春夏季长江口邻近水域仔稚鱼种类组成和丰度的月变化

Temporal variation in the composition and abundance of fish larvae and juveniles off the Yangtze River Estuary in spring and summer

利用2015年4—7月在长江口邻近水域的调查数据,对春夏季该水域仔稚鱼种类组成和丰度的月变化特征进行了观测。结果表明,共采获62种、35839尾仔稚鱼,分别属于14目、30科、45属。各月种类数范围为22~36种,从4月到6月,先是缓慢增加然后快速增加,至6月达到高峰期,7月则大幅降低。各月的丰度范围为11.45~114.31 ind/(100 m3);丰度随时间的推移而持续增加。各月主要种类数范围为5~13种,具有较大的波动性;优势种主要为小黄鱼(Larimichthys polyactis)、小公鱼属(Stolephorus sp.)、六丝矛尾虾虎鱼(Chaeturichthys hexanema)、鳀(Engraulis japonicus)、红狼牙虾虎鱼(Odontamblyopus rubicundus)、斑尾刺虾虎鱼(Acanthogobius ommaturus)、属(Callionymus sp.)等。优势种随时间推移表现出较大的更替性。种类数以20 m以浅水域最多,不同水深范围的月变化有一定的差异性。20 m以浅海域的种类数与表层水温的关系在4—6月为显著正相关(r=0.997,P<0.05),6月到7月表现为相反的变化趋势;各月的丰度与表层盐度呈显著负相关(r=-0.91,P<0.05)。从春季到夏季,仔稚鱼高丰度区从浅水区向深水区转移。

The present study investigated the monthly variation in species composition and abundance of fish larvae and juveniles from April to July 2015 off the Yangtze River Estuary.A total of 35839 larvae and juveniles were collected,and these included 62 species from 45 genera,30 families,and 14 orders.Species richness ranged from 22 to 36,depending on month,increased from April to June,and then declined sharply in July.Meanwhile,the total abundance of larvae and juveniles ranged from 11.45 to 114.31 individuals per 100 m3 and increased throughout the study period,with small increases during the first three months and a greater increase in July.The number of dominant species varied by month,ranging from 5 to 13,and the dominant species mainly included Larimichthys polyactis,Stolephorus sp.,Chaeturichthys hexanema,Engraulis japonicus,Odontamblyopus rubicundus,Acanthogobius ommaturus,and Callionymus sp..The dominant species showed greater replacement over time.The greatest species richness was observed in the nearshore water（20 m depth）,and the spatial pattern of species richness along the depth gradient varied among months.Surface temperature and species richness were positively correlated（r=0.997,P0.05）from April to June but negatively correlated from June to July,and in every month,abundance and surface salinity were negatively correlated（r=-0.91,P0.05）in the nearshore water（20 m depth）.The high-abundance region shifted away from the shore over time.