日本鳗鲡补充群体的日龄、全长、出生时间及耳石生长的变化

在中国大陆沿岸6个取样床搜集了日本鳗鲡白仔鳗,191尾用于长度测定,112尾鉴定了日龄及测定了耳石半径,近中心核的标记轮直径、耳石生长轮的宽度.补充群体长度平均值从(53.4±2.2)mm到(58.1±1.7)mm,长度与补充群体的地理分布之间无内在联系.补充群体日龄从(138.2±6.7)d至(155.2±9.0)d,长江口和温州地区补充群的日龄最低,以此为中心,向高纬度和低纬度走向分布,补充群的日龄都逐渐增大,补充群出生时间从1993年8月15日至1994年1月10日.低纬度的群体补充的时间早,其出生时间也早.纬度越高,补充的时间越迟,出生时间也晚.补充群耳石半径平均值从(142.5±8.4)μm至(155.8±14.5)μm,具有显着性差异(p<0.01).标记轮直径从(10.36±0.85)μm至(10.81±1.26)μm,其差异不具显著性(p>1.01).耳石生长轮平均宽度为(0.996-1.097) μm,其差异具有显著性(p<0.01),生长轮平均宽度以温州和长江口群体最大,以此为中心,向高纬度和低纬度分布的补充群的平均值分别逐渐减小.补充群耳石从中心至边缘生长轮宽度变化的共同点是在第90轮处平均宽度值最高.

Interrelationship among daily age, body length, birth date and sampling loaction at recruitment of Anguilla japonica elvers in the Chinese coast

A total of 191 Anguilla japonica elvers,collected at 6 locations along the Chinese coast were observed in order to determine age and to measure body length.The average length of elvers at 6 locations ranged from (53.4±2.2) to (58.1±1.7) mm(X±S.D).There were no relationship between body length and location of elvers distribution.The average daily ages of elvers at 6 locations ranged from (138.2±6.7) to (155.2±9.0) d(X±S.D).The maximum radius,check around the nucleus,average growth increment width and the changes of the increment width of otolith were compared.The average radius of otoliths of elvers at 6 locations ranged from (142.5±8.4) to (155.8±14.5) μm(X±S.D).The average maximum diameters of the check around the nucleus of the otoliths ranged from (10.36±0.85) to (10.81±1.26) μm (X±S.D),there was no significantly different among them (p>0.0l).The average increment width of otoliths ranged from 0.996 to 1.097 μm,there was significantly different among them (p<0.0l).The growth rate of the otolith was the highest at Wenchou and the Changjiang Estuary.The growth rate of the otoliths declined gradually at other locations towards both lower and higher latitude,respectively.The increment width of the otoliths was the highest at approximately 90-days old at 6 locations.The average daily ages of elvers at the Changjiang Estuary and Wenchou were the youngest.The daily ages of elvers declined gradually at other locations towards both lower and higher latitude respectively while the position of Wenchou and the Changjiang Estuary was the center at 6 locations.Estimated birth date based on the daily ages at 6 locations ranged from 15 August,1993 to 10 Janaury,1994.The individual at lower latitude is earlier birth but no younger,and recruit earlier.