The Oregon Seal Oregon Department of Fish and Wildlife
  » Home  » Current Projects  » Salmonid Life-cycle Monitoring  » Methods  » Background and Site Criteria   {Close This Window}  


User Name:


Forgot your password?

HomeCurrent ProjectsProject ArchivesReportsLinks
Corvallis Research Lab
Background and Site Criteria
Salmonid Life-Cycle Monitoring


Table of Contents

A. Description

B. Responsible Party

C. Questions Addressed

D. Considerations

1. Coho Salmon

2. Chinook Salmon

3. Chum Salmon

4. Steelhead

5. Searun Cutthroat Trout

E. Locations

F. Trapping Site Selection Criteria


Trap adult and juvenile salmonid migrants (all species) in selected index streams.



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:



  • 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 Project)
  • What are the influences of climate and land-use activities on coho salmon survival rates?
  • 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)



  1. 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.


    Coho Salmon

    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 measures:


    Chinook Salmon

    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

    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 trap.


  2. 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 map):

North Fork Scappoose Creek North Fork Nehalem River (lower and upper basins)

East Fork Trask River

Mill Creek (Siletz River)

Mill Creek(Yaquina River)

Cascade Creek (Alsea River)

West Fork Smith River

Winchester Creek


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 Criteria

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 be arranged.

 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 years) monitoring.

 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 weir).

  • ODFW Home | News and Highlights | Agency Information | Fish Division | Wildlife Division | Lands Programs
    Fishing Resources | Hunting Resources | Viewing Resources

    Driving Directions | Employee Directory |

       4034 Fairview Industrial Drive SE   ::   Salem, OR 97302   ::    Main Phone (503) 947-6000 or (800) 720-ODFW [6339]

    Questions or Comments Contact:

       © ODFW. All rights reserved.