Study on resource dynamics of Coilia nasus from Duchang waters in Poyang Lake based on otolith microchemistry before and after implementation of Yangtze River fishing ban

In order to understand the effect of fishing ban on Coilia nasus resources in the southern Duchang waters in the Poyang Lake, we conducted an electron probe microanalysis (EPMA) to study the migratory ecological characteristics of C. nasus in the waters before (2014) and after (2019) fishing ban. The results show that the otolith of all individuals had three significant fluctuation phases of Sr/Ca ratios of <3, 3–7 and <3 from the core to the edge, indicating a typical anadromous migration history. The number of samples (17 tails) after fishing ban was significantly higher than that before the ban (2 tails), and the body length of the former (28.1±2.3) cm was longer than that of the latter (21.3±4.7) cm, which was also longer than that of the former reported before fishing ban. In addition, the length of low-value area on the otolith edge showed diverse characteristics (125.0±63.6) μm, 80–170 μm in 2014, (173.5±73.6) μm, 20–290 μm in 2019, which suggests the phenomenon of mixed habitat of multiple upstream groups in the local waters. Considering that most of the individual gonads in the area were not mature, and that the southern Duchang waters (Dajishan to Hehe Township) are the only way for the population to enter and exit the central and southern waters of the Poyang Lake and the rivers connecting the lake (Such as Raohe River and Xinjiang River), it is strongly suggested that corresponding effective protection of this key habitat should be enhanced since the area mainly plays the ecological function of migration channel for C. nasus.