Today, the 24th October 2020, marks #WorldFishMigrationDay 2020, a global celebration to raise awareness of the challenges faced by migratory fish. Across the world, organisations plan events, webinars and content to celebrate migratory fish and the work being carried out to save them. This international day of events is coordinated by the World Fish Migration Foundation.

But what is a migratory fish? Well, all fish migrate to some degree – whether that is a short daily occurrence to preferable feeding grounds, an annual journey, or one which takes part even less frequently. The distances travelled by fish during migration can range from a few metres to thousands of miles, but when we talk about migratory fish species, we are talking about those that migrate on a larger scale and duration than those arising during normal daily activities. Such migration usually revolves around the pursuit of food or reproduction, but there are cases where the reason for migration isn’t totally clear. Some migratory fish travel up and down rivers, while others journey between rivers and the ocean, or oceans alone. In Wales, our migratory fish include the salmon and sewin (sea trout), which migrate up rivers to spawn in the same river they were born, the European eel, which is thought to be spawned (born) in the Sargasso Sea and travels a huge distance to continue its lifecycle in rivers before heading back to the Sargasso sea, and also the lamprey and shad.

While we were unable to run an event to celebrate this day this year due to current restrictions, we wanted to take this opportunity to celebrate the work we have been doing to improve fish passage over the last few months. We have been somewhat quiet on social media recently, and this is because the WWRT team have been working our way through ecological surveys, detailed designs, in-stream working consents and all of the other factors that come into our work to help improve fish passage as well as the natural flows of our rivers, coupled with some extremely high river levels and Covid restrictions!

So, this #WorldFishMigrationDay, as the season for in-river working has come to an end and the rain is pouring ready for our salmon and sewin (sea trout) to come back up the river, here are three fish pass projects we have completed this Autumn:

  1. Removal of Vicars Mill weir, Eastern Cleddau:Weir removal - West Wales Rivers Trust

After six years of planning, the upper reaches of the Eastern Cleddau are now open to migratory fish once more. A joint project between Natural Resources Wales (NRW) and the West Wales Rivers Trust (WWRT) saw the removal of a weir at Vicar’s Mill. This will play a vital role in improving the health of the River Cleddau, enabling its fish population to thrive.

The weir at Vicar’s Mill was built in the 1800s to harness water power for milling. More recently, the weir was heightened to provide water for a fish farm, and a fish pass was built to enable migration up the weir. However, the fish pass didn’t work as intended: it became blocked with debris on a regular basis, becoming redundant for the purpose it was intended.

In three days, the weir was removed. Imagine that; an obstacle which has impeded fish migration since the 1800s can vanish in just a matter of days! Removing the weir means the re-opening of over 20 km of upstream fish habitat. It is also hoped to restore the natural river geomorphology. These changes will provide a much-needed boost for salmon and sea trout populations—something which will also benefit local fisheries.


2.  Rocky ramp easement on the Afon Sannan, Carmarthenshire

This project worked to improve fish passage on a concrete Irish road bridge comprising of three culverts approximately 8 metres in length with a large perched sill that fish had to jump to get through the culverts. As a main road to a village, we were unable to remove the weir completely, so the next best option was to create a ‘close to nature’ rocky ramp easement which broke up the large drop from the bridge into three smaller, easily navigable ones with deep pools for the fish to be able to sit in before making the next jump.


3. Larinier style fish pass on the Afon Clywedog, Teifi.

Wherever possible, our main aim is to remove river barriers, or where this is not possible, to put in a close to nature fish pass, as above. However, at some sites, site constraints unfortunately do not allow this, for example with a lack of access for machinery, as was the case for the Afon Clywedog. This project worked to improve fish passage on a substantial concrete weir, used to support a small road bridge leading to a private house. There was no pool immediately below the weir, limiting the potential for fish to traverse the head height. WWRT worked with a contractor to come up with a design for a larinier style fish pass that would benefit salmon and sewin passage over the bridge footings. This was an extremely good value project and we will be monitoring its success over the Winter. If successful, this could be a low cost option installed on sites previously considered low priority or written off from improvements due to difficult access conditions.


We have now entered the closed season for in-river working, and as it continues to rain we welcome up our salmon and sea trout and hope that they will make great use of their newly accessible stretches of river! We will be back in in the Spring to help improve more barriers, and much more planning for this will take place over Winter.

We will leave you with this video from our friends at South East Wales Rivers Trust where we joined the trust and filmmakers and TV presenters Iolo Williams, WIll Millard, Jack Perks to talk about our favourite migratory fish and what we can do to protect them!

Thank you to Natural Resources Wales and Welsh Government for supporting our fish passage improvement works this Winter!