Purpose To ascertain the current situation of fish resources in Yangzonghai Lake, and to analyze the changes of fish, providing basic data for fish management and lake water ecological restoration.
Methods Four field surveys were conducted in March, May, August and October 2022 at 10 sampling points in Yangzonghai Lake, using eight types of mesh gillnets and two types of ground cages. Relative importance index was used to identify dominant species, and the Shannon-Wiener diversity index, Pielou’s uniformity index and Margalef richness index were used to analyze fish diversity.
Results A total of 32976 fish individuals weighing 791694 g, belonging to 24 species, 23 genera, 11 families and 7 orders were collected. Among them, there were 11 species of Cyprinidae (45.83%), 19 exotic species (79.17%), and with dominant species of Neosalanx taihuensis, Hypophthalmichthys molitrix, H. nobilis, and Rhinogobius giurinus. The highest number of individuals (41.62%) were caught in March, with the maximal species (95.83%) and weight (40.84%) in August; Mingzhuwan had the highest number of individuals (22.06%) and weight (15.82%), with the maximal species (91.67%) in Yangzongdahekou; the number of small fish accounted for 95.04%; the number of exotic species accounted for 99.27%, and the weight accounted for 97.40%. Fish diversity was low to average. Compared with the historical record, the community structure of fish in Yangzonghai Lake had undergone great changes, and only five species of the 20 endemic indigenous species had been collected from the historical records, and they were widely spread and widely adapted species. Mylopharyngodon piceus, Hemiculter leucisculus, Paramisgurnus dabryanus, Silurus asotus, Pelteobagrus vachelli and Mugilogobius myxodermus were recorded for the first time.
Conclusion Yangzonghai Lake fish are mainly composed of exotic species, the miniaturization is obvious, and the introduction of exotic species and habitat destruction are the main influencing factors.
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