Dear Ian
 
I dont know much about trout,but my guess is, that the
species'reproduction and the hydrology of your rivers is not properly
synchronized (e.g. there are very low flow rates shortly after
spawning or very high discharges after the fry leaves the gravel).
 
best wishes
Irene
 
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Irene Zweimueller            e-mail: [log in to unmask]
Inst. of Zoology            phone:  ++43 1 31 336 1337 or 1342
Dept. of Limnology          fax:    ++43 1 31 336 778
Althanstr. 14
A-1090 Wien
AUSTRIA - EUROPE
 
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