长江口沿岸碎波带刀鲚仔稚鱼摄食习性与浮游动物分布的相关性研究

为探明长江口沿岸碎波带浮游动物的分布与刀鲚仔稚鱼摄食的关系,2006年7~12月每月大潮期间在长江口沿岸碎波带设置13个站位点,用浮游Ⅰ型生物网(口径30 cm,网目0.2 mm)在表层拖曳采集浮游动物78次,采集到浮游动物72种,平均密度 3 278.95 个/网;用小型拖网(1 m×4 m,网目1 mm)拖曳234次,采集到刀鲚仔稚鱼 37 170 尾,平均密度158.85尾/网。通过胃含物分析共鉴定刀鲚仔稚鱼饵料生物15种(类)(浮游动物11种,浮游幼体4类),平均摄食密度1.306个/尾。研究结果表明:前弯曲期仔鱼偏好摄食哲水蚤、剑水蚤和枝角类;弯曲期仔鱼偏好摄食猛水蚤和桡足类桡足幼体;后弯曲期仔鱼除偏好摄食桡足类幼体以外,也偏好摄食游泳能力较强的糠虾;稚鱼对糠虾有极强的偏好。水温和盐度对刀鲚仔稚鱼的摄食量影响较小;浮游动物分布并不直接影响刀鲚仔稚鱼分布,相关性较小。

STUDY ON RELATIONSHIP BETWEEN DISTRIBUTION OF ZOOPLANKTON AND COILIA nasus LARVAE FEEDING FEATURES IN THE SURF ZONE OF YANGTZE RIVER ESTUARY

To clarify the relationship between the distribution of zooplankton and Coilia nasus larvae and juveniles feeding features in the surf zone of Yangtze River estuary, zooplankton and Coilia nasus larvae and juveniles were both collected at the 13 stations by a zooplankton net (30 cm mouth-diameter, 0.2 mm mesh-aperture) and a seine net (1 m×4 m, 1 mm mesh-aperture) during the spring tide from July to December 2006, respectively. During the study period, 78 zooplankton net hauls were made, 72 species of zooplankton were collected, 234 seine hauls were made, and 37 170 individiuls of Coilia nasus larvae and juveniles were caught. The average density was 158.85 individuals per haul. Through the stomach content analysis, 15 species of food organisms (11 species of zooplankton and 4 kinds of planktonic larvae) were observed. Among them, the number of Calanoida was the highest, accounting for 69.21% of the total; Cladocera accounted for 17.30%; the lowest was Gastropods larvae, only accounting for 0.14%. The average feeding density of Coilia nasus larvae and juveniles was 1.306 ind/ind. The average feeding density of larvae in preflexion stage was 0.195 ind/ind; larvae in flexion stage was 0.692 ind/ind; larvae in postflexion stage was 0.890 ind/ind; and juveniles was 4.697 ind/ind. The feeding density of Coilia nasus larvae and juveniles was higher at the middle and lower reaches than at the upstream of Yangtze River estuary. And the average empty gut rate of Coilia nasus larvae and juveniles was 63.70%. There was a strong negative correlation between empty gut rate and body length of Coilia nasus larvae and juveniles. All these results indicated that, larvae at pre-flexion stage with weak swimming ability chose to feed on Calanoida, Cyclopoida and Cladocera, such as Schmackeria poplesia, Sinocalanus sinensis and Bosmina coregoni. With their swimming ability improved in flexion stage, they fed on copepod larvae and Harpacticoida. Post-flexion stage larvae preferred to feed on copepod larvae and Acanthomysis longirostris. Juveniles also had a strong preference on Acanthomysis longirostris. The relativity analysis between the abundance of Coilia nasus larvae and juveniles and zooplankton showed that the temperature and salinity had small influence on the feed of larvae and juveniles; and the abundance of larvae and juveniles did not directly affected by the distribution of zooplankton, the correlation between them was not significant; the swimming ability was weak for larvae in preflexion stage, and their feeding affected by the density of zooplankton and the density of Coilia nasus of the integrated influence.