APPENDIX A

ESU Strata---\
Ecological Zone and Life-History Type

The high degree of local adaptation exhibited by Pacific salmon is
thought to be the product of their homing fidelity and the ecological
diversity found in the Pacific Northwest. The life-history strategies
exhibited by salmonids may reflect adaptations to specific freshwater
environments. In the Willamette-Lower Columbia (WLC) recovery domain,
there are (Table A.1):

-   three major life-history types that are generally recognized for
    chinook salmon---spring run, fall run, and late-fall run;

```{=html}
<!-- -->
```
-   two types for steelhead---winter run and summer run; and

-   one for chum salmon---fall run.

The WLC Technical Recovery Team (TRT) felt that each of these
life-history strategies represented a substantial portion of the
evolutionary legacy of the evolutionarily significant unit (ESU).
Furthermore, there was concern that this subdivision of the ESUs still
did not capture the essential diversity elements. For example, fall-run
chinook salmon in the short, rainfall-influenced coastal tributaries
were distinct from those in the large, snowmelt-influenced tributaries
along the Cascade Crest, or the shorter tributaries in the rain shadow
of the Cascade Crest. The concept of life-history/ecological strata was
developed to describe this important level of between-population
life-history diversity.

There are a number of methods of classifying freshwater, terrestrial,
and climatic regions. Physiogeographic provinces were described from
Washington and Oregon by Baldwin (1964), Fenneman (1931), and
Easterbrook and Rahm (1970). Franklin and Dyrness (1973) identified
natural vegetation zones in Oregon and Washington. The U.S.
Environmental Protection Agency (EPA) has established a system of
ecoregion designations based on soil content, topography, climate,
potential vegetation, and land use (Omernik 1987). These ecoregions are
similar to the physiographic provinces identified by the Pacific
Northwest River Basins Commission (PNRBC 1969) for the Pacific
Northwest. Furthermore, the National Marine Fisheries Service (NMFS)
coastwide status reviews found a high correspondence between
life-history trait distribution and Level III EPA ecoregions for coho
salmon (Weitkamp et al. 1995), steelhead (Busby et al. 1996), chum
salmon (Johnson et al. 1997), and chinook salmon (Myers et al. 1998).
Additionally, Waples et al. 2001 indicated a high degree of correlation
among ecology (as defined by modified ecoregions), life history, and
biochemical genetics for Pacific salmonids. The TRT concluded that the
EPA Level III ecoregions provided a useful measure of appropriate scale
to characterize ecological diversity within the ESUs. However, the EPA
ecoregions do correspond exactly to how salmon experience the
environment. For example, all chinook in the Upper Willamette ESU use
both the Willamette Valley and the Cascade EPA ecoregions, and it seemed
reasonable, from a fish perspective, to identify a new ecological unit
encompassing the eastern Willamette Basin above Willamette Falls. To
avoid confusion with the EPA ecoregions, the TRT initiated the term
ecological zone to describe the modified EPA ecoregions. Using the
ecological zone as a reference, in combination with an understanding of
the ecological features relevant to salmon, the WLC-TRT designated four
ecological areas in the domain: (1) Coast Range zone, (2) Cascade zone,
(3) Columbia Gorge zone, and (4) Willamette zone. The boundaries of
these regions are shown in Figure A.1.

Another advantage of the ecological zone concept is that it provides
geographic structure to the ESU. Maintaining each life-history type
across the ecological zones reduces the probability of shared
catastrophic risks. Additionally, ecological differences among zones
reduce the impact of climate events across the entire ESU. The inclusion
of a biologically based ESU substructure into possible recovery
scenarios buffers the ESU against uniform declines.

![](media/image1.png){width="6.314566929133858in"
height="4.839763779527559in"}Ecological Zones

The **Coast Range ecological zone** commences at the mouth of the
Columbia River and extends upstream to the mouth of the Cowlitz River in
Washington and to the mouth of the Willamette in Oregon (Figure A.1). In
Washington these basins drain the Willapa Hills. The climate is
dominated by moist Pacific marine air, with wet and mild winters and
cool dry summers. Average annual precipitation is 200 to 240 cm, with
approximately 80% occurring as rain between October and March.
Streamflow is dependent on rainfall since drainage elevations do not
exceed 500 m. River flows peak in December and January as a result of
winter rainstorms. There is very little precipitation in July or August
and corresponding flows are at the lowest with the highest water
temperatures occurring in August. These rivers are especially prone to
low flow during periods of drought. This region was originally forested
with Sitka spruce, western hemlock, Douglas fir, and western red cedar.

The **Cascade ecological zone** extends from the mouth of the Cowlitz
and Willamette Rivers to the Washougal and Sandy Rivers. Basin
topography is dominated by the volcanic peaks of Mount Rainer, Mount St.
Helens, Mount Adams, and Mount Hood, with each peak above 3,000 m. The
lower portions of these basins pass through the Puget Lowland or
Willamette ecoregion. At lower elevations, climate is similar to the
Coast Range ecoregion, with wet mild winters and cool dry summers.
Precipitation varies from 114 to 381 cm annually and generally occurs
between October and March. Much of the precipitation above 1,000 m
occurs as snow. In higher elevation basins, snowmelt adds to the surface
runoff and provides a secondary peak in flow during the spring.
Vegetation is similar to the Coast Range, except at higher elevations,
where Pacific silver fir, noble fir, subalpine fir, mountain hemlock,
and lodgepole pine occur.

The **Columbia Gorge ecological zone** encompasses the Columbia River
Gorge, which extends from the mouth of the Sandy and Washougal Rivers to
the Hood and White Salmon Rivers. The drainages in this region consist
of short, steep streams that often limit anadromous passage to less than
1.6 km in smaller creeks. In larger systems, falls in the lower rivers
often limit passage of salmon and steelhead. The climate and vegetation
in this area are transitional between the high rain/snowfall area of the
Cascades and the drier Columbia Plateau to the east. Stream flow is low
in the summer except for larger basins influenced by snowmelt. Rivers in
the Cascade and Gorge ecoregions are subject to catastrophic risks due
to volcanic eruptions, such as occurred at Mount St. Helens in 1980.

The basins in the **Willamette ecological zone** occur in the Willamette
Valley and Cascade ecoregions. In general this is an extension of the
Cascade zone (Lower Columbia River ESUs), although it also includes
presumptive populations that may have existed on the western slope of
the Coast Range. The higher elevation portions of the Clackamas,
Santiam, McKenzie, and Upper Willamette Rivers drain the Cascade
ecoregion, which is described above. The remainder of the streams in the
Willamette Valley occur in the Willamette Valley ecoregion. This
ecoregion sits in a rain shadow, and annual precipitation is less than
120 cm. River flows peak in December and January, and low flows occur in
August and September. Willamette Falls, at RM 42, was a natural barrier
at low flow and only allowed for fish passage in the winter and spring
for spring chinook and winter steelhead.

Life-History Types

**Spring-run chinook** **salmon** enter the Columbia in March and April,
well in advance of their spawning time in August or September.
Freshwater entry coincided with higher-than-average discharge in
snowmelt rivers. Downstream migrant sampling suggests these fish migrate
as subyearlings but enter the Columbia River later in the year than fall
chinook.

Fall chinook salmon are divided into tule and bright populations. **Tule
fall-run chinook** **salmon** spawn in all Lower Columbia River
tributaries. Adults enter freshwater from August to October, with peak
spawning in October. When tule fall Chinook enter freshwater, they are
in their spawning colors.

**Bright fall-run chinook** **salmon** are present in the Lewis and
Sandy Rivers. These fall chinook enter the Columbia River from September
through January, with peak entry in October. Spawning time is protracted
and fish have been observed spawning through the winter in the Lewis
River. Current distribution of these fish is limited to the Lewis and
Sandy basins.

**Winter steelhead** are present in most Lower Columbia River
tributaries. These fish enter the Columbia River from November to May as
mature fish. Spawning occurs from February through June with peak
spawning in late April or early May.

**Summer steelhead** are present in the Kalama, Lewis, Washougal, Wind,
and Hood Rivers. They enter freshwater as immature adults between March
and October. All native summer steelhead in these basins historically
occupied habitat above barrier falls, which excluded other salmon
species.

**Chum salmon** spawn in most Columbia River tributaries from the mouth
to Celilo Falls. Presently, chum salmon return to freshwater from
October through December. Historic catch data indicate that chum salmon
were occasionally caught in August. These may have been the early
portion of the large fall run, or they may have been summer chum salmon.

Literature Cited

Baldwin, E. M. 1964. The geology of Oregon. University of Oregon Coop.
Bookstore, Eugene, Ore. 165 p.

Busby, P. J., T. C. Wainwright, G. J. Bryant, L. J. Lierheimer, R. S.
Waples, F. W. Waknitz, and I. V. Lagomarsino. 1996. Status review of
West Coast steelhead from Washington, Idaho, Oregon, and California.
U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-27, 261 p.

Easterbrook, B. J., and D. A. Rahm. 1970. Landforms of Western
Washington. Union Printing, Bellingham, Wash. 156 p.

Fenneman, N. M. 1931. Physiography of the western United States.
McGraw-Hill, New York. 534 p.

Franklin, J. F., and C. T. Dyrness. 1973. Natural vegetation of Oregon
and Washington. U.S. Forest Service, Portland, Ore. 417 p.

Johnson, O. W., W. S. Grant, R. G. Kope, K. Neely. F. W. Waknitz, and R.
S. Waples. 1997. Status review of chum salmon from Washington, Oregon,
and California. U.S. Dept. of Commer., NOAA Tech. Memo NMFS-NWFSC-32,
280 p.

Myers, J. M., R. G. Kope, B. J. Bryant, D. Teel, L. J. Lierheimer, T. C.
Wainwright, W. S. Grant, F. W. Waknitz, K. Neely, S. T. Lindley, and R.
S. Waples. 1998. Status review of chinook salmon from Washington, Idaho,
Oregon, and California. U.S. Dept. of Commer., NOAA Tech. Memo
NMFS-NWFSC-35, 443 p.

Myers, J., C. Busack, D. Rawding, and A. Marshall. 2002. Identifying
historical populations of chinook and chum salmon and steelhead within
the Lower Columbia River and Upper Willamette River Evolutionarily
Significant Units. 10 May 2002 Co-Manager Review Draft. Willamette/Lower
Columbia River Technical Recovery Team document, Northwest Fisheries
Science Center, National Marine Fisheries Service, Seattle, Wash. 70 p +
appendices.

Omernik, J. M. 1987. Ecoregions of the conterminous United States. Ann.
Assoc. Am. Geogr. 77(1): 118--125.

Pacific Northwest River Basins Commission (PNRBC). 1969. Columbia-North
Pacific region comprehensive framework study of water and related lands.
Appendix II, The Region. PNRBC, Vancouver, Wash. 147 p.

Waples, R. S., R. G. Gustafson, L. A. Weitkamp, J. M. Myers, O. W.
Johnson, P. J. Busby, J. J. Hard, G. J. Bryant, F. W. Waknitz, K. Neely,
D. Teel, W. S. Grant, G. A. Winans, S. Phelps, A. Marshall, and B. M.
Baker. 2001. Characterizing diversity in salmon from the Pacific
Northwest. J. Fish. Biol. 59A: 1--41.