A number of man-made obstacles to fish movement exist within the River Annan. These structures can be anything from large weirs on the main river to small culverts on the tributaries. Barriers fragment habitats and prevent the movement of fish to potential spawning grounds. Its not just salmon and sea trout that are impacted. Eels and some species of lamprey also migrate out to sea. Fish species that remain in the river are also known to move between the main river and its tributaries for spawning. The Water Frame Work Directive requires member states to achieve good ecological status by 2027 (or good ecological potential for heavily modified waterbodies). It is recognised that one of the most effective mechanisms to achieve this is to mitigate for the impact of barriers on fish movement. The River Annan Catchment has been downgraded to poor ecological status because of the impact of Milnbie Caul Weir on Eels. In the last few years a solution has been found to two high impact barriers on the River Annan (see below). The RAW project will build upon the work of the River Annan Trust and contribute to the potential removal or easement of barriers.
Examples – The Wamphray Water
TThe Wamphray Weir under the West Coast Mainline was the biggest barrier to fish migration on the River Annan. In 2015/16 with a lot of input from SEPA and the River Annan District Salmon Fishery Board a solution was found. Network Rail installed a new bypass channel and fish pass with construction undertaken by AMCO Rail. Salmon and sea trout will now have access to the whole of the Wamphray Catchment (approximately and extra 12km) where there is excellent habitat for both species.
Examples – The Duff Kinnell
In about 1820 Raehills Estate built a weir to provide water for the ornamental lake in front of the house. Unfortunately, it subsequently barred access to this water course, with about 20mile of spawning and nursery habitat, to migratory salmonids becoming unavailable. In 2012 a purpose built Alaskan A fish pass was installed on the weir and fish can once again use their ancestral spawning locations. The fish pass was designed by Fishway Engineering from data supplied by the River Annan DSFB. There will no doubt be a few salmon above it in the future but we except the biggest beneficiary from this project will be sea trout which already spawn in close proximity to this area. In times of low sea trout returns this type of project is incredibly important.
Barrier Assessment & Mapping
Not all solutions need to be as grandiose as the two above and for many smaller obstacles they are not suitable solutions. Quite often quick and simple solutions will suffice. When people think of barriers to fish migration they are normally thinking of large structures like dams and weirs but a great many other structures can cause problems. On the Annan we are particularly concerned about sea trout and we need to look at the areas that sea trout will chose to spawn. These are often well into the head waters in the tiny ‘Lilliputian’ burns. These areas can easily be forgotten but there are often significant barriers for the fish to cross before they spawn. Road and track crossings can be of particular concern with small culverts commonly used to get the water from one side to the other as quickly as possible. Many of these culverts are fine but some a real fish stoppers and a succession of difficult ones will have a demonstrably bad effect on the numbers of fish present within a river. A desk top exercise to identify all road crossings and potential obstacles began in 2014 and a huge number (nearly 2000) locations were found. A processes of assessing and prioritising for easement began got underway in 2015.
Read the Assessment of Man-made Barriers to Fish Migration in the River Annan Catchment