长江口南支水域刀鲚仔稚鱼数量变动的研究

Distribution and abundance of Coilia nasus larvae and juveniles in the southern branch of Yangtze River Estuary

为了探明长江口南支刀鲚仔稚鱼的丰度和分布变化,2014年3-9月在长江口南支设置8个站点,采用大型仔稚鱼网（口径1.3 m,网目0.5 mm）在每月大潮期间按月进行表层水平拖网。共拖网91网次,采集刀鲚仔稚鱼1 270尾,体长范围为3.56-50.88 mm,发育阶段由卵黄囊期仔鱼期到稚鱼期。其中涨潮期间采集刀鲚仔稚鱼1 013尾,平均密度0.27 ind/m3,平均体长10.00 mm。其中St.8密度最高,达0.268ind/m3,平均体长为9.44 mm。退潮期间采集刀鲚仔稚鱼163尾,平均密度0.01 ind/m3,平均体长为20.08 mm。St.8昼夜调查表明,夜间采集刀鲚94尾,涨潮期间密度为0.056 ind/m3,小于白天涨潮密度,退潮期间密度为0.003 ind/m3,小于白天退潮密度,涨潮平均体长为13.86mm,大于白天;夜间退潮平均体长为22.01 mm,与白天相当。比较沿岸碎波带研究结果,长江口南支出现的刀鲚仔稚鱼个体较小,有必要加强对江面刀鲚早期资源漂流水域的保护。

To clarify the distribution and abundance of Coilia nasus larvae and juveniles,8 stations were set along the southern branch of Yangtze River Estuary from March to September 2014. A total of 1270 individuals of C. nasus were collected at the spring tides by a larval net（ 1. 3 m mouth-diameter,mesh aperture 0. 5 mm）. The body length ranged from 3. 56- 50. 88 mm,with developmental stages from yolk-sac larvae to juveniles. A total of 1 013 individuals of C. nasus were collected at flood tide. The average density was 0. 27 ind / m3,the average body length was 10. 00 mm. The highest average density was 0. 268 ind /m3 at station 8,average body length was 9. 44 mm. St. 6- 8 were simultaneously sampled at ebb tide,and a total of 163 individuals of C. nasus were collected. The average density was 0. 01 ind / m3,the average body length was 20. 08 mm. At St. 8,a total of 94 individuals of C. nasus were collected at night time. The average density was 0. 056 ind / m3 at flood tide and 0. 003 ind / m3 at ebb tide,both smaller than the day time. The average body length at flood tide was 13. 86 mm,the average body length at ebb tide was 22. 01 mm.Compared with the study on the surf zone,the average body length of C. nasus larvae and juveniles in the southern branch of Yangtze River estuary was smaller,and it is necessary to protect the early resources of C.nasus.