Habitat Assessment

A river habitat survey describes the physical characteristics of the area including vegetation cover, substrate composition and flow type. The habitat assessment gives a detailed list of the issues apparent in the catchments and ways to improve the area for fish.

River Habitat Surveys.

Habitat surveys are conducted to assess the suitability and availability of riverine habitats for supporting healthy salmonid populations. At present most systems in the west Sutherland area contain healthy if small populations of both salmon and trout, although a few are predominantly trout catchments.

Walkover surveys are sometimes appropriate for covering larger areas where data is collected on potential obstacles to fish movements, erosion, riparian cover and basic instream characteristics. More detailed River Habitat Surveys following the standard Scottish Fisheries Coordination Centre (SFCC) protocol are carried out where greater resolution is necessary. The SFCC River Habitat Survey focuses particularly on salmon and trout and their requirements. Data is collected regarding:

Instream characteristics (water depth, flow type, substrates and vegetation cover)
Bank and riparian features (types and extent of erosion, canopy cover, grazing pressure and land use)
Available spawning habitat
Obstacles to migration
possible causes for unsuitable habitat or a lack of fish (such as pollution sources)

The system is walked and the various characteristics of the site recorded in order to determine the available area and its suitability for fish at different life stages (fry, parr, adult). During this survey any issues restricting fish populations are noted, and recommendations made to help improve the habitat. These detailed Catchment Management Plans are then given to the proprietors to act on as they see fit.

Pristine habitat (C Daphne)

Good parr habitat

Narrow upland burn

Natural waterfalls are potential obstacles

Salmonid Habitat requirements

Salmon and trout have different habitat requirements at different life stages. Optimal flow characteristics and substrate composition are highly dependent on the size and age of the fish, whilst water temperature affects egg and fry survival and development. Basic requirements include:

clean, well oxygenated water
suitable vegetation cover and substrate composition to provide shelter from predators and adverse conditions
suitable feeding territories (particularly parr)
food availability
availability of suitable spawning habitat (adults)