Riverscape recruitment: A conceptual synthesis of drivers of fish recruitment in rivers

Most fish recruitment models consider only one or a few drivers in isolation, rarely include species’ traits and have limited relevance to riverine environments. Despite their diversity, riverine fishes share sufficient characteristics that should enable predictions of recruitment. Here we synthesize the essential components of fish recruitment hypotheses and the key features of rivers to develop a model that predicts relative recruitment strength, for all fishes, in rivers under all flow conditions. The model proposes that: interactions between flow and physical complexity will create locations in rivers, at meso-scales, where energy and nutrients are enriched, the resultant production of small prey concentrated, and prey and fish larvae located (through dispersal or retention) so that the larvae can feed, grow and recruit. Our synthesis provides a rationale for how flow and physical complexity affect fish recruitment, and provides a conceptual basis to better conserve and manage riverine fishes globally.