Results and lessons of 17 years of monitoring at the tidal fish pass Roptazijl (The Netherlands)

Description

Sluices, weirs and pumping stations form a migratory obstacle for diadromous
fish in estuaries and deltas around the world resulting in decreased recruitment
success and biodiversity of fish fauna in estuarine-riverine systems. In the
Dutch Wadden Sea intertidal fish passes have been built to facilitate
diadromous migration. The fish pass of Roptazijl was built in 2002 and is one
of the first fish passes in the Wadden Sea. The fish pass functions for part of
the tidal cycle. To attract diadromous fish, the fish pass pumps fresh water
over the dyke to a small basin on the Wadden Sea-side. The contents of the
basin, including fish, is siphoned towards the polder every two hours. Passage
of fish has been monitored using a fyke net, every spring, since 2002. In
addition, the presence of diadromous fish on the Wadden Sea-side and
seasonal abundance was monitored in 2014, 2015 and 2016 using cross nets.
Fish pass functioning was logged by the water authority. Results show that the
fish pass is often out of order impairing fish migration. Fyke net monitoring
shows that predominantly sticklebacks and glass eels use the fish pass. Cross
net monitoring on the Wadden Sea-side shows that arrival of stickleback and
glass eels at the fish pass has a relation to the tidal cycle. As such, the
research at Roptazijl, shows that in the design and building of tidal fish passes,
possible temporal window of opportunities for migratory diadromous fish, can be an important design criterion.

Period	24 Sep 2019
Event title	International SWIMWAY Conference
Event type	Conference
Location	Hamburg, Germany