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<br /> <br />igure 1. Native freshwater fishes of selected river systems. <br /> <br />~>.s~;;3.ge area is a result of several processes. Total area of <br />l;~ic,i.stream ~rface increases with drainage area, yielding <br />};i>:'~oncomltant increases in numbers of individuals and <br />""species (Preston 1962). Furthermore, the fusion of <br />.~1Dall, low-order (Strahler 1957) streams with increas- <br />ing drainage area forms larger streams, which provide <br /> <br /> <br />@ <br /> <br />@ <br /> <br />@ <br /> <br />igure 2. Distribution of federally listed endangered <br />ishes. Taxa restricted to a single state (8) are dis- <br />t~,!guished from those in two or more states (0). <br /> <br />ConseIVation of Stream Fishes 151 <br /> <br />MISSISSIPPI <br />^' 300 <br /> <br />additional habitats. Predictable changes in habitat, com- <br />position, and diversity of the fish fauna with increasing <br />stream order are well documented (Thompson & Hunt <br />1930; Kuehne 1962; Sheldon 1968; Horwitz 1978). Spe- <br />ciation rates may be greater in larger drainages if isola- <br />tion by distance and intervening high order streams re- <br />duce gene flow among populations of small-stream <br /> <br /> <br />. <br />. <br /> <br /> <br />@ <br />@ <br /> <br /><:J <br /> <br />THREATENED <br />._...../ <br />Figure 3. Distribution of federally listed threatenea <br />fishes. Symbols as in Figure 2. <br /> <br />Conservation Biology <br />Volume 2, No.2, June 1.988 <br />