Cooperative Fish and Wildlife Research Units Program:
Education, Research and Technical Assistance for Managing Our Natural Resources

Human-induced changes to large Anthropocene rivers requires engagement of diverse stakeholders across a broad range of sociopolitical boundaries and balancing multiple objectives. Competing objectives often constrain options for ecological restoration of large rivers and subsequent conservation of native fishes. Fewer competing objectives may exist in a subset of tributaries than in large mainstem rivers. Further, tributaries contribute toward building a “portfolio” of river ecosystem assets through physical and biological processes that may present opportunities to enhance the resilience of large river fishes. Our goal is to review roles of tributaries in enhancing mainstem large river fish populations. We present case histories from two greatly altered and distinct large-river tributary systems that highlight how tributaries contribute four portfolio assets to support large-river fish populations: 1) habitat diversity, 2) connectivity, 3) ecological asynchrony, and 4) density-dependent processes. Finally, we identify future research directions to advance our understanding of tributary roles and inform conservation actions.