Effects of fine sediment accumulation on the redd environment and the survival rate of masu salmon (Oncorhynchus masou) embryos |
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Authors: | Hiroyuki Yamada Futoshi Nakamura |
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Institution: | (1) Environmental Informatics Laboratory, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan;(2) Forest Ecosystem Management Laboratory, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan |
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Abstract: | In recent years, fine sediment, produced by run-off associated with forestry activity and agricultural development that accumulates
on riverbeds, has exerted a deleterious influence on lotic ecosystems. This study examined the Oroennukibetsu River, a tributary
of the Nukibetsu River, which has been affected by high loads of suspended sediments. Effects of accumulation of fine sediment
on the survival rate of masu salmon embryo and also on the redd environment (permeability and intragravel dissolved oxygen
concentration) were quantified through a field experiment. Results show that the interchange of DO between intragravel and
surface water was not affected directly by permeability or the accumulated fine sediment and that intragravel flow rates can
be an important factor controlling embryo survival. A decrease in permeability associated with accumulation of fine sediment
lowered the survival rate of embryos by suffocation because the flux of DO that should be supplied to the embryo was severely
limited. This situation might be created by the combined effects of an accumulation of fine sediment on the redd and a low
DO concentration in the surface water because the DO concentration almost coincided with the intragravel DO. |
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Keywords: | Dissolved oxygen Eyed egg Flux Hyporheic Pool-riffle |
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