The Issues

Up to 75% of salmon smolts on the Usk fail to reach the tide during dry springs

Read more 

This is an all too common problem, banks are being eroded by stock and severe floods, we still have too many weirs and dams impacting fish migration and geomorphology and streams are still being straightened

How and why habitat degradation happens.

What the Foundation does to restore habitat in streams and rivers.

Read more about barriers to migration and the Foundation’s work to restore access.

Read more about Elan gravel project 

Twenty years ago the streams of the upper Wye and Irfon catchment appeared to be in pristine condition. But taking a closer look would reveal they were lifeless – no fish, invertebrates, plant life or even slime on the stones.

This had been caused by an increase in the frequency and intensity of flushes of acidity flowing into them after rainfall. The result was devastating not just for fish but for the ecology of the whole area.

Read more about acidification, how it came about and what the Foundation and its partners have done to correct it. 

In the past we had problems with sheep dip, now a new suite of chemicals is impacting on our rivers

Our rivers should not go green/olive brown

Algal blooms have occurred in both rivers for some years. However, since 2016 these blooms have become much more severe and prolonged, turning the water anything from a light green to dark brown in colour.

The problem is caused by a combination of sunlight, low flows and elevated levels of phosphate in the water.

Read more on the causes and problem with algal blooms along with what the Foundation is doing to tackle this issue.

All fish species are subject to predation by other fish, by avian predators such as herons, dippers and kingfishers and by mammals such as otters.

These predators have existed in the Wye and Usk catchments for millennia and are an important part of the natural environment.

However, the impacts of predation are more significant when the population of a prey species is already depleted. Such impacts may be even more adverse when a new predator species arrives on the scene.

Read more about predation in the Wye and Usk and what the Foundation has done to mitigate the effects on already-depleted fish species.

The Wye and Usk have suffered pollution from various sources over the years.

The Foundation invests much time and effort in stopping pollutants from entering watercourses. Where they have, we restore the ecology of the rivers and streams that have been affected.

Read more about pollution, it’s sources and our work to prevent pollution in the Wye & Usk catchments.

Implications of High Water Temperatures on Salmon and Trout Fisheries:

A Scientific Perspective

Increasing water temperatures are having a serious affect on the ecology of the Wye and Usk and the fishery they support.  As global temperatures inexorably rise, unless we change how we are managing our catchments to mitigate rather than exacerbate climate change the effects will become ever more pronounced and serious.

1. Physiological Stress on Fish: Salmon and trout exhibit physiological stress responses when exposed to high water temperatures. As water warms it holds less dissolved oxygen, increasing the impact of any pollution that also lowers oxygen levels. If it doesn’t kill them, this stress compromises their overall health, affecting survival rates and reproductive success.
2. Metabolic Effects: Increased water temperatures elevate the metabolic rates of salmonids. While this may enhance growth and extend growing seasons, this is not always good news as salmon that smolt after only 1 year are smaller than salmon that spend 2 years in the river. Smolt size is a major determinant in smolt survival. Sustained high temperatures can lead to increased energy expenditures for basic physiological functions, leaving less energy available for essential activities such as reproduction and predator avoidance.
3. Feeding Behaviour and Foraging Efficiency: High water temperatures influence the feeding behaviour of salmon and trout. Warmer waters can decrease the availability of suitable prey species, impacting the foraging efficiency of these fish. Changes in feeding patterns may have cascading effects on the entire aquatic food web.
4. Impacts on Reproductive Success: Successful reproduction is intricately tied to specific temperature requirements during spawning and egg incubation. A delay in the annual cooling of river water temperatures in late autumn caused the spawning failure in 2015. Rivers temperatures stayed too high for too long that winter. Elevated water temperatures can disrupt the synchronization of reproductive cycles and lead to fish emerging from gravel too early when their food is not there, reducing juvenile survival.
5. Catch-and-Release Mortality: Catch-and-release is safe until water temperatures rise to a defined point after which mortality increases exponentially. For cold water species such as salmon trout and Pike this is around 19 degrees C, whilst for most coarse fish it is around 25 degrees C. Carp are the most resilient with little effect until water temperature gets to 29 degrees. The increasing summer water temperatures is why WUF has had to close fishing for on much of the passport for 80 days in 2023.
6. Ecosystem-wide Consequences: The impacts of high water temperatures extend beyond individual fish. Changes in fish populations can disrupt the intricate balance of freshwater ecosystems, affecting predator-prey relationships and biodiversity. These ecological shifts have broader implications for the health and resilience of aquatic environments.

Scientific insights into the consequences of high water temperatures on salmon and trout provide a sobering perspective on the challenges ahead. As we grapple with climate change, adopting science-based management strategies becomes imperative for preserving the ecological integrity of freshwater systems and sustaining the delicate balance of these iconic cold-water fish populations.

https://old.wyeuskfoundation.org/blogs/e-news/in-more-hot-water/

Soil loss from land infills gravel, suffocating fish eggs and reducing invertebrate numbers.

Read more about pollution, it’s sources and our work to prevent pollution in the Wye & Usk catchments.

Invasive species outcompete the natural ecology we all know and love.

read more about tackling invasive species