Introduction

The Northwest Power Planning Council's Independent Advisory Board and the salmon managers have placed a high priority on the protection and enhancement of naturally spawning populations including fall Chinook and chum spawning in the mainstem Columbia River. Spawning of fall Chinook and chum in the mainstem Columbia River has been documented just below Bonneville and John Day Dams and is also occurring below The Dalles and McNary dams.  Very little was known about the existence and/or size of these populations and their associated genetic composition, spawning timing, emergence timing, juvenile rearing duration, and juvenile to adult survival rates. Additionally, little was known about the habitat requirements for these populations and the effect changing flows and water temperatures have on spawning location and success (measured by outmigrating juveniles and returning adults).  

The purpose of this project is fourfold:  (l) Document the existence of fall Chinook populations spawning just below Bonneville, The Dalles, John Day, and McNary dams;  (2) profile stocks for important population characteristics; including spawning time, emergence timing, emigration size and timing, and juvenile to adult survival rates, and relate these population characteristics to river flows and water temperatures; (3) determine habitat requirements that are necessary for successful fall Chinook and chum spawning and rearing in the mainstem Columbia River; and (4) conduct chum spawning ground surveys from The Dalles Dam downstream.  The primary goal of this project is to collect data concerning fall Chinook and chum spawning just below the four lowermost Columbia River mainstem dams so that the hydrosystem can be managed in a manner to protect and enhance these spawning populations.

Background

Historically fall Chinook were known to spawn in the mainstem Columbia River where adequate habitat existed; however, with the development of region, hydroelectric facilities that were built along the length of the Columbia River inundated the majority of the spawning habitat in the mainstem Columbia River.  Currently the free flowing stretch of river between McNary and Priest Rapids dams know as the Hanford Reach contains the vast majority of the remaining mainstem spawning habitat in the Columbia River.  A significant self-sustaining wild population of fall Chinook does use and depend on this stretch of the Columbia River for spawning and rearing purposes.  Similar but limited type habitat may exist below other mainstem Columbia dams and self-sustaining populations may exist in these areas also.  There had been little effort to determine if fall Chinook are spawning in the mainstem Columbia River below the other dams.  However, fall Chinook spawning in the mainstem Columbia River just below Bonneville Dam was documented in recent years.  Spawning ground surveys were conducted in the area around Ives and Pierce Islands during 1998 - 2005 and based on these surveys it is believed that fall Chinook and chum were successfully spawning in this area.  Through 1997, limited sampling of adult carcasses had occurred and surveys but had been inadequate for purposes of estimating spawning population size.  Additionally, no data had been collected concerning juvenile production or habitat characteristics of these spawning locations.  

Similar fall Chinook spawning populations may also exist just below McNary, John Day, and The Dalles dams.  Significant spawning has been documented below John Day Dam from 2002 - 2005.  It is well documented that this area was a productive mainstem spawning area prior to the construction of John Day Dam and which is now supported by current observations.   A similar situation may have occurred below McNary Dam which was also known to support a spawning population of fall Chinook.  In fact in December of 2005 reconnaissance level surveys revealed that at some spawning is occurring below The Dalles and McNary Dams.

In recent years as it has become apparent that a self-sustaining spawning population of fall Chinook and chum exists just below Bonneville Dam, primarily near Ives and Pierce Islands, and it has also become apparent that fluctuating flows may be negatively impacting this population through redd dewatering, lack of access to prime spawning areas, and possible stranding of juveniles.  Chum salmon have also been documented spawning downstream of the Bonneville areas near Multnomah Falls and Interstate 205. Physical and hydraulic factors affecting these populations however, are not known.  Additionally, it became apparent that data concerning this population was necessary to determine how flows and temperatures might effect this population and to develop management plans to protect these stocks.  Finally, fall Chinook fisheries management under the ESA requires accountability of all fall Chinook stocks returning to the Columbia River.

The federal agencies that operate or market power from the Federal Columbia River Power System (FCRPS), namely BPA, the U.S. Army Corps of Engineers, and the U.S. Bureau of Reclamation reinitiated consultation to consider the effects of the Federal Columbia River Power System on the six species listed during 1999.  Those species listed under the Endangered Species Act at that time included Lower Columbia River Chinook (listed as threatened on March 24, 1999) and Columbia River chum salmon (listed as threatened on March 25, 1999).  The objective of this consultation was to determine whether the operation of the FCRPS is likely to jeopardize the continued existence of any newly species or likely to destroy or adversely modify designated critical habitat.

NMFS (now NOAA Fisheries) anticipated using six types of information to determine whether the Ives Island spawners constituted an independent population.  That information included genetic differentiation, environmental and habitat characteristics, life history and morphological traits, correlations in abundances, rate of exchange between spawning aggregations, and geographic distribution.  The first four parameters are the subject of ongoing studies by ODFW, PSMFC, and USFWS.  However, the last two were not adequately evaluated or the focus of the proposal titled "Evaluate Spawning of Salmon Spawning Below the Four Lowermost Mainstem Dams", Project Number 199900301.

NMFS understanding of the current geographic distribution and spatial dynamics of spawning aggregations was incomplete.  Futlon (1970) identified 24 historical chum spawning areas in the Columbia River basin.  Kostow (1995) cited reports of 23 spawning areas in Oregon tributaries.  However, spawning populations of Columbia River chum salmon were recognized only on the Washington side of the Columbia River.  Those areas included the Grays River, Hardy and Hamilton creeks, and the Ives Island complex.

During consultation, NMFS informed the Action Agencies that this type of information will be critical to determining the appropriate long-term operation of the FCRPS to ensure the survival and recovery of Columbia River chum salmon.  So that the Action Agencies will have sufficient information to satisfy the Section 7 (a) (2) obligations, NMFS proposed to estimate the numbers of chum salmon spawning in Oregon and Washington tributaries below The Dalles Dam.

The chum spawning ground surveys are more intensive in terms of geographic coverage and level of effort than those previously performed.  This information required by NMFS is used to determine the importance of Ives Island spawners to the population structure of the ESU.  In addition, the surveys provide preliminary information regarding chum salmon spawning habitat quality in lower Columbia River tributaries and opportunities for habitat restoration.  The work on performed on this project includes Oregon Department of Fish and Wildlife and Pacific States Marine Fisheries Commission response to that request.

Study Design

This project is primarily composed of four closely related activities. Each agency is responsible for completing one activity with Pacific States Marine Fisheries Commission leading the adult portion, Oregon Department of Fish and Wildlife leading the juvenile portion, and the U.S. Fish and Wildlife Service leading the habitat portion of this project.  Oregon Department of Fish and Wildlife and Pacific States Marine Fisheries Commission will be conducting chum spawning ground surveys from The Dalles Dam downstream.  All four portions of the project are designed to work together to achieve the purposes of this project and each agency took the lead on an objective based on their special skills and/or knowledge in those areas.  Study results from PNNL's work contribute to all three tasks.

The primary function of the adult sampling portion of this project is to profile and estimate the fall Chinook and chum spawning populations in the mainstem Columbia below Bonneville Dam.  Surveys for live fish and carcasses will be the basis for determining the size of that population.  Spawning ground surveys, which consist of fish and redd counts, will also be used to determine time and location of spawning and redd locations will be recorded using a GPS.  In conjunction with the spawning ground surveys, carcasses will be examined for the purpose of determining genetic heritage, spawning success, sex ratios, and age composition.

Oregon Department of Fish and Wildlife and Pacific States Marine Fisheries Commission will perform stream surveys for chum on Columbia River tributaries from The Dalles Dam downstream.   Streams that historically supported chum runs but are no longer surveyed will be primarily targeted.  In addition, streams that currently support fish will also be surveyed.  Surveys would begin in mid-October and last through December.  Multiple surveys to count live and dead fish plus redds will be made.  Rough population estimates will be generated based on Area Under the Curve method using the live fish counts.  Spawning locations will be recorded on a GPS and mapped on a GIS.  Water temperatures will be taken at the spawning sites to determine if spring sources are present.  Scales samples taken will provide data necessary to determine age composition on the natural spawning population.  DNA, and otolith samples will be taken for future analysis to profile the genetic heritage of the naturally spawning chum populations.    

The primary purpose of the juvenile sampling portion of this project is to determine emergence timing and emigration size and timing and relate these indices to flow and water temperature.  Spawning areas identified in the adult sampling objective will be sampled for emergence timing and monitored for possible dewatering.  In conjunction with this work stranding of juvenile fall Chinook and chum in the study area will be noted.  Additionally, CWT's will be applied to juvenile fall Chinook for the purposes of determining juvenile to adult survival rates and relating production and recruitment of the stocks to flow and temperature experienced during juvenile stages of life.

The primary purpose of the habitat sampling portion of this project is to accurately describe the kind of mainstem Columbia River habitat fall Chinook and chum prefer to spawn in and how different flow levels impact spawning and rearing habitat.  Habitat will be mapped for the purpose of developing hydraulic models for fall chinook and chum spawning and rearing areas.  Spawning and rearing habitat descriptions will include a description of type of substrates and the associated water velocities and depth.  The effects of elevated flows on the spawning behavior and redd-site selection of chum salmon will be investigated using a two-dimensional acoustic array to obtain a continuous record of the locations of fish fitted with acoustic transmitters.  Experimental flows from Bonneville Dam will be requested to determine the flows and velocities that alter spawning behavior, and to determine if fish spawn at higher riverbed elevations under higher flows.

The adult, juvenile, and habitat sampling objectives will be concentrated just below Bonneville Dam.  The adult sampling objective will determine where populations currently exist, begin a monitoring program for existing populations, and determine which populations would benefit from additional study.  The juvenile and habitat sampling crews will perfect their sampling designs in the area just below Bonneville Dam, specifically near Ives and Pierce Islands, and will branch out into other areas as additional populations are identified.