Tidal Fish Passage & Connectivity

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WDFW is working with tribal partners and contractors to complete a study of fish passage, particularly juvenile salmon in tidal environments, such as embayments and river deltas. This project will explore how various design alternatives for culverts and bridges in intertidal environments affect fish use.

Background

Restoration of natural processes is difficult to achieve in the built Puget Sound environment due to necessary constraints (i.e., culverts, tidegates or bridges) associated with maintaining landowner access, property protection, and public safety. However, technical guidance for barrier evaluation and design of tidal water crossing structures is limited, with project sponsors struggling to determine “how much is enough” to provide fish access and habitat connectivity. Lack of fish use/movement data prohibits meaningful restoration in constrained environments due to these uncertainties. Without improved technical guidance, projects may not realize maximum potential on constrained sites or make effective use of available funds.

This study will provide technical background for improvement of technical guidance for water crossing structures (culverts, bridges, tidegates, etc.) in the tidal environment. In absence of adequate technical guidance, project proponents frequently struggle during project development to determine most effective use of funding for tidal water crossing structures. While the ideal approach to habitat restoration is to completely remove stressors, improvements to culverts, tidegates, bridges or water control structures are often included within the scope of restoration projects to address project specific constraints and ensure project support from stakeholders. While larger structures eliminate or significantly reduce ecological impacts, they are often many times more expensive (cost of structure itself, costs related to elevation of structure, landownership constraints, etc.) and evaluating alternatives is challenging without more information on the environmental consequences of the range of design options. There is rate of diminishing returns where reducing a water crossing structure size to accommodate constraints (cost, land availability, access, etc.) no longer provides adequate ecological benefits to warrant the project cost

We know that tidal events may naturally preclude migration during certain time periods, and that undersized culverts and water crossing structures increase water velocities that can further reduce migration periods, particularly for juvenile salmon. Little is known about to what extent fish behavioral ecology is modified or how to assess the duration and extent of negative effects to fish migration during the tidal cycles. While fish behavior is notoriously difficult to quantify, an understanding of when move within the tidal cycle is key to providing technical guidance. Designs based on geomorphic principles (i.e. a design that replicates the natural conditions/processes, e.g. stream simulation design in freshwater systems) can reduce the need to fully consider fish behavior, but these designs may not always be achievable or cost effective in tidal environments.

Current study

Juvenile salmonids, particularly Chinook and chum salmon, need access to intertidal habitats for rearing in early marine life history. Little is known about fine-scale fish movement related to the tide and was identified as a key data gap in a literature review (Greene et al. 2017). This study will focus on fish movement in tidal areas in Puget Sound.

Washington Department of Fish and Wildlife (WDFW) is working with the Nisqually Indian Tribe, Skokomish Indian Tribe, Port Gamble/S'Klallam Tribe and the Skagit River System Cooperative to monitor fish movement in reference tidal channels. Several techniques have been attempted (GoPro, BlueView sonar, nets) but the most informative method has been using PIT tagged juvenile Chinook salmon and antenna arrays in tidal channels in the Nisqually and Skokomish estuaries in 2018 and 2019. Preliminary analysis is underway.

Partners & Roles

  • Project Lead - Padraic Smith, PE & Doris Small, Washington Department of Fish & Wildlife
  • Nisqually Tribe - Chris Ellings & Sayre Hodgson
  • Skokomish Tribe - Lisa Belliveau, Anthony Battista, Joseph Pavel, Alex Gouley
  • Port Gamble/S'Klallam - Hans Daubenberger & Emily Bishop
  • Skagit River System Cooperative - Eric Beamer
  • Blue Coast Engineering - Jessica Cote & Traci Sanderson
  • ESA - Paul Schlenger

Technical Advisory Group

Tasks

  1. Develop project plan with Technical Advisory Group
  2. Develop Wiki pages
  3. Pilot field work in 2018
  4. Field work in 2019
  5. Final report
  6. Final project presentation

Resources