Abstract:Coilia nasus, which can be migratory or sedentary, is a substantial economic fish in China and used to be an important anadromous fish in the Yellow River. It is a model organism for studying fish resource conservation. However, the C. nasus resources in Yellow River gradually depleted in the late 1980s because of river disconnection, water conservancy project construction, environmental pollution, and overfishing. With the promotion of the Yellow River water-sediment regulation and implementation of the Yellow River Fishing Ban period system, C. nasus has reappeared in the Yellow River basin. C. nasus has developed into a dominant population in Dongping Lake and Nansi Lake, but no large-scale population has been found in the channels and estuaries of the lower Yellow River. Some morphological differences can be observed between the samples from the Yellow River estuary and those from Dongping Lake and Nansi Lake. According to the relationship between age, body length, and weight, the samples from Dongping Lake and Nansi Lake collected in previous studies were basically 1+ age, and the proportion of 2+ age individuals was small, indicating miniaturization and younger age. Different geographical populations of C. nasus showed rich genetic diversity. Although the population of C. nasus in Dongping Lake appeared later than that in Nansi Lake, it was slightly more genetically diverse possibly owing to the unique geographical location of Dongping Lake. The convergence of the three major river systems, the Yellow River, the Wenhe River, and the Jinghang Canal, may be conducive to the reproduction and diffusion of C. nasus in Dongping Lake. Using mitochondrial control region (D-loop) gene sequencing, combined with the historical data and fishery monitoring results of Nansi Lake, we found that the C. nasus population in Nansi Lake was closely related to the population in the Yangtze River and Huaihe River. The C. nasus populations in Nansi Lake possibly originated from lakes in the Yangtze River by the urgent ecological water diversion in 2002. The population composition is not well understood because of the few samples in the main stream and estuary of the Yellow River. The habitat history of C. nasus in the Yellow River estuary is complicated. In history, the main migration channel of C. nasus in the Yellow River was the main stream of the Yellow River, the spawning ground was Dongping Lake, and the feeding and overwintering grounds were in the estuary of the Yellow River and offshore waters. Dongping Lake, as the only lake in the lower reaches of the Yellow River and once an important spawning ground for C. nasus, is still blocked by sluice at present. However, the water area of Pangkou Bay outside the sluice is in a significant position, and a certain amount of C. nasus resources already exist, which is the only habitat found at present. The resources of C. nasus in the Yellow River show a positive trend, but the resource amount and habitat conditions remain unclear. This review introduces the current research status of the biological characteristics, resource status, genetic diversity, and habitat history of C. nasus in the Yellow River and discusses the development trend and research direction. It may serve as a reference for the effective resource management, conservation efforts, and sustainable use of C. nasus in the Yellow River.
