Diversity of river fishes influenced by habitat heterogeneity across hydrogeomorphic divisions

Abstract

Freshwater fish communities are structured through complex interactions among multiple spatial scales. Efforts to conserve and rehabilitate fish communities in riverine systems can benefit from an understanding of how processes across spatial scales influence species diversity patterns. We assessed species diversity at different hierarchical spatial scales and changes in species composition along the longitudinal gradient of the Niobrara River basin, Great Plains, USA. We assessed the contribution of αand β-diversity components to γ-diversity at five spatial scales (i.e., mesohabitat, site, reach, segment, and river) using an additive partitioning approach. The observed mean β-diversity was significantly greater than expected at the site, reach, and segment spatial scales. The most significant difference between expected and observed β-diversity occurred at the segment spatial scale and suggests differences in community structure along the Niobrara River. Additive partitioning of diversity components provided a framework with which to assess patterns at multiple hierarchical levels.Our results suggest that changes in channel geomorphic and hydrologic conditions provide the impetus for species sorting resulting in unique fish assemblages along the Niobrara River. Conservation of species diversity for Great Plains fishes and other similar systems will likely benefit from considering species filtering processes at multiple spatial scales and maintaining intact hydrologic regimes across unique geomorphic boundaries.

Influence of preservation methods, sample medium and sampling time on eDNA recovery in a neotropical river

“…This variance may be due to several factors including the distribution of eDNA (i.e., which might be heterogeneous and show different spatial structures—Hänfling et al, 2016), and variation of eDNA transport distances between species (Deiner & Altermatt, 2014). Additionally, differences found within treatments may be due to natural differences found in community composition across samples sites as the structure of freshwater fish communities are influenced by complex interactions and by heterogeneity of freshwaters along the river gradient (e.g., geomorphic and hydrologic conditions, microbiota, temperature, pH, acidity, and chemical composition) (Spurgeon, Pegg, Parasiewicz, & Rogers, 2018). Also, as shown by Macher and Leese (2017) community composition can change even when sampling the same location in a time frame shorter than 1 minute and our findings also agree with earlier authors in that patterns of persistence of eDNA in rivers can be irregular.…”

River-Wide Habitat Availability for Fish Habitat Guilds: Implications for In-Stream Flow Protection

“…In contrast, habitat availability for the riffle guild is consistent across discharges in segment 3 where channel geomorphology (i.e., single channel with defined banks) constrains river water and maintains habitats needed by fishes in the riffle guild. Changes in habitat availability across discharge levels and segments due to geomorphic changes in valley width along the length of the river may influence the composition of the Niobrara River fish community [17,29]. Furthermore, if water availability within the Niobrara River changes substantially either through increased human use or changing climate patterns the current structure of fish habitat guilds may be altered as habitat abundance and distribution is tightly linked to discharge patterns.…”

The Effects of Sampling-Site Intervals on Fish Species Richness in Wadeable Rivers: A Case Study from Taizi River Basin, Northeastern China

“…Smith and Jones [10] found that 76-115 sampling sites were needed to collect the estimated species richness of firstto third-order streams in the Great Lakes watershed. This indicates that increasing the number of sampling sites may better represent the fish assemblage because fish assemblages distribute in patches in the river due to habitat heterogeneity [19,20]. Increasing the number of sampling sites will help in obtaining more species information, but this will inevitably reduce the sampling intensity (e.g., time spent sampling, distance sampled, etc.)…”