Abstract

The Yangtze finless porpoise (Neophocaena asiaeorientalis) is critically endangered. Finless porpoises rely on small fish as their primary food source. Fish distribution is impacted by topography and vorticity (i.e., water flow patterns), which are markedly more complex in river channel confluences than in other aquatic habitats. Thus, the hydrodynamic conditions imposed by confluences may influence habitat selection by fish and the subsequent behavior and predation strategies of porpoises. However, hydrodynamic effects and driving mechanisms for porpoise occurrence, distribution, and feeding strategies remain unclear. Based on survey data and hydrologic measurements, we created a hydrodynamic model to investigate the driving mechanism of porpoise clustering in a confluence of the Wanhe River Estuary, China. We showed a preference for vorticity in the range 0.001 s−1–0.0015 s−1. Our multivariate logarithmic linear model revealed a fit of R2 = 0.792, indicating consistency between theoretical and actual occurrence values. Certain patch parameter effects suggest that vorticity fragmentation affects porpoise habitat selection and utilization. Our study provides a new perspective on the ecological impact of the Yangtze River wading project and the habitat protection of aquatic animals in rivers and aids future research examining hydrodynamic effects on the feeding behavior of freshwater cetaceans.