Abstract

The ex situ conservation of the first-class protected animal in China, Yangtze finless porpoise (YFP), have
gained preliminary success. As the last step in ex situ conservation, reintroduction is an inevitable requirement for
achieving the goal. Under this circumstance, two male YFPs from the ex-situ group in Tian-e-Zhou Oxbow were translocated
to Laowan branch in April 2021 for the very first acclimation training attempt to study the adaptive process of
their behavior and vocalization, and to figure out whether they can adapt to the harsh environment in terms of feeding
behavior and diel activities. The attempt is expected to accumulate experience for the large-scale reintroduction adaptation
training of the porpoise into Yangtze River in the future. After one year of training and continuous monitoring, the
results showed that the density of fish in Laowan branch is significantly lower compared to that of Tian-e-Zhou Oxbow.
The shoal of fish is unevenly distributed during the wet season, and the density being higher in upstream than that in the
middle and downstream. The average time expense of YFP in the upstream is significantly higher than that in the
middle and downstream. Spearman correlation analysis shows that there is a significant correlation with the density distribution
of fish. During the first two months of entering the branch, the time required for YFP to cruise downstream
gradually increased to a peak, then decreased and stabilized. In the training of ship noise adaptability, the average
breathing interval of porpoises decreased significantly in the presence of ship interference, and gradually recovered to
the level of non-interference with the increase of interference times. Our study indicates that the two porpoises have
kind adaptability to the high flow velocity, low fish resource density and artificial vessel noise interference in the
branch and are feasible to release into the Yangtze River. This is the first time that the adaptation training of YFP in a
completely natural environment has been implemented, which will provide technical support for large-scale release and
promote the recovery of YFPs’ natural population. (Article in Mandarin)