Migration and distribution of adult hatchery reared Yangtze sturgeons ( Acipenser dabryanus ) after releasing in the upper Yangtze River and its implications for stock enhancement

Abstract

The Yangtze sturgeon (Acipenser dabryanus) is a most important aquatic animal at the national level. Influenced by human activities such as dam constructions and overfishing, its natural population in the wild has almost disappeared. Since 2000, its natural reproduction has not been detected. In May 2018, in the Yibin reaches of the upper Yangtze River, 40 adult hatchery reared Yangtze sturgeons with their gonads at or above stage III, body length ranging from 92 to 146 cm were ultrasonically labeled and released. Results of fixed station and mobile surveys showed that only one individual did not receive ultrasonic signals. Our study indicated that: (a) In terms of longitudinal migration along the river, most individuals were mainly distributed in the main section of the downstream Jinsha River below Xiangjiaba Dam after releasing, except one individual conducting a relatively long‐distance migration; (b) Compared with the released juvenile fish which performed a descending migration, adult Yangtze sturgeons preferred an anadromous migration and a settled life in the wild; (c) The habitat water depth of the released Yangtze sturgeons ranged from 0.61m to 27.74 m with the mean value of 8.65 ± 3.89m (mean ± standard deviation). There was a significant difference in daytime and nighttime habitat water depths (p < .01), and the average habitat water depth in daytime was significantly lower than that at night. In this study, ultrasonic telemetry was used to quantitatively assess the migration and spatial distribution of the released adult Yangtze sturgeons for the first time. Our results would provide a scientific basis for the subsequent reconstruction and restoration of the wild populations and future stock enhancement.

Foundation and Prospects of Wild Population Reconstruction of Acipenser dabryanus

“…By tracking and monitoring mature sturgeons released into the wild, it was found that they rarely migrated a long distance downstream, unlike the migration of young sturgeons following release [13]. Furthermore, mature sturgeons were predominantly distributed in the Jinsha River below Xiangjiaba Dam and the mainstream of the upper reaches of the Yangtze River [15]. The distribution of released juvenile fish covered approximately 500 km from Yibin to Fuling, and the primary gathering area was from Yibin to Hejiang River (Figure 3).…”