关键词: 钉螺, 不同年代, 分布特征, 影响因素, 鄱阳湖

Abstract:

Objective To investigate the spatial and temporal distribution of Oncomelania hupensis in Poyang Lake area and the influencing factors related to the spread of O. hupensi, so as to provide a scientific basis for formulating measures for the control of O. hupensi in the endemic lake area. Methods Total 35 marshland blocks located at the confluences of rivers at the north and south banks of Poyang Lake were chosen as survey sites. The data for three surveys including area with O. hupensi, the area with infected O. hupensi, average density of living O. hupensi and average density of infected living O. hupensi, hydrologic water level, the bank marshland height and O. hupensi control measures were collected. Average density of living O. hupensi and infected living O. hupensi were analyzed by using rank sum test. Results For the 1^st, 2^nd and the 3^rd O. hupensi survey（1982, 20012, 2017）, the area with O. hupensis was 8 574.5, 9 014.3 and 5 099.8 hm², the area with infected O. hupensiwas 172.0, 91.0 and 0 hm², the average density of living O. hupensi was 0.7(48 833/69 750), 1.6 (134 534/83 387) and 0.3/0.1 m² (33 189/97 315), and the average density of infected O. hupensis was 2.5 × 10^-3 (172/69 750), 1.1 × 10^-3 (91/83 387) and 0 hm², respectively. Except 1985, the average annual maximum water level during 1980-2002(including 1^st and 2^nd snail surveys) was higher than the upper elevation of marshland(18 m), and the average annual minimum water level was lower than the lower elevation of marshland (13 m). From 2003 to 2016 (including 2^nd and 3^rd surveys), the mean annual maximum water level was lower than the upper elevation of the marshland for 7 years, and the mean annual minimum water level was lower than that during 1980-2002. After the second survey, the lower lake water level was not able to merge the marshland during the flood season and the basin of lake was exposed for a longer time and the marshland was dried out during the drought season. There was no change for the elevation of marshland among the three surveys. The mean elevation of marshland from high to low was Xinjiang (16.7 m), Ganjiang North Branch(16.5 m), Fu River (16.5 m), Xiuhe and Ganjiang confluence (16.4 m), Ganjiang South Branch (16.3 m), Rao River (15.7 m) and river entry channel (15.0 m). For the first survey, the average density of living O. hupensi in the areas with and without O. hupensis control was 0.5/0.1 m² （18 227/34 531）and 0.9/0.1 m²（36 605/35 219）, the density of infected O. hupensis in the areas with and without O. hupensis control was 1.7 × 10^-3/0.1m²(58/34 531) and 3.2 × 10^-3/0.1 m² (114/35 219), respectively. For the second survey, the density of living O. hupensis was 1.1/0.1 m² （37 494/34 755） in O. hupensis control area and 2/0.1 m² （97 041/48 632） in area without O. hupensis control, the density of infected O. hupensis was 1.7 × 10^-3/0.1 m²(58/34 755) in O. hupensis control area and 0.7 × 10^-3/0.1 m² (33/48 632) in area without O. hupensis control. For the third survey, the density of living O. hupensis in the areas with and without O. hupensis control was 0.3/0.1 m²（15 180/44 417）and 0.3/0.1 m²（18 009/52 898）, the density of infected O. hupensis in the areas with and without O. hupensis control was 0, respectively, without statistical significance (P > 0.05). Conclusion The growth and spread of O. hupensis in Poyang Lake area was affected by lake water level, elevation of marshland and the snail control intervention. O. hupensis in the higher elevations of marshland in the Southern Lake Area show a trend of retreating to the northwest and the low elevations of marshland in the Northern Lake Area. Application of molluscicides can quickly reduce the O. hupensis density on the marshland, but has low effect on the snail control when the snail density is low.

Key words: Oncomelania hupenis, Different years, Distribution characteristics, Influencing factors, Poyang Lake