24 October 2011

I've just completed the invert checks for this month at Turn Dub and New Inn.  No obvious problems as the results at Turn Dub are almost identical to the same period for the past three years.  New Inn showed a slight drop in overall numbers (but not families) compared to last year, but this could be due to many factors (weather, water levels etc).  What is noticeable when I look back over my notes for the four years I have been doing monthly checks here is the way the river substrate has changed.  It's now a lot more bouldery with less gravel and small cobbles.  This is making the kick sampling more of a challenge and is likely to alter the number of inverts that come into the net.

Why the substrate should be changing like this I have no firm idea.  We don't seem to be getting more frequent or more powerful spates and nothing has been done to the river that would alter the flow, but none the less the bed is markedly different just below New Inn bridge from how it was four years ago.

Maybe the very fact that I kick around the bed every month has had an effect although this seems most unlikely.  Thoughts would be welcome.


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