Why our ‘dirty rivers’ are fishing so well...
THE state of England’s rivers was laid bare in 2020, with a series of damning Government reports revealing that the vast majority of our waterways fail to meet European ecological standards.
Why is the poor state of our rivers not showing in angler’s catch reports?
Indeed, they were deemed to be the dirtiest across the whole continent, with not a single river, lake or coastal water in the country being rated as ‘chemically good’.
You might think that this would result in meagre catches and stunted fish growth, but the reality couldn’t be more different. Over the past few months, bumper bags of prime silverfish have been winning river matches up and down the country, and in the specimen fishing world the story is the same. Immense barbel, chub, roach, perch and dace are all being banked this season from running water venues that appear – on the surface at least – to be in rude health.
In a bid to understand how the two apparently contradictory situations can co-exist, and how our supposedly polluted waterways are places in which coarse fish can not only survive, but also thrive, we asked the experts at the Environment Agency. The answer, it seems, lies not in the amount of pollution, but its type.
Heidi Stone, the EA’s Fisheries Partnerships Manager, told us:
“Some pollutants are obviously highly toxic and pose a massive threat to fish stocks, while other, organic, pollutants can actually lead to increased levels of invertebrates, resulting in more food for fish.
“Just because a river fails to meet water quality standards doesn’t necessarily make it toxic or dirty. It could be nutrient-rich and home to certain species that are thriving – it just hasn’t met all the required criteria.”
Some organic pollutants can actually lead to increased levels of invertebrates, resulting in more food for fish
This was a view largely echoed by fish expert Dr Paul Garner who revealed that not only is there a wide range of pollutants in our rivers, not all of which are harmful, but that certain species are better armed to deal with them than others.
“Just about everything we humans do, from flushing the loo or washing the car, right the way through to farming, creates pollutants that sooner or later will enter a river. The result is a really complex mix of chemicals in our rivers that impact the ecosystem in different ways. Some might affect the plants, while others influence the invertebrates, or stimulate algal growth – all of which have a knock-on effect on the fish.
“Most coarse fish are tolerant of low-level pollution, particularly organic pollution, which – as has already been mentioned – can stimulate growth of organisms in a river. However, there comes a point where you go past this and start having problems, such as those posed by low dissolved oxygen levels.
“But other pollutants can impact the fish in different ways, and not just in terms of water quality. Take soil entering a river because of run-off from intensively farmed land, for example. This could settle on the riverbed and cause siltation, which would affect species like barbel and dace that need clean gravels for spawning.”
Paul also revealed how the most susceptible and fragile of species when it comes to pollutants are typically salmonids such as trout, salmon and grayling, but that some of our coarse fish are far more hardy when it comes to dealing with apparently dirty rivers.
“Fish that are more ‘generalist’, in that they eat a wide diet, spawn on whatever substrate is available, and mature at a young age, will be less affected. Roach fall into this category, as well as chub to a lesser extent. Those with a more selective diet and spawning habitat, such as barbel and bream, are more likely to suffer.”
However, Paul was keen to add a note of warning that, although fish populations currently appear to be healthy in many rivers, the long-term situation might be very different.
“Just because there are lots of roach in, say, the River Trent, at the moment, it doesn’t mean that they’ll be there for future generations. With a bigger population comes ever more pollution, so for now we’ve got to make hay while the sun shines,” he added.
For now we’ve got to make hay while the sun shines!