Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Monitoring the Penobscot River Restoration Project: Baseline Data to Inform Ecosystem Response (#56)

Molly L Payne Wynne 1 , Joshua Royte 1 , Timothy Sheehan , Rory Saunders
  1. THE NATURE CONSERVANCY, Brunswick, MAINE, United States

Dam removal is increasingly being used as a tool to restore aquatic habitats and recover imperiled species. However, many presumed effects of dam removal (i.e. fish community changes, water quality improvements) are largely un-documented. Given significant investments being made in dam removal, rigorous monitoring is needed to elucidate ecological impacts and allow for informed decision making when allocating restoration resources. The Penobscot River Restoration Project in Maine, USA, is an innovative restoration project aimed at restoring self-sustaining populations of diadromous fish through increased connectivity via dam removals and fish passage improvements, while maintaining hydropower output. Beginning prior to dam removal in 2009, independent researchers began documenting baseline conditions via a multi-disciplinary, coordinated monitoring framework. The framework has continued through project implementation, following a before-after study design. Monitoring focuses on geomorphology, water quality, fish community, fish passage, habitat use, shoreline revegetation and marine-freshwater nutrient transfers. As before-after comparative analyses continue to unfold, this presentation aims to provide the most current results of this monitoring effort, highlighting several patterns which have emerged to-date: 1) all native diadromous species of fish are present in the river, many successfully reproducing on their own; 2) diadromous species persist despite access to only a small percentage of their historic habitat, many now beginning to increase in number; 3) the former lowermost dam, represented a near complete barrier to migration for most species and is now traversed by many similarly to free-flowing sections; 4) large changes to flow, sediment regime, and habitat (except in the immediate vicinity of the former dam sites) were unexpected and did not occur; and 5) water quality did not appear to be limiting for most species. This effort provides an objective, credible basis for evaluating ecosystem response to dam removal and a knowledge base to support restoration approaches in other systems.