Lessons Learned from Long‐Term Effectiveness Monitoring of Instream Habitat Projects

Abstract

AbstractThe placement of instream structures to improve habitat for salmon and other fishes is one of the oldest and most common habitat improvement techniques. Since 2004, the Washington State Salmon Recovery Funding Board (SRFB) has been evaluating 23 instream habitat restoration projects by using a before–after control–impact (BACI) design. Sites (i.e., paired impact and control reaches) were monitored once before restoration implementation and several years after implementation on a rotating schedule (at years 1, 3, 5, and 10). Vertical pool profile area, mean residual profile depth, large wood (LW), and fish densities were quantified. Volume of LW increased significantly by year 10, while vertical pool profile area, mean residual profile depth, and fish densities did not significantly increase or meet the management targets (20% increase) by year 10. Increases in LW were expected given the restoration treatments (LW and engineered log jam additions). Vertical pool profile area and mean residual profile depth initially significantly increased (at years 1 and 3), though the results were no longer significant by year 10. The lack of a significant response in geomorphic metrics and juvenile fish by year 10 may be due to the low number of sites that were monitored for 10 years after restoration, but it is more likely due to challenges with implementing the monitoring program. These challenges included sample timing across years, poorly matched impact and control reaches, data management, and limitations in the monitoring protocols and metrics that were used. Our results demonstrate the importance of proper implementation of monitoring programs and suggest that future research and monitoring of instream projects should consider stratifying by ecoregion, seasonal fish sampling (summer and winter), improved habitat survey methods, more rigorous selection of impact and control reaches, critically assessing and clearly defining success, and the use of a posttreatment design.