Development of a Conceptual Chum Salmon Emergence Model for Ives Island Page: 4 of 23
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The objective of this project was to develop a conceptual model for the U.S. Army Corps of
Engineers, Portland District, that can be used to predict the timing of chum salmon (Oncorhynchus keta)
emergence in the Ives Island area. Researchers at the Pacific Northwest National Laboratory developed
the model using real-time hourly temperature data from three locations in the Ives Island spawning area
that were instrumented with paired hyporheic and river sensors beginning in 2003. These data were
supplemented by additional temperature data collected in the Ives Island area during 2006-2007,
including 5 additional paired hyporheic and river sensors and 32 hyporheic sensors that measured
temperature at approximately 15 cm below the bed surface of the Columbia River.
Using these data, we calculated accumulated thermal units (ATUs) for each sensor location; we
assumed emergence occurred at 932 ATUs based on the time to 50% emergence in previous laboratory
studies. We found that mixing various proportions of hyporheic and river temperature data from the real-
time sensors could be used to reproduce the number of days to emergence for the full range of sensor
locations in 2006-2007. The number of days to emergence that were mapped in the Ives Island area were
spatially coherent, with much shorter time to emergence in the western part of the channel relative to
more easterly parts of the channel. These results are similar to those of earlier studies showing that bed
temperatures in the Ives Island area tend to be spatially continuous and mappable and that cooler
hyporheic water is found in the eastern part of the channel.
A pre-season estimate of emergence dates is determined by interpolating the days to emergence for
each redd location from the map of 2006-2007 redds and temperatures. The map is then used to identify
the mixture of hyporheic and river temperature data from the real-time system that would provide the
closest match for the estimated days to emergence for each redd location. The identified mixture is then
used to update the emergence estimates for each redd during the incubation season as new hyporheic and
river temperature data become available from the real-time system. This method assumes that the spatial
distribution of areas with warm and cool hyporheic temperatures near Ives Island tends to be relatively
constant, as suggested by the results of earlier mapping studies. A case study was prepared using redd
location data from 2009-2010 to illustrate use of the conceptual model. The case study showed
differences in emergence estimates resulting from variations in the river and hyporheic temperatures from
year to year.
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Murray, Christopher J.; Geist, David R.; Arntzen, Evan V.; Bott, Yi-Ju & Nabelek, Marc A. Development of a Conceptual Chum Salmon Emergence Model for Ives Island, report, February 9, 2011; Richland, Washington. (https://digital.library.unt.edu/ark:/67531/metadc829321/m1/4/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.