The settling chamber was used for the first time in August 1995, sampling ambient water during the active spawn of a very large return of salmon (26,456) to O'Ne-eil Creek. On this first use, 23 individual particles were identified and tracked for 46 settling velocity determinations, but the data set was not characterized visually for particle type (Table 4.2). The visual identification of floc and compact particles was first undertaken and reported9 for the 1996 settling population. When the two subpopulations (i.e., floc and compact particles) are plotted as diameter against density (Figure 4.1) it is clear that while both floc and compact particle diameters range between 300 to 1300 ^m, the larger particles tend to be flocs and they exhibit lower densities. In this data set flocs with the equivalent diameter as compact particles are always of lower density. An exponential decrease of density with increasing size is apparent for the compact particle population as it exhibits a wider range of densities. Figure 4.2 shows the same general pattern for the August and October 2000 settling data. The total population of settled particles exhibits the exponential decrease in density with diameter more clearly than in the 1996 data in Figure 4.1. Note that a third set of particles, visually identified as compact-organic, is also shown here. They tend to fall into the central part of the size-density spectrum.

Table 4.2 provides a summary of particle numbers and types identified in the ambient and resuspended settling chamber runs of 1996 and 2000. Visual identification of particle types was not undertaken in 1995 or 1997. In each case

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