Enhancing conservation of large‐river biodiversity by accounting for tributaries

Abstract

Alteration of rivers for human use has resulted in substantial biodiversity declines, particularly for species restricted to the largest rivers. Conservation and restoration efforts on large rivers often focus on the mainstem, but societal reliance on benefits derived from these alterations generally prevents complete restoration of the river. We propose that certain tributaries, by virtue of their lower degree of alteration, offer underappreciated opportunities for conserving large‐river biota. Using the distribution patterns of large‐river specialist fishes from the Mississippi River Basin, we identify a threshold discharge (166 cubic meters per second) beyond which tributaries support all or most of these species. We merge our macroecological analysis of assemblage structure with data on dam locations to identify tributaries where restoration efforts offer the highest potential conservation gains for 60 of the 68 large‐river specialist fish species that are of state, federal, or international conservation concern. Given the highly altered state of many mainstem rivers, this analytical approach could be used to select tributaries that will aid in the conservation of large‐river species worldwide.

More of the Same: High Functional Redundancy in Stream Fish Assemblages from Tropical Agroecosystems

“…This last goal is the main factor associated with functional redundancy in the studied region. Notably, riparian restoration in small tributaries can introduce additional benefits, since riparian restoration in small tributaries is most likely to result in improved environmental conditions that may extend downstream and consequently improved the quality of larger rivers (Pracheil et al 2013), thus securing benefits for terrestrial ecosystems in several ways (e.g., Fukui et al 2006;Chan et al 2008;Lorion and Kennedy 2009;Gonçalves et al 2012). It is noteworthy that according to several authors (e.g., Harding et al 1998;Teels et al 2006;Lévêque et al 2008), the maintenance of aquatic biodiversity and ecological processes depends on the protection of a large percentage of the watershed area.…”

Projected Risk of Population Declines for Native Fish Species in the Upper Mississippi River

“…Our study area also included the Illinois River, a major tributary of the Mississippi River (Figure 1). This river was included in our analyses because of the importance of tributaries for conserving river system biodiversity (Pracheil et al, 2013). Within this system, six separate commercial navigation reaches have been identified in which long-term data have been collected on fish abundance (refer to the succeeding texts).…”

Pulsed flows, tributary inputs and food‐web structure in a highly regulated river

“…Tributaries deliver sediment (Rice, Greenwood, & Joyce, ; Sabo et al., ) and organic matter and nutrients (Cross et al., ; McClain & Naiman, ; Wu et al., ), resetting the longitudinal profile of the main stem by creating physical discontinuities in terms of discharge, sediment and materials (Benda et al., ; Stevens, Shannon, & Blinn, ). Tributaries can also provide corridors for recolonization of native fishes and other organisms from upstream catchments (Pracheil, McIntyre, & Lyons, ), and in some cases, they provide hotspots of biological activity (Katano et al., ; Kiffney, Greene, Hall, & Davies, ; Sabo & Hagen, ). Tributaries of the regulated Colorado River in the Grand Canyon, for example, are the point source of boulders and coarse sediment (Hanks & Webb, ; Webb, Pringle, & Rink, ), organic matter (OM) for the aquatic food base (Cross et al., ), and breeding and rearing grounds for migratory native fish (Coggins et al., ; Douglas & Marsh, ; Yackulic, Yard, Korman, & Haverbeke, ).…”