Temporal Variability Patterns and the Distributional Patterns of Stream Fishes

Abstract

The coefficients of variation of daily discharge and the logarithm of daily discharge were calculated from long term records in 15 river systems, including runoff—fed prairie rivers in Illinois and Missouri, groundwater— and spring—fed upland rivers in Southern Ohio, Southern Illinois and the Missouri Ozarks, and the snowmelt—fed Powder River in Wyoming. In almost all cases variability was lower in downstream sections. The patterns of temporal variability were consistent with the hydrology of the basins, with source of flow and size important determinants. Diversity patterns of fishes were tabulated for the same rivers from literature records. In all rivers, diversity increased rapidly from upstream to downstream sections, almost entirely the result of addition of new species with little replacement of the upstream fauna. Maximal species richness was usually in the lowest sections (order VI or greater). Headwater diversity was lowest in the rivers with the most variable headwaters, the increase in diversity downstream steepest for those rivers with the steepest decrease in variability, and the number of species in downstream sections was greater in rivers with more constant downstream sections. Longitudinal replacement rates were very low in all rivers studied, but were generally larger in the most temporally constant rivers. Literal replacement was moderate between small tributaries, but was low between major tributaries. The diversity gradients of individual feeding groups were similar to the gradient for all species, with an increase in richness from headwaters downstream in all groups with intermediate maxima sometimes seen. Piscivores showed consistently steeper diversity increases. These observations were related to hypotheses of factors controlling stream fish distributions. They are most consistent with hypotheses relating control to extermination—recolonization dynamics or the interspecific competition mediated by temporal variability and habitat structure.

Urban Influences on Stream Chemistry and Biology in the Big Brushy Creek Watershed, South Carolina

“…Headwater streams naturally tend to have lower fish abundance and diversity than larger rivers, presumably because of factors such as lower habitat diversity and availability, as well as more variable flow and habitat conditions in the headwaters (Horwitz, 1978;Schleiger, 2000). As such, it is likely that Gambusia holbrooki was restricted to the downstream rural sites because of its preference for low gradient, slow water habitats (Meffe & Snelson, 1989).…”

Fish assemblage structure in a first order stream, southeastern Brazil: longitudinal distribution, seasonality, and microhabitat diversity

“…In several temperate U.S. drainages, Horwitz (1978) verified primarily addition process for 15 streams, including diversity increases from headwaters to stream mouth. In a stream in the upper Rio Paraná basin, Brazil, the longitudinal addition of species also was observed by Garutti (1988) and was considered the main succession process acting in tropical streams characterized by slight topography (Caramaschi 1986).…”

“…Upstream areas are hypothesized to demonstrate less structured assemblages due to abrupt seasonal changes, whereas downstream sites would have higher stability due to the larger catchment area and the consequent reduction of disturbing hydraulic effects (Horwitz 1978, Peres-Neto et al 1995. In fact, some streams, particularly those located on the slopes are strongly disturbed as a consequence of seasonal variations in water flow (Caramaschi 1986).…”

Hydrologic connectivity driven natural stream fish assemblages in mountain streams in the Yangtze River basin: implications for stream fish conservation in monsoonal East Asia

“…Freshwater fish assemblages along the spatial gradients of streams and rivers are generally assumed to be influenced by both natural factors and anthropogenic disturbances (Vannote et al, 1980;Allan, 2004;Kennard et al, 2006). Under natural conditions, patterns and processes observed in fish assemblages are strongly influenced by multiple factors operating over a range of spatial and temporal scales (Horwitz, 1978;Schlosser, 1987;Tonn, 1990;Oberdoff et al, 1995;Ostrand & Wilde, 2002;Hoeinghaus et al, 2007). On a local scale, physical and chemical factors appear to determine species richness in variable environments (Gorman & Karr, 1978;Rahel, 1986;Schlosser, 1991;Matthews, 1998;Bond & Lake, 2003;Gerhard et al, 2004), while biological ones are more important in stable environmental conditions (Ross et al, 1985;Grossman et al, 1990).…”