博斯腾湖鱼类密度季节变化及其环境影响因素

Seasonal variation of fish density and its environmental impact factors in Lake Bosten,China

为了解博斯腾湖鱼类资源现状及其与环境因素的关系,于2019年5月(春季)、7-8月(夏季)、10月(秋季),采用分裂波束回声探测仪(Simrad EY60,120 kHz)开展全湖水声学探测,并对水环境指标进行现场测量。结果显示,博斯腾湖鱼类密度在夏季最高,平均值为(8783±2611)ind./hm^(2);春季和秋季间无显著性差异,平均值分别为(709±141)、(743±499)ind./hm^(2)。根据目标强度与体长关系经验公式推算,春季、夏季和秋季鱼类的平均体长分别为8.8、4.0和5.1 cm。相关分析结果显示,博斯腾湖鱼类密度与水温和电导率呈极显著正相关(P<0.01),而与透明度呈显著负相关(P<0.05)。随机森林模型的特征重要性排序结果显示,电导率是鱼类密度最重要的预测因子,其次为溶解氧、盐度和水温等。推测鱼类密度的季节变化与环境变化、食物来源、繁殖习性等因素密切相关,环境因子可能通过直接或间接的方式影响鱼类的生态环境需求。

To understand the current status of fish resources in Lake Bosten and their relationship with environmental factors,a lake-wide acoustic survey was conducted in May(spring),July-August(summer),and October(autumn)of 2019 using a split-beam echosounder(Simrad EY60,120 kHz),along with on-site measurements of aquatic environmental indicators.The results showed that fish density in Lake Bosten was the highest in summer,with an average value of(8783±2611)ind./hm2.There was no significant difference between spring and autumn,with the average values of(709±141)and(743±499)ind./hm2,respectively.Based on the empirical formula between target strength and body length,the average total length of fish in spring,summer,and autumn was estimated to be 8.8,4.0,and 5.1 cm,re⁃spectively.Correlation analysis indicated that the fish density in Lake Bosten was significantly positively cor⁃related with water temperature and electrical conductivity(P<0.01),but significantly negatively correlated with transparency(P<0.05).The feature importance ranking of the random forest model revealed that electrical conductivity was the most important factor influencing fish density in Lake Bosten,followed by dissolved oxygen,salinity,and water temperature.Seasonal variation in fish density is presumed to be closely related to environmental changes,food sources,and reproductive habits.Environmental factors may directly or indirectly affect the ecological and environments needs of fish.