UC Davis

To determine whether large wood (LW, ≥1-m length, ≥10-cm diameter) plays a role in Chinook salmon (Oncorhynchus tshawytscha) redd (i.e. egg nest) placements in a regulated, Mediterranean-climate, medium-sized river (where channel width is less than the upper quartile of length of potential instream wood pieces), characteristics of 527 large wood pieces, locations of 650 redds, and mesohabitat delineations (riffle, run, glide, pool) were collected during a spawning season along a 7.7km reach directly below Camanche Dam on the Mokelumne River, CA. LW was regularly distributed across the study reach an average 70 LW pieces km-1. Some LW clustering was evident at islands and meander bends. Spawners built 85% of redds within one average channel width (31m) of LW. Spawners utilized LW within a 10m radius 36% of the time in the upper 3km rehabilitated reach, and 44% of the time in the lower 4.7km marginal habitat reach. A greater percentage of LW was utilized in riffles in the upper 3km reach where 90% of redds were built, while a larger percentage of spawners used LW in riffles in the lower 4.7km reach. LW-redd interactions occurred at greater rates than by random chance alone in the lower 4.7km reach, which implies that LW aids spawning in marginal habitats. River managers and salmonid spawning habitat rehabilitation (SHR) projects should take LW additions into consideration as an important component of river rehabilitation. © 2010 John Wiley & Sons, Ltd.