RE: NANFA-- Spawning in high water

Hoover, Jan J ERDC-EL-MS (
Tue, 29 May 2001 12:02:41 -0500

Some fish have special behaviors that improve their abilities to hold a
position in fast water. Sturgeon and darters "hunker." They press their
bellies to the stream bottom, arch their backs, and hold their pectoral fins
at an angle, all to increase drag. Some minnows "grasp" objects with their
mouths. They swim forward, lock their jaw(s) around a small stationary
object, and hang on.

>>Could you expand on this? I have always wondered how fish stay in an area
when there is excessive water flow.<<

>Fish associated with the stream's substrate experience little flow relative

to what's going on higher in the water column. This is due to several
- what's called a "boundary layer", where the friction of the water on the
actual substrate reduces wayer velocity there, creating calmer conditions
- the morphology some benthic fishes have evolved, such as sculpins, with
their streamlined upper bodies which the water passes over and actually
pushes the fish closer to the substrate.
- protection offered by the substrate itself, such as from boulders and
such too large to be moved by water.<

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