Living with the Ladies: Brown Trout and Grayling

Though both native to the UK, brown trout and grayling (the ​“Ladies of the Stream”) have a complex history. Today, our deeper understanding of river conservation means that we can give a helping hand to both species, but what might that look like? In this blog, which originally appeared in the Grayling Society​’s magazine, our Conservation Officer Andy Thomas ponders that very question.

Without wishing to incur the wrath of the passionate graylingista, I have a grave confession to make. I know that what I’m about to say will raise a few eyebrows, and some may view it as being decidedly out of step with modern views about the value of healthy grayling populations. Looking back on my time working on chalk rivers like the Kennet, Lambourne and Pang (and also the limestone Cotswold Streams), the reality – at least in my experience – was that the ​“ladies” were considered by some to be nothing more than a pest. So much so, that I must confess to personally catching tens of thousands of them during the 1980s, to relocate them from sections of river that were specially preserved for trout fishing.

On reflection, I have asked myself many times if this was a sound management strategy for the rivers that were being stripped of healthy, naturally produced grayling. After many years of experience, I can confidently say that most of the work was, at best, a complete waste of time and money. At worst, it was a gross act of environmental vandalism. Did removing all of those grayling improve opportunities for brown trout? Well, we know that the two species have different habitat needs, and stockies were favoured on many angling beats at the time, so the answer is a categorical ​“no”! To underscore the futility of the whole thing, highly productive recruitment and rapid growth rates meant that the pilfered grayling populations simply sprang back, sometimes in the blink of an eye.

The story was a bit different for the relocated fish. In one or two cases, they went on to build thriving, self-recruiting populations in rivers where grayling had been obliterated by pollution. But in my experience, this is relatively rare – in the rivers that were totally unsuitable for them, as many were, the fish rarely stayed long enough to even think about spawning. It’s probably just as well, as they would have struggled to find good quality spawning habitat, let alone anything remotely appropriate for juveniles. Most of the fishing clubs that received them, which were deemed coarse fisheries, willingly accepted the transfers in hopes of experiencing proper winter grayling fishing for the first time. And most did… but only for a month or two, and then the fish were usually gone. So did they really provide any sustainable sport for the anglers that craved them?

Today, a lot of our rivers have more in common with those coarse fishing beats, in that burgeoning grayling recruitment is rare. The fish are still present, but usually only in much more modest numbers than the hoards that we regularly captured back in the 1980s. Among the theorised reasons for their demise – as often discussed in the various publications of the Grayling Society – are habitat degradation, increased predation pressures, and the ways in which climate change has impacted both water temperatures and river hydraulics, thereby interfering with key moments in the grayling life cycle.

All of these factors will have taken their toll, both separately and collectively, and especially when coupled with the current water quality crisis. One example is the grim situation that can arise when warming river temperatures combine with enrichment caused by both agricultural diffuse pollution and exposure to poor quality effluent – the latter coming courtesy of various water companies. When raw sewage or slurry-rich run-off hit our rivers, you can expect not only a dip in the available dissolved oxygen, but also deadly spikes of unionised ammonia – a certain death sentence to a tiny fish. If those conditions coincide with the emergence of fry in the spring, then whole year classes can be lost. It is sometimes surprising that we have any grayling left at all, but I still hold out hope for signs of a genuine recovery!

Despite facing similar pressures, our wild brown trout are a little more sheltered from this doom and gloom. They lay their eggs in the depths of winter, usually burying them in well-constructed redds on the riverbed. The eggs take 3 – 4 times longer to hatch than grayling eggs, and the alevins will typically be well developed before they emerge from the gravels, having subsisted on the remains of their yolk sacs. What’s more, when they do emerge, the water is still mighty cool, and therefore able to hold much more dissolved oxygen.

Hatching grayling may not be so lucky, emerging from their shallow scrapes only a few short weeks after springtime spawning. Warmed by the sunshine, the water may be oxygen depleted and compromised by algal blooms that are fuelled, in part, by agricultural and sewage pollution. The furry film of diatoms that coats many riverbeds in this season can’t be doing our delicate grayling eggs any favours. This may well be another reason why grayling recruitment has become less reliable, and why wild brown trout are (secretly; don’t tell anyone!) doing comparatively well in many rivers – even ones like the Kennet, where grayling appear to be nowhere near as numerous as they once were.

Another contributor to the dramatic change in the ecology of our rivers is the arrival of the dreaded signal crayfish. Grayling redds are definitely ​“prefab” compared to their deep and well-constructed brown trout counterparts, making them easier to plunder. But timing is also a factor: springtime spawning coincides with the signals stirring from their winter torpor, ready to consume anything vaguely organic and stationary. Grayling eggs are therefore much more vulnerable to these voracious predators, which are often present in such high densities that the survival of any fish seems truly incredible.

What does all this mean for those who aim to improve the fortunes of our native fish, as we do at the Wild Trout Trust? Well, I think it’s fair to say that we have given much thought to the way in which river habitat either supports, or in some cases thwarts, the success of the species we love. I know the Grayling Society have also explored the options available to clubs and fishery owners who want to improve the conditions for grayling. However, in our experience, there is so much more that could be done to help our fish communities – in some cases through active management, and in others by stopping certain activities that can be popular with the anglers, but problematic for the fish.

A common example might be going through a classic shallow glide after a storm, raking out all of the fallen brash in fear that it might play havoc with a drifting nymph or a trotted gilt tail. But that brash, in that location, just might play a crucial role in fish survival. In comparison to the more solitary and elusive brown trout, grayling are gregarious and naturally gravitate towards open areas. This can make them extremely vulnerable to exploitation by avian predators like herons and egrets. A corridor of low, overhanging tree cover provides terrestrial insect food for hungry fish, but can also discourage predators that need quick and easy access to the river. That cover may provide opportunities for kingfishers, but it is not favourable for gangs of cormorants that are looking to hunt together in comfort.

Every club and fishery owner should be able to pinpoint the areas where grayling are spawning, and spending time on the riverbank in April can reveal these to you. It may be, however, that you don’t have any habitat for grayling to spawn on. If this is the case, then you have a golden opportunity to create some! As a bonus, that same habitat may well be used by wild trout come the autumn. Our Wild Trout Survival Guide and the Grayling Society’s Grayling Conservation Guide will give you lots of ideas for creating and maintaining high quality habitat for both species, through all their life stages. While the theory isn’t difficult, though, there can be pitfalls to implementing it, and so we are keen to help.

Thanks to our collaboration with the Environment Agency, our Conservation Officers can make free Advisory Visits anywhere in England (and usually at a subsidised rate elsewhere in the UK and Ireland). We ​“wildies” have years of valuable lessons learned from practical experience, so if you want to understand your options, then please give us a buzz on 023 9257 0985 or pop an email over to projects@​wildtrout.​org. We’d love to be in the mix!