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Chapter 6 -- Changes and Trends in Stream Habitat and Fisheries (continued)

Changes in Fish Access

The location, timing, and effect of barriers to anadromous salmonid migration on the Smith River have not been inventoried as of 1997. Access for migrating fish at present may be similar to historic conditions. On the lower river, water depth is probably always sufficient for migration even during low flows.

Aggradation or degradation of the channel has the potential to change fish access. The lower river is more aggraded than at the time of early historical descriptions. There were once "many pools deeper than twenty feet" on the lower river, and now there are few if any. The loss of deep pools does not directly prevent fish migration, although the deep pools were probably important for other reasons. Apart from effects on migration, aggradation tends to increase predation on all life stages.

Another factor that can effect fish access is large woody debris. In bedrock-controlled streams where significant aggradation is highly unlikely, the presence or absence of large woody debris can influence fish access. Although log jams were once considered access barriers, fisheries biologists now believe that beneficial effects of accumulations of large woody debris outweigh the effects on fish access. Besides the extreme case of log jams, the presence or absence of large woody debris can influence channel characteristics and influence migration access. Logs and root wads in the channel tend to create pools and trap gravel. These velocity barriers can result in easier migration especially for juvenile fish.

On Monkey Creek, a tributary of the Middle Fork, access has improved due to removal of a small dam.


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