Looking over that bridge the water looks clear but we know it contains a cocktail of chemicals, agricultural, domestic and industrial that surely cannot be doing good. Indeed, you can cogently argue that the largely organic waste of Halford’s time was helpful to fish and bugs. Anyone who went sailing in the days when yachts vented waste directly into the sea will know there is nothing fish like more than s**t!
If anyone asks me what has changed most in my time on the chalkstreams it would be rising fish, or more particularly the lack thereof. Now, I cannot tell you definitively why this is. Some people point to the stocking of triploid trout, effectively a genetically modified trout. I’d go along with this except in my experience unstocked streams seem to have an equal lack of rising fish. Maybe, if the report is correct and the nymph population is on the rise, canny trout are not wasting time and effort on floating flies but rather munching away to their hearts content on the growing sub-surface population.
Part of my bafflement with regard to the lack of rising fish is the hatches. Now, it is often said we lack the hatches of old but I’ve not noticed that on a scale that would stop trout looking upwards. Often, I see a river thick with flying bugs, which supports the findings in the paper, but nary a fish moves. Are they, to repurpose that old British Rail excuse, the wrong type of flies? It could well be which brings us nicely around to the meat of the Total Environment paper.
The highlights of the paper (their words not mine) are that river macroinvertebrate richness has increased throughout England over the past 30 years with a recovery of pollution sensitive invertebrates reaching the reference condition, the improvement seen across all river types. If like me you find some of the jargon unhelpful ‘macroinvertebrate’ are bugs that can be seen with the human eye and ‘reference condition’ the expected population level in normal conditions. In short, the report is saying the assumption that pollution is causing biodiversity decline should be challenged because their data, which draws on solid monitoring going back 30 years, suggests something different.