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<br />Suitability Index (SI) Graphs for Model Variables <br />Suitability indices for variables in the lacustrine (L) and riverine (R) <br />HSI models should be determined from the following set of curves. <br />Habitat Variable <br />L,R V, Ratio of spawning <br />habitat to summer <br />habitat [area that is <br />less than 1 m deep and <br />vegetated (spring), <br />divided by total <br />midsummer area]. <br />1 .0 <br />~ 0.8 <br />v <br />c <br />a 0.6 <br />0.4 <br />N 0.2 <br />0.0 <br />Suitability graph <br /> A <br /> B <br /> C <br /> D <br />0.0 0.1 0.2 0.3 <br />Quotient <br />Use the appropriate curve, according to the density of vegetation or <br />plant debris within the area included as spawning habitat. Do not include <br />areas covered with filamentous algae, living or dead, as suitable spawning <br />habitat. <br />A. Vegetation obscures most (> 80%) of the bottom; plant material dense <br />throughout the 15 cm of the water column above the substrate. When <br />submersed, plant material not tightly compacted. Vegetation provides <br />extensive surface area to which eggs may adhere, abundant cover for <br />eggs and fry, and allows for circulation of water around the eggs <br />(e.g., flooded sedge or grass meadow). <br />6. Plant growth less lush than in A, but covers much of the substrate <br />and occupies much of water column directly above the sediments. <br />More than 60% of the bottom obscured in vertical projection from <br />depth of 15 cm above the bottom. Plant material not compacted when <br />under water. <br />C. Vegetation or debris covers much of the bottom, but plant material <br />does not occupy much of the water column immediately above the <br />substrate. This category may include compacted vegetation, branches <br />of woody plants, and leaves of deciduous trees. <br />• <br />17 <br />