Hull International Fisheries Institute Electric Fishing Survey of Trout in the Town Ranunculus Planting Site
Here is a video showing just one of a long series of ongoing surveys on a site that was impacted by dredging activities. The Environment Agency re-introduced large boulders and also installed some marginal plants to help the site to begin to recover. Subsequent to that, volunteers from SPRITE- a group set up in Sheffield through the Trout in the Town project applied for permission and carried out re-planting of water crowfoot to improve the structural and invertebrate community diversity within the channel. The method for doing this in spate rivers is highly original and was developed primarily by Dave Woodhead — a central and long-standing SPRITE member, with Ranunculus collection from biologically clean headwater sites and planting work parties being run by Dave and Paul Hughes.
SPRITE also carried out some wildflower seed planting and have joined with other local volunteers to reduce the amount of Himalayan Balsam in reaches upstream of this section.
The video shows how important complex submerged cover is to trout (especially). In much simpler habitat almost all of the trout would have been caught at the upstream barrier after the activity of the survey team had flushed them all the way up through simple habitat that lacked refuge opportunities. However, whilst Ranunculus does not provide much defense against being stunned by a small electric field it (and other complex submerged cover such as tree roots, submerged fallen tree crowns and root wads) does provide significantly improved protection against natural visual predators.
Studies have shown that fish-eating bird predation efficiency drops greatly in the presence of complex submerged cover — and predators give up after a shorter duration to try elsewhere because their calorific return for the energy they need to expend to catch more prey makes the effort unprofitable.
Check out Richard Noble’s survey team in action in the video above and see the fruits of volunteer labour (and note how most of the trout that are caught in the middle of the reach are hugging the Ranunculus!). This water plant is also excellent habitat for a number of aquatic invertebrate species and can contribute to improved diversity in flow velocities and associated substrate particle and nutrient-sorting over the cross-section of a channel.