[slowing Down For fishermen]

yes kill fishermen!

[slowing Down For fishermen]

From the anglers viewpoint a boat going through at full steam ahead can stir up the bottom silt and spoil the care with which they have ground baited their "swim" to attract the fish. A boat going through at a slower speed avoiding where they are actually fishing (normally the far bank so straight down the middle slowly is good) will lessen the effect and can sometimes encourage fish feeding by gently stirring things up a bit.

 

But I think also it just shows courtesy to another canal user and much more likely to attract a "good morning" and a smile rather than a shaken fist and a scowl.

 

I quite agree. As I used to fish myself, I know what it's like to have both considerate and inconsiderate boat users go past me - believe me it really makes a difference.