珠江中下游鳡鱼苗的发生及其与水文环境的关系

为了解珠江中下游地区鳡资源状况, 为鱼类资源保护和生态修复提供科学依据, 2005年—2006年在西江肇庆江段, 通过弶网定点连续采样监测对珠江中下游鳡早期资源进行了调查。结果表明, 2006年珠江中下游鳡繁殖期跨度105 d, 鳡鱼苗集中出现在5—7月, 占鱼苗总量的0.29%。鳡鱼苗发育至眼黑期至卵黄吸尽期, 体全长(8.89?0.25) mm。鳡鱼苗密度和鱼苗总密度均呈现明显的昼夜变化规律, 表现为晚上密度一般高于白天。鳡鱼苗密度与水温、上游干支流的径流量、水位的相关分析和交互协方差函数分析表明: 鳡鱼苗密度与官良水文站的径流量和水位呈显着相关关系(P<0.05, n=126), 罗定江是影响珠江中下游鳡鱼苗发生的主要河流之一。推测罗定江下游、罗定江口至梧州江段可能为珠江中下游鳡鱼的主要产卵场分布区域, 该区域鳡鱼产卵规模占珠江中下游鳡鱼苗总量的41.4%。

Occurrence of larval Elopichthys bambusa and its relationship with hydro-logical conditions in the middle and lower reaches of Pearl River

For studying Elopichthys bambusa resource status in the middle and lower reaches of Pearl River, which could be used to guide fish resources protection and ecological restoration, larval Elopichthys bambusa were surveyed at Zhaoqing section in 2005 and 2006. Sampling was conducted continuously by Jiang net. The result show that reproduction period of E. bambusa lasted 105 days, and the larval was mainly occurred from May to July, accounted for 0.29% of the total fish larvae in 2006. The larval E. bambusa were 8.89?0.25 mm in total body length, and ranged from melanoid eye stage to yolk-exhausted stage. The density of E. bambusa and total fish larvae regularly changes with day and night. The density was higher at night than day time. Correlation and cross-covariance function analysis show that it was significantly correlated between density of E. bambusa larvae, discharge and water level in Guanliang hydrometric station (P<0.05, n=126), Luoding River was one of the main rivers that affected E. bambusa reproduction. It was also inferred that Luoding River and from Luoding River estuary to Wuzhou section were the main spawning grounds, which were contributing about 41.4% of the total E. bambusa larvae in the middle and lower reaches of Pearl River.