Coast Coho Juvenile Spatial Distribution Monitoring Design
Spatial Design
Temporal Design
Response Design
Inference Design
Evaluation Thresholds
References
Spatial Design
The design is described in detail in Stevens (2002). A GIS coverage of streams was used as a frame for
the population. The coverage was based on USGS 1:25,000 topographic maps, modified by ODFW to
correspond to the target population of streams for each population. Inference is made only for Monitoring
Areas (MA; equivalent to Strata with the exception of the Lakes Stratum which is part of the Mid-South
Coast MA). Generalized Random Tessellation Stratified designs (GRTS) achieve a spatially-balanced
random point distribution (Stevens, 1997; Stevens & Olsen, 1999; Stevens & Olsen, 2003; Stevens and
Olsen, 2004) and this approach was used.
Temporal Design
A rotating panel design was used to accommodate the need for repeat visits while continuing to expand
the scope of the sample every year. Sets of panels are visited on different cycles. The design consists of
40 panels, with one panel defining sites visited every year, 3 panels defining sites visited on a 3-year
cycle, 9 panels defining sites visited on a 9-year cycle, and 27 panels defining sites visited on a 27-year
cycle. An equal number of sites were allotted to each panel. The three-year cycle parallels the coho life
cycle.
Response Design
Field crews identified and enumerated juvenile salmonids in pools in a one kilometer stream reach
encompassing the GRTS point. Before 2010 all pools larger than ≥6 m2 in surface area and ≥40 cm in
maximum depth were snorkeled. The depth criterion was lowered to ≥20 cm in the 2010 field season in
response to results from the Smith River Verification study (Constable and Suring, in prep.) which
suggested that lowering the maximum depth threshold to ≥20 cm would allow surveyors to sample a
larger and more consistent portion of the juvenile coho and steelhead populations.
Snorkeling was conducted during the minimum flow period from July to October using a single pass of
one to six snorkelers, depending on stream width. Juvenile coho, chinook, steelhead ≥90 mm, and
cutthroat ≥90 mm were counted in each pool. Presence was noted for dace, shiners, and trout <90 mm.
Sites with poor water clarity were electrofished using a single pass without block nets to determine pool
occupancy for coho and site occupancy for steelhead and cutthroat. To assess repeatability and quality
control supervisory staff resurveyed ≥10% of the wadeable sites in each MA.
Inference Design
Site occupancy
The percent of sites with at least one fish, calculated by dividing the number of sites with fish by the
number of surveyed sites for each MA, ESU, or DPS.
%Occ = SitesOcc/SitesTotal * 100
Where SitesOcc = Number of successfully-surveyed sites that meet the occupancy threshold
And SitesTotal = Total number of successfully surveyed sites.
Evaluation Thresholds
Juvenile distribution is not one of the six criteria identified for assessment under the Coast Coho
Conservation plan, and there are no established goals for this metric.
References
EPA. 2009. Aquatic Resource Monitoring. http://www.epa.gov/nheerl/arm/
Nickelson, T. E., J. D. Rodgers, S. L. Johnson, M. F. Solazzi. 1992. Seasonal changes in habitat use by juvenile
coho salmon Oncorhynchus kisutch in Oregon coastal streams. Canadian Journal of Fisheries and
Aquatic Sciences 49:783-789.
Rodgers, J. D., M. F. Solazzi, S. L. Johnson, and M. A. Buckman. 1992. Comparison of three techniques to
estimate juvenile coho salmon populations in small streams. North American Journal of Fisheries
Management 12:79-86.
Stevens, D.L., Jr. (1997). .Variable density grid-based sampling designs for continuous spatial populations’.
Environmetrics 8: 167-195.
Stevens, D.L. (2002). Sampling design and statistical analysis methods for integrated biological and physical
monitoring of Oregon streams. OPSW-ODFW-2002-07, Oregon Department of Fish and Wildlife,
Portland, Oregon.
Stevens, D.L. (2006). Spatial properties of design-based versus model-based approaches to environmental
sampling. 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and
Environmental Sciences. Edited by M. Caetano and M. Painho. pp. 119-125.
Stevens, Jr., D. L. and A. R. Olsen. (1999). Spatially Restricted Surveys Over Time for Aquatic Resources. Journal
of Agricultural, Biological, and Environmental Statistics 4:415-428.
Stevens, Jr., D. L. and A. R. Olsen. (2004). .Spatially Balanced Sampling of Natural Resources. Journal of the
American Statistical Association 99:262-278.
Stevens, Jr. D.L., and N.S. Urquhart. (2000). Response Designs and Support Regions in Sampling Continuous
Domains. Environmetrics 11:13-41.
Stevens, Jr., D.L., and A. R. Olsen. (2003). .Variance Estimation for Spatially Balanced Samples of Environmental
Resources. Environmetrics 14:593-610.