Drifting with Flow Versus Self-Migrating ― How Young Anadromous Fish Move to Sea

Abstract

The downriver migration process of larval or juvenile fish has a far-reaching impact on the survival rate of fish and the efficacity of hatchery-reared fish release and remains fragmented. Moreover, the quantitative mechanism of dam impact on the fish remains unclear. The Chinese sturgeon in the Yangtze River is a typical example or model organism of anadromous or dam-affected fish. Here, we propose a novel theoretical framework to reveal the downriver migration process of young Chinese sturgeons in the Yangtze River. We clarify the effects of active swimming of fish and the river’s hydrologic elements on the downriver migration, and the parametric traits of the migration stages. Then we show that the young fish migrate downriver along the inshore waters in a gradual transforming manner from passive movement to active swimming. Furthermore, we evaluate the impact of the Gezhouba Dam (GD) on the downriver migration of the young fish and achieve the lifecycles of Chinese sturgeon in the Yangtze River pre- and post-GD.