Effect of Substrate Composition and Stock Origin on the Survival to Emergence of Brown Trout: A Laboratory Study
Few researchers investigating the survival to emergence of embryonic salmonids have simultaneously compared the predictive
ability of the percentage of fine sediment less than a given diameter, the geometric mean particle size, and the fredle index.
We quantified the relation between these different measures of substrate composition and survival to emergence of two stocks
of brown trout, Salmo trutta, and also examined the effects of substrate composition on the timing of emergence and size of
alevins. The geometric mean particle size generally accounted for the greatest proportion of variation in survival to emergence,
whereas the percentage of fines less than a given size was usually the poorest predictor. Substrate composition also influenced
days to first emergence and 50% emergence and the length of the emergence interval. We found no difference in the survival
to emergence of the two stocks. We concluded that the geometric mean particle size was the best predictor of survival to emergence
for brown trout and that substrate composition may alter other ecological characteristics of emerging fry.
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