Can our drought-ravaged trout streams recover?

WTT Director Shaun Leonard and Conservation Officer Andy Thomas share their thoughts on the impact of the drought on trout populations

The recent hot weather, hard on the heels of exceptionally dry weather, has resulted in many of our rivers, streams and natural lakes suffering very badly. For many areas and particularly in the chalk streams which usually have stable flows and cool water temperatures, last winter’s lower than average rainfall has been compounded by a bone-dry spring and summer, with the double whammy of record high temperatures. Many of the rivers of the UK and Ireland, if they’re still flowing, will currently have water close to 20⁰C, tough conditions for any fish but especially for cool water trout, salmon and grayling. 

Maybe, given time, though we are relentlessly knocking lumps out of the world around us. The rate of any recovery to a seriously damaged waterbody, and its fish, plant and invertebrate communities is dependent on three factors (the ​‘three-legged stool’) of water quantity, water quality and habitat. The river habitat and its physical characteristics can help – or hinder — the ecological recovery of a river when flows and water quality are good. One of the key focus areas for the WTT’s habitat advice and project work is to try to build in ​‘resilience’ to drought, floods and pollution so that the river and its wildlife is given the best possible chance to recover from whatever we throw at it. 

Many of us can help to influence stream resilience, either by sharing information, or even rolling up our sleeves and helping to create the habitat necessary to give our fish populations the best possible chance of survival and bouncing back. It would be easy to write-off our trout communities, with images of dead fish in stagnant pools being beamed into our homes via the media. We must learn lessons from the past and realise that the fish we love are remarkably robust and tenacious if we only give them a chance. It is understandable why some might turn their backs on what appear to be damaged streams because weather patterns similar to those we are experiencing this year are likely to be a far more regular occurrence into the future. We think that would be a tragedy and doesn’t reflect the ability of the trout to be one of nature’s great survivors.

Firstly, we must understand that just because a section of river or stream has run completely dry that it is not dead and gone forever – providing flows do return. This is particularly the case with spring-fed systems which often have drying headwaters (winterbournes), with many species evolved to cope with drought by moving downstream and moving back upstream when flows return. On rain-fed rivers, instinct drives the fish to find cooler, deeper water downstream; provided there are not impassable structures, once the flow returns, so will the fish. Trout are hard-wired to move upstream to spawn where they can find suitable habitat, with stronger fish reaching places that smaller, weaker fish may not be able to reach. This often enables eggs to be deposited into freshly flowing sections that a couple of months before were completely dry. All trout are migratory more-or-less but rivers that are blessed with sea-run trout have better capacity to bounce back because, even if the entire river dries up, or is battered by a deadly pollution, killing every last fish in the river, there will always be a cohort of the river’s population away at sea feeding on sand eels, just ready to come back to the river when flows return, starting the cycle of life all over again.

A single dry year, or possibly even two or three in a row, is unlikely to finish off our trout for good, but we must try harder to build in the necessary resilience to rivers. We must 

• redouble our efforts to make sure fish can navigate both up and down our rivers and streams
• undertake sensitive maintenance work and put the comfort of the fish before our own desires to make fishing for them easier
• create more shade, promote deep, cool holding pools for adult trout and thick, tangled, shaggy fringes adjacent to shallow spawning glides and riffles for fry and parr
• encourage that vital and natural connection between the river and its floodplain.

Habitat is just one leg of the three-legged stool. We must all stand up to the water companies, government and its regulators and demand more and fast action for improved water quality and much more investment into sustainable water resources. We need better water networks and vastly improved winter water storage. For every single one of us in our homes, we can also do our bit by valuing each drop of water we use and re-use. The WTT’s focus is on practical action to improve resilience but of course we support and provide evidence for the groups that campaign to improve water quality and water quantity. Perhaps this year will finally be the wake-up call that we’re in a climate emergency and massive investment is needed to protect our precious water environments and the wildlife that depends on it.