Re: NANFA-- Spawning in high water

Bruce Stallsmith (
Sun, 27 May 2001 15:47:15 -0400

>In a message dated 5/27/01 1:02:44 PM US Eastern Standard Time,
> writes:
><< A lot of minnows or darters would be surprisingly
> unaffected, because the hydrology along benthic surfaces may not be as
> altered as we would think. >>
>Could you expand on this? I have always wondered how fish stay in an area
>when there is excessive water flow.
>Chuck Church
>Indianapolis, Indiana USA
At the interface between flowing water and the bottom of the creek (or
whatever...) you have what's called a benthic boundary layer. Water flow is
uneven from the water surface down to the molecular layer where water
molecules directly contact the bottom. Water is imperfectly fluid, that
means there's friction, or drag, between the lowest layers of the water
column and the bottom. So high velocity water is often measurably slower and
less turbulent right along the bottom, even upwards for several centimeters.
This is what creates turbulent flow in the water column, because the top
layers rush along faster than the bottom layers and in short you get chaotic
system. The long and the short for many fishes is that if they hang on the
bottom and have the right physical build, they can avoid being swept away by
most high flow conditions. From our perspective it's _all_ chaotic
fast-flowing waters, but there's more happening than meets the eye at first.

Greetings to anyone reading this who's at the AKA Convention in Buffalo!

--Bruce Stallsmith
Huntsville, AL

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