Determinants of Fish Assemblage Structure in Northwestern Great Plains Streams

Abstract

Prairie streams are known for their harsh and stochastic physical conditions, and the fish assemblages therein have been shown to be temporally variable. We assessed the spatial and temporal variation in fish assemblage structure in five intermittent, adventitious northwestern Great Plains streams representing a gradient of watershed areas. Fish assemblages and abiotic conditions varied more spatially than temporally. The most important variables explaining fish assemblage structure were longitudinal position and the proportion of fine substrates. The proportion of fine substrates increased proceeding upstream, approaching 100% in all five streams, and species richness declined upstream with increasing fine substrates. High levels of fine substrate in the upper reaches appeared to limit the distribution of obligate lithophilic fish species to reaches further downstream. Species richness and substrates were similar among all five streams at the lowermost and uppermost sites. However, in the middle reaches, species richness increased, the amount of fine substrate decreased, and connectivity increased as watershed area increased. Season and some dimensions of habitat (including thalweg depth, absolute distance to the main-stem river, and watershed size) were not essential in explaining the variation in fish assemblages. Fish species richness varied more temporally than overall fish assemblage structure did because common species were consistently abundant across seasons, whereas rare species were sometimes absent or perhaps not detected by sampling. The similarity in our results among five streams varying in watershed size and those from other studies supports the generalization that spatial variation exceeds temporal variation in the fish assemblages of prairie and warmwater streams. Furthermore, given longitudinal position, substrate, and stream size, general predictions regarding fish assemblage structure and function in prairie streams are possible.

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

“…Li et al (2012) found a significant temporal fish assemblage change between January and May, and between May and July. Seasonal variability in fish assemblages has been often attributed to the species reproduction and spawning migrations (Gorman, 1986;Simier et al, 2004;Arceo-Carranza & Vega-Cendejas, 2009;Mullen et al, 2011) or seasonal changes in physical conditions of river ecosystems (Mullen et al, 2011). In our system, reproductive migration could be an important reason to explain the temporal variability.…”

“…For example, the environmental variables differed between high and low flow seasons in coastal rivers of the Andalien drainage as well as Meridional Amazonian streams in the Neotropics, while the fish assemblage compositions did not differ between two seasons (Habit et al, 2007;Fernandes et al, 2013). Spatial variation exceeded temporal variation in fish assemblages in five northwestern Great Plains streams and the Upper Mississippi River System (Mullen et al, 2011). In such case, local fish fauna and life history traits of species (e.g., migration, production, feeding) might play an important role in temporal trends in assemblage composition.…”

“…The influences of downstream spatial factors on fish assemblages were illustrated in other river systems. In general, fish species richness declines with increasing distance to larger stream confluences of tributaries (Hitt & Angermeier, 2008), distance to stream mouth (Mullen et al, 2011) or a mainstem river (Pinto et al, 2009;Thornbrugh & Gido, 2010), and distance to ocean (Mercado-Silva et al, 2012), forward selection procedure were selected. The first and second axes accounted for 30.1 and 9.3% for the variation of species data, respectively.…”

Reach and catchment‐scale characteristics are relatively uninfluential in explaining the occurrence of stream fish species

“…For example, Mullen et al . () found that four samples spread across seasons are sometimes needed to detect all of the fishes that occur at a particular site in prairie streams. Inclusion of temporal variability in fish assemblages and habitat conditions or detection probability in species‐habitat models has been suggested by other authors to improve accuracy (Wiley et al ., ; Hayer et al ., ; Steen et al ., ; Falke et al ., ) and may have improved the number of significant reach and catchment‐scale models in this study.…”

“…Matthews () in a study of fish communities in riffle habitats of the Roanoke River, Virginia, U.S.A., and Mullen et al . () in a study of Montana prairie streams, however, have both found that spatial variation in fish assemblages was greater than temporal variation. Furthermore, Shearer & Berry () found long‐term persistence of most native prairie fishes between dry and wet periods due to the tolerance of these species to variable physicochemical conditions, and Matthews & Marsh‐Matthews () found that the influences of drought on fish assemblages in prairie streams of Oklahoma, U.S.A., may be short lived as recolonizations of fishes may be rapid during improved conditions.…”