Barriers and obstructions in freshwater rivers

What is it: 

Scotland’s river network contains many barriers to fish migration, both natural and man-made.

MS Maps NMPi has two layers:

  1. Obstacles to Fish Passage (SEPA WMS)
  2. Impact of Impassable Barriers on River Connectivity – this is a sub-set of layer (1).

Layer (1) is maintained by the Scottish Environment Protection Agency and represents the natural and artificial obstacles to the migration of fish, mainly salmonids, in Scotland. The data originate from information collated since the 1980s by Marine Scotland while identifying the distribution of salmon in Scottish rivers.

Layer (2) is based on work undertaken by University of Aberdeen, Marine Scotland, James Hutton Institute and Leibniz Institute of Freshwater Ecology and Inland Fisheries to assess the impact of impassable man-made barriers on juvenile Atlantic salmon production and provide a tool for prioritising barrier removal, where red indicates a high priority for management and green indicates low priority. Improving river connectivity increases the amount of available salmon habitat.

Links to Scotland's Marine Atlas: 
Chapter 5: Salmon and Sea Trout Fishing
Data originators: 
Scottish Environment Protection Agency (SEPA)
Scottish Government (Marine Directorate)
This information page is part of the theme: 
Salmon and Sea Trout Fishing
More Information: 

Obstacles to Fish Passage (SEPA WMS) contains information on the location of barriers on the river network, whether they are natural or man-made and whether they are impassable or passable to fish under certain conditions. The legend accompanying the WMS displays Barrier Type. Clicking on an individual barrier in the layer displays further details including Permeability, Description and Comments. The dataset is also available as a downloadable shapefile (see ‘Data Sources’ tab for link).

The Impact of Impassable Barriers on River Connectivity subset was created from SEPA Obstacles to Fish Passage as at 11.04.2018. Only barriers in Scottish mainland and Hebrides rivers with catchments greater than 10 square kilometres were used in the analysis. Any impassable man-made barriers in smaller rivers were not ranked.

The legend is as in Figure 3 of the paper ‘Buddendorf et al (2019)’ (see ‘Data Sources’ tab for link).  The data show the increase in river connectivity that would result from the removal of impassable man-made barriers (IMBs) and so provide a basis for assessing the impact of barriers on Atlantic salmon and the potential benefits of barrier removal / easement. By ranking the connectivity scores it has been possible to develop an approach for prioritising management action.

Barriers are one of the High Level Pressures on Atlantic Salmon and as such feature in current initiatives relating to the conservation of wild salmon (see ‘Additional Information’ tab for links).

This page was last modified on : 
Thursday, January 31, 2019 - 07:26

Links and Resources

Map Type Click title for metadata and licence informationsort descending Date of data View Map
Map Layers (NMPi) Impact of Impassable Barriers on River Connectivity 2018-11-21 Access this map on NMPi
Map Layers (NMPi) Obstacles to Fish Passage (SEPA WMS) Access this map on NMPi
Type Link Titlesort descending External Link
Marine Scotland Data Portal Ranking of impassable man-made barriers to fish migration from Buddendorf et al 2019, STOTEN data.marine.gov.scot
Data Portals, Web link SEPA - Environmental Data www.sepa.org.uk
Type Title External link
Reports Marine Scotland - High Level Pressures on Atlantic Salmon www2.gov.scot
Web link Integration of juvenile habitat quality and river connectivity models to understand and prioritise the management of barriers for Atlantic salmon populations across spatial scales (Buddendorf et al 2019) doi.org
Web link Marine Scotland - Conservation of Wild Salmon www2.gov.scot