What the "L " does this mean for the angler?
The concept of 'behavioural drift' has led me to rethink the way I imagine
underwater insect activity when there is no obvious surface activity associated
with a hatch. I now realise that I was concentrating too much on a straight
vertical line from river bed to surface.
I was thinking in terms of a very few dislodged nymphs when there was
no visible hatch. Then the pupa ascending through the water column, breaking
through the water surface, shedding its exoskeleton and emerging as a dun.
Now my thinking is more
shaped. I have added the horizontal component to represent behavioural
Behavioural drift explains why it is worthwhile fishing an appropriate
imitation close to the bed of the river to represent a drifting insect,
especially when there is little surface activity.
This is worth doing during the day because:
- some species - particularly smaller insects and chironomids - may drift
throughout the day (Allan, 1978)
- there may be
fewernatural insects in the drift to compete with your fly for the
- most importantly, trout
expectto find food drifting close to the bed of the river