Trinity River restoration: Evaluating rehabilitation actions

The Trinity River Restoration Program is rehabilitating the river channel and increased flows after 40 years of channel simplification due to diversions.  Loss of fishery habitats up to 90% in the Trinity River Basin was estimated due to sedimentation and insufficient stream flows. The Trinity River Restoration program’s goal is to restore juvenile salmonid habitat. To evaluate construction activities and flows that are part of the restoration efforts, we developed a juvenile density index using generalized random tessellation stratification (GRTS) for the 41 miles below Lewiston Dam. Ten sites were snorkeled twice, once in March and again in April, 2009. Snorkeling was done in downstream direction thus may have underestimated densities of fish less than 50mm.  Mean number of all salmonids was 1.36 in March and 2.05 in April after the hatchery release of steelhead and Coho. Comparisons with 1988 data (mean of 4.41 in March 1988) indicate that densities were lower in 2009. Adult runs were lower in 2008 than in 1987.  We integrated juvenile density with run size and redd distribution to assess effects of returning adult on juvenile density.   Over time we plan to estimate trends in carrying capacity in response to rehabilitation and flow.