habitat suitability index models and instream flow suitability curves

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Table 1.(concluded).VariableAssumptions and sourcesNo information was available on D.O. requirements of spotted bassembryos. D.O. levels lethal to smallmouth bass embryos in thelaboratory [< 2.5 mg/l (Siefert et al. 1974)J are therefore usedhere, and are considered to be poor. Levels coinciding with areduction in survival of smallmouth bass embryos are rated fair[< 4 mg/l (Siefert et al. 1974)J. Levels ~ 6 mg/l are assumed tobe excellent for spawning and embryo survival of spotted bass.Spotted bass are most abundant in deep, relatively infertilereservoirs (Roseberry 1950; Jenkins 1975; Webb and Reeves 1975;Vogele 1975a), therefore, oligotrophic-mesotrophic conditions areconsidered to be excellent. Eutrophic conditions are consideredto have fair-poor suitability because largemouth bass are moreabundant than spotted bass under these conditions (Patriarche1953; Olmsted 1974). Because growth of spotted bass in highlyoligotrophic Lake Fort Smith, Arkansas (total alkalinity = 10 to30 ppm) was very low (Olmsted 1974), we assumed that reservoirswith very low fertility would be less suitable.Interpreting ModelOutputsThe riverine and lacustrine models described above are generalizeddescriptors of habitat requirements of spotted bass and thus the model outputshould not be expected to discriminate among different habitats with a highdegree of resolution (Terrell et al. 1982).A spotted bass HSI determined by application of the models may not reflectthe population level of spotted bass in the study area since other variablesmay have a more significant influence in determining spotted bass abundance.A positive relationship between HSI's generated by these models and themeasureable indices of population abundance (e.g., standing crop) is assumed,but this hypothesized relationship has not been tested other than by inferencesdrawn from the literature during the model-building process. The properinterpretation of the HSI is one of comparison. If two areas have differentHSI's, the area with the higher HSI should have the potential to support morespotted bass than the one with the lower HSI. Outputs of these models shouldbe interpreted as indicators (or predictors) of excellent (0.8 to 1.0), good(0.5 to 0.7), fair (0.2 to 0.4), or poor (0.0 to 0.1) habitat for spottedbass.The models should be useful as a basic framework for formulating revisedmode 1s that incorporate site-specifi c or project-specifi c factors affect i ng19
habitat suitability for spotted bass (see Terrell et al. 1982). The individualsuitability indices may also be useful for identifying habitat variables thatmay be limiting, without aggregating the SIl s into an HSI. Results of testingan earlier version of a riverine HSI model for spotted bass (Layher 1983)suggest an important point. That is, if a more precise index of populationabundance is required, use of the HSI models derived from suitability indicesaggregated by nonstatistical methods may not be appropriate or should bepreceded by evaluating the model in the field. Testing the model will betterdefine which variables are important descriptors of habitat quality in theproposed area of model application or under the post-project conditions.ADDITIONAL HABITAT MODELSDescriptive ModelsThe following models are simplified descriptions of optimum habitat forspotted bass as detailed in the Habitat Use Information section of thissummary. These models should be useful for "reconnaissance-grade" applicationswhere the relative quality of habitats for spotted bass must be judged usingminimal data.Riverine model. Optimum riverine spotted bass habitat (assuming waterquality is not limiting) is characterized by:1. Average summer temperatures in the range of 20 to 24° C;2. Rocky substrates;3. An approximate 3:2, pool :riffle ratio; and4. Cover present in pools.HSI = number of attributes present4Lacustrine model. Optimum lacustrine spotted bass habitat (assumingwater quality is not limiting) is characterized by:1. Summer water temperatures in the range of 20 to 24° C, .with adequateD.O. levels are available;2. Rocky substrates;3. Low turbidity (> 5 m Secchi depth);20
Page 2 and 3: MODEL EVALVATION FORMHabitat models
Page 4 and 5: FWS/OBS-82/10.72September 1984HABIT
Page 6: PREFACEThe Habitat Suitability Inde
Page 9 and 10: ACKNOWLEDGMENTSw. G. Layher (Kansas
Page 11 and 12: Age, Growth, and FoodSpotted bass t
Page 13 and 14: Embryo. Because nests in reservoirs
Page 15 and 16: TurbidityV spH V 6Water Quality HSI
Page 17 and 18: Reproduct i on component. Spawni ng
Page 19 and 20: For explanations on why temperature
Page 21 and 22: R,L V 4 Percent cover 1.0(boulders,
Page 23 and 24: R,L V lO Minimum dissolved 1.0oxyge
Page 25 and 26: Table 1.(continued).VariableAssumpt
Page 27: Table 1. (continued).VariableAssump
Page 31 and 32: for a fish species as a function of
Page 33 and 34: Category four curves (conditional p
Page 35 and 36: x0.01.0100.0x0.00.51.0100.0Coordina
Page 37 and 38: Coordinatesx 1-0.0 1.01.0 0.0100.0
Page 39 and 40: 1.0'r- 0.4.0ttl+->Coordinates>< 0.8
Page 41 and 42: 1.0x0.00.20.51.01.52.0100.0Coordina
Page 43 and 44: CoordinatesxY0.0 1.00.2 1.01.0 0.42
Page 45 and 46: Spawning depth. Vogele (l975a) obse
Page 47 and 48: Cross, F. B. 1954. Fishes of Cedar
Page 49 and 50: Mohler, H. S. 1966. Comparative sea
Page 51 and 52: 50272 '101REPORT DOCUMENTATION 1. R
Page 53: DEPARTMENT OF THE INTERIORu.s. FISH

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