Event Title

Concurrent Sessions D: Fish Passage at Tidal Barriers: Herman Wanningen and Greg Apke - Innovative Fish Migration River Between Wadden Sea and Lake Ijsselmeer

Location

Agriculture Science Theater, Oregon State University

Start Date

25-6-2013 3:30 PM

End Date

25-6-2013 3:50 PM

Description

The Rhine is one of the largest rivers on the European continent. It runs from Switzerland through Germany and the delta covers almost half of the area of the Netherlands. The river basin covers185.000 km2.In early ages the river ended in the estuary ‘Zuiderzee’, an open, tidal estuary that provided habitat for many species of fish. The Zuiderzee was particularly famous for its rich fishery grounds. To prevent future flooding and to develop new agricultural polders the Zuiderzee was closed off and separated from the Wadden Sea in 1932 with a 32km long dike, the ‘Afsluitdijk’. The dike served as a protection against storm floods and as salt levels gradually decreased this new lake ‘IJsselmeer’ transformed into a huge freshwater storage with significant economic benefits. On the downside, the gradual intertidal fresh-saltwater gradient disappeared, and so did many of the characteristic fish like smelt, houting, sea trout, sea lamprey, herring, alosa, anchovy, etc. The Afsluitdijk had become a barrier between salt and fresh and closed off one of the main doors for fish migration into the river Rhine. The current tidal discharge sluices only open to release superfluous freshwater in the rainy season and most of the time water currents are too high to allow fish to migrate from sea into the lake and hence the rivers upstream of the lake. The negative effects on fish populations resulted in a strong decrease of fishery. Commercial fishermen had to adapt to the new situation and their fishery had to change gradually into freshwater fishery. But nowadays this freshwater fishery is decreasing as well. It is widely accepted that opening the door for fish will greatly improve local and migratory fish populations and both biologists and engineers have proposed several solutions in the past. The major challenge in design remains the fact that the inland lake needs to remain fresh at all times. This limits the possibilities for the ideal solution; an open connection with free tidal characteristics. In 2012 both economic and nature conservation stakeholders have launched the idea of the Fish Migration River, designed to break the barrier. The idea is to construct an artificial river connecting the tidal saltwater Wadden Sea with the freshwater IJsselmeer, with enough length to buffer the saltwater flowing in during high tide. Situated next to the main sluices, a working Fish Migration River can serve multiple goals. It facilitates the return of freshwater fish unintentionally flushed out by the discharge sluices. It opens the dike for a wide range of migratory fish, and provides them with a gradual habitat for physiological adaptation. Furthermore this location has an added value for recreational and education activities. A visitor center is included in the plan as well.The plan has received positive reactions by local, regional and national government and a feasibility study has resulted in a primarily design.For an optimized design further research is needed. It is essential to understand both (local) ecological demands of the fish and potential morphological effects on the Wadden Sea.

Comments

Herman Wanningen is an aquatic ecologist with more than 15 years’ experience in freshwater ecology and water management. He has worked for the regional Water Authority Hunze and Aa's (The Netherlands) on estuary, river, and lake restoration projects. In 2007 Herman started Wanningen Water Consult. He develops fish migration visions and policies and gives advice on implementing different types of fishway techniques. He gives advice on national and international projects dealing with the theme fish migration and river connectivity. He organizes conferences, network meetings and is founder of the World Fish Migration Network and Fish Ecology Network on LINKEDin Sea to source (2006). Herman is coordinator of the worldwide guidance From sea to source, International guidance for the restoration of fish migration highways (2012).

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Jun 25th, 3:30 PM Jun 25th, 3:50 PM

Concurrent Sessions D: Fish Passage at Tidal Barriers: Herman Wanningen and Greg Apke - Innovative Fish Migration River Between Wadden Sea and Lake Ijsselmeer

Agriculture Science Theater, Oregon State University

The Rhine is one of the largest rivers on the European continent. It runs from Switzerland through Germany and the delta covers almost half of the area of the Netherlands. The river basin covers185.000 km2.In early ages the river ended in the estuary ‘Zuiderzee’, an open, tidal estuary that provided habitat for many species of fish. The Zuiderzee was particularly famous for its rich fishery grounds. To prevent future flooding and to develop new agricultural polders the Zuiderzee was closed off and separated from the Wadden Sea in 1932 with a 32km long dike, the ‘Afsluitdijk’. The dike served as a protection against storm floods and as salt levels gradually decreased this new lake ‘IJsselmeer’ transformed into a huge freshwater storage with significant economic benefits. On the downside, the gradual intertidal fresh-saltwater gradient disappeared, and so did many of the characteristic fish like smelt, houting, sea trout, sea lamprey, herring, alosa, anchovy, etc. The Afsluitdijk had become a barrier between salt and fresh and closed off one of the main doors for fish migration into the river Rhine. The current tidal discharge sluices only open to release superfluous freshwater in the rainy season and most of the time water currents are too high to allow fish to migrate from sea into the lake and hence the rivers upstream of the lake. The negative effects on fish populations resulted in a strong decrease of fishery. Commercial fishermen had to adapt to the new situation and their fishery had to change gradually into freshwater fishery. But nowadays this freshwater fishery is decreasing as well. It is widely accepted that opening the door for fish will greatly improve local and migratory fish populations and both biologists and engineers have proposed several solutions in the past. The major challenge in design remains the fact that the inland lake needs to remain fresh at all times. This limits the possibilities for the ideal solution; an open connection with free tidal characteristics. In 2012 both economic and nature conservation stakeholders have launched the idea of the Fish Migration River, designed to break the barrier. The idea is to construct an artificial river connecting the tidal saltwater Wadden Sea with the freshwater IJsselmeer, with enough length to buffer the saltwater flowing in during high tide. Situated next to the main sluices, a working Fish Migration River can serve multiple goals. It facilitates the return of freshwater fish unintentionally flushed out by the discharge sluices. It opens the dike for a wide range of migratory fish, and provides them with a gradual habitat for physiological adaptation. Furthermore this location has an added value for recreational and education activities. A visitor center is included in the plan as well.The plan has received positive reactions by local, regional and national government and a feasibility study has resulted in a primarily design.For an optimized design further research is needed. It is essential to understand both (local) ecological demands of the fish and potential morphological effects on the Wadden Sea.