Joseph,
    I physicist would know less than you about the physiology of fishes, a
physiologist  might have the information on the temperature regulation of
fishes.   It is an interesting question.  I don't personally have any
scientific information on thermoregulation in fish.  But based on past fishing
experience, rainbow trout (Oncorhynchus mykiss) and other freshwater fishes do
have a habitat preference for deep holes in streams.  The deep holes however
may be preferred for other reasons besides temperature.  The deep holes may be
more important as rest areas, due to decrease stream flows in the area and
they may provide better protection from predatory birds, etc.  Undoubtedly
shady areas are important refuges for fish in shallow slow moving streams, but
are probably less important in major rivers which have high volumes of cold
water.  I hope I helped the discussion.

                                                 James Stark
                                       Research fisheries biologist
                                 Alaska Fisheries Science Center
                                National Marine Fisheries Service
                                              Seattle, WA



Joseph Ebersole wrote:

> Greetings,
>
> In my analysis of fine-scale patterns of habitat use by stream fishes in
> relation to temperature, I've been confronted with a potential problem.
> The temperature recording devices I use absorb solar radiation when
> deployed in water <20cm deep, thus record water temperatures greater than
> the actual ambient water temperature.  Does anyone know to what degree
> body temperatures of fish may be elevated by exposure to direct solar
> radiation in shallow water? I've been assuming it's minimal, given
> presumed ability of the fish to integrate various sources and sinks of
> heat - and that the ambient water temperature (conduction) is the
> predominate factor influencing fish body temperature. But I'm no physicist
> by any means and might be missing something!
>
> I'd appreciate any replies, and will summarize all responses and post back
> here.
>
> Thanks in advance,
> Joe
>
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> Joseph L. Ebersole                                   541-737-1979 (office)
> Dept. of Fisheries and Wildlife, Nash Hall 104       [log in to unmask]
> Oregon State University
> Corvallis, OR 97331
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