The River Bladnoch Scallop Shell Project aims to investigate the potential use of waste scallop shells for mitigating acidification in watercourses. A total of 692 tonnes of waste scallop shells were laid along forest tracks and placed into watercourses. This project is being run as an experimental trial and will be monitored for 5 years.
The River Bladnoch originates from the outflow of Loch Maberry and is approximately 56 km long with a catchment area of roughly 340 square kilometres. The River Bladnoch was designated a Special Area of Conservation (SAC) status in 2005 for Atlantic salmon, with the aim of ensuring that its Atlantic salmon population remains in a favourable condition. However, some areas of the upper catchment are downgraded by acidification which negatively impacts Atlantic salmon by preventing the successful spawning of adult fish. In acidified watercourses, the enzyme which allows salmonid eggs to hatch is prevented from being released which causes the eggs to remain shut. The inability for eggs to hatch is called recruitment failure and more eggs are unable to hatch as acidity increases. Atlantic salmon have disappeared from some areas of the upper catchment. GFT undertake annual water quality monitoring across Galloway’s catchments and the 2023 and 2024 monitoring of the River Bladnoch highlighted the key areas most impacted by acidification. The data from this monitoring project was used to select the sites for the scallop shell applications. Galloway is extensively covered in peatland but historical land use practices have drained and damaged much of the deep peat causing water quality problems including acidification. The degradation of peatland lowers the water table and exposes the peat to aerobic decomposition which leads to the carbon previously stored in the peat being released into the environment.
The Galloway Fisheries Trust (GFT) began developing the Scallop Shell Project in June 2024 following interest from the River Bladnoch District Salmon Fishery Board (RBDFSB) to investigate the potential impacts of scallop shells on acidified watercourses. This project trials using scallop shells to help improve water quality by increasing the pH within key acidified watercourses. Scallop shells, like all marine mollusc shells, are made up of calcium carbonate which can be used as an effective acid neutraliser. The project involved both terrestrial applications of scallop shells onto old style forest tracks which drain into nearby watercourses, and instream applications of scallop shells hand placed directly into watercourses. A total of 692 tonnes of scallop shells were used in this project. 680 tonnes of king scallop shells, a harder and more robust shell, were crushed and laid along forest tracks. A further 12.3 tonnes of queen scallop shells, a small and softer type of shell, were hand placed into selected watercourses. The project is being monitored with various techniques, including water quality monitoring (with a strong focus on pH), electrofishing and invertebrate surveys, and visual surveys of shell breakdowns and movements. Baseline monitoring began in September 2024 prior to the project works commencing in March 2025. The project will be monitored for 5 years and an annual report on the findings will be produced.
This project was guided by a similar study conducted in Maine, USA which looked at the impacts of using clam shells in acidified streams. This project produced positive results, however the study included no control sites to confirm the accuracy of the pH changes. The River Bladnoch Scallop Shell Project includes several control sites which will give insight into the potential efficiency of sea shells on mitigating acidification.
This project involves partnerships with GFT, RBDSFB, Forestry and Land Scotland (FLS), Scottish Woodlands, and private landowners, with additional input from NatureScot and SEPA. The project was funded by the Salmon Scotland Wild Fisheries Fund and GFT. There has been alot of interest in the project including an appearance on the BBC One Show in June 2025 ( https://www.youtube.com/watch?v=lhiljNmIDTg ) and a poster presentation viewed by John Swinney at the annual FMS conference in March 2025.
If the River Bladnoch Scallop Shell project is successful, the techniques used could provide a useful short term solution for encouraging the recovery of salmon and trout while larger scale projects and long term land use changes are put into place to address acidification. Scallop shell applications may help support long term efforts such as forestry to bog peat land restoration, opening up of riparian zones, and forestry restructuring. It is an interesting project and we look forward to collecting and sharing the results.
SEPA have been undertaking a review of the current CAR license which the Galloway Hydro Scheme operates under.
On Saturday 26th August we held our annual Kirkcowan Fishing Competition. 35 adults and 12 juniors entered the competition this year, providing a fund of £211 that is put back into the event via prizes and a buffet.
Riparian zones bridge the gap between land and river, creating an important habitat for insects while also providing shade and protection against erosion. We do a lot of habitat work mainly to help aquatic species like fish, but we are keen to monitor and understand the wider biodiversity benefits.
