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Galloway Fisheries Trust

Fisheries House, Station Industrial Estate, Newton Stewart, Dumfries & Galloway, Scotland. DG8 6ND
Telephone: 01671 403011 · Fax: 01671 402248 · Scottish Registered Charity No. SC020751

Looking downstream on the River Cree

Brown Trout

Looking upstream on the River Bladnoch

Felling of commercial forestry in Galloway Forest Park

Looking upstream on the River Luce

North American Signal Crayfish

The sandy beach at Loch Grannoch

Belted Galloway Cattle, or 'Belties'

Fly fishing on the River Cree

Murray's Monument

A small upland burn

A stoneloach

The High Cree, looking towards Cairnsmore of Fleet

A small waterfall on the Buchan Burn

A salmon from the Kirkcudbrightshire Dee

Liming research to ameliorate acidification


Surface water acidification in the headwaters of many of Galloway’s rivers has had a devastating impact on the fish populations. Acidification has been caused by acid rain (wet deposition) as a result of air pollution. Extensive plantations of commercial forestry (primarily Sitka spruce) which have been planted across the upper reaches of the river catchments have exacerbated the acidification by concentrating the acid delivery to running waters through the increased scavenging of pollutants from the air (dry deposition). Acidification has occurred because the base-poor underlying geology of these areas of land is unable to neutralise these increased acid inputs.

Photograph of the heavily afforested Water of Fleet, one of the most acidified rivers in the UK

Photograph of the heavily afforested Water of Fleet, one of the most acidified rivers in the UK

The early life stages of salmon are partly susceptible to acidification, whilst older fish can be killed by the elevated levels of aluminium associated with low pH. The death of these young fish results in recruitment failure and, over time, the larger scale loss of fish populations. As a result of the large scale afforestation and acidification, over 240 km of rivers and burns are classed as ‘acidified’ in Galloway and are unable to support healthy fish densities.

Improved air quality and targeted contemporary forestry planning and design are the main drivers to promote the recovery of the pH required to sustain healthy fish populations. Liming has also been used in many countries to help the recovery of acidified waters.

GFT is undertaking a number of research projects using a variety of liming techniques to look at the practical issues of undertaking such work and examining the benefits or otherwise on the aquatic ecology and water quality. Liming work is expensive and its effect does have a finite lifespan. Our interest is in whether affordable liming could be used to improve water quality in the short/medium term until natural recovery from improved forest design/air quality improves the situation in the longer term.

High Cree – limestone gravel work

This project is looking at targeted liming to locally improve salmon spawning opportunities and success in the High Cree. It is known that adult salmon are again spawning in parts of the High Cree but the survival rate of their eggs and alevins is very low due to acid flushes. The younger life stages of salmonids are the most vulnerable to acidification. Limestone gravels of the sizes used by salmonids for spawning have been added to the river to create spawning beds. The increased water pH and calcium levels within the interstitial spaces should improve the survival of salmonid eggs and alevins in redds within the gravels. This technique does not aim to influence water quality of the water flowing within the watercourse but is targeted only towards improving the pH of the interstitial water within the substrate of the riverbed. The limestone gravel which is added is made up of a suitable composition of sizes aimed at creating optimal spawning conditions for salmonids.

In 2010, 49 tonnes of limestone gravel was added to two locations on the Cairnderry Burn. This limestone was used to create two 25 m long spawning beds.

Photograph of work taking place to add limestone gravel to the Cairnderry Burn

Work taking place to add limestone gravel to the Cairnderry Burn

In 2011, after detailed monitoring the of Cairnderry Burn works, a further 500 tonnes of limestone gravel was added to four locations on the High Cree to create large spawning beds suitable for salmon. A further 200 tonnes of gravel (non-limestone) was added to various sites to form ‘control’ sites to help us understand exactly what benefits the limestone gives.

In 2013, following an assessment of the previous work by an expert geomorphologist (Professor Malcolm Newson of River Catchment Services) a further 766 tonnes of limestone gravel was added to five sites around Dalnaw and Barjarg on the High Cree.

Photograph of limestone gravel being added to the High Cree

Limestone gravel being added to the High Cree

The limestone gravel work on the Cairnderry Burn and the High Cree has been, and will continue to be, monitored through water quality testing (both the interstitial water and main water column above), egg box research, electrofishing and visual survey.

Electrofishing results from Summer 2013 found evidence that wild Salmon spawning is taking place in the limestone beds and fry are surviving through to parr successfully.

The limestone gravel work started as part of our River Cree Rare Fish Project (now completed) but we have chosen to continue it. The additional work has been part-financed by the Scottish Government and the European Community, Dumfries and Galloway LEADER 2007 – 2013 Programme and the SEPA Water Environment Fund.

Photograph of salmon fry and a salmon parr recorded at a liming site

Salmon fry and a salmon parr recorded at a liming site

Big Water of Fleet – hydrological source liming and limestone sand addition

The liming work on the Fleet is based on similar work being undertaken in Wales by the Wye and Usk Foundation which they report to have helped in the recovery of fish populations in their acidified headwaters. These techniques of liming aim to improve the downstream water quality within the watercourses. The Water of Fleet has been heavily impacted by acidification and is an ideal catchment to trial liming methods to improve water quality in the short term.

Two techniques have been used:

  • Hydrological source liming – this liming involves the application of limestone powder to clearfell sites in the forest over natural hydrological sources of tributaries. In this way the very source water of a tributary is targeted. The powder is added to the land at a high application rate but is targeted over only a small area. The powder forms a crust and it is suggested from the work on the Wye that the influence on water quality can last for many years. Over 200 tonnes of limestone powder has been applied to date.

Photograph hydrological source liming in the Benmeal Burn sub-catchment, Big Water of Fleet

Hydrological source liming in the Benmeal Burn sub-catchment, Big Water of Fleet

  • Addition of limestone powder to small watercourses – this liming involves adding limestone sand (larger than the powder used in hydrological source liming) into small tributaries or ditches. During a flood event, when the acidification peak occurs, water within these small drains, ditches and watercourses aggravates and moves the limestone sand, helping to raise pH. This type of liming does require annual top ups as the sand is washed downstream into larger watercourses. Over 90 tonnes of limestone sand has been added to date.

Photograph of limestone powder being placed in small ditches

Limestone powder being placed in small ditches and forestry drains in the Little Water of Fleet headwaters

The limestone sand addition on the Big Water of Fleet is monitored by GFT (electrofishing and water quality sampling) and is also covered by SEPA sampling sites (ecology and water quality).

The project will continue in 2013, subject to funding. The work to date has been part-financed by the SEPA Water Environment Fund, Fleet District Salmon Fishery Board and SWEAT.

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