The Ness catchment is the largest in the North Highlands and drains 2,103 square kilometres of land. The upper reaches extend almost to the west coast, close to Loch Hourn and Loch Nevis. The land drains east and north through the Great Glen before entering the sea in the Moray Firth at Inverness. For management purposes the district can be sub-divided into seven key management units.
Each of these management units is described in further detail below:
- Ness Coastal – Inverness Firth and smaller coastal burns, particularly important for sea trout but also salmon;
- River Ness – The temperature of the main River Ness is kept artificially high by Loch Ness, so it has no temperature barrier. This unit also incorporates the key tributaries of the main river, including the Holm Burn and Allt na Skiach Burn;
- Loch Ness and Small Tributaries – The famous loch extends to 37km with smaller tributaries, the mouths of which are important spawning areas for salmon, trout and Arctic charr;
- Rivers Enrick and Coiltie – Flowing into Urquhart Bay and supporting one of only a few alluvial woods remaining in the United Kingdom, designated as a Site of Special Scientific Interest (SSSI). Also thought to be important spawning areas for summer and autumn salmon and grilse;
- River Moriston – Designated as a Special Area of Conservation (SAC) for freshwater pearl mussel and Atlantic salmon. It supports an important ‘spring’ salmon fishery and is heavily impacted by large scale hydro-electric schemes;
- Rivers Garry and Oich – The River Oich runs parallel to the Caledonian Canal, with extensive modifications being made to its course during the construction of the canal. The two rivers are separated by Loch Oich. Both the Garry and Oich support important ‘spring’ salmon fisheries and are heavily impacted by large scale hydro-electric schemes; and
- Rivers Tarff, Foyers and Farigaig – All support salmon populations to a greater or lesser degree and form important juvenile and nursery areas. They are, however, less important in terms of angling. The Tarff and Foyers are impacted by hydro-electric schemes.
In addition to the above, the Caledonian Canal intersects the Ness system at various points. The canal runs some 60 miles (97 km) from north-east to south-west. Only one third of the entire length is man-made, the rest being formed by Loch Dochfour, Loch Ness, Loch Oich and Loch Lochy (in the neighbouring catchment).