Re: [RML] notes on recent angfa pubs
HH (Harro.Hieronimus at t-online.de)
Mon, 8 Mar 1999 16:47:56 +0100
Doug Collom schrieb:
> Peter Unmack wrote -
> .I think many people assume fish get washed downstream,
>
>
> Peter,
>
> On one occasion I stood on the banks of the Boyne River when it was in
> flood, with the water level well over the banks among the gum trees.
>
> I noticed quite a lot of splashing about and activity among the trees, and
> at one point was able to go in on higher ground right to the edge of the
> water.
>
> There were swirling back eddies everywhere, and fish by the thousands, many
> of them rainbows, all advancing steadily upstream.
>
> By the roaring torrent midstream I'm sure any casual observer would have
> assumed that no fish could hold on against such a flow.
>
> I don't know for certain what happens when the flood slows, and the river
> drops back to within its banks, still flowing strongly, but generally in
> such conditions there are strong counter currents swirling just downstream
> of bends, on the inside of the bend, so its quite possible that many of the
> fish I saw could advance well upstream, and hold on to those gains.
>
> I know there have been some thought given recently here in Queensland by UQ
> to using dye marking to start some experiments on frestwater stream fish
> movements.
>
> Doug Collom
>
The question is if the fish is positive rheotactile or not. Most fish are, so
they have a natural born tendency to swim against the stream, and they do it
more intensive the stronger the current is.
Best regards
Harro Hieronimus, Solingen, Germany
harro.hieronimus at t-online.de
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No fish - no fun
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