Drifting with Flow versus Self-Migrating—How Do Young Anadromous Fish Move to the Sea?

The downriver migration process of young anadromous fish has a far-reaching impact on their survival rate and the efficacy of hatchery-reared fish release, but it is poorly understood. Moreover, the impact of dams on the fish remains unclear. The Chinese sturgeon is an anadromous and dam-affected fish in the Yangtze River. Here, we propose a novel theoretical framework to reveal the migration process of young Chinese sturgeon. We clarify the effects of active swimming of fish and water flow on the downriver migration and the parametric traits of the migrational stages. Then, we show that the young fish migrate downriver along the inshore waters in a gradually transforming manner from passive drift to active swimming. Lastly, we evaluate the impact of the Gezhouba Dam (GD) on the migration of the young fish, as well as demonstrate the life cycles of Chinese sturgeon in the Yangtze River pre- and post-GD.