THE ULTIMATE ANGLING BUCKET LIST

The higher the combined score, the better the water quality. So animals which need high levels of
dissolved oxygen and pristine conditions, such as mayflies and stoneflies, score higher than species
which can tolerate very low dissolved oxygen levels and gross pollution.
Organic pollution tolerant animals include chironomid midge larvae and tubificid worms, both of which
have the ability to store oxygen in their bodies using haemoglobin, which is the reason why, like blood,
they are bright red. And accordingly there are all measures of tolerance in between such as water louse,
freshwater shrimps, beetle larvae, and the rest.
Pollutants fall in to two basic categories – those which are of themselves toxic, such as cyanide, and
those which suffocate such as raw sewage.
Not suffocation in the sense of clogging up an animals gills, though that can happen with some fine
particulate materials in suspension. More a case of suffocation by virtue of being organic in nature and
providing 'food' for the decomposer network such as bacteria, which then explode in numbers and
therefore respiration loading, in turn depriving other animals of dissolved oxygen to take from the water
to be able to breath.
Under normal circumstances, the number of bacteria present at any given aquatic location will be in
balance with the environment, where they are sustained by the decomposition of dead animals and plant
material brought about by natural causes.
Put an organic pollutant into the water such as silage liquor, or milk from dairy washings, both of which
are hundreds of times more polluting than raw sewage, and you can very quickly have a major situation
on your hands.
Bacteria reproduce by splitting themselves into two units which each 'half' can again do every twenty
to thirty minutes, dependant on species. Due to food availability, any given environment can only
support so many bacteria, which is what keeps their numbers in check. Suddenly increase that food
supply and you trigger a population explosion.
For ease of calculation, let's say that bacteria divide in response to increased food availability every
thirty minutes. One bacteria becomes two, then becomes four, and so on. At that rate, in ten hours a
single bacteria can result in excess of one million offspring.
Now imagine them all doing that at the same time. Overnight there will be literally billions of the things,
and all requiring oxygen to survive, which deprives everything else in the water of the ability to breath.
Fish can in theory swim away from the
problem, though rapid onset inputs
taking them by surprise, coupled to
their inability to 'think' the problem
through and make their escape, often
sees them taken out anyway.
Invertebrates on the other hand can't
escape, which is what makes them such
a vital source of data to present to the
courts.
Milk – one of the most potent organic pollutants there is
But why is milk classed as an extreme
aquatic pollutant. It's a food, and it's
exactly that designation that makes it
so lethal in this context. Milk has
evolved to be quickly broken down for
nourishment and growth, therefore
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