长江口沿岸碎波带刀鲚仔稚鱼的数量分布

Distribution and abundance of larval japanese grenadier anchovy Coilia nasus in the surf zone of the Yangtze River estuary

2007年5-10月,每月大潮期间在长江口沿岸碎波带13个站位用小型拖网各采样1次。195次拖网共采获刀鲚(Coilia nasus)仔稚鱼9358尾,体长范围为3.0～61.2mm,优势体长为6.0～25.0mm,以10.0～16.0mm的弯曲期和13.0～21.0mm的后弯曲期仔鱼为主。采获数量以7月最高,占总数55.0%,主要分布在长江口南支和北支上游,有3个站位(St.5、St.7、St.10)数量较高。其中有1个站位(St.7)刀鲚仔鱼的平均体长按月呈递增趋势,表明刀鲚仔稚鱼有利用沿岸碎波带作为早期生长场所的习性。根据刀鲚仔稚鱼在长江口沿岸碎波带分布和数量变动的调查结果,结合目前刀鲚成鱼资源量贫乏的现状,建议有关部门限制鳗苗定置网等作业,并加强对沿岸碎波带保育场的保护。

The Coilia nasus（Clupeiformes,Engraulidae）is a diadromous species widely distributed in China river estuary as a main commercial fish and high in production.In recent years,due to the increase of fishing intensity and water pollution,the resource of Coilia nasus have decreased sharply.Yangtze River estuary,as an important immigrant channel and nursery ground,was selected as the study site to clarify the situation of recruitment stock along the surf of the estuary.A total of 9 358 individuals of Coilia nasus larvae and juveniles were collected monthly by a seine net（1 m×4 m,mesh aperture 1 mm）at 13 stations in the surf zone of Yangtze River estuary from May to October 2007,respectively.The body length of Coilia nasus larvae and juveniles ranged from 3.0 to 61.2 mm.The dominant body length was from 7.0 to 23.0 mm,mainly including flexion larvae（10.0-16.0 mm）and postflexion larvae（13.0-21.0 mm）.The highest abundance occurred in July,accounting for 55.0%of the total abundance,then reduced from August to October.The Coilia nasus larvae and juveniles distributed mainly in the upper reaches of south branch and north branch of Yangtze River estuary,among which St.5,St.7 and St.10 have relative high level of abundance.And the mean body length of Coilia nasus larvae showed an increasing tendency monthly at St.7,which showed Coilia nasus larvae could utilize the surf zones as its nursery grounds.Based on the analysis of seasonal occurence,and in consideration with the situation that Coilia nasus resources are not abundant at present,it is suggested that the improper use of gears should be limited and more attention should be paid to the preservation of fish larvae and juveniles habitat in the surf zones.