The Columbia River Estuary

and

the Columbia River Basin

Fish and Wildlife Program

Independent Scientific Advisory Board

Northwest Power Planning Council

National Marine Fisheries Service

851 SW 6th Avenue, Suite 1100

Portland, OR 97204

Peter A. Bisson

Charles C. Coutant

Daniel Goodman

Robert Gramling

Dennis Lettenmaier

James Lichatowich

Eric Loudenslager

William Liss

Lyman McDonald

David Philipp

Brian Riddell

November 28, 2000

ISAB 2000-5
ISAB 2000-5 Estuary Report

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EXECUTIVE SUMMARY

The Northwest Power Planning Council (Council) requested the Independent Scientific

Advisory Board (ISAB) to undertake a review of the impacts of estuarine conditions on

the Council’s mission to “protect, mitigate and enhance” fish and wildlife in the

Columbia River as affected by development and operation of the hydroelectric system.

The ISAB agreed to undertake the review but cautioned that it was unlikely that it could

quantify the impact of changes in the estuary relative to specific program or management

actions taken in the upper river. The ISAB could, however, provide a historical

perspective and qualitative assessment of impacts, identify potentially useful

collaborations, and provide recommendations concerning future efforts needed to more

quantitatively address this issue (letter to Council, Jan. 26, 2000).

While conducting this review the ISAB became aware that there was extensive overlap

between a study by the National Marine Fisheries Service (NMFS) and this ISAB

assignment. The ISAB expects the NMFS study will add significantly to an informed

response to the Council. Consequently, this report has been prepared as a preliminary

reply, with additional detail possible following publication of the NMFS study.

Before human influence, the Columbia River estuary was a high-energy environment

dominated by physical forces, with extensive sand-beds and highly variable river flows.

Several authors have suggested that the biological processes in this environment may

have been unique on the Pacific coast. The estuary of today, however, has been

extensively modified in terms of physical and biological processes. The development

and operation of the hydroelectric system have contributed significantly to these changes.

Direct effects have been through changes in seasonal flow rates, reduced sediment

discharge, and resultant changes in the estuary’s energy balance.

There is extensive documentation about changes in the estuary over the past century.

The major changes resulting from development of peripheral wetlands and their isolation

from the estuary, development and deepening of the Federal Navigation Channel, and

regulation of upper Columbia River flows for hydrosystem needs and flood control. The

effects of these changes do not function discretely. The estuary is a complex interaction

of physical features (predominated by the energy balance between river flow and tidal

forces), resultant changes in circulation, salinity intrusion, sediment processes, and

ultimately the biological consequences of these changes. Superimposed on this dynamic

environment have been changes in water quality, introduction of exotic species, and the

enormous investment in hatchery production of salmonids to mitigate for related losses

due to the hydrosystem.

The question of the potential biological impacts associated with these changes is more

complicated than detecting the physical impacts. Changes in the biological processes

varied from a fundamental alteration in the basis of the food web to the exclusion of subyearling chinook and chum salmon from a large portion of the tidal marshes. The effects

of these specific changes, however, are difficult to partition from the effects of numerous

other impacts in the Basin. Furthermore, our ability to assess impacts of estuarine
ISAB 2000-5 Estuary Report

ii

conditions on the Fish and Wildlife Program has been limited by a lack of appropriate

and available data. Information necessary to meet the 1994 Program objectives was

simply not acquired for the estuary. Similar obstacles were expressed to the ISAB by the

NMFS study team who noted that the data are insufficient to even determine the extent of

modern estuarine use by salmonids.

While the ISAB recognizes the limitations of data to directly assess impacts of changes in

the estuary on the Fish and Wildlife Program, after our review it is our assessment that

these changes have been detrimental to salmonids and the rebuilding objectives of the

Program. We base this advice principally on three major issues:

1. The significant loss of peripheral wetlands and tidal channels; these habitats are

important to the early rearing, survival and growth of chum salmon, sub-yearling

chinook, and smaller coho salmon in other west coast estuaries.

2. The extent of change to seasonal flows following development of the hydrosystem.

The affects of these changes are closely associated with the impact of the

development of the navigation channel. In combination these developments have

resulted in changes to estuarine circulation, deposition of sediments, and biological

processes.

3. The need for precautionary advice given the current state of most salmonid

populations in the Basin, the magnitude of change in the estuary, and the lack of

investigations upon which to base alternative advice.

As the 2000 Fish and Wildlife Program is developed, the ISAB recommends an

aggressive experimental program targeted to reduce the likelihood of prolonged

uncertainty about the impact of estuarine conditions. Such a program should incorporate

monitoring of the physical environment (such as currently begun via the CORIE

program, Oregon Graduate Institute) combined with evaluation of large-scale

manipulations of estuarine habitats. The intent of these manipulations would be to study

changes presumed to have had negative impacts and to conduct these at a scale that can

be measured within the natural environment. These types of programs would be

consistent with the vision statement in the 2000 Fish and Wildlife Program:

“Wherever feasible, this program will be accomplished by protecting and restoring the

natural ecological functions, habitats, and biological diversity of the Columbia River

Basin.”

The types of large-scale programs that are envisioned include:

a) removal of dykes in the lower river and upper estuary to restore connections

between peripheral floodplains and the river or fluvial zone of the estuary;

b) actively managing sources of salmonid predation in the estuary through restoration

of natural habitats, removal of habitats artificially created due to channel construction

and/or maintenance, or controlling predator populations.

c) establish an allocation of water within the annual water budget for the Basin, that

would simulate peak seasonal discharge, increase the variability of flows during

periods of salmonid emigration, and restore tidal channel complexity in the estuary

(aided by removing pile dykes where feasible).
ISAB 2000-5 Estuary Report

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Initially, we anticipate that people will think that such programs are unnecessary and/or

impractical. To achieve the vision statement of the 2000 Fish and Wildlife Program in

the estuary province, however, programs of these magnitudes are likely necessary given

the magnitude of the estuary and the stated desire to evaluate these actions. The

Columbia River estuary is the interface between a highly modified freshwater system and

the open ocean environment. All of the investment and effort in the Fish and Wildlife

Program flow through this unique environment, but interaction of change in the estuary

with projects of the Fish and Wildlife Program, and their combined effect, has basically

been ignored. The ISAB strongly recommends that the Council recognize the potential

value of the estuary to the Fish and Wildlife Program and the immediate need to improve

our understanding of its ecological processes.
ISAB 2000-5 Estuary Report

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TABLE OF CONTENTS

INTRODUCTION............................................................................................................. 1

THE ESTUARY ENVIRONMENT................................................................................ 2

HISTORICAL CHANGES TO THE ESTUARY.......................................................... 6

CHANGES TO ESTUARY HABITATS................................................................................... 6

COLUMBIA RIVER FLOW REGULATION ............................................................................ 8

SEDIMENT LOADS AND THE FEDERAL NAVIGATION CHANNEL...................................... 13

EXOTIC SPECIES ............................................................................................................. 17

WATER QUALITY AND POLLUTANTS.............................................................................. 18

HATCHERY PRODUCTION OF SALMONIDS....................................................................... 19

CHANGES RELATIVE TO THE FISH AND WILDLIFE PROGRAM ................. 21

1994 FISH AND WILDLIFE PROGRAM ................................................................... 25

DISCUSSION .................................................................................................................. 27

LITERATURE CITED................................................................................................... 31
ISAB 2000-5 Estuary Report

1

The Columbia River Estuary and the Columbia River Basin Fish and

Wildlife Program

Introduction

The Northwest Power Planning Council (Council) requested the Independent Scientific

Advisory Board (ISAB) to undertake a review of the impacts of estuarine conditions on

the Council’s mission to “protect, mitigate and enhance” fish and wildlife in the

Columbia River as affected by development and operation of the hydroelectric system.

The ISAB agreed to undertake the review but cautioned that it was unlikely that they

could quantify the impact of changes in the estuary relative to specific program or

management actions taken in the upper river. The ISAB could, however, provide an

historical perspective and qualitative assessment of impacts, identify potentially useful

collaborations, and provide recommendations concerning future efforts needed to more

quantitatively address this issue (letter to Council, Jan. 26, 2000).

Since undertaking this assignment, the ISAB has reviewed an extensive literature about

the estuary, toured the estuary (July 2000), and met with a National Marine Fisheries

Service (NMFS) study team (June 2000) that is presently completing a major

investigation of the estuary and its linkages with Pacific salmon. The latter study was

developed in response to the 1996 Amendment to the Northwest Power Act of 1980 and

the 1997 Council paper (NWPPC 1997) on consideration of ocean conditions in the Fish

and Wildlife Program. That study is the first holistic consideration of salmon and their

estuarine ecosystem and the potential effects of upstream development on this linkage.

The NMFS study documents historical changes in the estuary, develops new conceptual

models that include application of new data linking these physical changes to biological

diversity in Columbia salmonids, and will evaluate management strategies to improve

estuarine conditions for salmonids. Furthermore, a team of researchers with extensive

knowledge of this estuary (see Small 1990) is conducting that study, and there is

extensive overlap between the NMFS study and the ISAB assignment. The ISAB expects

that the results of the NMFS study would add significantly to an informed response to the

Council. Consequently, this report has been prepared as a preliminary reply, with

additional detail possible following publication of the NMFS study.

Literature concerning the estuary is extensive 1 but the vast majority of the work concerns

specific species or questions and spans short time periods. There had not been a

coordinated publication of physical and biological characteristics of the estuary until the

Columbia River Estuary Study Taskforce (CREST) report (Seaman 1977) or a

comprehensive research program until the Columbia River Estuary Data Development

Program (CREDDP 1978-1981, see Simenstad et al. 1984). The latter describes the

estuary at the ecosystem level of organization and integrates the final reports of 13

 

1 Morgan et al. (1979) and CREDDP (1980) provide other useful literature surveys and annotated

bibliographies concerning investigations before 1980. Costello (1996) relates references to Pacific salmon

and the Columbia River estuary to Measure 7.1A of the Council’s 1994 Fish and Wildlife Program.
ISAB 2000-5 Estuary Report

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CREDDP work groups or topics. The data collected during CREDDP has been

extensively used in many subsequent publications because no other large-scale ecosystem

level program has been undertaken since. Simenstad et al. (1984) is a large, two-volume

compendium of CREDDP results but more concise publications providing excellent

overviews are Small (1990) and Simenstad et al. (1992). The journal volume edited by

Small (1990) consists of ten journal papers dedicated to the physical, chemical, and

biological characteristics of the Columbia River estuary and historical changes to the

estuary over the past century. In that volume, Sherwood et al. (1990) conclude that

changes in the estuary, as well as changes in the fluvial part of the system, have

contributed to the dramatic decline in salmon populations in the Columbia River.

The Estuary Environment

In common use, an estuary may be considered the portion of a river that is influenced by

ocean tides. Neal (1972) identified three different influences of tides:

1. The maximum distance upstream at which tidally induced water-level fluctuations are

observed.

2. The maximum distance upstream at which tidal inflow causes the river flow to

reverse.

3. The maximum distance upstream at which measurable amounts of seawater are

found.

In the Columbia River, tidally induced changes in water level are observed as far

upstream as Bonneville Dam (RM2 146) during low river flow, and reversal of river flow

has been measured as far upstream as Oak Point (RM 53). Intrusion of saltwater is,

however, generally less than 23 miles (near Harrington Point) at the minimum regulated

monthly flow (Neal 1972), although when lower daily flows occur, salt intrusion can

extend past Pillar Rock (approx. RM 28).

The area influenced by the intrusion of saltwater is most consistent with technical

definitions of an estuary.

“An estuary is a semi-enclosed coastal body of water which has a free connection

with the open sea and within which sea water is measurably diluted with fresh

water derived from land drainage.” (Lauff 1967)

The CREDDP study, however, included about 46.5 miles (75km) of the river-estuarine

continuum, stretching from the river mouth to approximately 20km above the maximum

extent of salinity intrusion during low river flows (Simenstad et al. 1990, see Figure 1).

Although it is unlikely that the upriver extent of this area ever receives saltwater, it is

likely that the area would be influenced by the [salt?] intrusion and reversal of river flow

on a daily basis. The area examined then includes the true estuary plus the area likely to

be influenced biologically by ocean tides.

 

2

 Distance along the Columbia River is measured by the convention of ‘River Miles’ used to indicate

distance up-river from the ocean entrance of and along the navigation channel (Simenstad et al. 1990)
ISAB 2000-5 Estuary Report

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Figure 1. Basic map and bathymetry (circa 1980) of the Columbia River estuary (Simenstad et al. 1990). Places named in the report

are shown. The convention of river miles upstream is shown as distance upstream of the river mouth and through the navigation

channel (RM = 0 at outer margin of the north and south jetties).
ISAB 2000-5 Estuary Report

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The Columbia River estuary region (defined in this text as the CREDDP study area) is a

large, high-energy environment (strong tidal currents and large river flows) with high

temporal variability in circulation, sedimentation, and biological processes (Sherwood

and Creager 1990, Jay and Smith 1990, Jay et al 1990).

Two estimates of the surface area and habitats in the Columbia River estuary exist

(Thomas 1983, Simenstad et al. 1984). Both estimates used the same basic data (1958

NOAA bathymetric survey), but employed slightly different definitions for habitat strata.

Overall, however, the analyses are similar (range of areas from 412 to 482 sq. km.) and

actually only differ substantively in their estimates of area in tidal flats (Table 1). Based

on maps outlining the areas surveyed in these two reports, it seems that Thomas (1983)

included more area in the peripheral bays than the Simenstad et al. (1984).

Table 1. Estimates of the total surface area in the Columbia River estuary by habitat

type, based on the 1958 NOAA bathymetric survey. Areas estimated by Thomas (1983)

and CREDDP (Simenstad et al. 1984) were expressed in different units and have been

converted to (sq. km.) for comparison (1 sq. mi. = 2.59 sq. km.)

Habitat type Thomas CREDDP Comments

1) Deep Water (area below

18’ depth)

131.8 122.2 Reports used same definition,

CREDDP designated this habitat

as Channel Bottom

2) Medium depth or

Demersal slopes

104.1 130.8 CREDDP defined stratum down to

3’ below mean low low water, but

Thomas used 6’ below MLLW3.

3) Tidal flats and shallows 181.2 99.6 Difference associated with

comment above.

4) Tidal marshes 37.2 28.5 CREDDP defines down to 3’

above MLLW but Thomas used

MLLW as boundary.

5) Tidal swamps 28.1 30.8 Discretion in defining upper

boundary of tidal marshes.

 TOTAL 482.5 411.8 Difference associated with areas in

peripheral bays that were included.

While the Columbia estuary is a large, highly dynamic environment, three other features

differentiate it from other major estuaries and are important within the context of the Fish

and Wildlife Program. First, while changes in estuarine habitats will be noted, overall the

Columbia River estuary is substantially less disturbed than other large westcoast estuaries

 

3

 Diurnal tides are not equal in strength, consequently there will be two levels of low and high tides per

day. The designation of a low low water is the lower water height of the two low tides in a day. The Mean

low low water is the average height of the lower of the two daily low tides over a specific time interval. By

definition, the elevation of the MLLW is set to zero.
ISAB 2000-5 Estuary Report

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(see Nichols et al. 1986, Sacramento-San Joaquin; and Northcote and Larkin 1989, Fraser

River, BC). For example, while the upper Fraser River is certainly not as disturbed as

the upper Columbia River, the lower Fraser River and estuary is highly channelized, with

extensive loss of wetlands and major urban development along the lower 100 km of the

river. Second, river flows in the Columbia River are now highly regulated and different

from its historical flow pattern. The extent of flow regulation and its interaction with

tidal energy are closely related to changes in physical and biological features of the

estuary (Jay et al. 1990). Third, the extensive development of the lower Columbia River

for shipping and the use of jetties and dredging to stabilize dredged channels have altered

the physical environment of the estuary. Sherwood et al. (1990) provides a concise

history of these developments but the scale of the dredging activity alone is informative.

These authors estimate that between 1909 and 1982 dredging operations each year

removed one-third to one-half of the annual fluvial sediment supply to the estuary!

Although it is convenient to discuss individual features or changes in the estuary,

essentially all of these changes interact. Some may interact to amplify impacts while

others may compensate. For example, regulated river flows now substantially reduce the

peak freshet flow and reduce sediment input to the estuary. Channel dredging though

concentrates flow in a main channel and reduces flows in the peripheral areas, allowing

greater retention of sediments in those areas. These interactions become increasingly

complicated, especially when their effects on biological processes are considered.

While this report will focus on the Columbia River estuary region, we should note that

the river habitats upstream to Bonneville Dam are also certainly important to salmon.

This area of the lower Columbia River has been classified into habitat categories in a

manner comparable to Thomas (1983). Graves et al. (1995) reported on these habitat

categories for the river and estuary downstream from Portland (Table 2).

Table 2. Historical habitat area (circa 1880) and classifications for the lower Columbia

River based on Thomas (1983, Columbia estuary region) and Graves et al (1995, up-river

of estuary to Portland), data are presented in acres (1 acre = 4047 sq.m. = 0.004 sq.km.).

Habitat categories Columbia R. Estuary Lower Col. R. above estuary

Medium and Deep water 69,350 43,967

Sub-tidal and flats 40,640 4,237

Tidal marsh and swamps 46,200 13,753

Non-tidal wetlands 50 29,645

Uplands, non-tidal 1,930 17,676

 Total Area (acres) 158,170 109,278
ISAB 2000-5 Estuary Report

6

Historical Changes to the Estuary

Changes to Estuary Habitats

Two significant assessments both indicate a loss of estuary habitat area but the extent of

change is highly dependent on the location in the estuary and the type of habitat. For

example, Thomas (1983) reports major loss of tidal marsh and swamp habitats, but

Cathlamet Bay was much less disrupted than other peripheral bays and the upper estuary.

Combining the Sherwood et al. (1990) analysis with Thomas’ estimate for tidal marsh

and swamps results in an overall estimate of estuary habitat loss of 25% (by area)

between 1868 and the 1958 USGS survey.

A rich archive of maps, bathymetric charts, photographs and notes about the estuary in

the later 1800s and early 1900s permit comparison of the present estuary with habitats

that existed before most development occurred. After examination of these materials,

Thomas (1983) selected charts issued by the U.S. Coast Survey for 1868-1873 as the best

available representation of undeveloped estuary and compared these charts to the 1958

NOAA bathymetric survey. The historical records allowed Thomas to define five habitat

types listed in Table 1.

1) Deep Water: surface areas below the eighteen-foot bathymetric contour.

2) Medium depth Water: surface areas for water between the 18’ contour up to the sixfoot contour.

3) Shallow and tidal flats: surface areas shallower than the 6’ contour up to the edge of

tidal marsh or swamp vegetation, or the mean higher high water level if vegetation

mappings were absent.

4) Tidal marshes: areas dominated by emergent vegetation or low shrubs, and found

from MLLW too slightly above MHHW.

5) Tidal swamps: shrub and forest dominated wetlands extending up to the line of nonaquatic vegetation (these swamps may only be inundated during spring tides but they

also extend down to MHHW).

Thomas estimated a 24% reduction in overall surface area of the estuary with the greatest

change occurring in the shallow water and shore-land habitats (Table 3). If only change

in the latter habitats is considered, then the proportion of habitat lost over time increases

substantially. Thomas provides a detailed description of habitat changes by sub-areas

and the processes involved both natural and human induced. The largest single factor

involved in these changes has been dyking of low elevation wetlands in the peripheral

bays and upper estuary fluvial sub-area. Dykes remove areas entirely from the estuarine

system, and reducing surface area and water volume, rather than change areas from one

habitat type to another. Thomas identifies shoaling as the second most important cause

of change and notes the increase in shallow water and tidal flat habitats. The vast

majority of this increase, however, occurs in one sub-area (Baker Bay) followed by much

smaller increases in the upper estuary habitats.
ISAB 2000-5 Estuary Report

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Sherwood et al. (1990) conducted an analysis similar to Thomas (1983), but focused their

assessment on sub-tidal areas. Estimates of “surface area” in several depth strata were

made using bathymetric charts for three survey periods: 1867-1877, 1926-1937, and

1949-1958 (corresponding to the 1868, 1935 and 1958 U.S. Coast Survey charts). This

analysis was a more in-depth assessment of changes in the water column than was

possible with the resolution of habitat types used by Thomas (1983).

Table 3. Past and present estuary habitat types and surface area as estimated by Thomas

(1983). Area is expressed in acres, 1 acre = 4046.9 square meters.

Habitat type Pre-development 1958 survey % Change or Comment

Estuarine Habitats:

Deep Water 35,140 32,580 loss of 7.3% of area

Medium Depth Water 34,210 25,720 loss of 24.8% of area

Shallows & Flats 40,640 44,770 gain of 10.2% of area

Tidal marsh 16,180 9,200 loss of 43.1% of area

Tidal swamps 30,020 6,950 loss of 76.8% of area

Total 156,190 119,220 loss of 23.7% of total area

Non-Estuarine

habitats:

Developed Floodplain 0 23,950 Diked floodplain in use for

agriculture, residential, or other.

Uplands 1,930 7,590 Natural or filled uplands, mostly

through disposal of dredge

material.

Wetlands 50 7,410 Areas of undeveloped, dyked

floodplain or reverted to

wetlands that remain separated

from the estuary.

Sherwood et al. (1990) reported that a shift from shallow sub-tidal to greater depths was

apparent between 1868 and 1958. Much of the shift was accounted for in the Entrance

area to the estuary but similar trends were also evident in the South Channel (southern

navigation channel) and in the Upper Channel area (upper estuary fluvial area). In

contrast, Baker Bay and Cathlamet Bay sub-areas have filled more uniformly. Sherwood

et al. (1990) concluded that the net effect of these changes has been to reduce the surface

area of the estuary, while shifting a larger percentage of the sub-tidal area and water

volume to deeper water habitats.
ISAB 2000-5 Estuary Report

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Columbia River Flow Regulation

Many of the physical, and indirectly the biological, features in the Columbia estuary are

strongly effected by the energy balance between ocean tides and river flow (Jay et al.

1990). As most people are aware, however, development upstream of the estuary has

been extensive, and river flows have been altered substantially. Sherwood et al. (1990)

provided a concise description of changes in river flow that were due to reservoir storage

(between 1933 and 1982, 21 large dams on the Columbia and Snake rivers were built),

irrigation for interior basin agriculture, and climate change. Information presented below

is similar in content to their report but up-dates the flow data through 1999 (data provided

by David Jay and Pradeep Naik, Oregon Graduate Inst., pers. comm.).

To summarize the changes in Columbia River flows:

a) annual flows measured as the adjusted flow at The Dalles, OR have decreased by

approximately 15% relative to pre-1900 river flows;

b) regulation of flows in the upper Columbia became significant about 1969 and has

greatly reduced the average flows in the spring freshet (-50 to 55%) and increased the

flows in the winter months (+35% October through March);

c) flow from lower Columbia drainages contribute substantially to winter flow

conditions into the estuary but in the pre-regulated flow period did not contribute

much to the spring freshet or summer flow;

d) since increased flow regulation in the upper river, the lower Columbia drainages are

more important as a source of water but spring and summer flows are still dominated

by upper river flows;

e) this analysis did not fully examine changes in maximum or minimum flows, or the

temporal variability of flows.

Since June 1878, daily flow in the Columbia River has been recorded at The Dalles,

Oregon. To examine annual variability and time trends, these data have been

summarized as annual average flows (Fig. 2). In using this long time series of flows,

however, some of the observed flows will be unregulated (pre-development) and others

regulated. To account for this change, ‘adjusted’ flows were estimated for the years with

regulated observed flow data. Adjusted flows are the natural flows that would have been

expected in a year if the effect of storage was removed (Orem 1968).

Although Figure 2 includes fifteen years of daily flow data added to the analysis

presented by Sherwood et al. (1990), the results are very similar; except for a second

period of very low flows from the mid-1980s to mid-1990s. Overall, there is

approximately a 15% reduction in average annual flow from the late 1800s until the late

1900s (a little less than indicated by Sherwood et al. 1990). The variability in average

flow between years, however, often seems at odds with this degree of average change.

The NMFS study team will be examining the variability of flows in much greater detail.
ISAB 2000-5 Estuary Report

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Figure 2. Time series of average annual flow (cu. m/sec) for the Columbia River at The

Dalles, 1879-1999. Flows have been corrected for the effect of storage (adjusted flows)

and the smoothed curve was estimated as a 10-year moving average.

Historical data for Columbia River flows at The Dalles, OR (USGS station gauge

14105700) were also used to examine changes in annual flow profiles by month. Flows

averaged by month over years were compared for two periods: flows through 1968 and

those after. Sherwood et al. (1990) noted that reservoir capacity doubled in the Columbia

basin between 1967 and 1975 providing the capability to dramatically alter flow pattern.

Before completion of the Grand Coulee Dam, however, the observed and adjusted flows

were equal. To demonstrate the change in adjusted and observed flow, Figure 3a presents

average monthly flow between 1941-1968, and Figure 3b compares flows between 1969-

1999. Figure 4 expresses the difference in observed minus adjusted flows as a percentage

of the observed average flow by month for the period of regulated flows, 1969-1999.

The magnitude of change in monthly flow from the upper Columbia River is apparent in

Figure 4. During spring freshet months (May-June), regulated flows have, on average,

been reduced by 50-55%. During the winter period (October through March) regulated

flows have, on average, been increased by 35%.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1879188318871891189518991903190719111915191919231927193119351939194319471951195519591963196719711975197919831987199119951999

Adjusted Flow (cu.m/sec)

Annual 10Yr Historical Adjusted flows at Dalles
ISAB 2000-5 Estuary Report

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Figure 3a. Observed and adjusted river flow (cu. m/sec) for the Columbia River at The

Dalles, OR 1941-1968. The similarity of these curves demonstrates that average monthly

flow was not altered much by storage capacity or regulation during this period.

Figure 3b. Observed and adjusted river flow (cu. m/sec) for the Columbia River at The

Dalles, 1969-1999. In this period, spring freshets in May, June, and July were greatly

reduced and flows in other months increased.

0

2000

4000

6000

8000

10000

12000

14000

16000

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec

Flow Volume (cu.ft./sec)

1941-68 ADJ

1941-68 OBS

0

2000

4000

6000

8000

10000

12000

14000

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec

Flow (cu.m/sec)

>1968OBS

>1968ADJ
ISAB 2000-5 Estuary Report

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Figure 4. Differences between Observed and Adjusted flows in Figure 3b expressed as

(Observed – Adjusted)/Observed flows (% change relative to Observed flow by month).

While these changes are significant, they do not indicate the monthly flow profile

observed in the Columbia River estuary since they are measured at The Dalles. Flows in

the estuary result from up-river input plus inflow from rivers in the lower Columbia

River. The contribution of lower Columbia drainages to flow in the estuary is observed

by contrasting flow at The Dalles with flow near the mouth of the Columbia River, both

before (Figure 5) and following (Figure 6) significant regulation. Prior to regulation,

flow from lower Columbia drainages appears especially important during the winter

period but has little effect, on average, during the spring freshet and summer period

(Figure 5). To examine regulated flows, the observed flow (cu. m/sec) for the USGS

gauge (#14246900) at Beaver Terminal (RM 53.8) in the lower Columbia River4 was

compared to the observed flow at The Dalles (from Figure 3b) for the period 1969-1999

(Beaver Creek data provided by D. Jay and P. Naik, Oregon Graduate Inst). The monthly

mean observed flow at Beaver Terminal shows the continued importance of the lower

Columbia drainages during the winter months (as in Figure 5). It also indicates that an

increased portion of the flow occurs during spring and summer months (Figure 6), and

illustrates the major reduction in spring freshet from up-river.

 

4

 River drainages that flow directly into the estuary are relatively small drainages and contribute only a few

per-cent of the annual Columbia River flow. However, they may have important localised effects.

-60.0%

-40.0%

-20.0%

0.0%

20.0%

40.0%

60.0%

Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec

Flow Deviation (cu.m/sec)

1969-1999 1879-1968
ISAB 2000-5 Estuary Report

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Figure 5. Adjusted flow (cu. m/sec) expected at the mouth of the Columbia River, near

Astoria OR (squares, data from Orem 1968 and Seaman 1977) compared with the

adjusted flow of the Columbia River at The Dalles (circles, data from Figure 3a,

<1969ADJ data). The early period data was used in this comparison since the data for

the Col. R. mouth was for the period 1928-1968 (data converted from cu.ft/sec).

Figure 6. Observed Columbia River flow (cu. m/sec) at the Beaver Terminal compared to the

observed flow in the upper Columbia River at The Dalles, average monthly flow for 1969-1999.

Beaver Creek data = squares, The Dalles = circles.

0

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Flow (cu.m/sec)
ISAB 2000-5 Estuary Report

13

The presentation of flow data in these simple comparisons of mean annual or monthly

flows do not portray the full degree of change in flow patterns that have occurred. For

example, regulation of flow has greatly reduced peak or maximum flows, slightly

increased minimum flows, and significantly reduced variability of flows (measured as the

co-efficient of variation).

These changes can also be significant in their effect on the estuary habitats due to

reductions in sediment transport or reduced flooding of wetlands. Because a complete

analysis of flow variability and peak flows will not be included in this report, readers are

referred to Sherwood et al. (1990) until the NMFS analyses that are currently being

completed area available.

Sediment Loads and the Federal Navigation Channel

The transport of sediments by the river and the morphology of the estuary have both been

substantially changed over the past century. The supply of sediment to the estuary is a

function of the type of sediments available to the river (e.g., fine clays versus larger sand

particles) and river discharge. The deposition of sediment in the estuary results from the

balance between fluvial and tidal energies, and morphology of the sediments is a function

of circulation in the estuary. Changes in the sources of sediments and regulation of upriver flows makes these considerations complicated ... but the added development of the

shipping channel makes this situation even more so. Recent analyses of sediment loads

in the Columbia River indicate about a 50% reduction in annual average sediment load

relative to the pre-dam period. Physical changes in the estuary and regulation of river

flow have also altered the dynamics of seawater intrusion, circulation, and sedimentation

processes in the estuary.

Assessing a change in sediment carried by the river is much less certain than examining

the change in river flow. Sediments entering the river depend on the land-use practices

and development, historical river flows, and basic soil types or geology. Sediment loads

in the river before major development are not known. Sherwood et al. (1990), however,

used the limited sediment discharge estimates that were available plus the historic flow

data (at The Dalles OR) to back-calculate sediment loads into the late 1800s. For the

period 1868 through 1934 (until the first Columbia River dam), they estimated an annual

sediment discharge rate of 14.9 million tonnes per year. They contrasted that estimate

with more recent flows (for 1958-1981) and report a decrease in average sediment

discharge of nearly 50% to 7.6 million tonnes per year.

Recently, D. Jay and P. Naik (Oregon Graduate Institute) have re-examined relationships

between sediment load and flow (cu. m/sec), reconstructing the historical sediment loads

as reported in Sherwood et al. (1990). Their methods and calculations will be included in

the NMFS study report, but they provided these data to the ISAB up-dated through 1999.

For the pre-dam period (1879-1935) the estimated annual total sediment load averaged

15.1 million tonnes/year but decreased to 9.7 million tonnes/year between 1936 and

1999. If only the period following completion of the hydrosystem is included (1975-
ISAB 2000-5 Estuary Report

14

1999) then the annual average flow is reduced to 7.3 million tonnes/year; a 51% average

reduction relative to the pre-dam period (Figure 7).

Recently, the U.S. Army Corp of Engineers (1999) has also estimated annual sediment

loads for the period 1980 through 1995. Their estimate of sediment volumes is much

lower than Jay and Naik’s and is largely based on an assumption that sand supply to the

lower Columbia River has been substantially reduced due to the dams. This seems to be

a reasonable assumption except that observations in the past four years annual discharge

and tonnes of sediment have increased over the 1975-1995 period (Figure 7).

Figure 7. Annual sediment transport (millions of tonnes per year) and flow (cu. m/sec) of

the Columbia River at The Dalles, 1879-1999. Sediment transport back-calculated by P.

Naik (Oregon Graduate Institute).

The number of years with actual data used in any of these comparisons is very limited

and variation between years could be very high for several reasons: development of the

hydrosystem during observations, annual variation in climate, number of dams developed

and patterns of flow control, location of sampling, etc. What is important, however, is

the magnitude of the reduction. Average annual sediment input to the estuary has likely

declined over 50% following development of the upper Columbia and flow control.

Two mechanisms are noted as the principal causes of this decline: storage capacity of the

reservoirs and reduction in peak flow discharges. To our knowledge, the effect of the

0

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1875 1885 1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995

SPM in M tons

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Flow in m 3 s-1

SPM Flow
ISAB 2000-5 Estuary Report

15

reservoirs has not been quantified but the reduction of flow through them must allow

larger suspended material to settle out, and restrict any bedload transport (movement of

sediment along the riverbed when energy is sufficient). The reduction in peak flows,

however, is known to greatly reduce the river’s capacity to transport sediment and

especially sand (Jay et al. 1990). Flows are usually sufficient to transport fine

sedimentary material (silts, clay, and fine sands) but this material may be supply limited,

whereas sand is usually capacity limited (Sherwood and Creager 1990). Sandy material

may be available but the capacity of the river to transport sand is limited by discharge.

The capacity of water to transport sediment increases as a power of the flow discharge

and at higher discharge sand constitutes a greater portion of the sediment carried. Before

regulation, peak flow events would have provided a very large portion of the sand

transported into the estuary. With regulated flows, however, the reduction in sand

transported to the estuary is disproportionately greater than the changes in flow and total

sediment load.

The proceeding analyses and Figure 7 only address sediment from the Columbia River

above the Willamette River. The Willamette and other lower Columbia rivers also

provide sediment but their input will not compensate for the estimated 50% reduction

from the upper river. Except for an unusual event such as the eruption of Mount St.

Helens in 1980 that produced an estimated 250 million tonnes of sediment in one year.

Within the estuary, the distribution of sediment is closely related to the energy balance

between ocean tides and river flows. Jay et al. (1990) evaluated an energy budget for the

estuary and defined three regions within the estuary based on differences in energy

balances, and consequently, sedimentary properties. The lower estuary (downstream of

about Rm13) is dominated tidally, the upper fluvial region (above about Rm35) is

dominated by river flow, and the intermediate region5 where both tidal and river

processes are important but their energy inputs are much weaker than in either other

region. As fluvial energy decreases in the intermediate zone the capacity for sand

transport decreases and sand is deposited. The region is also associated with a zone of

maximum turbidity that entrains and concentrates fine sediments, detritus and food

particles, and feeding organisms (Simenstad et al. 1990). The location and strength of

the maximum turbidity is associated with the extent of salinity intrusion (tidal energy)

and its upstream extent limited by fluvial energy gradients (river flows).

Sherwood et al. (1990) suggest that “effects of human alterations of estuarine flow

patterns on the turbidity maximum have had large ecosystem-level consequences.”

These alterations involve changes to flow and sediment loads (as discussed above) and

changes in the estuary morphology associated with jetties, dyking, and development of

the shipping channel. Construction of the Columbia and lower Willamette River

navigation channels was authorized in 1878 with a minimum depth of 20 feet. However,

over the next 100 years the channel was expanded to a 40 ft depth and 600 ft width (US

Corp Engineers 1999). To develop and maintain these channels large sediment volumes

are dredged annually (Figure 8) and 236 pile dikes have been built throughout the

channels to focus flows, reduce erosion, and provide disposal sites. Dredged materials

 

5

This region is referred to by Jay et al. (1990) as the energy flux divergence (EFD) minimum region.
ISAB 2000-5 Estuary Report

16

are disposed of in-water (ocean disposal or in the flow lane adjacent to the channel),

along shorelines, or on upland sites. The volumes of material dredged annually do not

reflect the rate of sedimentation in the river since most of disposal methods result in rehandling of material, and since a period of riverbed adjustment will follow each channel

development action. Annual maintenance dredging since completion of the 40 x 600 ft

channel (after 1976) has averaged 3.5 M cu.yd. per year in the estuary region (RM 4-50)

plus 5.3 M cu.yd. per year in the Columbia River mouth (RM 0-4).

Figure 8. Annual volume (million cu. yd.) of dredged material handled during the

development of and maintenance of the Columbia River navigation channel in the

Columbia River estuary (Rm 4 to 50), 1900 to 1996. Data provided by U.S. Army Corp.

(Portland, OR).

How did the construction of the navigation channel affect the estuary and its associated

ecosystems? Basically, the navigation channel has concentrated flow in one deeper main

channel, with several linked physical effects:

- reduced flow to side-channels and peripheral bays,

- reduced total surface area and volume of the estuary (tidal prism reduced 15%),

- reduced saltwater intrusion from its historical range and salinity throughout the

estuary,

- reduced tidal currents relative to past (for comparable tidal ranges),

- altered the balance of circulation between the northern and southern channels,

- increased stratification of water column and reduced mixing,

- increased shoaling rates in the intermediate zone and peripheral flats, and

- altered habitat types.

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1900190419081912191619201924192819321936194019441948195219561960196419681972197619801984198819921996

Volumne (x1000 cu.yd.)

ESTUARY ( RM 4 to 50)

1934 Miller Sands,

channel re-aligned
ISAB 2000-5 Estuary Report

17

The latter, for example, includes the disposal of dredge material and creation of barren

land or islands. These habitats have increased availability for certain avian species and,

thereby, contributed to increased predation on esutarine fishes, including salmonids

(program currently underway, see Collis et al. 2000, Roby et al. 1998). Furthermore,

when combined with regulated river flows, flushing time of particles or organisms in the

estuary will increase relative to the past, due to reduced tidal exchange and river flows.

Flushing time will also be less variable seasonally, but likely more variable spatially.

Concentrated tidal and river flows in the main channels will reduce flushing from the

peripheral channels and allow for increased deposition of fine sediments in those areas.

These physical processes associated with the navigation channel, plus the changes in

estuary habitats and regulation of river flows, provide strong inference that the turbidity

maximum and biological production are likely to have decreased substantially over time.

Unfortunately, the magnitude of change can not be assessed because no information

exists on physical and biological processes before development. For the estuary in its

current configuration, however, Simenstad et al. (1990) clearly emphasized the biological

importance associated with the turbidity maximum and the intermediate energy zone of

the estuary:

“Abstract – Consumption processes at several trophic levels tend to converge in the

central (estuarine-mixing) region of the Columbia River estuary, where living and

detrital food resources are entrained within the energy null of the turbidity maximum

zone. Primary consumers in this region are generalists and omnivorous feeders, capable

of exploiting both autotrophic and heterotrophic food web pathways. In the presence of

higher standing stocks of their prey resources, feeding by secondary and tertiary

consumers is also concentrated, or more effective, in the estuarine mixing region of the

estuary. ...”

Exotic Species

The introduction of exotic species has almost always proven harmful to native fish

communities and ecosystems and has seldom been controlled (Courtenary and Robins

1989, Tyus and Saunders 2000). Unfortunately, we know very little about the impact of

these exotic species until it becomes all too obvious. Of 30 fishes that became extinct in

the United States during the 20th century, introduced fishes were implicated in 24

extinctions and were the only factor acknowledged in two (Miller et al. 1989). For the

Columbia River estuary, Weitkamp (1994) summarised the presence of 16 exotic fish and

four exotic invertebrates known to date. Since then, however, two invasive crab species

have been noted on the Pacific coast, the Green crab, Carcinus maenas, and the Chinese

Mitten crab, Eriocheir sinensis6. As in most other situations, little can be quantified

concerning the effect of these introductions but both species are considered to be

significant predators in estuarine environments.

By far the most abundant exotic fish species is the American Shad, Alosa sapidissima.

Shad were introduced to the Sacramento River in 1871 from the eastern seaboard, and

 

6

 for additional information on Green crabs see: http://www.wa.gov/wdfw/fish/shelfish/greencrab.htm and

for Mitten crabs see: http://www.delta.dfg.ca.gov/mittencrab/life_hist.html
ISAB 2000-5 Estuary Report

18

were observed in the Columbia estuary in 1876 (Craig and Hacker 1940). Harvest in the

Columbia estuary began in 1888, but Craig and Hacker suggest that the early catch record

was not indicative of abundance but “more nearly an index of the demand for or rate of

disposal of the shad.” Recently, however, there is no doubt about their abundance

(Figure 9); the only question centers on what their impact might be in the estuary. Shad

juveniles (from age 0 to 2) are found in the estuary throughout the year (Bottom et al.

1984, Haertel and Osterberg 1967) and can be very abundant, emigrating from freshwater

in their first fall at about 3-5 inches.

Figure 9. Minimum run size (x000 fish) of American Shad entering the Columbia River,

1938-1998 (WDFW & ODFW 1999). Run size does not include spawning populations

below Bonneville Dam.

Water Quality and Pollutants

In an estuary that has relatively low industrial development and relatively high flushing

rates, we may not expect water quality or accumulation of pollutants to be a major

concern for the Columbia River. However, results of a recent study conducted by NMFS

in several Pacific Northwest estuaries provides evidence for concern (NMFS NWFSC,

Seattle, WA). Juvenile salmon collected from East Sand Island near the mouth of the

Columbia River contained relatively high concentrations of DDTs and PCBs. These

results raise questions about the source(s) of the contamination but have not yet been

investigated.

0

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1938194219461950195419581962196619701974197819821986199019941998

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ISAB 2000-5 Estuary Report

19

Studies of sub-lethal exposure of juvenile salmon to contaminants in urban estuaries

suggest that these contaminants could affect the survival, growth, and fitness of salmon

(Casillas et al. 1996). A series of studies with laboratory and natural exposure of fall

chinook salmon to aromatic and chlorinated hydrocarbons in Puget Sound estuaries

demonstrate sub-lethal effects such as impaired growth, reduced immunocompetence,

and increased susceptibility to diseases (Stein et al. 1995, Arkoosh et al. 1998a, Arkoosh

et al. 1998b, Stehr et al. 2000). Furthermore, a recent study using the organophosphate

insecticide, Diazinon, reported reduced antipredator and homing response in treated

chinook salmon (Scholz et al. 2000).

Given the presence of these contaminants in some fishes collected in the Columbia

estuary and sub-lethal effects that the contaminants may cause, the potential overall effect

of this water quality issue could be reduced productivity in species that use the estuary

for rearing, such as fall chinook and chum salmon. An in-depth report on water quality in

the Columbia River estuary has been completed by the Lower Columbia River Estuary

Program and can be accessed at: http://www.lcrep.org/home.htm

Hatchery Production of Salmonids

The production of hatchery fish in the Basin is clearly not a response to physical changes

or loss of production in the estuary. The development of hatchery production through

time, however, has proceeded assuming that capacity for survival and growth of hatchery

fish would not be limited in the estuary or ocean (Brannon et al. 1999, Lichatowich

1999). Indirectly then, the expansion of hatchery production may limit production of

naturally produced salmonids. The scale of hatchery production alone is a significant

change in estuary use (Figure 10). Hatchery releases were summarized from the NRC

(1995) database for the releases years 1950 through 1993. Data for release years 1994

through 1998 were summarized from agency records exchanged annually through the

Pacific Salmon Commission. The latter data are maintained at the Pacific Biological

Station, Nanaimo, BC (B. Riddell, pers. comm.). Releases of fall chinook salmon are

also presented since under-yearling fall chinook migrants are known to use the estuary

extensively for rearing.

Figure 10 indicates the scale of hatchery releases but is not very informative unless they

can be related to historical production of naturally produced salmonids. Obviously any

such estimation involves several assumptions, but rough estimates can be derived from

peak historical catches by species, and applying reasonable (but conservative) values for

terminal harvest and marine survival rates. For example, using historical catch data from

Chapman (1986) and Craig and Hacker (1940), the following range of estimates for

historical production of salmonid emigrants were derived (Table 4).
ISAB 2000-5 Estuary Report

20

Figure 10. Total releases of salmonids (millions) in the Columbia River basin for release

years 1950-1998, including releases of Fall chinook salmon. Releases of Fall chinook

were only summarized for the period 1975-1998.

Table 4. Estimated numbers of naturally produced smolts emigrating from the Columbia

River during peak catch periods, as identified by Chapman (1986)7, numbers of smolts

expressed in millions. Hatchery contributions during these periods would have been

negligible to none.

Marine survival rates, smolt to adult (%)

Species

Historical

Peak

Catches

Terminal

Harvest

Rates 2.5% 5% 10% 15%

Sockeye 1,400,000 0.50 56,000 28,000 18,667

Summer chinook 1,400,000 0.70 40,000 20,000 13,333

Spring chinook 400,000 0.50 16,000 8,000 5,333

Fall chinook 1,100,000 0.40 110,000 55,000 27,500

Coho 476,000 0.33 28,850 14,425 9,616

Chum 359,000 0.33 43,515 21,758 10,879

Steelhead 382,000 0.25 30,560 15,280 10,187

 

7

 The historical peak catch for sockeye is less than in Chapman (1986). Chapman’s value averaged each

annual value but was strongly influenced by one year. The peak value in this table is calculated as one

expansion estimated over the sum of the 5 years used by Chapman.

0.0

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250.0

19501953195619591962196519681971197419771980198319861989199219951998

Release Year

Salmonids released

Fall Chinook Total Releases
ISAB 2000-5 Estuary Report

21

The bold values in the table are those values for each species that are most likely and

total over 200 million smolts. Whether these levels of production could be supported

within one year is not known. Overall, however, there are some notable changes (e.g.,

the loss of chum and summer chinook production), particularly since the vast majority of

upper river spring and summer chinook, and lower river spring and fall chinook are now

produced in hatcheries. It may also be notable that under the assumptions used, the

hatchery production of fall chinook (Fig. 10) plus current natural production of Columbia

River Bright fall chinook would equal or exceed the historical production of fall chinook

smolts. Given the changes in estuary habitats, the survival and growth of these fall

chinook in the present estuary should be a concern. Furthermore, the timing of

emigration of hatchery fish through the estuary is much more compressed in duration and

season than in the past.

We should also note, however, that all the salmonids released in the Columbia River

basin above Bonneville Dam will not reach the estuary. In recent years, the Fish Ecology

Division, NWFSC NMFS has calculated the annual “percentages of listed wild and

hatchery fish at selected Columbia and Snake River projects” (provided by Protected

Resources Division, NOAA NMFS, Portland, OR 97232). For example, the total release

of hatchery fall chinook in 1998 was reported to be 64.2 million (for all agencies in the

Columbia Basin); but the estimated number of hatchery plus wild fall chinook expected

to reach the Columbia estuary (to Tongue Point, under a full transportation with spill

scenario) was only 61 million subyearling smolts (Feb. 11, 1998 NMFS memorandum,

F/WNC3 – M. Schiewe).

Changes relative to the Fish and Wildlife Program

Before human influence, the Columbia River estuary would have been a high-energy

environment dominated by physical forces, with extensive sand-beds and highly variable

river flows. Several authors have suggested that the biological processes in this

environment may have been unique on the Pacific coast. The estuary of today, however,

has been extensively modified in terms of physical processes and is substantially less

variable than in the past. The effects of these changes on fish and wildlife would be

mediated through changes to biological processes within the estuarine ecosystem and

depend on the susceptibility of a species to these changes.

Seamen (1977) provided the first comprehensive inventory of the fish and wildlife

inhabiting these estuarine habitats. Wildlife extensively use the estuary, but a linkage of

change in wildlife use or abundance with hydrosystem development and operation is not

obvious. There are possible exceptions though, such as reduced peripheral wetland

habitats due to flood suppression, increased availability of haul-outs for marine

mammals, or increased abundance of marine birds (see Collis et al. 2000, Roby et al.

1998). The effects of greatest relevance, however, involve the use of estuary by fishes

and changes to their ecosystem.

The fish communities of the Columbia River estuary are similar to other Pacific

northwest estuaries (Haertel and Osterberg 1967, Bottom et al. 1984, Bottom and Jones
ISAB 2000-5 Estuary Report

22

1990). Changes in communities (species composition) were associated with salinity

gradients and seasons, and the distribution of fish abundance was strongly influenced by

prey density. Bottom and Jones (1990) provide an excellent example of how the physical

processes described previously are interrelated with biological processes and fish

production.

“We speculate that river discharge, circulation energy, and sedimentation

processes that influence the retention of organic materials and the maintenance of

zooplankton populations within the Columbia may ultimately control the feeding

environment and production potential of the estuary for fish.” (pg. 266)

Seasonal changes in communities were related to life history stages of the marine and

anadromous fishes. The abundance of salmonids was greatest during the spring and early

summer, and their use of the estuary was similar to that of species in other estuaries

(Healey 1982, Simenstad et al. 1982)8. In general, species or life history types with large

smolts (coho, steelhead, and yearling chinook) tend to use the outer portions of estuaries

(deeper water habitats) and have a short residence period. Smaller smolts (sub-yearling

chinook, chum, or early migrants) utilize the estuary for extended periods (a few to

several weeks) and may comprise a large portion of the fish community. As these fish

grow, they move offshore from the shallower more protected environments to deeper

water channels. Sub-yearling chinook and chum salmon show the most extensive use of

estuaries. Healey (1982) describes the use of tidal creeks, sloughs, and marsh habitats in

the upper estuary by chum and chinook fry. On high tides, fry feed along the tidal fringe

and on low tides retreat into tidal creeks or channels for shelter. As these fry grow

through the season, they move seaward to the outer estuary. Observations on emigration

timing and estuary use in the Columbia estuary are consistent with these observations

(coho salmon, Durkin 1982; sub-yearling chinook, McCabe et al. 1986; and salmonids,

Dawley et al. 1986). These papers add two additional observations: larger smolts tend to

emigrate first, and smolts migrating from further upstream tend to move through the

estuary more quickly. Little seems to be known about the use of the Columbia estuary by

chum or sockeye salmon, or cutthroat trout (likely due to their infrequent recoveries).

Because of extended rearing in the estuary, fry and sub-yearling chinook, chum salmon,

and smaller coho salmon are the most likely salmonids or life history stages to be

affected by the potential effects of changes in the estuary. Just in terms of the physical

features, Healey (1982) suggested that the complexity of estuarine habitats “all contribute

to the carrying capacity for young salmon, and that the appropriate configurations must

be conserved if salmon production is to be maintained.” This has certainly not been the

case in the Columbia River estuary.

If this is not the case, then what biological processes have been affected? The most

notable effects have likely been on the estuarine food web. Most food webs (the linkage

between consumers and their food resources) in Pacific northwest estuaries are based on

 

8

 Description of the estuary use by pink salmon differ between these authors but pink salmon are not of

concern in the Columbia River estuary. Healey reports that Fraser River sockeye salmon have limited use

of their estuary but little is known about sockeye use of the Columbia River estuary.
ISAB 2000-5 Estuary Report

23

detritus (organic debris from decomposing plants or animals), but the composition of the

organic matter varies among different estuaries, and its value as a food source may vary

(Simenstad 1997). Sources of detritus may include emergent plants in peripheral

wetlands (macrodetritus), benthic algae, plankton produced in estuarine waters, and

fluvial inputs of plankton from up-river sources when mixed with estuarine sources.

Given the loss of peripheral wetlands (Thomas 1983), increase in water storage in the

hydrosystem, and reduced flooding and flow variation, the recruitment of macodetritus

from within the estuary has been substantially reduced from the pre-development period

(Sherwood et al. 1990). Development of the upper river has, however, resulted in an

increased influx of freshwater phytoplankton that lyse when mixed with estuarine waters,

producing microdetritus. For the estuary that was sampled during the early 1980s,

Simenstad et al. (1990) concluded “that suspended detrital particles, originating

principally from upriver but also produced within the estuary at the freshwaterbrackishwater interface and washed in from peripheral marshes, essentially supported the

estuarine food web.”

The relative value or productivity of the endogenous macrodetritus-based food web

compared to the current exogenous microdetritus-based web is uncertain. Some authors

suggest that the microdetritus-based system has lower energetic value, but also that the

material is more labile than larger organic particles from macrodetritus. Simenstad

(1997) has also suggested that the quality of the organic matter is fundamentally more

important than the “bulk” of the matter, and that the supply of detritus varies by season

and proximity to habitats. The availability of food sources or prey to a species of interest

may be an equally important question. The macrodetritus-based system likely involved

greater diversity of feeding habitats and prey in peripheral wetlands and tidal flats, that

subsequently contributed to communities in the estuary mixing zone. The microdetritusbased system is closely associated with suspension feeding zooplankton and the turbidity

maximum zone (located in the water column of the estuary’s central mixing zone).

Subyearling chinook and chum salmon, for example, are not likely to benefit from prey

production in the central estuary when their rearing habitats are peripheral flats and

marshes.

The availability of prey introduces two other biological processes: competition and

predation. Fishes in the Columbia River estuary consume a wide variety of prey, but the

bulk of the food is usually comprised of only a few species, and the distribution of fish is

strongly influenced by prey availability (Haertel and Osterberg 1967, Bottom et al. 1984,

Bottom and Jones 1990). Among species, McCabe et al. (1983) reported substantial diet

overlap comparing salmonid and non-salmonid fishes, particularly between sub-yearling

chinook and American shad, threespine sticklebacks, and starry flounder. These three

species are numerically abundant in the estuary. The only evidence for density

dependent interactions that may limit growth and survival of salmonids, however, has

been presented by Bottom et al. (1984), and subsequently in Bottom and Jones (1990).

Mean feeding intensity for sub-yearling chinook in the Columbia estuary was lower than

reported for a few other estuaries. Bottom et al. (1984) expressed caution in comparing

feeding intensity between surveys, and their data for feeding intensity were only based on

one year of data, 1980. In Bottom and Jones (1990), though, these data were compared to
ISAB 2000-5 Estuary Report

24

three other studies that consistently indicated higher levels of feeding intensity in other

estuaries (two studies in Oregon, one in British Columbia). Bottom and Jones (1990)

state that “these observations (and the apparent relationship between stomach fullness

and densities of potential prey) cause us to question whether fish consumption and

production in the Columbia may be limited by availability of prey or the feeding

efficiencies of predators in a highly turbid and dynamic environment.”9 Obviously, no

conclusions should be drawn from a single year of sampling that was conducted under

unusually high turbidity conditions, but these results and the numbers of hatchery fish

being introduced to the system certainly generate concern about the potential for density

dependent limitations. There does not appear to be any information concerning

interactions of sub-yearling chinook and chum salmon, presumably reflecting the few

chum collected during these studies (Bottom et al. 1984). Furthermore, during this study

period, predation on juvenile salmonids by non-salmonids and other juvenile salmonids

was insignificant (McCabe et al. 1983). In other estuaries, however, inter-specific

predation between salmonids is known (Simenstad et al. 1982), and many marine fishes

are known to prey on salmonids.

The potential interaction of hatchery reared salmonids with naturally reared salmonids

could involve intra-specific competition and/or inter-specific competition and predation

(Myers and Horton 1982, Simenstad et al. 1982). Based on observations to-date and

specifically within the Columbia estuary, however, the rapid movement of larger smolts

through the estuary apparently minimises these interactions (although detailed

investigations of these concerns do not seem to have been conducted). A potential

indirect interaction though, may be the role of hatchery production in stimulating

predator responses to a consistent annual supply of food delivered through a narrow

“time window” in the estuary. Natural populations are inherently more variable in size,

timing, use of habitats, etc. These natural variations may indirectly play an important

role in spreading predation risk on natural populations.

In the Columbia River estuary, the largest known source of predation is due to marine

birds. Studies currently being conducted have demonstrated extensive predation on

migrant salmonids and have provided the first quantitative estimates of these losses.

Collis et al. (2000) estimated that during 1998, five species of marine birds consumed

16.7 million smolts (range 10.0-28.3 million) or 18% (range 11-30%) of the smolts that

reached the estuary. Caspian terns alone accounted for 65% of the mortality. The

largest known Caspian tern (Sterna caspia) breeding colony in North America (about

8,000 breeding pairs in 1998) existed on Rice Island, a dredge disposal site, in the upper

Columbia River estuary (Collis et al 2000). Studies of diet composition have

demonstrated that terns at the Rice Island colony are highly dependent on salmonids

(75% of diet composition by mass in 1997 and 1998), and that terns in the lower estuary

are much less dependent upon salmonids. This reduced dependence in the lower estuary

presumably reflects the greater diversity of marine fishes for prey in that region. Other

avian predators were similarly much less dependent on salmonids when nesting in the

lower estuary.

 

9

 Recall that the eruption of Mount St. Helens on May 18, 1980 greatly increased the turbidity of the

estuary during this study period.
ISAB 2000-5 Estuary Report

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Emmett (1996) has also identified the predation on juvenile and adult salmonids by

marine mammals. Evidence for predation as a limiting factor to salmonid production in

the Columbia River seems to be limited to the presence of wounds on adults (Fryer

1998), diet composition studies (Browne et al. 1999, Laake et al. 1999) and the increasing

population size of Harbour seals in the estuary. Harbour seals are generalist feeders and

differences in frequency and number of prey probably reflect the temporal availability

and abundance of prey rather than selection by the predator. However, in some estuaries

predation on adult salmon can be substantial (Brown and Mate 1983, Bigg et al. 1990,

Olesiuk et al. 1996). These estuaries though tend to be smaller with less turbidity and

frequently involve some condition that aggregates the salmon so that their vulnerability

increases. The channelization of the Columbia River estuary suggests such a condition

but the area involved is still very large and the turbidity high. Consequently, the impact

of marine mammal predation on salmonids remains uncertain.

1994 Fish and Wildlife Program

The Council’s interest in this topic has been well founded given the extent of physical

and biological change documented in the Columbia River estuary. Effects of change in

this estuary operate through a highly energetic, integrated physical environment.

Biological processes are closely linked to changes in circulation, salinity intrusion, and

sedimentation. The development and operation of the hydroelectric system have

contributed significantly to these changes. Direct effects occur through changes in

seasonal flow rates, reduced sediment discharge, and resultant changes in the estuary’s

energy balance. Indirect effects occur because of changes to freshwater ecosystems,

establishment of introduced species, and the enormous investment in hatchery production

of salmonids to mitigate for related losses. So how has the Council’s Fish and Wildlife

Program (NWPPC 1994) addressed these changes and impacts?

The ISAB has been aware of concerns that the Program did not adequately address the

importance of the estuary to fish and wildlife. The Program does make only limited

reference to wildlife and the estuary, and each reference pertain to the impact of predators

on salmonids (Secton 5.7). On the other hand, the Program does specifically address the

prevailing hypotheses about how estuarine environments influence the production of

salmonids. They serve as a “window of opportunity” to optimize survival due to a

temporal coherence of factors, or act as a “bottleneck” that limits the carrying capacity of

the estuarine environment (see Simenstad 1997).

The Program’s section 5 on juvenile salmon migration acknowledges that the overall

survival of fish is the cumulative effect of many life stages and environments.

“The relationship between actions taken in the river and overall fish survival is not

simple. Survival from the smolt stage to adult spawner is the result of a host of factors,

only a few of which are under human control. Important relationships can be obscured

because improved survival at one life stage can be negated by changes in survival at

other life stages. Some survival conditions in the ocean, for example, can vary

independently of survival conditions in the river or estuary.” page 5-8 (NWPPC 1994)
ISAB 2000-5 Estuary Report

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The mechanism affecting survival in this section though, involves both the timing of

arrival of smolts to the estuary and a “physiological window” to enhance survival.

“d. At the estuarine stage, flow/water velocity could influence survival through its

effect on migration speed and fish condition. This in turn can affect the date of entry

into the estuary to coincide with food availability or predator concentrations and/or by

influencing the arrival to the estuary within a physiological window that enhances the

likelihood of a successful salt water transition.” page 5-11 (NWPPC 1994)

Section 7.2D also strongly implies a “window of opportunity” concept for the estuary. In

referring to the need to improve hatchery propagation, the Program states that

“downstream migration must be programmed to coincide with the most favorable

conditions of food availability, ...” (page 7-16). The term “programmed” refers to

matching release time to changes in river and estuary conditions.

The principle reference to the estuary occurs in Section 7, Salmon Production and

Habitat. Section 7.1 addresses evaluation of carrying capacity for salmon in Columbia

basin environments. In particular, Section 7.1.A essentially encompasses all aspects of

investigation, management, and monitoring to evaluate “salmon survival, ecology,

carrying capacity, and limiting factors” in all Columbia basin environments, i.e. “... of

tributary, mainstem (including reservoirs), estuary, plume, and near-shore ocean”. This

section also relates back to the “window of opportunity” concept by calling for a

monitoring program “to identify optimal timing for residency in the estuary and the nearshore environment”. The Program subsequently (Section 7.1G) calls for adjusting the

total number of hatchery fish released to stay within the Basin carrying capacity, noting

that the capacity of the Basin to support young fish has decreased during this time

(reference to the late 1800s).

Because the next amendment of the Fish and Wildlife Program is currently in review

(NWPPC 2000), we will not undertake detailed comments on these specific measures in

the 1994 Program. With respect to the estuary, we definitely support the ecosystem

approach of the 2000 Program, but are concerned about the possible inclusion of specific

measures as expressed above. The objectives that an “optimal” window for salmon

survival can be determined, and that hatchery production can be “programmed” to

coincide with the “most favorable” estuary conditions are likely not achievable. They

perpetuate a technical or engineered attitude that there exist a single optimal period for

survival and that we can understand the complex of cues that salmon utilize in their

migration timing. That attitude does not seem to acknowledge the degree of uncertainty

that must exist in the highly modified river-estuary linkage or the importance of diversity

in coping with this modified environment. The idea of a carrying capacity, as a fixed

level of fish production that can be sustained, tends to simplify production potential into

single species and/or single environment issues, ignores the potential interaction between

environments, and minimizes the inherent annual variability in these production

processes. Furthermore, establishing the carrying capacity of altered habitats in the

Columbia basin may identify limiting factors in certain environments but is not likely to
ISAB 2000-5 Estuary Report

27

be informative about potential production levels or processes. A conclusion by

Simenstad (1997) clearly supports the shift from specific measures to the more general

ecosystem-based Program objectives:

“Ultimately, we must recognize that increased knowledge about the influence of

dynamic ecosystems such as estuaries on salmon is more likely to elucidate the

constraints upon alternative salmon management strategies rather than predictable

relationships that can be used to “take advantage” of estuaries.”

Discussion

The ISAB was asked to review the impacts of estuarine conditions on the Council’s

mission to “protect, mitigate and enhance” fish and wildlife in the Columbia River as

affected by development and operation of the hydroelectric system. The intent of this

report has been to provide a summary of more technical documents (see Seaman 1977,

Simenstad et al. 1984, Small 1990, Thomas 1983) and to relate changes in the estuary to

the Fish and Wildlife Program. Those technical documents provided excellent

background materials on physical aspects of the estuary, and drew extensively on the

1980-81 biological data collected by the Columbia River Estuary Data Development

Program. Our ability to assess impacts of estuarine conditions on objectives of the

Program, however, has been limited by a lack of appropriate and available data10.

Information necessary to meet the 1994 Program objectives described in the previous

section has simply not been acquired for the estuary. Similar obstacles were expressed to

the ISAB by the NMFS study team who noted that the data are insufficient to even

determine the extent of modern estuarine use (reference to salmonids).

While data limitations prohibit us from concluding what impacts that altered estuarine

conditions have had on the Council’s mission, we can comment on components of the

question, such as:

1) How have estuarine conditions changed through time?

2) Is there evidence for potential impact of these changes on objectives of the Council’s

Program? and

3) What actions in the estuary might be anticipated to be consistent with the proposed

new Program?

Clearly there is extensive documentation about changes in the estuary over the past

century, the major changes resulting from development of peripheral wetlands and their

isolation from the estuary, development and deepening of the Federal Navigation

Channel, and regulation of upper Columbia River flows for hydrosystem needs and flood

control. The effects of these changes do not function discretely. The estuary is a

complex interaction of physical features (predominated by the energy balance between

river flow and tidal forces), resultant changes in circulation, salinity intrusion, and

sediment processes, and ultimately the biological consequences of these changes.

Superimposed on this dynamic environment have been changes in water quality,

 

10 These comments do not pertain to surveys or data on water quality since we have not examined that type

of information.
ISAB 2000-5 Estuary Report

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introduction of exotic species, and major increases in the production of hatchery reared

salmonids.

The question of the potential biological impacts associated with these changes is more

complicated than detecting the physical impacts. Changes in the biological processes

varied from a fundamental alteration in the basis of the food web to the exclusion of subyearling chinook and chum salmon from a large portion of the tidal marshes. The effects

of these specific changes, however, are difficult to partition from the effects of numerous

other impacts in the Basin. For example, one might ask whether the reduction of estuary

habitat caused the decline in Columbia River chum salmon or has it been a minor

component of a species in decline at the southern range of its natural distribution? Or,

have the changes been detrimental to one species but beneficial to others? Given the

magnitude of the Columbia basin and the number of species involved, there are of course

a myriad of questions such as these. If, however, we focus only on salmonids, it is the

ISAB’s assessment that the impact of change in the estuary has been detrimental to

salmonids and the rebuilding objectives of the Fish and Wildlife Program.

We base this advice principally on three major issues:

1. The significant loss of peripheral wetlands and tidal channels; these habitats are

important to the early rearing, survival and growth of chum salmon, sub-yearling

chinook, and smaller coho salmon in other west coast estuaries.

2. The extent of change to seasonal flows following development of the hydrosystem.

The affects of these changes are closely associated with the impact of the

development of the navigation channel. In combination these developments have

resulted in changes to estuarine circulation, deposition of sediments, and biological

processes.

3. The need for precautionary advice given the current state of most salmonid

populations in the Basin, the magnitude of change in the estuary, and the lack of

investigations upon which to base alternative advice.

Investigators working in the estuary are to be complimented for their quality of work and

use of the limited biological data available. The use of historical bathymetric charts,

combined with tidal data, and numerical modelling have provided significant insight into

the energetics of the estuary, changes in circulation, definition of habitat zones in the

estuary and lower river. Biological data, however, has not been collected at appropriate

temporal and spatial scales. Biological relationships follow very few physical rules; their

responses to stochastic events are unpredictable and the outcome in the life cycle of an

individual result from the cumulative effects over numerous habitats and time periods.

Consequently, to understand the importance of the estuary in determining specific life

histories or in controlling production from a population will require vastly greater

investment in research than has occurred. As a result, we can not at this time provide

adequate responses for the Council on how the estuary has affected objectives of the Fish

and Wildlife Program. Given the specific measures identified in the 1994 Fish and

Wildlife Program, expenditures for appropriate and necessary estuarine studies have

simply not been adequate.
ISAB 2000-5 Estuary Report

29

Because this work on biological relationships has not been conducted, it does generate

the question whether the detailed studies should now be undertaken, whether they are

consistent with the goals of the 2000 Fish and Wildlife Program, and how the research

should be conducted? We also note that the 2000 Fish and Wildlife Program calls for the

establishment of monitoring and evaluation programs to isolate freshwater and marine

sources of mortality. The inclusion of the estuary as a province in the freshwater life

phase could compromise the ability to separate freshwater and marine mortality. For

example, it is important to consider how the number of salmonids entering the ocean

plume environment will be estimated, or how to delimit survival in freshwater and marine

phases of the life cycle?

Some detailed basic biological studies will be necessary just to design appropriate

monitoring and evaluation programs. To reduce the likelihood of prolonged uncertainty

about the impact of estuarine conditions, however, the ISAB recommends an aggressive

experimental program targeted to study known changes to the estuary. That program

should incorporate monitoring of the physical environment (such as currently begun via

the CORIE program, Oregon Graduate Institute) combined with evaluation of large-scale

manipulations of estuarine habitats. The intent of these programs would be to address

changes that are presumed to have had negative impacts and to conduct studies at a scale

that can be measured within the natural environment. These types of programs would be

consistent with the vision statement in the 2000 Fish and Wildlife Program:

“Wherever feasible, this program will be accomplished by protecting and restoring the

natural ecological functions, habitats, and biological diversity of the Columbia River

Basin.”

The types of large-scale programs that are envisioned include:

a) removal of dykes in the lower river and upper estuary to restore connections between

peripheral floodplains and the river or fluvial zone of the estuary. Clearly such a program

would depend on the use and ownership of these old floodplains but there are likely areas

that are no longer in use for agriculture and/or the use may benefit from periodic

inundation by the river and its sediments. Productivity of flooded versus dyked

peripheral plains and use of flooded plains should be monitored.

b) actively manage sources of salmonid predation in the estuary through restoration of

natural habitats, removal of habitats artificially created due to channel construction and/or

maintenance, or controlling predator populations. For example, Rice Island was created

from dredge material and in recent years has supported the largest Caspian Tern colony in

North America. Research has demonstrated the substantial predation impact of these

birds on salmonids (Collis et al. 2000, Roby et al. 1998). Management of this colony

could have immediate benefits for conserving salmon migrants and have beneficial

effects on the long-term viability of the Caspian Tern in this region. Historically,

Caspian Terns nested in numerous small colonies but have more recently shifted to fewer

and larger colonies on human-created habitats along the Pacific coast (Gill and Mewaldt

1983). However, fewer and larger colonies increase the risk to the species through

catastrophic events, possibly via disease, predators, or an environmental event.
ISAB 2000-5 Estuary Report

30

Restoring the natural population structure of this species could reduce the risk of loss and

improve its productivity, and reduce salmonids losses.

c) establish an allocation of water within the annual water budget for the Basin, that

would simulate peak seasonal discharge, increase the variability of flows during periods

of salmonid emigration, and restore tidal channel complexity in the estuary (aided by

removing pile dykes where feasible). The reduction in peak seasonal discharge under the

current hydrosystem is one of the most significant changes in river-estuary system.

Short duration pulses of controlled but higher flows would be intended to increase

turbidity to reduce predation, increase movement through the estuary, increase sediment

transport into the estuary, and connect the river system with restored floodplain habitats.

Initially, we anticipate that people will think that such programs are unnecessary and/or

impractical. To achieve the vision statement of the 2000 Fish and Wildlife Program in

the estuary province, however, programs of these magnitudes are likely necessary given

the magnitude of the environment and the stated desire to evaluate these actions. Large

programs though do have their logistic and management concerns. In the estuary, for

example, is there an appropriate organization to identify and prompt ecosystem studies,

develop experimental procedures, and evaluate and report results? Such programs are

inherently costly and require a commitment of resources for several years; how can these

resources be provided and protected over time?

The ISAB also notes that while these logistic and management concerns were identified

pertaining to the estuary, we expect that under the broader ecosystem objectives of the

2000 Fish and Wildlife Program that similar concerns will develop throughout the Basin.

Finally, in the lower Columbia River and estuary, the interests of the Council seem

consistent with the interests of the Lower Columbia River Estuary Program (LCREP

1999), developed as part of the National Estuary Program. Clearly, the development of

any major program or institutional arrangement in the estuary province should consider

their work and objectives.

Acknowledgements

The ISAB wishes to acknowledge and thank organizations and individuals that assisted

during this review. The Columbia River Estuary Study Team (CREST, Astoria, OR)

provided a number of important documents and maps. The U.S. Army Corp. (Portland,

OR) provided historical data on annual dredging volumes. Dr. D. Jay and N. Paik

(Oregon Graduate Institute) freely provided data on stream flows and sediment volumes,

and provide advice on numerous inquiries. Dr. M. Schiewe, J.E. Stein and E. Casillas

(NMFS, Seattle, WA) and R.A. Koch (NMFS, Portland, OR) provided useful literature

citations, reprints, and memos concerning several topics in the review. Dr. D. Roby

(Oregon State Univ., Corvallis, OR) and K. Collis (RTR Consultants, Bend, OR)

provided unpublished materials concerning avian predation in the Columbia River

estuary and useful advice. Ms. Kay Dewar (Civil and Environ. Engineering, Univ.

Washington, Seattle, WA) kindly produced the map used in this text. Mr. David Liberty
ISAB 2000-5 Estuary Report

31

and the StreamNet Library (Portland, OR) provided invaluable service in finding

reference materials. Finally, staff of the Point Adams Station (Hammond, OR) and

NMFS provided an invaluable site visit to the Columbia River estuary. The assistance of

all has been greatly appreciated.

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