珠江中下游鲮早期资源分布规律

Drifting larval resources of mud carp(Cirrhina molitorella) in middle and lower reaches of Pearl River

2006–2007年通过网定点周年采样和圆锥网流动采样相结合的方法,在西江肇庆江段对珠江中下游鲮（Cirrhina motitorella）早期资源进行了调查。鲮全年有多次产卵活动,鲮鱼苗主要出现在5–9月;鲮鱼苗全长（5.5±0.4）mm,主要发育到鳔一室期至卵黄吸尽期。根据发育期和平均流速推断,鲮产卵场主要位于距离采样点170-380 km的黔江和浔江江段。鲮鱼苗占漂流性鱼苗总量的3.71%。鲮鱼苗晚上的密度显著高于早上和中午（n=29;P〈0.05）。鱼苗总密度与采样点离岸距离有关,靠近两岸的鱼苗总密度极显著高于河中央鱼苗总密度（n=6;P〈0.01）。鱼苗总密度、鲮鱼苗密度与水温、径流量、水位和浊度之间存在极显著相关关系（P〈0.01）,与水温、采样时间存在显著相关关系（P〈0.05）。

Drifting larvae of mud carp（Cirrhina molitorella） were surveyed in the middle and lower reaches of Pearl River at Zhaoqing section in 2006 and 2007.Sampling was conducted using Jiang net and conical net.Mud carp larvae were found in the samples from May to September,with multiple spawning peak periods in a whole year.The larvae were（5.5±0.4） mm in total length,and ranged from one-chamber-air-bladder stage to yolk-exhausted stage.These larvae were considered drifting from the spawning grounds and spreading between the Qianjiang River and the Xunjiang River,which are 170-380 km upper stream of the sampling site.Mud carp lar-vae accounted for 3.71% of the total drifting fish larvae.The estimated density of mud carp larvae was higher at night than in the morning and at midday（n=29;P〈0.05）.Total drifting fish larvae density varied with the distance off the bank.It was higher at riverside than in the midchannel（n=6;P〈0.01）.Density of mud carp larvae were extremely significantly correlated with water discharge,water level and turbidity（P〈0.01）,and were significantly correlated with water temperature and sampling time（P〈0.05）.