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RIVER LOCH AND WETLAND

Introduction

Water is a key feature of the Caithness landscape, with distinctive wildlife as well as social and economic uses.

Rivers and lochs are important for recreation and sport, and the quality and quantity of our waters is heavily dependent on the management of habitats within their catchments. In addition to the small areas of wetland that exist on many farms and crofts, Caithness holds some large areas of marsh, fen and reedbed, which attract rare birds and plants.

Rivers and lochs

Habitats and species

Caithness holds approximately 33.5 km2 of inland water, and its rivers and burns are highly regarded by local people for their recreational, scenic and environmental value. These pristine waters sustain important populations of Atlantic salmon, sea trout, brown trout, sticklebacks, eels, European otters, water voles and freshwater pearl mussels.

The county is bisected by its two principal rivers, the
Wick and the Thurso. Their flood plains form a fertile band of land running south-east and northwest through the county respectively. These rivers along with the Forss, Berriedale, Langwell and Wester emanate from mineral rich springs and peatland burns deep in the heart of Caithness.

In places, these rivers have cut gullies, whose steep sides harbour rich vegetation including pyramidal bugle and prostrate juniper. The nationally rare estuarine sedge (Wick sedge) and holy grass can be found along the river banks.

Boats on Loch Watten

Caithness lochs range from nutrient-poor peat lochans (oligotrophic) throughout the peatlands, to nutrient-rich lochs (eutrophic) such as St Johns Loch.  In between are a number of lochs with intermediate nutrient levels (mesotrophic) such as Loch Hempriggs.

The biodiversity of the lochs is highly dependent on their water chemistry, which in turn is influenced by the nature of the surrounding rocks and soils. A good number of lochs have a base of calcium-rich, pale mud known as marl, and these lochs are particularly rich in character.

Most Caithness lochs sustain healthy populations of fish, notably brown trout, sticklebacks and eels, while Loch Calder also has ferox trout and Arctic char. Some, like Loch More, may contain salmon at certain times of the year.

Virtually all lochs have an immense diversity of insect life including an abundance of mayfly, caddis fly and damsel flies. Molluscs and crustaceans such as pea mussels, snails and freshwater shrimps are abundant in the fertile lochs of Caithness. These invertebrates form an important part of the diet of trout, ducks and whooper swans. Trout in turn are eaten by otters and rarer birds like black-throated, red-throated and great northern divers and osprey.

Brown trout

Aquatic plants range from bogbean to stonewort, and many lochs contain weed beds, which provide important shelter for fish and insects.

Main issues

• Agricultural fertilisers and pesticides, forestry run-off and septic tank leakage are all potential sources of pollution and over enrichment in the aquatic environment. In recent years, farming and forestry techniques have improved and existing forestry plantations are being restructured to reduce their effect on freshwaters. 

• Imprudent use of chemicals including herbicides, pesticides and sheep dip can have a serious detrimental effect on all water courses. Land managers should adhere to existing codes of good practice regarding the use of such chemicals.

• River and lochside developments, bank engineering, gravel extraction, water supply schemes and hydropower projects can irrevocably alter freshwater systems. Care must be taken not to modify the structure and patterns of water flow to the detriment of freshwater habitats and species. Road works and maintenance in particular can sometimes interfere with the movement of migratory fish and animals such as the otter.

 
Whooper swan

Habitat Map

Main issues (cont)

• In some areas, emergent and bank side vegetation has been lost due to land drainage, flood defence, bank protection works, cultivation or heavy grazing. Heavily trampled river banks are susceptible to erosion during floods. Limiting grazing on banks and planting deep rooted trees such as willow and alder will help to stabilise the riversides, whilst installing water troughs discourages animals from trampling at the waters edge. Agri-environmental grants may be available to help pay for some of this work.

• Invasive, non-native species of fish, mammals, invertebrates and plants have caused problems for water courses elsewhere in Scotland, and we should avoid releasing such species in Caithness. Minnows are already an introduced non-native species in many of the county’s lochs. Rainbow trout and American brook trout are stocked in one fishery and the utmost care is needed to avoid any escape.

• The migratory geese population may possibly be a source of nutrient enrichment and associated damage to some watercourses.

• Acid rain remains a threat to our watercourses, and organisations such as Scottish Natural Heritage are working to quantify the size of this issue and how to address it.

• There are many flooded quarries in Caithness, which are now important habitats in their own right and could be at risk from illegal dumping
  and landfill.

Current biodiversity projects

Members of Caithness and Sutherland Trout Angling Group have conducted improvements to watercourses and bank habitats. For example, some in-stream and bankside works were undertaken on a small trout spawning burn at Broubster, including tree planting to stabilise banks.

Black-throated diver

The Caithness Ranger Service and RSPB Scotland undertake a number of practical biodiversity projects such as the building of rafts to help nesting birds like black-throated divers.

At St John’s Pool, rafts were constructed to help breeding waders, and the relationship between breeding terns and waders, and predators such as foxes and otters, is being monitored.

Raft building

The Thurso Rotary Club undertook a restoration project on the River Thurso walkway. This has improved access in a manner sensitive to the riverbank habitats.

Wick Community Council has initiated a paths project to improve access and interpretation on the Wick Riverside.
Scottish Environmental Protection Agency and the Scottish Agricultural College have been surveying the nutrient inputs to Loch Watten since February 2000.

 

Opportunities for action Demonstrate the importance of freshwater habitats and best practice with regard to instream and bank management through practical projects, e.g. restoration of spawning burns for wild trout and salmon, use of fenced buffer strips and planting of broadleaved trees to prevent bank erosion. Undertake a demonstration ‘nutrient budgeting and waste management’ project on a farm in the Loch Watten catchment, building on the results of the survey mentioned above. Source funding for the upkeep of bird nesting rafts on St. John’s Pool.  Map sites with freshwater pearl mussels, and ensure riparian management is appropriate to the needs of this species. Raise awareness of the biodiversity value of our rivers and lochs through e.g. a salmon life cycle car trail along the Thurso River or a self-guided wildlife walk along the Wick River. Disseminate best practice amongst all water users, e.g. on field ditch management and pollution for farmers and crofters, or on the non-use of livebait for anglers. Investigate the impact of seals on the salmon and trout populations at the mouth of the River Thurso, the species interactions between ferox trout and Arctic char in Loch Calder, and the viability of the sea trout population in the Loch of Wester. Determine reasons for the decline in breeding waders and Arctic terns at the Loch of Mey, and the effects of nutrient enrichment on species living in and around watercourses. Monitor the impacts of the removal of plantation forestry on the hydrology of lochs and watercourses associated with the LIFE Peatlands Project. Conduct a countywide survey on water voles and develop a strategy for controlling mink (not present in the county yet). Undertake a study to investigate the biodiversity value of flooded quarries in the county. Use the results of any surveys to feed into management of these areas.