River Crossings and Migratory Fish: Design Guidance

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FOREWORD

Migratory fish such as salmon and sea trout are an important recreational and commercial resource in Scotland, as well as being integral components of Scottish biodiversity. The associated tourism and angling industries are also important contributors to the Scottish economy, particularly in rural areas. However, salmonid populations in Scottish waters are currently under pressure. The decline has been attributed mainly to a reduction in the numbers of fish surviving to return after the marine part of their life cycle. The causes for this reduced survival are not clear but changes in the marine environment are undoubtedly involved. There is little we can do directly to reverse any changes there have been in the ocean, so we are left to exercise control where we can, particularly by ensuring that the freshwater environment is as productive as it can be.

River-crossing structures such as culverts can, if not properly designed, form a barrier to the movement of migratory fish. That is why two Scottish Executive Departments, in consultation with fishery interests and practitioners involved in the road design process, have developed this guidance. It is our aim to implement the approach detailed in this document on all trunk road new-build and maintenance projects.

The approach adopted in 'River Crossings and Migratory Fish' ensures that the free passage of migratory fish is not impeded by new river-crossing structures associated with the trunk road network. This will assist in the sustainable management of fish stocks by maximising the area of habitat available to spawning fish, which will in turn enable the populations to better withstand the many stresses to which they are currently exposed. The approach also prevents habitat fragmentation, which is a principle detailed in the Scottish Executive publication 'Trunk Road Biodiversity Action Plan'. But the guidance contained in this document should not be limited to the trunk road network. We hope that all those involved in designing river-crossing structures will adopt the guidance offered.

While practitioners will find 'River Crossings and Migratory Fish' of immediate use, only through application, feedback and development can the document's robustness be established. We have therefore initiated a twelve-month consultation period, during which you are formally invited to apply the document's contents and provide comments and suggestions for its improvement. Arrangements are also being made towards taking 'River Crossings and Migratory Fish' forward for inclusion in the UK Design Manual for Roads and Bridges.

We commend 'River Crossings and Migratory Fish' to you and look forward to feedback on its use and application.

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