en Aa’sis one of the 25 regional water management organizations in The Netherlands and is positioned in the NE corner of the country. The main responsibilities are water level management, flood defense and water quality management in the regional lakes, canals and river systems. As part of the water management tasks, RWA Hunze en Aa’s operates several tidal gates that discharge water from the regional rivers into the estuary of the River Ems. These gates play an important role as access to the hinterland for several diadromous species like smelt, Atlantic eel, three spined stickleback, flounder and river lamprey. In the past these tidal gates showed to be an almost impassable barrier for these species. Since 2001 several projects have been carried out to adjust the management and make it more fish friendly. The presentation will give an impression about the practical discussions (salinity, sediment, safety) and monitoring results for 3 of these tidal gates

Ruimte voor natuur bij onderhoud aan watergangen

De Gedragscode Flora- en faunawet vormt sinds 2007 een belangrijke richtlijn voor de bescherming van kwetsbare en zeldzame planten- en diersoorten bij het onderhoud aan watergangen door waterschappen. Deze bescherming staat inmiddels stevig op de agenda bij de waterschappen, maar is dit voldoende? In een onderhoudsproef zijn met succes onderhoudsconcepten ontwikkeld en toegepast, gericht op peilbeheer, veilig werken én de leefomgeving van planten- en diersoorten. Hierbij was de insteek het onderhoud te richten op verbetering van de leefomgeving van soorten, in plaats van de bescherming van (individuele) soorten

Ruimte voor natuur bij onderhoud aan watergangen

De Gedragscode Flora- en faunawet vormt sinds 2007 een belangrijke richtlijn voor de bescherming van kwetsbare en zeldzame planten- en diersoorten bij het onderhoud aan watergangen door waterschappen. Deze bescherming staat inmiddels stevig op de agenda bij de waterschappen, maar is dit voldoende? In een onderhoudsproef zijn met succes onderhoudsconcepten ontwikkeld en toegepast, gericht op peilbeheer, veilig werken én de leefomgeving van planten- en diersoorten. Hierbij was de insteek het onderhoud te richten op verbetering van de leefomgeving van soorten, in plaats van de bescherming van (individuele) soorten

Factors influencing the downstream passage of European silver eels (Anguilla anguilla) through a tidal sluice

Tidal sluices are a frequent element in the tidal regions of Europe's rivers and may hinder downstream migrating European eels Anguilla anguilla. Sea level rise will reduce the possibility for tidal sluices to freely discharge water, further compressing windows of opportunity for the passage of eels. Understanding how eels utilize the discharge events of tidal sluices and which conditions facilitate successful passage is pivotal for the design of effective fish migration measures. To investigate eel migration at a tidal sluice, acoustic receivers were placed at the tidal sluice Nieuwe Statenzijl and in its tributary of the Westerwoldse Aa, the Netherlands. Of the 30 tagged eels, 26 eels reached the tidal sluice and passage success was 100%. The mean migration speed of eels in the unobstructed part of the tributary was slow (0.14 m s−1). The eels were delayed in their migration by the sluice and delay was right-skewed distributed with most eels showing moderate delays (<2 days), while about 10% of the tagged individuals experienced extensive delays of more than 3 weeks. The number of missed sluicing events prior to successful passage was influenced by biological characteristics such as migration speed in the tributary, weight and condition. In addition, sluicing events with rapidly increasing and high maximum discharge levels increased the success rate of an individual eel to pass the sluice. Compromising sluicing duration in favour of higher and faster increasing discharge could facilitate eel migration at tidal barriers and contribute to the recovery of this endangered species

Van open riool naar leefbare beek, een flinke stap in de goede richting

Een beek in het Noorden van het land waarover in 1941 wordt gemeld dat in de benedenloop meer dan 5000 pond dode vis is afgevoerd en rond 1961 vrijwel alle vis uit het water verdwenen blijkt te zijn. Ook het water waar een monsternemer in 1964 meldt dat de roggebroden tijdens het uitvoeren van de metingen voorbijdreven. Het is erg moeilijk voor te stellen dat we het hier hebben over de Drentsche Aa, één van de meest intacte beeksystemen van Nederland. De beek heeft de laatste eeuw grote veranderingen in waterkwaliteit ondergaan, zowel in positieve als negatieve zin. Welke oorzaken lagen hieraan ten grondslag, hoe reageerde de beekgebonden natuur hierop en wat is er nodig voor verder herstel