The Effect of Forest Practices on Fish Populations
نویسندگان
چکیده
Analysis of frozen cores of chum salmon egg pockets collected in the fall revealed that spawning activity purged about 75% of the fine sediments Corn the stream bed. The egg pocket was one of four distinct vertical strata detected in the cores. There was an undisturbed layer below the egg pocket and cover and bridge strata above the egg pocket, defined by their particle size distributions. However, by spring most of the egg pockets had been SItrated with fines approaching background levels. The most likely physical factors responsible for these results were: 1) intrusion of fine sediments through the cleaned surface gravel, 2) lateral sub-surface migration of fme sediment into interstitial voids, 3) scour of the cleaned surface gravel and subsequent deposition of a sand rich bedload, and 4) superimposed spawning activity of other fish, causing disturbance ofthe cleaned surface gravel and exposing the egg pocket to intrusion of fines. Our results indicate that sediment transport processes and tine bedload flux are more important to the assessment ofthe sahnonid incubation environment than is background stream bed composition.
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