Project concept
The project was conceived between 2 EA Fisheries officers (Chris Bell & Kye Jerrom) seeking a way to alleviate the lack of passage for coarse fish in the Cut-Off Channel to enable them to make their way further upstream on the River Wissey near Stoke Ferry, Norfolk UK. The navigable Wissey water levels are tightly controlled by sluices and flood banks. This in itself presents a considerable problem, especially for conventional fish passes. Despite the need to provide a solution, it was clear that whatever was proposed must not impact upon the current flood defences. In order to progress the work an innovative solution was needed. This came in the form of a Dutch invention, a Fish Syphon. Yes, they really do exist! Fish syphons are used throughout the Netherlands and work in low-head situations.
- Wissey Fish Syphon
Outline
The Fish Syphon was designed and built in the Netherlands and brought over and installed by Aquatic Control Engineering (ACE). Monitoring of the novel Fish syphon was undertaken by Fishtrack utilising RFID technology. Two RFID aerial loops were installed during manufacture to the top and bottom sections of the syphon. This enables the system to be monitored from both directions as well as for
determination of the fish Syphon's efficacy. Assessment of specific fish species performance can be evaluated too. Over a 4-5 year period fish were routinely captured tagged and released and observed in relation to their association with the Fish Syphon as well as their passage performance
Detail
The River Wissey was failing Water Framework Directive (WFD) target of Good Ecological Status and the reasons for failure were fish migration. The 2 principal impediment to migration were determined to be the 2 large sluice gates (Diversion sluices) of the Cut Off channel. This project addresses these concerns and evaluates the potential of Fish Syphons in the UK.
The fish Syphon is a 'pool and weir' type fish pass, enclosed in a tube. It measures 72m in length, diameter ranges from 1.8m to 1.6m and it includes 26 baffles spaced 1.5m apart. It has been modified to pass a variety of coarse fish species as well as salmonids known to frequent the waterways. during the monitoring of the Syphon >270 fish have successfully used the Fish Syphon. Twelve different species have been identified successfully using the Fish Syphon including several sea trout. fish were captured by electrofishing surveys and tagged before being released in the proximity of the lower end of the syphon. Additional capture of fish upstream was also undertaken to cause forced migration. Both methods were evaluated and passibility of the Syphon was assessed. Additional methods were employed using hydroacoustic tags and remote tracking technology via acoustic receivers. the receivers were deployed both upstream of the Syphon extending into the headwaters of the Wissey as well as down stream towards the Relief Channel. Several sea trout were captured and tagged with both technologies. Of the sea trout, 80% moved successfully upstream via the new Syphon. These fish were later detected 20km further upstream at the next barrier to migration. This indicated spawning runs for the sea trout which suggests a reevaluation of the WFD classification for this river to incorporate migratory species such as sea trout. The implications are such that restoration of the upper Wissey should be considered a priority.
Results
The monitoring project ran for 4 years. During this time >250 fish have successfully passed through the Syphon. A total of 12 different species ranging from 62-513mm passed through the Syphon to gain access to the upper Wissey above the sluice and out of the cut Off channel. The largest fish to pass was a brown trout and the fastest passage was made by a sea trout (51mins 58 secs).The average passage time was 5 hrs 14 mins. the syphon creates important refuge habitat for fish at the end of the Cut Off channel as evidenced by the number of detections of tagged fish at this end of the Syphon (>13000 detections between July 2012 & June 2014). peak activity around the Syphon and through the pass was during autumn and early winter. Some of the data has been analysed and presented at conference (IFM Tagging Conference, Leeds, 2014) and the remainder is programmed in for full analysis and reporting in the near future.
Background
The River Wissey, located in the East of England on the edge of the Fens, is 50Km long, comprising of flood relief channels with stretches of naturalised channel. There are various structures that are thought to impede the access of fish seeking to move throughout the river system.
Within the river are both coarse and salmonid fish species. In the upper reaches, wild brown trout (Salmo trutta) are present. Coarse fish are found throughout the river, and at Stoke Ferry where the river is widened and intersects with the flood relief Cut Off channel, there are a wide range of fish species.