长江中游洪湖至宜昌江段鱼类空间分布特征的水声学研究

HYDROACOUSTIC SURVEYS ON TEMPORAL AND SPATIAL DISTRIBUTION OF FISHES IN THE SECTION FROM HONGHU TO YICHANG OF THE YANGTZE RIVER MIDDLE REACHES

为了解长江中游洪湖至宜昌江段鱼类时空分布变化,于2014~2015年的秋季、春季和夏季,使用Simrad EY60鱼探仪对该江段的鱼类时空分布特征进行了3次水声学调查。结果表明：鱼探仪探测获得的鱼类回波信号与湖底反射信号的图像均比较清晰,且图像的背景噪声较小,长江干流的鱼类多以个体形式进行活动,探测时未发现鱼群。夏季鱼类目标强度（TS值）最高（–47.2±8.6）d B,春季鱼类TS值最低（–60.0±6.4）d B,非参数检验结果显示,3个季节的鱼类TS值差异极其显著（P〈0.01）;3个季节该江段鱼类资源水平分布不均匀,鱼类最大密度分别为63.7 ind./1 000 m3（秋季）、141.4 ind./1 000 m3（春季）和266 ind./1 000 m3（夏季）,且3个季节鱼类水平分布差异极显著（F=151.08,P〈0.01）;垂直水层方向上,3个季节的鱼类密度均表现出相同的分布特征,即表层〉中层〉底层,各水层3个季节之间的鱼类密度存在极显著性差异（df=2,P〈0.01）;在方差齐性下,采用LSD方法对3个季节各水层之间鱼类密度进行多重比较,结果显示秋季仅表层与底层之间鱼类密度均存在显著性差异（P〈0.05）;春季表层与中层、中层与底层之间鱼类密度均存在显著性差异（P〈0.05）;夏季表层、中层和底层两两之间鱼类密度均存在显著性差异（P〈0.05）。该江段鱼类时空分布差异与鱼类的越冬、索饵、产卵等因素有关。

In order to better understand the spatial-temporal distribution of fish in the middle reach of Yangtze River from Honghu to Yichang section in 2014 and 2015, we applied hydroacoustic analysis with Simrad EY60 split-beam echo sounder, in autumn （ October to November,2014）, spring （ April to May ,2015）, and summer （ July,2015）. The results showed that the echo image detection of the fishes in the Yangtze River are relatively clear, and the background noise is small, the lake bottom reflected signals are strong, the fish populations of the Yangtze River is relatively small, mostly individual activities. Nonparametric test results suggested the target strength （TS） of the fish varied significantly among seasons （ P〈0.01）, being highest in summer （47.2±8.6） dB and lowest （60.0±6.4） dB in spring. The horizontal distribution of fish density was not homogeneous, and varied significantly among seasons （F=I 51.08, P〈0.01）. The maximum density was 63.7 ind./1000 m3, 141.4 ind./1000 m3, and 266 ind./1000 m3 in autumn, spring, and summer, respectively. Vertically, the fish abundance followed the following order： the surface layer 〉 the middle layer 〉 the bottom layer, and the distribution was the same in the three seasons, and fish density varied significantly in the same water layer among 3 seasons （df=2P〈0.01）. Under the homogeneity of variance, the LSD method was applied for multiple comparison of fish density between each water layer in 3 seasons. The results suggested that the fish density varied significantly between surface layer and bottom layer in autumn （P〈0.05）, the fish density was not significantly different between surface layer and bottom layer in spring （P〉0.05）, the fish density varied significantly among layers in summer （P〈0.05）. The distribution was possibly caused by the winter migration, feeding migratory, reproductive migration, and some other factors.