habitat suitability index models and instream flow suitability curves

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Table 1. Sources of information and assumptions used in constructionof the suitability index graphs. "Excellent" habitat for spotted bassrefers to an SI of 0.8 to 1.0, "good" an SI of 0.5 to 0.7, "fair" 0.2to 0.4, and "poor" habitat 0.0 to 0.1.VariableAssumptions and sourcesSpotted bass are most abundant in streams with well-definedriffles and deep pools (Howland 1931; Lewis and Elder 1953; Ryanet al. 1970; Fajen 1975; Trautman 1981), therefore, a mixture ofriffles and pools is considered excellent. Zero percent rifflesis considered poor habitat because spotted bass are rare inbackwaters and other areas lacking at least some current (Fajen1975; Vogele 1975a; Ryan et al. 1970). High percent riffles isalso poor because: (1) spotted bass in streams occupy large,deep pools (Howland 1931; Fajen 1975); (2) channelizationadversely affects spotted bass populations (Robbins and MacCrimmon1974); and (3) stocking success of spotted bass was very poor inrivers with extensive channelization (Fajen 1975). The generalshape of the graph for Vi was based on the following standingcrop data from Kansas streams (Layher 1983):Fraction ofPercent No. of Mean maximum mean standingriffles stream sites standing crop crop = SI< 15 302 0.82 0.2515-30 62 2.09 0.6230-45 26 3.35 1. 0045-60 5 0.00 0.0060-7575-90 3 0.00 0.00> 90 1 0.00 0.00Shallow pools are deemed poor because stocking success (Fajen1975) and abundance of spotted bass (Howland 1931; Trautman 1981)is low in streams where shallow pools predominate. Average pooldepths ~ 1 m are rated good to excellent because spotted bass aremost abundant in large, moderately deep pools (Howland 1931; Ryanet al. 1970; Robbins and MacCrimmon 1974; Fajen 1975; Trautman1981) and standing crop of spotted bass was highest in Kansasstreams having mean depths 1.2 to 1.8 m (Layher 1983). Spottedbass prefer areas with some current, which is most characteristicof small- to moderate-sized streams « 30 m wide) (Ryan et al.1970; Robbins and MacCrimmon 1974; Vogele 1975a; Layher 1983),thus, the suitability of depths ~ 5 m was determined to be onlyfair.15
Table 1.(continued).VariableAssumptions and sourcesIt is assumed that habitat suitability is proportional to theamount of rocky substrates present in streams and reservoirsbecause: (1) spotted bass are most abundant in streams (Howland1931; Lewis and Elder 1953; Cross 1967; Fajen 1975; Layher andMaughan 1982), reservoirs (Roseberry 1950; Aasen and Henry 1981),and reservoir sections (Olmsted 1974; Roussel 1979) with rockysubstrates; (2) spotted bass prefer rocky substrates as spawningsites (Olmsted 1974; Vogele 1975b; Aasen and Henry 1981);(3) crayfish are a primary component of the diet of spotted bassand crayfish are most abundant in rocky substrates that providethem shelter (Aggus 1972; Emery 1975; Loring and Hill 1976); and(4) spotted bass, especially juveniles (e.g., Smith and Page1969), eat aquatic insects and production of aquatic insects ishighest on gravel-cobble substrates (Hynes 1970). Spotted bassare absent from areas of dense emergent vegetation and mud bottom(Olmsted 1974), and stocking was unsuccessful in Missouri streamswith shifting sand substrate (Fajen 1975), therefore thesesubstrate types are deemed poor.The strong preference of spotted bass for building their nestsnear brush or other forms of cover (Vogele 1975b; Vogele andRainwater 1975; Aasen and Henry 1981), the use of cover by fryafter leaving their nests (Vogele 1975b), the attraction ofspotted bass to man-made midwater structures (Smith et al. 1980)and rocky outcroppings in reservoirs (Robbins and MacCrimmon1974), and the common listing of abundant cover as a habitatcharacteristic of spotted bass streams (e.g., Viosca 1932; Ryanet al. 1970), suggests that some cover is necessary for optimumconditions. Zero percent cover is assigned an SI of 0.2 becausea stream or reservoir may still be able to support spotted bass,although at a much reduced level. The selection of ~ 25% cover asoptimum is our best estimation based on available information.Although spotted bass are found over a wide range of turbidities(Robbins and MacCrimmon 1974; Vogele 1975a), low turbidities areconsidered excellent because spotted bass are most abundant inclear streams and reservoirs (e.g., Lewis and Elder 1953; Cross1967; Olmsted 1974; Vogele 1975a; Webb and Reeves 1975). The SIgraph was constructed primarily on the basis of the followingstanding crop data from Kansas streams (Layher 1983):16
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: R,L V lO Minimum dissolved 1.0oxyge
Page 27 and 28: Table 1. (continued).VariableAssump
Page 29 and 30: habitat suitability for spotted bas
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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