Intensively Monitored Watersheds Program: An Updated Plan to Monitor Fish and Habitat Responses to Restoration Actions in the Lower Columbia Watersheds

The Lower Columbia Intensively Monitored Watersheds (IMW) program is designed as a Before-After Control-Impact (BACI) study in order to determine whether and how habitat restoration activities influence abundance of salmon and steelhead. The study is conducted in Mill, Abernathy, and Germany creeks which flow into the lower Columbia River downstream of Longview, Washington. The goal of this updated monitoring plan is to summarize results from baseline (�"pre-treatment”) monitoring, use baseline information to determine whether fish responses should be detectable, and identify the types of fish and habitat data necessary to test hypothesized responses to restoration activities. Results from 8 years of baseline monitoring have demonstrated that annual smolt production is correlated among watersheds, enabling use of the BACI design for detecting future changes in the treatment (i.e., �"impact”) populations. Results also suggest that over-winter survival is an important limiting life stage for coho salmon in these watersheds. A 47 to 82% increase in the freshwater production of coho and steelhead is likely to be detected after 5 years of post-treatment monitoring. We demonstrate that this level of increase may be expected given the currently proposed projects for these watersheds and the magnitude of fish responses to habitat restoration elsewhere in Washington State. In the last section of this updated plan, we hypothesize the mechanisms by which culvert replacement, inchannel large woody debris placement, off channel reconnection, and nutrient enhancement may influence fish and habitat in these watersheds, and we describe the types of data that will be used to identify these mechanisms. Cause and effect will be demonstrated by combining the population response (e.g., more smolts in treatment stream) and a causal mechanism (e.g., increased growth or over-winter survival in treatment stream). The success of the IMW program will be based on the ability to determine whether and why fish populations respond to habitat restoration efforts. This result relies on BACI study design and on successful monitoring of key life stages and habitat hypothesized to respond to restoration actions.