COMMUNITY STRUCTURE AND INFECTION CHARACTERISTICS OF NEMATODES IN THE COILIA NASUS IN ANQING SECTION OF THE YANGTZE RIVER

Coilia nasus is an anadromous fish, and the parasitic nematodes are a confirmation of its habitat history. In order to understand the relationship between the migration time of C. nasus and its nematodes, the infection and community structure of nematodes in C. nasus were investigated from April to July 2018 in Anqing section of the Yangtze River. The results showed that the infection rate of C. nasus was 96.0%, the average intensity was (8.06±7.26), and the average abundance was (7.74±7.29). A total of 7 species were identified by ITS molecular markers, including 2 species of Anisakis, 4 species of Hysterothylacium and 1 species of Raphidascaris. All of them are marine parasites and can be used as evidence that C. nasus has seawater life. Anisakis pegreffii (84.5%) had the highest infection rate, followed by Hysterophylaxium aduncum (31.0%). The average intensity and abundance were also high. The average intensity were (6.40±6.08) and (2.81±2.49), and the average abundance were (5.41±6.05) and (0.87±1.90), respectively. The average intensity and abundance of A. pegreffii showed an upward trend in the early stage of migration, and decreased slightly but not significantly in late June (P>0.05), while the H. aduncum showed a downward trend. The community structure of C. nasus nematode varied at different migration times. The richness, mean richness and the Brillouin index showed a downward trend, but the dominant species has always been A. pegreffii, and the number in the intestinal and pyloric caecum accounts for 46.13% and 30.02% respectively. The study will provide a reference for the later development of impact of nematode parasitism and population supplement, and also provide a new method for using parasite markers to study the migratory ecology of C. nasus.