What is a migratory fish?
Many types of fish migrate regularly - whether's that a daily occurrence, 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 must take place on a larger scale and duration than those arising during normal daily activities. 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. Salmon, for example, migrate up rivers to spawn in the same river they were born. The European eel, on the other hand, is born in the Sargasso Sea but travels a huge distance to continue its lifecycle in rivers.
Why celebrate World Fish Migration Day?
Sadly, many migratory fish species endangered. The main culprit? Man-made barriers. These disrupt the flow of rivers, preventing fish from following their normal migratory routes. This can have devastating impacts on fish populations, with many unable to reproduce or feed sufficiently.
The impact of this effects far more than the fish themselves. Migratory fish play a crucial part in creating healthy, thriving freshwater ecosystems. In addition, millions of people around the globe rely on these fish species for food security or their livelihoods. We need to take the decisive action needed for migratory fish to survive - not just now, but for future generations. Raising awareness of the plight of these fish is the first step towards driving real change.
Change in actionAcross the UK and Ireland, our local Trusts are fighting to improve fish passage. Below, we've highlighted a few of our favourite examples from across the Rivers Trust movement.
Don Catchment Rivers Trust and the Salmon of SteelNo, that's not the title of a new Harry Potter book. Recently, Don Catchment Rivers Trust completed the last of a series of fish passes on the River Rother. The result? Salmon are being seen in the heart of Sheffield for the first time in over 200 years. During the Industrial revolution, weirs were built across the river, powering water mills which enabled the development of Sheffield's steel industry. For the past 20 years, a collection of organisations have been fighting to enable fish passage over these weirs - creating a "migration super highway" from the sea all the way to Sheffield. Researchers at the University of Sheffield are using environmental DNA (eDNA) to detect the presence of salmon in the river, and to determine how far upstream they are swimming. Most excitingly, though, the community are become more engaged with the river and its inhabitants. An exhibition called 'the Salmon of Steel' is taking place as part of the Festival of the Mind. At the heart of the exhibition is the Salmon of Steel itself; a seven foot sculpture of a leaping salmon, made by Scrap Metal Artist Jason Heppenstall. In addition, a walking trail has been designed which tells the story of the winding river itself—from the vital role the river played in early industry, to the tragic disappearance of the salmon, and their recent resurgence thanks to Don Catchment Rivers Trust and partners.
Weir today, gone tomorrow: West Wales Rivers TrustPhotos courtesy of 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.
Wessex Rivers Trust: a dramatic before and afterhttps://youtu.be/KZr-JHHOROc In honour of the 'how it started' challenge, we just had to include this case study; this is one of our favourite before and afters! In 2019, Wessex Rivers Trust undertook a huge project to restore a degraded section of the River Test to its former glory. With the removal of six barriers to fish passage and the installation of six fish-passable structures, this project signalled a huge improvement for fish accessibility. It's hoped that this work will provide a much-needed boost for fish populations in the local area and beyond.
Having monitored fish populations prior to work commencing, Wessex Rivers Trust are hoping to conduct post-restoration surveys to monitor change. However, we think the footage speaks for itself!
We're incredibly proud to be a partner of DiadES. This project aims to enhance the ecosystem services provided by diadromous fishes in the Atlantic Area by creating innovative tools to ignite a transnational management under present and future climatic conditions.