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Habitat surveys

Waterfall above Talladale (River Ewe system)

The productive area accessible to salmon and sea trout is limited in many river systems in Wester Ross by impassable waterfalls like this one above Talladale (River Ewe system)

The suitability of any stretch of water for fish production depends very much upon the quality of habitats therein. Different species of fish have different habitat requirements. Small fish are able to hide from predators in the streambed if there are suitable voids between stones. Larger fish usually require deep water, though even an adult sea trout or salmon may seek somewhere to hide between boulders where available. Growth and production of juvenile fish is also dependent upon a food supply. In Wester Ross, many streams are infertile; production of fish and other wildlife is limited by the availability of nutrients, especially phosphorus, P.

WRFT field biologists have surveyed many hundreds of km of riverbank since 1999. An SFCC protocol forms the basis of surveys. Rivers and streams are surveyed section by section. Data is recorded to describe the dimensions (length and width), depth, flow type (pool, glide, run, riffle, etc.), substrate composition (silt, sand, pebbles, cobbles, boulders, bedrock, etc.) and stability of the section, and to describe the river bank and nearby land. Photographs are taken and sketches made to highlight features of concern to fisheries.

More recently, indicators of fertility and food supply have also been recorded. These include the diversity and relative abundance of invertebrates, both in the water and on nearby river banks. Moles are indicators of healthy earthworm populations which are found where soils are healthy. In some parts of Wester Ross, New Zealand Flatworms have reduced earthworm populations to levels where moles are no longer able to find enough food. So WRFT field teams note the presence / absence of moles, New Zealand flatworms, Alder trees and an increasing list of other things. It's all about making the most of time in the field (especially if working in a remote area) and gaining some understanding of the big picture.

Landfill Tax Credit Scheme logo

River Habitat Surveys in Wester Ross have been supported with grant funding from the Landfill Tax Credit Scheme.