POPULATION BIOLOGICAL CHARACTERISTICS AND STOCK ASSESSMENT OF CULTER MONGOLICUS (BASILEWSKY 1855) IN QIANDAOHU LAKE

Piscivorous fish species play a crucial role as top predators in the aquatic food webs, contributing significantly to the structure and functioning of ecosystem. Qiandaohu Lake (QDH) has mainly focused on stocking-based aquaculture, particularly with filter-feeding fish such as silver carp and bighead carp, which have become a model for large-scale ecological aquaculture in China. However, little attention has been given to piscivorous fish species in this important ecosystem. Therefore, this study aimed to investigate Culter mongolicus, which is one of the dominant piscivorous fish in QDH. Samples were collected monthly from March 2021 to September 2022, and the population’s biological characteristics such as age, growth, reproduction, mortality, and stock resources were evaluated. The results indicated that the age structure of the C. mongolicus population in QDH was complete, with the 2—3 years age group being the most prevalent and exhibiting slow ageing phenomena. The relationship between standard length and body weight followed a power function indicating positive allometric growth. By fitting the Von Bertalanffy growth equation, this population belonged to the fast-growing type and had a growth coefficient (k=0.33) that was higher than that of other populations in previous research. Different growth stages correlated before and after the inflection point, which occurred at 3.23 years old. The population of C. mongolicus has a long breeding time, high population fecundity, and a unimodal distribution of oocyte diameter, which conforms to the characteristics of a single batch of spawning, and shows a periodic reproductive strategy as a whole. The exploitation of C. mongolicus population rate was evaluated to be 0.86 which showed an over-exploited phenomenon. Finally, we provided suggestions for the fisheries management of piscivores fishes in QDH based on the findings.