Fisheries Impact Assessments

Many developments, including water abstraction for hydropower generation, can affect fish populations. These include effects on fish passage (both upstream and downstream), changes in migration patterns, alterations in habitat quality and quantity, morphological changes to the river corridor and physical damage to individual fish.

Assessing the impact of proposed developments

Fishtek have previously carried out a very large number of assessments looking at the impact of proposed developments on aquatic fauna and flora.

A typical impact assessment for a hydropower installation would evaluate the sensitivity of the site in terms of species present, habitat quality and type, and the potential impact on migration patterns. Sites vary significantly in terms of sensitivity and it is not possible to apply a generic abstraction regime to all sites. Other components of a fisheries study may include the following:

Spawning and juvenile habitat availability and quality
Fish population surveys, including electro fishing
Eel surveys using specialist eel traps
Macro invertebrate studies
Assessment of fish migration/fish passage issues. This includes assessments of barriers to migration.
Redd surveys
PHABSIM studies and habitat assessments. This includes assessments of the existing quality of habitat and how a proposed development may impact upon this habitat, with suggested mitigation as appropriate.

Habitat Assessments

Improvements as well as assessments

Our previous work assessing habitats has included the design of physical habitat improvements, including the creation of new spawning areas, calculations of appropriate flow regimes in off-channel habitat features and the design of artificial man-made channels to replicate ‘natural’ habitat features.

Redd surveys are conducted to establish the importance of an area for migratory salmonid spawning. This provides a specific level of detail of relevance to proposed hydropower developments on rivers containing salmonids. Redd surveys are conducted during the spawning season (typically November – February) and species identification can be made from observation of the redds.