|Salmonid Life-Cycle Monitoring
Table of Contents
B. Responsible Party
1. Coho Salmon
2. Chinook Salmon
3. Chum Salmon
5. Searun Cutthroat
F. Trapping Site Selection Criteria
Trap adult and juvenile salmonid migrants (all species) in selected index
The Salmonid Life-Cycle Monitoring Project of the Western Oregon Fish Research
and Monitoring Program is responsible for this work.
This program is
administered by the Northwest Region, and is supervised by Erik Suring (541) 286-5328 email: Erik.Suring@oregonstate.edu
- Are there trends in abundance of adult or downstream migrant anadromous
salmonids in selected index streams?
- Are trends in abundance of adult coho salmon in selected index streams
primarily due to changes in freshwater survival or to changes in marine survival?
- Are there geographic differences in the patterns of freshwater and marine
survival of coho salmon?
- Are ther correlated trends in freshwater and marine survival of coho
salmon in western Oregon?
- Are geographic patterns of freshwater survival of coho salmon associated
with differences in habitat quality? (Addressed in conjunction with the Aquatic Inventory
- What are the influences of climate and land-use activities on coho salmon
- How do survival rates of wild and hatchery coho salmon compare? (Addressed
in conjunction with the Stock Assessment Project)
- What are the life history characteristics (time, size, and age at juvenile
and adult migration) of the anadromous salmonids in the index streams?
- How accurate are methods of estimating spawning abundance of different
anadromous salmonid species? (Addressed in conjunction with the Oregon Coastal Salmonid
Inventory and Sampling Project)
- Because of life history differences among anadromous salmonid species, the
questions addressed by life-cycle monitoring vary by species. The following is a species-specific
description of the type of information that the program will provide.
Juvenile coho salmon, (at least the large majority of those life history types
that still exist), spend their entire freshwater residence in or near their small natal streams.
If trapping sites are located on large enough streams such that juvenile rearing occurs primarily
above the trap sites, adult and juvenile migrant trapping will provide information on the
freshwater and marine survival of coho salmon. Marine survival, as we use it here, encompasses the
survival of fish from the time the smolts migrate out of the study stream until the adults return
to the stream. Thus, this survival includes migration through mainstems and estuaries as both
smolts and adults. With the survival information, the trapping program for coho salmon can address
the following question that is critical to evaluating the effectiveness of plan
In Oregon coastal streams, most fall chinook juveniles migrate out of their
natal stream by the early summer, and continue rearing in the mainstem rivers and estuaries before
migrating to the ocean in late summer and fall. Because of this life history pattern, the trapping
program will not be able to estimate marine survival rates for chinook salmon. Trapping will
provide estimates of the number presmolt chinook leaving the streams each year. In addition,
information on size of migrants and the timing of the migration will be collected.
Chum salmon may occur in some of the northern index streams. They have the
shortest freshwater life history of any of the anadromous salmonids in Oregon, with juveniles
migrating to the estuary shortly after emergence from the gravel. Thus, it will be possible to
make estimates of marine survival.
Steelhead juveniles may move and rear considerable distances from their natal
streams before they make their seaward migration. Therefore, unless trapping operations are
located near the ocean, no estimate of the total number of ocean migrating juvenile steelhead
produced from a known number of adult spawners can be obtained. Consequently, in most cases
trapping will not provide information on the marine and freshwater survival of steelhead. Those
sites located in the lower portions of river basins will provide information on smolt abundance
each year. The sampling will also provide information on the migration timing, and the size and
age of the migrants.
Searun Cutthroat Trout
The freshwater life history of searun cutthroat trout, which is similar to
that of steelhead, presents similar obstacles to using trapping information to estimate their
freshwater and marine survival. In addition, the small size of returning searun cutthroat trout
adults makes them difficult to trap. Most returning searun cutthroat are small enough to swim
through the upper picket fence in the adult trap. In most cases the spacing of the bars in the
picket fence cannot be reduced to insure the capture of all searun cutthroat because it would
result in the adult trap clogging with debris during high stream flows. Therefore, in most cases,
trapping will only enable monitoring of trends in the number of downstream juvenile migrant
cutthroat trout. Experiments are currently being conducted with an infrared fish counter that may
enable us to count returning adult searun cutthroat trout without actually capturing them in a
- The selection of streams for salmonid life-cycle monitoring is of critical
importance to the success of the program. To provide the most useful and accurate information, the
trapping program must select sites in the most unbiased way possible. Unfortunately, there are a
number of obstacles preventing the implementation of a totally unbiased trap site selection
process. One obstacle is the reality that not all streams have sites that are conducive to
successful trap operation. For example, streams may either be too large for traps to accurately
estimate migrant numbers, or too small so that the degree of error associated with the abundance
estimates masks any trends in abundance or survival. Other factors such as bank and substrate
stability, stream gradient, site access, and landowner cooperation also impairs the unbiased site
selection process. Funding realities and the logistics of maximizing the amount of information
obtained in relation to the dollars spent are another obstacle. For example, on a daily basis, one
person can run two downstream migrant traps successfully during most streamflow events only if the
sites are located within a 30-minute drive or less from each other. This means that in some cases,
some sites may be selected or rejected based on their proximity to another site, rather than on
their overall merit as being the most "representative" of other streams in the area.
All of these obstacles mean that only a limited number of streams will
effectively be a candidate for trapping. Because the number of sites is limited in relation to the
diverse nature of coastal streams, it is impossible to pick a suite of study streams that
"represent" all of the other streams present in a given salmonid ESU.
Based upon a preliminary review of potential candidates, many potential
streams have been identified for salmonid life-cycle monitoring). As a first cut, sites for
monitoring both smolts and adults are being established at the following locations (See attached
North Fork Scappoose Creek
North Fork Nehalem River (lower and upper
East Fork Trask River
Mill Creek (Siletz River)
Mill Creek(Yaquina River)
Cascade Creek (Alsea River)
West Fork Smith River
These streams will provide a relatively good latitudinal representation of
streams in four of the five Coho GCG Areas along the Oregon Coast. In addition, smolt trapping is
beginning in two Tillamook Bay tributaries (South Fork Kilchis River and Little North Fork Wilson
River) with the hope that funding can be secured for adult monitoring. We are also considering
other possibilities near the Smith River and Coquille River sites.
Trapping Site Selection
1. Good geographic spread of sites coast-wide. Currently, ODFW has partial
funding for field crews to be based in Tillamook, Newport, and Charleston. Without additional
funding, it will be difficult for ODFW to operate traps that are long distances from these three
areas (e.g. South Coast streams).
2. One person can run two traps. Paired sites should not be more than a
30-minute drive apart so that trap watcher can cycle between traps during high streamflows. This
is particularly important during smolt trapping. Trapping sites do not necessarily need to be
within 30 minutes of the field crews office if travel trailers, or some other means of housing can
3. Candidate streams should have spawning populations of coho,
steelhead, and cutthroat, and where possible, chinook.
4. To maximize the number of fish sampled, streams should be as large as
trapping technology allows. In practice, this generally means fourth to fifth order streams that
are no wider than approximately 30 meters active channel width.
5. Existing fish ladders should be used where possible as adult trap
sites. This will reduce construction costs and enable more adult traps to be operated, improving
the geographic range of the monitoring effort.
6. Sites must be of sufficient depth (> 2.5 feet) and of sufficient
velocity at low spring stream flows to allow operation of a rotating screw smolt trap (or the site
must be amenable to modification to meet these criteria). The site should also be neither too
constrained or high gradient so that the smolt trap will be damaged due to excessive water
turbulence, or be too unconstrained so that the stream becomes too wide and slow for efficient
screw trap operation during high stream flows.
7. Land owner willingness to allow access to site for long term (> 10
8. Candidate streams without existing fish ladders need to have sites
with the following characteristics to enable the construction of an adult weir:
a) Uniform (preferably bedrock) bottom and stable streambanks.
b) 1-2 percent gradient
c) Road access (close enough for delivery of materials needed to construct