The Malzie Burn supports an impressive range of native fish species which are important to protect and enhance, including Brook lamprey, Atlantic salmon, Brown trout and European eel. Both salmon and trout play an important role in the reproduction of the critically endangered Freshwater pearl mussel as their larvae (known as glochidia), spend part of their life cycle attach onto the gills of juvenile salmonids.
GFT surveys identified sections of the burn where habitats had become degraded and were unable to support good populations of fish or other aquatic species. Using funding from the SNH Biodiversity Challenge Fund, GFT undertook an exciting and varied programme of works to improve both instream and riparian habitats over a length of 11,000 m of the burn. Six different land owners were involved in the project.
A summary of the works completed during 2019 and 2020 are listed below:
Mature riparian conifers were removed from nearly 1,000m of the river bank. The heavy shading from these conifers had killed off the native bankside plants and reduced the primary production within the burn. This resulted in poor conditions for fish and was causing some bank erosion concerns. This work was fully funded by the landowner. A further 100m length of conifers close to the burn could not be removed so instead their lower branches were cut off, up to a height of 3 m, to allow light to reach the river bank.
New fencing was erected to remove livestock grazing from 1,400m of bankside to allow riparian vegetation to flourish thereby providing draped fish cover, preventing bank collapse and to assist protecting the planted trees until they were established.
Nearly 2000 native deciduous trees were planted close to the burn over a length of over 8,000m of bank. To ensure good survival rates these trees have all been protected in tubes for their early years of growth. Most of the trees are within fenced areas but in the lower burn large wooden tree shelters were built to provide protection instead. These trees are important to provide shade to help cool future predicted water temperature rises, to protect banksides from erosion, to input woody debris habitat in the future and to increase the number of aquatic invertebrates which are an important food source for fish.
Hundreds of boulders were placed into sections of the burn which had been dredged and straightened in the past. This work has improved instream conditions by providing important cover and creating a greater diversity of habitats which will suit a range of species at different life stages.
This ambitious project has already significantly improved both instream and riparian habitats over 11 km of the burn. Conditions will continue to improve as the planted trees grow and mature. GFT are committed to monitoring the works over the long term and to undertake any necessary maintenance. Electrofishing surveys in 2020 found improved densities of fish compared to 2019 which is an encouraging start.
This project was supported by NatureScot Biodiversity Challenge Fund. We are also grateful for the support and assistance from the various landowners involved.