Pool habitat characteristics and juvenile anadromous salmonids in two Oregon coastal streams

Graduation date: 1997Relations between the diversity of juvenile anadromous salmonids and pool features\ud were examined in a managed and a pristine watershed in Oregon during the summer of\ud 1990. There were no differences (p>0.05) in pool depth, velocity or pool wood volumes\ud between streams. However, the pristine system had twice the number of pools within\ud similar lineal distances. Pools in the pristine system also had larger substrates (percent\ud dominant within pools) and smaller pool area (p=0.01). Fish diversity was found to be\ud greater in pools in the pristine system than in the managed system using the Simpson's\ud Diversity and Shannon Evenness indicies (p=0.01). The Shannon-Wiener Diversity\ud index did not show any differences between streams. The difference in assemblage\ud diversity was due to differences in relative abundance and not species richness. Relative\ud abundance of juvenile steelhead and cutthroat trout and coho salmon was more even in\ud Cummins Creek, the pristine system, than in Cape Creek, the managed system. Relative\ud abundance of coho increased in the managed system possibly due to a change in pool\ud habitat characteristics, whose conditions favored coho salmon, but this relationship was\ud not clear. This study emphasizes the importance of assessing communities of juvenile\ud anadromous salmonids as opposed to studies involving a single species. Past land\ud management activities have focused upon single species' with regards to a particular\ud habitat component, which has decreased biodiversity and changed stream habitat\ud characteristics through cumulative effects. Resource managers should examine\ud interactions between habitat characteristics and salmonid communities in order to\ud maintain biological diversity or risk creating favored habitat for a single species within\ud stream systems