For the first time our once pristine, gin-clear English chalkstreams and rivers have been put under the microscope in a national survey to compare and investigate whether they are as healthy as they should be. And the results are truly shocking.
The 2015 Riverfly Census, undertaken by Salmon & Trout Conservation UK (S&TC UK) has identified that there were only 14 pristine, unimpacted sites out of a total of 120 sites sampled in the survey on rivers across England.
According to fisheries charity, Salmon & Trout Conservation UK, the threat to our rivers has moved from industrial pollution to a range of subtler but equally damaging impacts from sources such as agricultural and road run-off, poorly treated sewage, septic tanks and discharges from watercress and fish farms.
Although these forms of stress are less dramatic than fish-killing chemical spills, the long-term effects on flylife such as blue-winged olives are equally profound.
Paul Knight, Chief Executive of S&TC UK explains, “Most of the rivers we analysed were impacted to some extent, although the chalk rivers were the worst. England’s 200 or so chalkstreams form about 85% of the world’s total stock of this richly diverse and complex habitat. Almost all of them are in a dismal state of decline. Plants, insects, fish, mammals and bird-life are suffering as a result of the loss of flylife, which plays a crucial role in the aquatic food chain. Basically lose your flylife and you will lose many other important species too.”
Even figures from the Environment Agency, show that 83% of our rivers are failing to meet the standard of ‘Good Ecological Condition’ classification, measured by the European Water Framework Directive.
Riverflies and other invertebrates are excellent indicators of the underlying ecological condition of our rivers because different species of invertebrates demonstrate different tolerances to the various forms of stress from pollution. Traditional and less exacting methods of analysing water quality frequently struggle to capture the often combined impacts of nutrients, sediment and subtle organic enrichment on invertebrate life in our rivers.
The study was carried out by ecological consultants Aquascience Consultancy Ltd, on 120 sites in seven rain-fed rivers and five chalkstreams across the country. For the first time, the investigation used ground-breaking research and chemical analysis to accurately identify the problem.
Dr Nick Everall from Aquascience Consultancy says, “The national river survey showed a mixture of improving, stable and all too many sadly declining reaches in terms of overall ecological condition, environmental stresses and riverfly life in particular. Several rivers showed loss of condition with measures like mayfly species richness and freshwater shrimp population status over time. Breaking some of these river findings down with controlled laboratory tests has recently shown that raised levels of phosphate and sediment, akin to many of our stressed river conditions, has a detrimental impact upon the survival of early life stages of the base of the aquatic food chain for species such as the blue-winged olive.”
The Census identified that, although Hampshire’s River Avon – a chalkstream, came out best in the study, the next 6 places went to freestone rivers, mainly in the north and south west. Three of our most highly protected SAC chalkstreams; the Itchen, the Lambourn and the Wensum, rank poorly in the Census. These contained low riverfly richness and abundance in many reaches of these rivers. Indeed on the Itchen, populations of the blue-winged olive have collapsed, despite being relatively abundant in the early 1990s.
In addition, the River Test, which is an SSSI (one of our highest conservation classifications) showed that flylife is below that expected of a pristine river with many significant species impoverished and rarer species absent.
Freshwater shrimp (Gammerus pulex) an important element in the food chain for trout and salmon, recorded very low numbers and measured against historic Environment Agency records, are showing a long and marked decline.
Paul Knight says, “So far The Water Framework Directive’s measure of water quality struggles to capture the often combined impacts that pollution is having on the invertebrate life in our rivers. The biometric fingerprinting we used in the Census was like examining these systems with a microscope rather than a magnifying glass and, significantly, the results showed that water quality is often insufficient to sustain the life that our target rivers historically supported.”
In his forward to the Census, keen fisherman and journalist Jeremy Paxman laments the loss of our pristine rivers and says, “Something has gone very wrong. Yet experience tells us that almost everything in nature is connected. A decline in flylife on rivers will have consequences. The only way we can enlist popular support – and the possibility that someone might care enough to realise the risk we face – is to gather evidence. That is why the Riverfly Census matters.”
Nick Measham, author of the report and S&TC UK environmental consultant, concludes, “The aim of our Census was to provide, for the first time, an accurate picture of water quality in our rivers, to gauge the problems we are facing and to identify workable solutions to restore degraded watercourses to their pristine condition. The evidence from our Census is irrefutable. Increased human pressure is having a disastrous impact on our rivers.
“We will now challenge the Government to tackle these damaging sources of pollution before we reach the point of no return. We have a five-point plan of action involving working with the Environment Agency, but also challenging them where necessary, especially over the urgent need to identify and regulate polluters. However, we believe the best chance of reversing the degradation in our rivers is to work directly with those who, mostly inadvertently, are the sources of the stress on river water quality, and to show them that they can also benefit from adopting measures that protect watercourses. ”
The comment below is from Nick Denbow, who learned to fly-fish on the Itchen and Arle in the 80s, then studied Aquaculture at Sparsholt, before setting up the Western Caribbean Fly Fishing School in Mahahual, in the Yucatan, Mexico:
“Absolutely. This is exactly and completely what I wrote my Sparsholt thesis on in 1998. They should have listened then!
Hopefully now you are out of Europe you can have rules specific to each river individually.
A great start would be that water abstractions should only be allowed and licensed if the water is properly scrubbed to its original or better than its original quality parameters. This as far as I know still only happens in Holland.
The decline in species richness of Mayflies is almost completely due to habitat destruction. Poor river maintenance in the 90s during low water levels led to over widening and deepening of many sections of river so that they remained viable businesses as fisheries. Mayfly species distribution relies on a variety of habitats and only one of 47 in Hampshire is a burrower in silt, E. danica. Due to spending 4 years as a nymph this insect is more common on the lower stretches of any river system. The others are stone clingers, moss creepers, agile darters and laboured swimmers. Take away these habitats and replace it with silt and the bugs will move on at the rate of invertebrate drift. If this starts at the top of a river system (as that’s where most cress beds are) then you gradually remove all the favoured invertebrates from the river, gradually all the way down stream.
By creating favourable habitats on side streams or periodically in areas of micro habitat in poor quality areas it’s easy to ‘re-establish’ populations as adult (winged) may flies all migrate upstream to breed. So what I’m saying is its recoverable if the river acts together.
The lack of G. pulex, the freshwater shrimp, is not due to habitat but rather directly from chemicals used in water cress production, specifically zinc. It’s been proven for many years that the products used to spread on cress and its roots prevents crustaceans being able to build their shells. Spatial avoidance of G. pulex from areas of cress has been seen for years. Due to the Trout’s dependence on shrimps in the winter months due to lower fly hatches, it’s beleived to represent 80% of the Trout’s annual diet. Take that away and your Trout simply won’t survive the winter, which is their spawning time.”
BSc (Hons) Aquaculture and Fishery Management
STANIC Qualified instructor
The Western Caribbean Fly Fishing School, Mexico