Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 9119
Title: Multnomah Channel wetland restoration monitoring project (2014-2016)
Author/Editor: Regan A. McNatt, Brian Cannon, Susan A. Hinton, Luke D. Whitman, Rachel Klopfenstein, Thomas A. Friesen, Daniel L. Bottom
Publication Year: 2017
Publisher: National Marine Fisheries Service, Oregon Department of Fish and Wildlife, and Oregon State University
Contracting Agency: Oregon Metro Natural Areas Program

From 2014 to 2016, we surveyed the Multnomah Channel Marsh Natural Area to determine the temporal composition and abundance of fish assemblages, as well as habitat use and residency by juvenile salmonids.  Surveys were designed to evaluate the effectiveness of a 2014 restoration project at the Multnomah Channel Marsh

A primary objective was to document fish use of the wetland during the spring and early summer immediately preceding a planned restoration project to lower portions of the natural riparian berm separating the wetland from Multnomah Channel.  We also conducted a series of experimental releases of tagged salmon to evaluate salmon residence times and egress from the ponds. For juvenile salmon, we also conducted growth experiments and sampled diet and food availability.

Some of the highest-value aquatic habitat was consistently observed in the wetland tributaries of Patterson and Crabapple Creek.  These creeks were inhabited primarily by native fish and amphibians, including reticulate sculpin Cottus perplexus and coastal cutthroat trout Oncorhynchus clarki clarki.  In contrast, wetland ponds were inhabited by introduced taxa, including a high proportion of pollution-tolerant species.

Over the three study years, introduced species made up a substantial percentage of the catch in north and south wetland ponds.  However, three salmonid species were present in small numbers:  Chinook O. tshawytscha, coho O. kisutch, and coastal cutthroat trout.  A variety of potential salmonid predators also occupied the ponds, including an apparent resident spawning population of largemouth bass Micropterus salmoides.  For most sampling periods, native and non-native fish communities in the wetland ponds were more diverse than those in Multnomah Channel or in the mainstem Columbia River.

The Multnomah Channel Marsh area provides foraging opportunities and refuge from high flows for juvenile salmonids; however, the hydrologic disconnect of the Multnomah Channel Marsh from Multnomah Channel limits access of juvenile salmonids to the wetlands, provides habitat for non-native species, and degrades water quality.

Theme: Ecosystem approach to improve management of marine resources
Foci: Provide scientific support for the implementation of ecosystem-based management